AU2001214452B2

AU2001214452B2 - A hybrid electrical power system employing fluid regulating elements for controlling various operational parameters of the system

Info

Publication number: AU2001214452B2
Application number: AU2001214452A
Authority: AU
Inventors: Michael S. Hsu
Original assignee: ZTEK Corp
Current assignee: ZTEK Corp
Priority date: 2000-10-30
Filing date: 2000-10-30
Publication date: 2006-11-02
Anticipated expiration: 2020-10-30
Also published as: CN1503996A; JP2004538600A; EP1346425A2; WO2002037587A3; KR20030063368A; WO2002037587A2; AU1445201A; WO2002037587A8; CA2427419A1

Description

WO 02/37587 PCT/US00/29895 -1- A HYBRID POWER SYSTEM EMPLOYING FLUID REGULATING ELEMENTS FOR CONTROLLING VARIOUS OPERATIONAL PARAMETERS OF THE SYSTEM Background of the Invention This invention relates to high temperature electrochemical converters, such as fuel cells, and more specifically to high performance energy or power systems that employ electrochemical converters.

Electrochemical converters, such as fuel cells, convert chemical energy derived from fuel stocks directly into electrical energy. The key components in an electrochemical energy converter are a series of electrolyte units having electrodes disposed over its surfaces, and a series of interconnectors disposed between the electrolyte units to provide serial electrical connections. The electrolyte units have fuel and oxidizer electrodes attached to opposite sides. Each electrolyte unit is an ionic conductor having low ionic resistance thereby allowing the transport of an ionic species from one electrode-electrolyte interface to the opposite electrode-electrolyte interface under the operating conditions of the converter. Various electrolytes can be used in such converters. For example, zirconia stabilized with such compounds as magnesia, calcia or yttria can satisfy these requirements when operating at an elevated temperature (typically around 1000'C). The electrolyte material utilizes oxygen ions to carry electrical current. The electrolyte should not be conductive to electrons which can cause a short-circuit of the converter. On the other hand, the interconnector must be a good electronic conductor. The interaction of the reacting gas, electrode and electrolyte occurs at the electrode-electrolyte interface, which requires that the electrodes be sufficiently porous to admit the reacting gas species and to permit exit of product species. The electrochemical converter can have a tubular or planar configuration.

Electricity is generated through electrodes and the electrolyte by an electrochemical reaction that is triggered when a fuel, hydrogen, is introduced over the fuel electrode and an oxidant, air, is introduced over the oxidizer electrode.

Alternatively, the electrochemical converter can be operated in an electrolyzer mode, in which the electrochemical converter consumes electricity and input reactants and produces fuel.

WO 02/37587 PCT/US00/29895 -2- When an electrochemical converter, such as a fuel cell, performs fuel-toelectricity conversion in a fuel cell mode, waste energy is generated and should be properly processed to maintain the proper operating temperature of the electrochemical converter and to boost the overall efficiency of the power system. Conversely, when the converter performs electricity-to-fuel conversion in the electrolyzer mode, the electrolyte must be provided with heat to maintain its reaction. Furthermore, the fuel reformation process, often used with fuel cells, can require the introduction of thermal energy. Thus thermal management of the electrochemical converter system for proper operation and efficiency is important.

Thermal management techniques can include the combination of an electrochemical converter with other energy devices in an effort to extract energy from the waste heat of the converter exhaust. For example, U.S. patent No. 5,462,817 of Hsu describes certain combinations of electrochemical converters and bottoming devices that extract energy from the converter for use by the bottoming device.

Environmental and political concerns associated with traditional combustionbased energy systems, such as coal or oil fired electrical generation plants, are boosting interest in alternative energy systems, such as energy systems employing electrochemical converters. Nevertheless electrochemical converters have not found widespread use, despite significant advantages over conventional energy systems. For example, compared to traditional energy systems, electrochemical converters such as fuel cells are relatively efficient and do not produce pollutants. The large capital investment in conventional energy systems necessitates that all advantages of competing energy systems be realized for such systems to find increased use. Accordingly, electrochemical converter energy systems can benefit from additional development to maximize their advantages over traditional energy systems and increase the likelihood of their widespread use.

Conventional gas turbine power systems exist and are known. Prior gas turbine power systems include a compressor, a combustor, and a mechanical turbine, typically connected in-line, connected along the same axis. In a conventional gas turbine, air enters the compressor and exits at a desirable elevated pressure. This high-pressure air stream enters the combustor, where it reacts with fuel, and is heated to a selected elevated temperature. This heated gas stream then enters the gas turbine and expands O adiabatically, thereby performing work. One drawback of gas turbines of this N general type is that the turbine typically operates at relatively low system efficiencies, for example, around 25%, with systems of megawatt capacity.

OOne prior art method employed to overcome this problem is to employ a recuperator for recovering heat. This recovered heat is used to further heat the air Sstream prior to entering the combustor. Typically, the recuperator improves the system efficiency of the gas turbine upwards to about 30%. A drawback of this solution is that the recuperator is relatively expensive and thus greatly adds to the Soverall cost of the power system.

O 10 Another prior art method employed is to operate the system at a relatively high pressure and a relatively high temperature to thereby increase system efficiency. However, the actual increase in system efficiency has been nominal, while the system is subjected to the costs associated with the high temperature and pressure mechanical components.

Thus, there exists a need in the art for high performance power systems.

In particular, an improved gas turbine power system that is capable of controlling or regulating an operational parameter of the system would represent a major improvement in the industry. More particularly, an integrated electrochemical converter and gas turbine system that controls system operation, reduces the costs associated with providing interfacing thermal processing systems, while significantly improving the overall operability of the combined system would also represent a major improvement in the art.

Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art in Australia on or before the priority date of the claims herein.

SUMMARY OF THE INVENTION The present invention provides methods and apparatus for controlling an operational parameter of a hybrid power system, while concomitantly operating the system efficiently. According to the invention, an electrochemical converter, such as a fuel cell, is combined with a cogeneration or bottoming device, such as a gas turbine assembly, to form a hybrid power system. The electrochemical Sconverter and the bottoming device form an improved power system for Sconverting fuel into useful forms of electrical, mechanical or thermal energy.

I Devices that may be combined with a fuel cell include gas turbines, steam turbines, thermal fluid boilers, and heat-actuated chillers. The latter two devices are often incorporated in a Heating Ventilation and Cooling (HVAC) system.

C The hybrid power system of the invention regulates or controls one or more fluid flows in the system with a fluid regulating device. The fluid regulating device thus enables the system to control the power output or temperature of the fuel cell and/or the gas turbine assembly, as well as the speed of the turbine.

0 10 In accordance with a first aspect of the present invention there is provided a hybrid power system for producing electricity, comprising one or more compressors for compressing a first medium, one or more electrochemical converter systems positioned relative to said compressors to receive the first medium and a second medium, the electrochemical converter systems being configured to allow electrochemical reaction between the first and second mediums to produce electricity and fuel cell exhaust, one or more turbines in fluid communication with the electrochemical converter system and positioned relative to said electrochemical converter system to receive at least a portion of the exhaust, said exhaust operating as a drive fluid for the turbine, wherein said turbine produces turbine exhaust, and regulation means for regulating one or more operational parameters of the turbine with the exhaust of the electrochemical converter system.

In accordance with another aspect of the present invention there is provided a method for producing electricity with a hybrid power system, comprising the steps of compressing a first medium, providing one or more electrochemical converter systems for electrochemically reacting the first with a second mediums and to produce exhaust, providing one or more turbines to receive a portion of the electrochemical converter system exhaust, said exhaust operating as a drive fluid for the turbine, wherein said turbine produces turbine exhaust, and

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regulating an operational parameter of the turbine with the exhaust from the C electrochemical converter system.

c In accordance with another aspect of the present invention there is Cc provided a hybrid power system (290) for producing electricity, comprising one or more compressors for compressing at least a portion of a first medium to produce a compressed medium, I one or more electrochemical converter systems adapted to receive the first medium and a second medium, the electrochemical converter system being _configured to allow electrochemical reaction between the first and second mediums and to produce electricity and fuel cell exhaust, one or more heat exchangers in thermal communication with the electrochemical converter system and adapted to receive the compressed medium, said heat exchanger exchanging heat with the electrochemical converter system to condition the compressed medium when passing through the heat exchanger, and one or more turbines configured to receive the compressed medium exiting the heat exchanger, said compressed medium operating as a drive fluid for the turbine for electricity generation.

According to one embodiment, the hybrid power system employs one or more by-pass passages for transferring one or more fluids in the system in a selected manner. For example, a fluid regulating element and fluid conduit can be employed to by-pass a heat exchanger, an electrochemical converter system (or a constituent component of the system), and a gas turbine assembly (or a constituent component of the assembly). By operating one or more of the fluid regulating devices in a selected manner, the system can control the power output of the electrochemical converter system or of the gas turbine assembly.

According to another embodiment, the electrochemical converter system can employ a thermal control stack and a fuel cell, both of which are mounted within a pressure vessel. The thermal control stack can operate as a heat source or heat sink according to system needs. For example, upon start-up operation, the thermal control stack can operate as a heat source by generating heat that is

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O conveyed to the fuel cell in order to heat the fuel cell. During steady state C operation, the thermal control stack can operate as a heat sink by removing heat c from the fuel cell or as a heat source by providing heat to the fuel cell. The 0 thermal control stack can have any suitable shape.

According to still another embodiment, the hybrid power system may employ multiple heat exchangers and fluid conduit designs for regulating the exhaust temperature of the electrochemical converter system. For example, the hybrid power system may employ a fluid regulating device that regulates the _temperature of the drive gas for the gas turbine assembly by selectively intermingling low temperature compressor exhaust with the high temperature exhaust of the electrochemical converter system. This intermingling of different temperature fluids regulates the temperature of the drive gas, and thus controls the power output of the assembly.

According to yet another embodiment, the hybrid power system may selectively intermingle different temperature fluids in order to control the power output of the gas turbine assembly and/or the electrochemical converter system.

"Comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and advantages of the invention will be apparent from the following description and apparent from the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings illustrate principles of the invention and, although not to scale, show relative dimensions.

FIG. 1 is a schematic block diagram of one embodiment of a hybrid power system employing a plurality of fluid regulating elements to regulate an operational parameter of the system according to the teachings of the present invention.

FIG. 2 graphically illustrates the combined power efficiency of the hybrid power system of FIG. 1.

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O FIG. 3 is a schematic view of a multi-shaft gas turbine assembly which can c be employed in the hybrid power system of FIG. 1.

c FIG. 4 is a plan view, partially cut-away, of a pressure vessel enclosing the electrochemical converter system of the hybrid power system of FIG.1 according to the teachings of the present invention. FIG. 5 is a perspective view of one embodiment of a cell unit of an electrochemical converter assembly suitable for n use in the electrochemical converter system of the hybrid power system of the present invention.

_FIG. 6 is a perspective view of an alternate embodiment of the cell unit of the electrochemical converter of the present invention.

WO 02/37587 PCT/US00/29895 -6- FIG. 7 is a cross-sectional view of the cell unit of FIG. FIG. 8 is a cross-sectional view of one embodiment of the thermal control stack of FIG. 1 employing a porous structure for regulating the temperature of a fuel cell according to the teachings of the present invention.

FIG. 9 is a cross-sectional view of another embodiment of the thermal control stack of FIG. 1 employing a plate type structure for regulating the temperature of a fuel cell according to the teachings of the present invention.

FIG. 10 is a cross-sectional view of still another embodiment of the thermal control stack of the electrochemical converter system of FIG. 1 according to the teachings of the present invention.

FIG. 11 is a cross-sectional side view of the embodiment of FIG. FIG. 12 is a schematic block diagram of an alternate embodiment of the hybrid power system of FIG. 1 for regulating the temperature of the exhaust of the electrochemical converter system prior to entering the turbine expander according to the teachings of the present invention.

FIG. 13 is a schematic block diagram of an alternate embodiment of the hybrid power systems of FIGS. 1 and 12 for regulating the temperature of the exhaust of the electrochemical converter system according to the teachings of the present invention.

FIG. 14 is a schematic block diagram of an alternate embodiment of the hybrid power systems of FIGS. 1, 12 and 13 for regulating the temperature of the exhaust of the electrochemical converter system according to the teachings of the present invention.

WO 02/37587 PCT/US00/29895 -7- FIG. 15 is a schematic block diagram of an alternate embodiment of a hybrid power system for regulating the exhaust temperature of a compressor of the gas turbine assembly prior to entering the turbine expander according to the teachings of the present invention.

FIG. 16 is a schematic block diagram of an alternate embodiment of a hybrid power system for regulating the flow of the input reactants and the temperature of the electrochemical converter system according to the teachings of the present invention.

FIG. 17 is a schematic block diagram of an alternate embodiment of a hybrid power system for independent regulation of the temperature of the input reactants of the electrochemical converter system and the temperature of the exhaust introduced to the turbine expander according to the teachings of the present invention.

FIG. 18 is a schematic diagram of a gas turbine assembly employing fluid conduits penetrating an outer housing for communication with an external heat source suitable for use with the hybrid power system of the present invention.

FIG. 19 is an exemplary schematic illustration of the various arrangements of the thermal control stack and the fuel cell incorporated in the electrochemical converter system according to the teachings of the present invention.

Description of Illustrated Embodiments The hybrid power system of the present invention employs components that dynamically adjusts or controls an operational parameter of the system, such as the power output of a gas turbine assembly, while concomitantly maintaining suitable operating temperatures of both the gas turbine and the fuel cell system components.

FIG. 1 shows one embodiment of an integrated hybrid power system incorporating an electrochemical converter system 72 and a gas turbine assembly 74 according to the present invention. The gas turbine assembly 74 includes a compressor 76, a turbine expander 78, and a generator 80, all connected together by shaft 82. The shaft 82 can connect the compressor 76 to the turbine expander 78 in a serially in-line, WO 02/37587 PCT/US00/29895 -8aero-derivative configuration. The generator 80 is connected to the turbine expander 78 by any suitable coupling. The gas turbine assembly 74 typically operates on fossil fuel, preferably natural gas, and inexpensively and cleanly generates electricity. Although the gas turbine assembly 74 illustrates the compressor 76, turbine expander 78, and the generator 80 mounted on the shaft 82 in sequential order, other orders can also be utilized. For example, the generator 80 can be disposed between the compressor 76 and the turbine expander 78.

As used herein, the phrases gas turbine and gas turbine assembly are intended to encompass gas turbines of all power sizes, shapes and speeds, including microturbines operating at least at 50,000 RPM, and generally between about 70,000 and about 90,000 RPM. A suitable gas turbine can be obtained from Capstone Turbine Corporation of Tarzana, CA or from Allied Signal of Torrance, CA.

Air 84 from an air source is introduced to the compressor 76 by way of any suitable fluid conduit, where it is compressed and heated, and then discharged therefrom. The heated, compressed and pressurized air 86 can then be introduced to a heat exchanger 88, such as a recuperator, prior to being introduced to the turbine expander 78. For example, a portion of the heated air 86 can be introduced to the heat exchanger 88 along fluid conduit 90 where it can be further heated in a recuperative or a counterflow scheme by the turbine exhaust exiting the turbine expander 78.

Alternatively, a portion or all of the heated, compressurized air 86 can be introduced to the input of the turbine expander 78 along fluid conduit 92. A fluid regulating device 94 can be disposed in the conduit 92 to regulate or adjust the amount of heated compressed air 86 that is introduced to the input of the turbine expander 78.

As used herein, the terms heat exchanger or heat exchanging element are intended to include any structure that is designed or adapted to exchange heat between two or more fluids. Examples of suitable types of heat exchangers adapted for use with the present invention include recuperators, whether internally mounted in the gas turbine assembly 74 or mounted external thereof, radiative heat exchangers, counterflow heat exchangers, and regenerative type heat exchangers As used herein, the term "fluid regulating device" is intended to include any structure that is adapted or designed for regulating, controlling, adjusting or monitoring the passage of a fluid along a fluid pathway. Examples of suitable types of fluid WO 02/37587 PCT/US00/29895 -9regulating devices include diaphragms, rotating spheres, bellows, and multiple different types of valves, including two-way and three-way valves. The term regulate will be used hereinafter for the sake of simplicity when describing the function of the fluid regulating device.

As set forth above, a portion or all of the heated, compressed air 86 can be introduced to the heat exchanger 88 along fluid conduit 90. A fluid regulating element 96 is interposed in the fluid conduit 90 to regulate the amount of air introduced to the heat exchanger. The fluid regulating element 96 can be operated so as to regulate the amount of air introduced to the heat exchanger, and can also be employed to allow some or all the air passing through fluid conduit 90 to bypass the heat exchanger 88 along bypass conduit 98. The air passing along the bypass fluid conduit 98 is not heated by the turbine exhaust exiting the turbine expander 78, and hence is not further heated at this juncture of the system The air exiting the heat exchanger 88 or exiting the bypass fluid conduit 98 can be further introduced to the electrochemical converter system 72, or can be mixed with the exhaust of the electrochemical converter system 72. According to one practice, the illustrated electrochemical converter system 72 includes a fuel cell 112 and a thermal control stack 116 mounted within a pressure vessel 120. The illustrated fuel cell 112 can be any selected fuel cell, including a molten carbonate fuel cell, phosphoric acid fuel cell, alkaline fuel cell, and proton exchange membrane fuel cell, and is preferably a solid oxide fuel cell. The operating temperature of the fuel cell is preferably between about 'C and about 1500 The illustrated thermal control stack 116 can include any selected structure for interfacing with the fuel cell in order to control, adjust or regulate the temperature of the fuel cell, either alone or in combination with other temperature regulating structure. The pressure vessel 120 can be any suitable pressure vessel that is sized and dimensioned for housing the fuel cell 112 and the thermal control stack 116, while concomitantly functioning as a fluid collection vessel for collecting the exhaust of the fuel cell 112 and/or the thermal control stack 116.

With reference to FIG. 1, the fluid regulating element 100 can be employed to regulate the amount of air that is introduced to the fuel cell 112. Hence, the fluid regulating device 100 can be employed to regulate, adjust or control the amount of air passing through the fuel cell 112. By regulating the amount of heated air passing WO 02/37587 PCT/US00/29895 through the fuel cell, the system can regulate the power output thereof in accordance with system or user requirements.

An additional fluid regulating element 104 disposed between the heat exchanger 88 and the electrochemical converter system 72 can be employed to introduce some or all of the air passing through conduit 107 to the thermal control stack 116. The fluid regulating elements 100 and 104 can hence be operated to distribute the air between the fuel cell 112 and the thermal control stack 116 according to system needs. This arrangement is particularly desirable upon start-up operation of the electrochemical converter system 72 and during sustained system use. The system can further employ fluid regulating element 109 disposed between the fluid regulating elements 104 and 100 to regulate the amount of air passing through conduit 98 that is conveyed to conduit 107, and hence to the fuel cell 112. Those of ordinary skill will readily recognize that the thermal control stack 116 can operate both as a heating device upon system start-up, and as a cooling device or heat sink during established system use. The fuel cell 112 and/or the pressure vessel 120 can employ power leads 126 that couple the direct current electricity generated by the electrochemical converter system 72 with an inverter 125.

The inverter 125 may convert the direct current electricity generated by the electrochemical converter system 72 into alternating current for subsequent transfer to a power grid, power storage device, or power consuming apparatus. The inverter can communicate with the controller 140 in order to enable the system 70 to regulate one or more components based on the inverter output.

The thermal control stack 116 is in thermal communication with the fuel cell 112 and is also arranged to receive both fuel and air. The thermal control stack can function as a heating element or source by combusting fuel in the presence of air to generate heat for preheating the fuel cell 112. This operation continues to maintain an appropriate operating temperature, typically 1,000 'C whereby the fuel cell 112 continues to consume fuel and air in order to electrochemically react these reactants to produce electricity. Once the fuel cell reaches its desired operating temperature, the fuel supplied to the thermal control stack can be decreased or stopped, and air can continue to pass therethrough in order to assist in removing heat from the fuel cell 112. In this arrangement, the thermal control stack functions as a cooling element or heat sink for removing waste heat from the fuel cell during operation.

WO 02/37587 PCT/US00/29895 -11- The illustrated hybrid power system 70 also provides means for supplying a fuel through conduit 85 to the fuel cell 112, where it electrochemically interacts with the oxygen-containing gas, typically air, to produce electricity, waste heat and a high temperature exhaust gas. The fuel can be reformed by any suitable reforming apparatus, such as the reformer 132, in order to produce a relatively pure fuel stock. Although illustrated as being disposed external of the electrochemical converter system 72, the reformer 132 can also form part of the converter system 72. Multiple different types of reforming apparatuses are contemplated by the present invention, and a particularly suitable reformer is disclosed and described in U.S. Patent No. 5,858,314 of Hsu, the contents of which are herein incorporated by reference. The illustrated system 70 can also employ a second compressor 134 to compress and heat the fiel prior to introduction to the fuel cell 112. The illustrated reformer 132 and compressor 134 are optional features of the present invention.

The power system 70 can employ one or more fuel valves, such as fuel valves 89 and 91 to control, adjust or regulate the amount of fuel delivered to the fuel cell and/or thermal control stack 116. The fuel valves can communicate with the controller 140 for controlling operation of the valves. Specifically, the controller can regulate the amount of fuel introduced to the fuel cell and the thermal control stack in order to regulate an output parameter of each device. According to one practice, the controller 140 can control operation of the fuel valves to regulate the amount of fuel introduced to the electrochemical converter system 72 based on the output of the inverter 125.

Specifically, the controller can regulate the power output of the fuel cell or the thermal energy generated or received by the thermal control stack based on the power generated by the fuel cell.

The illustrated hybrid power system 70 also employs a fluid regulating device 108 that is coupled between fluid conduit 107 and the electrochemical converter system exhaust conduit 124. The electrochemical converter system exhaust traveling through conduit 124 is eventually introduced to the gas turbine assembly 74. In addition to the power generated by the electrochemical converter system 72, the gas turbine assembly 74 also produces power by serving as a bottoming cycle to convert the exhaust and waste heat generated by the electrochemical converter system 72 into usable electrical power, thus increasing the overall efficiency of the hybrid power system 70. Typically, WO 02/37587 PCT/US00/29895 -12the exhaust emitted from the electrochemical converter system 72 is in the range of about 1,000 The exhaust having this temperature may need to be heated further prior to introduction to the gas turbine assembly 74. In these applications, a secondary heating structure, such as an additional combustor, can be interposed between the electrochemical converter system 72 and the gas turbine assembly 74 in order to provide additional heat to the exhaust, such that the exhaust is more compatible with the operational conditions of the gas turbine assembly. In other applications, the exhaust exiting the electrochemical converter system is already closely matched with the gas turbine assembly 74, and hence the exhaust does not require additional heating. In still other applications, the exhaust temperature of the electrochemical converter system 72 may be higher than a desired level. For example, particularly in gas turbine assemblies employing smaller turbine units, the temperature of the input drive gas is generally within a range of between about 800 to 900 Hence, the 1,000 'C exhaust temperature exiting the electrochemical converter system is incompatible with the input temperature range of the gas turbine assembly. It is hence desirable to adjust, control or regulate the temperature of the exhaust of the electrochemical converter system 72 to match the operational requirements of the gas turbine assembly 74 during operation.

According to one practice, the fluid regulating device 108 can be controlled by the controller 140 to allow some or all of the air in conduit 107 to bypass the electrochemical converter system 72 and hence mix with the exhaust passing through conduit 124. The air passing through the fluid regulating device 108 is cooler than the exhaust collected in and passing through the conduit 124. Hence, the fluid regulating device 108 can regulate the temperature of the exhaust by mixing therewith a selected amount of cooler fluid exiting the heat exchanger 88 so that it is compatible with the operational requirements of the gas turbine assembly 74. The heated, pressurized air passing through conduit 107 can thus be diverted and reintroduced to the exhaust in order to create a lower temperature exhaust for subsequent introduction to the turbine expander 78. A significant advantage of this arrangement is that it is a relatively elegant and mechanically non-complex solution to adjusting or regulating the temperature of the exhaust of the electrochemical converter system 72. Other techniques for controlling or adjusting the exhaust temperature of the electrochemical converter system 72 exist, and will be later described in fuarther detail.

WO 02/37587 PCT/US00/29895 -13- As set forth above, the inputs to the hybrid power system 70 are an oxygen containing gas, typically air, and a fuel, which is typically natural gas, and which is principally composed of methane. The air and fuel hence function as reactants for the electrochemical converter system 72. The input oxidizer reactant is used for oxidizing the fuel in the fuel cell 112, which are compressed and heated by the compressors 76 and 134. The compressed, heated and pressurized air 86 is then heated in the heat exchanger 88 by the turbine exhaust exiting the turbine expander 78. Although the oxygen containing gas is typically air, it can be other oxygen-containing fluids, such as air partially depleted of oxygen, or air enriched with oxygen. The air and fuel reactants are consumed by the fuel cell 112, which in turn generates electricity and exhaust which is captured by the pressure vessel 120.

The thermal control stack 116 generates exhaust which is also captured by the pressure vessel 120. The thermal control stack exhaust intermingles with the fuel cell exhaust within the pressure vessel 120 to form a combined exhaust which exits the electrochemical converter system 72, and subsequently passes through fluid conduit 124.

The preferred design configuration of the fuel cell 112 and the thermal control stack 1 1 6 will be described in further detail below.

As described above, the turbine may not operate at as high temperature as the fuel cell. Accordingly, it may be necessary to reduce the temperature of the drive gas prior to introduction to the turbine expander 78. The fluid regulating element 108 disposed between the heat exchanger 88 and the electrochemical converter system 72 can be actuated to allow some or all of the air passing through fluid conduit 107 to bypass the electrochemical converter system 72 and to be intermingled with the exhaust and fluid conduit 124. According to an alternate embodiment, the optional fluid regulating element 94 disposed along fluid conduit 92 can be actuated to allow heated, pressurized air 86 to circumvent the heat exchanger 88 or the electrochemical converter system 72 and to be intermingled directly with the drive gas at the input of the turbine expander 78.

A significant advantage of providing a diverting fluid regulating element, such as fluid regulating elements 94 and 108, is that they provide a degree of control over an operational parameter of the hybrid power system 70, and specifically the gas turbine assembly 74. For example, by selectively controlling the temperature of the drive gas WO 02/37587 PCT/US00/29895 -14introduced into the gas turbine expander 78, the system can control the power output of the overall system, such as the power produced by the gas turbine assembly 74.

Moreover, the power output generated by the fuel cell 112 can be regulated by regulating the amount of fuel introduced thereto, thereby controlling the power output of the electrochemical converter system 72.

Referring again to FIG. 1, the illustrated hybrid power system 70 further includes a fluid regulating element 142 disposed along the fluid conduit 124. The illustrated fluid regulating device 142 performs multiple selected functions. For example, the fluid regulating device can regulate or control the amount of exhaust passing through the fluid conduit 124 which is subsequently introduced to the turbine expander 78. The fluid regulating device 1 42 can also prevent or inhibit the exhaust in fluid conduit 124 from reaching the turbine expander, while concomitantly controlling or regulating the amount of exhaust which is vented to atmosphere, or the amount of external fluid which is intermingled with the exhaust passing through the fluid conduit 124. The fluid regulating device 142 therefore provides for intermingling additional fluid to regulate the temperature of the exhaust passing through the conduit 142. The device 142 also enables the system to strictly regulate the amount of fluid which is introduced to the latter stages of the hybrid power system The hybrid power system 70 can further include an optional secondary combustor 144 disposed downstream of the fluid regulating device 142 to further heat the exhaust in fluid conduit 124 prior to introduction to the turbine expander 78. The secondary combustor 144 is particularly desirable in applications where the gas turbine assembly 74 operates at a temperature higher than the temperature of the exhaust generated by the electrochemical converter system 72. The exhaust forms a turbine drive gas which is then introduced to the turbine expander 78. The drive gas while passing through the turbine expander expands for electric generation and hence is depressurized, and subsequently dispelled therefrom as a turbine exhaust through fluid conduit 146.

The exhaust generated by the electrochemical converter system 72 forms the drive gas for the hybrid power system 70, and is eventually introduced to the turbine expander 78. The turbine adiabatically expands the exhaust and converts the thermal energy of the exhaust into rotary energy. Since the turbine expander 78, generator WO 02/37587 PCT/US00/29895 and compressor 76 can be disposed on a common shaft, the generator 80 produces AC or DC electricity, and the compressor compresses the input air reactant as described above.

Those of ordinary sdkill will readily recognize that the frequency of the electricity produced by the generator is at least 1000 Hz, and typically is from about 1200 to about 1600 Hz. The alternating current electricity produced by the generator 80 can be rectified by any suitable means, such as a rectifier, to convert the alternating current electricity to direct current electricity. This direct current electricity can be directly combined with the direct current electricity produced by the electrochemical converter system 72, prior to transformation by the inverter 125. In this arrangement, the electrochemical converter system 72 functions as an external combustor of the gas turbine assembly, which in turn functions as a bottoming plant for the system The illustrated hybrid power system 70 further includes serially connected fluid regulating devices 148 and 150 which provide additional degrees of control over the operating fluid of the system 70. The fluid regulating device 148 regulates the amount of turbine exhaust passing through the fluid conduit 146, while concomitantly regulating the amount of drive gas which bypasses the turbine expander 78 and which is directly intermingled with the turbine exhaust. By regulating the amount of exhaust exiting the turbine, the system 70 can regulate the power output of the gas turbine assembly 74.

The fluid regulating device 148 therefore provides for an additional mechanism for controlling an operational parameter of the gas turbine assembly 74 by controlling the power output of the gas turbine.

The controller 140 can further be coupled to the generator 80 to monitor or control the operation of one or more components of the system 70. For example, the controller can regulate the amount of exhaust introduced to the turbine expander 78 to control the power output of the gas turbine assembly 74. The controller 140 can control operation of the fluid regulating element 148 to regulate the exhaust flow. According to one practice, the controller 140 can control operation of the fluid regulating element 148 to regulate the amount of drive gas introduced to the turbine based on the generator output. Hence, the system can control the power output of the gas turbine assembly by regulating the drive gas input as a fmnction of the generator power. In particular, the controller can regulate the fluid regulating element 148 based on the generator output.

WO 02/37587 PCT/US00/29895 -16- The illustrated fluid regulating device 150 also regulates the amount of turbine exhaust passing through fluid conduit 146 that is introduced to the heat exchanger 188.

The illustrated fluid regulating device 150 cooperates with the fluid regulating device 154 to control the amount of turbine exhaust passing through the heat exchanger according to system demands and exigencies. Hence, the hybrid power system provides components for regulating the amount of hot exhaust gas which passes through the heat exchanger 88. This in turn regulates or controls the amount of recuperative heating of the air with valve 96 passing through the heat exchanger which occurs during system operation. For example, the temperature of the air passing through the heat exchanger can be regulated or controlled by regulating the amount of turbine exhaust passing through the heat exchanger. Hence, the system 70 can regulate the heating of the fuel cell 112 independently, while concomitantly allowing the gas turbine assembly 74 to maintain an appropriate operating condition and/or temperature. Those of ordinary skill will readily recognize that the turbine exhaust preheats the air passing through the heat exchanger prior to introduction to the electrochemical converter system 72. Those of ordinary skill will also recognize that the hybrid power system 70 can be arranged to preheat the air reactant in the heat exchanger 88 in a counterflow scheme. Other configurations and arrangements of the system components would also be realized by the ordinarily skilled artisan in light of the teachings herein, and which serve to control an operational parameter of the gas turbine assembly 74 during use. For example, the system can employ any number of fluid regulating elements between the heat exchanger 88 and the turbine expander 78, such as one element, or none of desired. Hence, the fluid regulating devices 150 and 154 can be regulated or controlled according to a selected programmatic scheme to ensure optimal or a desired amount of preheating of the air passing through the heat exchanger during different phases of operation of the illustrated hybrid power system A controller 140 can be provided to control, according to any selected user defined sequence, the input fuel and air reactants, as well as the fluid regulating devices 94, 96, 100, 104, 108, 142, 148, 150, and 154. The controller 140 can also be connected so as to regulate the gas turbine assembly 74 or the electrochemical converter system 72.

The controller can be of any conventional design, such as an industrial ladder logic controller, a microprocessor, a stand-alone computing apparatus, a computing apparatus WO 02/37587 PCT/US00/29895 -17that is coupled in a network configuration, or any other suitable processing device which includes suitable hardware, software and/or storage for effectuating control of the hybrid power system.

An advantage of the hybrid power system of FIG. 1 is that it allows electricity to be produced in an high efficiency system by the direct integration of a highly efficient, compact electrochemical converter with a gas turbine assembly operating as a bottoming plant. The integration of the electrochemical converter system 72 with a gas turbine assembly 74 produces a hybrid power system 70 that has an overall power efficiency of about or greater than 70%. This system efficiency represents a significant increase over the efficiencies achieved by prior art gas turbine systems and prior art electrochemical systems alone. The illustrated hybrid power system incorporates a fuel cell 112 to provide electricity and high grade thermal energy, while utilizing the benefits of fuel cells. For example, the fuel cell operates as a low NOx source, thereby improving environmental performance relative to conventional gas turbine generating plants.

The high system efficiency of the combined electrochemical converter and gas turbine assembly is graphically illustrated in FIG. 2. The ordinate axis of the graph denotes the overall system efficiency in percent and the abscissa denotes the power ratio of the hybrid system. The power ratio is defined as the quotient of the sum of the capacities of the electrochemical converter and the gas turbine (FC GT) divided by the capacities of the gas turbine Graph line 160 illustrates that the overall system efficiency can exceed 60% when utilizing a fuel cell having an efficiency of 50% and a gas turbine having an efficiency of 25%. Likewise, graph line 162 illustrates that the overall system efficiency can exceed 60% when utilizing a fuel cell having an efficiency of 55% and a gas turbine having an efficiency of 35%, and depending upon the power ratio, can approach or even exceed 70%. The graph lines 160 and 162 also illustrate that the capacities and efficiencies of the electrochemical converter and gas turbine can be selected to maximize the overall system efficiency. Additionally, the graphs illustrate that a correspondingly large increase in system efficiency occurs when a gas turbine is combined with an electrochemical converter; a result that was heretofore unknown. For example, as previously stated, the gas turbine power system employing an electrochemical converter has an overall system efficiency exceeding 60% and approaching or even exceeding 70%, depending upon the capacities and efficiencies of WO 02/37587 PCT/US00/29895 -18the constituent gas turbine and the electrochemical converter, and the manner in which the hybrid power system 70 is operated and arranged.

As described above, the gas turbine assembly 74 can have a single shaft, serially aligned configuration. Other configurations are also contemplated by the present invention for use in the hybrid power system 70 of FIG. 1. For example, the gas turbine assembly 74 can incorporate a multi-shaft design. FIG. 3 is a schematic representation of a partial embodiment of a hybrid power system 170 that integrates an electrochemical converter with a multiple-shaft gas turbine assembly. The remaining components of FIG. 1 can be incorporated into this embodiment but are omitted for purposes of clarity.

The illustrated power system 170 can be a conventional combustion turbine system that includes a pair of compressors C1 and C2, a pair of turbines T1 and T2, a generator 172, an intercooler 174, and one or more electrochemical converters 176. A pair of shafts 178 and 180 connect turbines T1 and T2 to mechanical compressors C1 and C2, respectively.

As shown, air from an air inlet enters the compressor C1 at its inlet and is compressed thereby. The compressed air then exits the compressor at its outlet and enters intercooler 174, which reduces the temperature of the compressed air prior to the air exiting the intercooler. The intercooler 174 receives a cooling fluid, such as water, at its inlet from a fluid source (not shown) and discharges the water at its outlet.

The cooled, compressed air then enters compressor C2, which again compresses the air prior to introduction to the first electrochemical converter 176. The air is transferred between the electrochemical converter 176 and compressor C2 along fluid pathway 182. The air, upon introduction to the electrochemical converter, reacts with fuel from a fuel source (not shown) to generate electricity.

The electrochemical converter exhaust is introduced to the turbine T2 along fluid pathway 184, the exhaust of which is introduced to a secondary electrochemical converter 176. The secondary converter generates electricity and reheats the exhaust prior to introduction to turbine T1. The exhaust of the turbine TI is preferably carried away from the system 170 along fluid pathway 186 for subsequent use. The rotary energy of the turbine T1 is preferably divided between the mechanical compressor C1 via the power shaft assembly 178 and the electric generator 172. The generator 172 can be used to generate electricity for a variety of residential and commercial purposes.

WO 02/37587 PCT/US00/29895 -19- Although the illustrated system 170 employs a pair of electrochemical converters 176, those of ordinary skill will recognize that only one converter may be used, with the other converter being replaced by a conventional combustor.

Other variations of the above designs exist and are deemed to be within the purview of one of ordinary skill. For example, a series of gas turbine assemblies may be employed, or any number of compressors, combustors and turbines may be used. The present invention is further intended to encompass the integration of an electrochemical converter with most types of gas turbines, including, single-shaft gas turbines, doubleshaft gas turbines, recuperative gas turbines, intercooled gas turbines, and reheat gas turbines. In its broadest aspect, the present invention encompasses a hybrid power system that combines an electrochemical converter and a conventional gas turbine.

According to one preferred practice of the invention, the converter replaces, either fully or partially, one or more combustors of the gas turbine power system.

The direct integration of an electrochemical converter with a gas turbine is aided when the fuel cell 112 is housed within a vessel 120. A preferred type of converter encasement is illustrated in FIG. 4, where a pressure vessel 120, which may also function as a regenerative or recuperative thermal enclosure, encases a series of stacked fuel cell assemblies 122, which are described in greater detail below. The pressure vessel 120 includes an exhaust outlet manifold 124, electrical connectors 126 and input reactant manifolds 128 and 130. In a preferred embodiment, the oxidizer reactant is introduced to the resident fuel cell assemblies through the manifolds 130, and the fuel reactant is introduced through the fuel manifolds 128.

The stacked fuel cell array 122 can vent exhaust gases to the interior of the pressure vessel 120. The pressure of the exhaust gases appropriate to the bottoming device used in conjunction with the pressure vessel can be controlled through use of a pump, such as the compressor 76 or 134, or through use of a blower as shown and described in U.S. Patent No. 5,948,221 of Hsu, the contents of which are herein incorporated by reference, for selectively pumping an input reactant into, and hence exhaust gases out of, the stacked fuel cell assemblies 122.

As described above, the electrochemical converter can be operated at an elevated temperature and at either ambient pressure or at an elevated pressure. The electrochemical converter is preferably a fuel cell system that can include an WO 02/37587 PCT/US00/29895 interdigitated heat exchanger, similar to the type shown and described in U.S. Patent No.

4,853,100, which is herein incorporated by reference.

The pressure vessel 120 can include an outer wall 136 spaced from an inner wall 138, thereby creating an annulus therebetween. The annulus can be filled with an insulative material 139 for maintaining the outer surface of the pressure vessel at an appropriate temperature. Alternatively, the annulus can house or form a heat exchanging element for exchanging heat with the pressure vessel. In one embodiment of a heat exchanger, the annulus and walls 138 and 136 can form a heat exchanging jacket for circulating a heat exchanging fluid therein. The heat exchanger formed by the walls exchanges heat with the pressure vessel and helps maintain the outer surface at an appropriate temperature. Of course, the use of the annulus as a coolingjacket does not preclude the additional use of an insulative material, located other than in the annulus, for reducing heat loss from the interior of the pressure vessel or for also helping to maintain the outer surface of the pressure vessel at an appropriate temperature.

In one embodiment of the invention, the heat exchanging fluid circulated in the pressure vessel heat exchanger, such as the cooling jacket formed by walls 136 and 138 is an input reactant, such as the air input reactant flowing in the manifolds 128. In this embodiment, the manifolds are essentially inlets that are in fluid communication with the portion of the annulus adjacent the top of the pressure vessel 120. Additional manifolding (not shown) fluidly connects the annulus to the fuel cell stacks 122 such that the air input reactant is properly introduced thereto. The preheating of the air input reactant by the cooling jacket formed by walls 136 and 138 serves several purposes, including preheating the air input reactant to boost efficiency by regeneratively capturing waste heat, and cooling the outer surface of the pressure vessel 120.

The pressure vessel can be a "positive pressure vessel," which is intended to include a vessel designed to operate at pressures such as 1 or 2 atmospheres, or a vessel designed to tolerate much higher pressures, up to 1000 psi. A lower pressure vessel is useful when the bottoming device used in conjunction with the electrochemical converter is, for example, an HVAC system that incorporates a heat-actuated chiller or a boiler. A higher pressure vessel is useful, for example, with the illustrated hybrid power system WO 02/37587 PCT/US00/29895 -21- Fuel cells utilize the chemical potential of selected fuel species, such as hydrogen or carbon monoxide molecules, to produce oxidized molecules in addition to electrical power. Since the cost of supplying molecular hydrogen or carbon monoxide is relatively higher than providing traditional fossil fuels, a fuel processing or reforming step can be utilized to convert the fossil fuels, such as coal and natural gas, to a reactant gas mixture high in hydrogen and carbon monoxide. Consequently, a fuel processor, either dedicated or disposed internally within the fuel cell, is employed to reform, by the use of steam, oxygen, or carbon dioxide (in an endothermic reaction), the fossil fuels into non-complex reactant gases.

FIGS. 5-7 illustrate the basic cell unit 10 of the fuel cell 112 and the fuel cell stacks 122, which is particularly suitable for integration with conventional gas turbines.

The cell unit 10 includes an electrolyte plate 20 and an interconnector plate 30. In one embodiment, the electrolyte plate 20 can be made of a ceramic, such as a stabilized zirconia material ZrO 2

(Y

2 0 3 on which a porous oxidizer electrode material 20A and a porous fuel electrode material 20B are disposed thereon. Exemplary materials for the oxidizer electrode material are perovskite materials, such as LaMnO 3 Exemplary materials for the fuel electrode material are cermets such as ZrO 2 /Ni and ZrO2/NiO.

The interconnector plate 30 preferably is made of an electrically and thermally conductive interconnect material. Examples of such material include nickel alloys, platinum alloys, non-metal conductors such as silicon carbide, La(Mn)CrO 3 and preferably commercially available Inconel, manufactured by Inco., U.S.A. The interconnector plate 30 serves as the electric connector between adjacent electrolyte plates and as a partition between the fuel and oxidizer reactants. As best shown in FIG.

7, the interconnector plate 30 has a central aperture 32 and a set of intermediate, concentric radially outwardly spaced apertures 34. A third outer set of apertures 36 are disposed along the outer cylindrical portion or periphery of the plate The interconnector plate 30 has a textured surface 38. The textured surface preferably has formed thereon a series of dimples 40, as shown in FIG. 7, which form a series of connecting reactant-flow passageways. Preferably, both sides of the interconnector plate 30 have the dimpled surface formed thereon. Although the intermediate and outer set of apertures 34 and 36, respectively, are shown with a selected number of apertures, those of ordinary skill will recognize that any number of WO 02/37587 PCT/US00/29895 -22apertures or distribution patterns can be employed, depending upon the system and reactant-flow requirements.

Likewise, the electrolyte plate 20 has a central aperture 22, and a set of intermediate and outer apertures 24 and 26 that are formed at locations complementary to the apertures 32, 34 and 36, respectively, of the interconnector plate Referring to FIG. 6, a spacer plate 50 can be interposed between the electrolyte plate 20 and the interconnector plate 30. The spacer plate 50 preferably has a corrugated surface 52 that forms a series of connecting reactant-flow passageways, similar to the interconnecting plate 30. The spacer plate 50 also has a number of concentric apertures 54, 56, and 58 that are at locations complementary to the apertures of the interconnect and electrolyte plates, as shown. Further, in this arrangement, the interconnector plate is devoid of reactant-flow passageways. The spacer plate 50 is preferably made of an electrically conductive material, such as nickel.

The illustrated electrolyte plates 20, interconnector plates 30, and spacer plates 50 can have any desirable geometric configuration. Furthermore, the plates having the illustrated manifolds can extend outwardly in repetitive or non-repetitive patterns, and thus are shown in dashed lines.

Referring to FIG. 7, when the electrolyte plates 20 and the interconnector plates are alternately stacked and aligned along their respective apertures, the apertures form axial (with respect to the stack) manifolds that feed the cell unit with the input reactants and that exhaust spent fuel. In particular, the aligned central apertures 22,32,22' form input oxidizer manifold 17, the aligned concentric apertures 24,34,24' form input fuel manifold 18, and the aligned outer apertures 26,36,26' form spent fuel manifold 19.

The textured surface 38 of the interconnector plate 30 has, in the cross-sectional view of FIG. 7, a substantially corrugated pattern formed on both sides. This corrugated pattern forms the reactant-flow passageways that channel the input reactants towards the periphery of the interconnector plates. The interconnector plate also has an extended heating surface or lip structure that extends within each axial manifold and about the periphery of the interconnector plate. Specifically, the interconnector plate 30 has a flat annular extended surface 31A formed along its outer peripheral edge. In a preferred embodiment, the illustrated heating surface 31A extends beyond the outer peripheral WO 02/37587 PCT/USOO/29895 -23edge of the electrolyte plate 20. The interconnector plate further has an extended heating surface that extends within the axial manifolds, for example, edge 31B extends into and is housed within the axial manifold 19; edge 31 C extends into and is housed within the axial manifold 18; and edge 3 1D extends into and is housed within the axial manifold 17. The extended heating surfaces can be integrally formed with the interconnector plate or can be coupled or attached thereto. The heating surface need not be made of the same material as the interconnector plate, but can comprise any suitable thermally conductive material that is capable of withstanding the operating temperature of the electrochemical converter. In an alternate embodiment, the extended heating surface can be integrally formed with or coupled to the spacer plate.

The absence of a ridge or other raised structure at the interconnector plate periphery provides for exhaust ports that communicate with the external environment.

The reactant-flow passageways connect, fluidwise, the input reactant manifolds with the outer periphery, thus allowing the reactants to be exhausted to the external environment, or to a thermal container or pressure vessel disposed about the electrochemical converter, FIG. 4.

Referring again to FIG. 7, the illustrated sealer material 60 can be applied to portions of the interconnector plate 30 at the manifold junctions, thus allowing selectively a particular input reactant to flow across the interconnector surface and across the mating surface of the electrolyte plate 20. The interconnector plate bottom contacts the fuel electrode coating 20B of the electrolyte plate 20. In this arrangement, it is desirable that the sealer material only allow fuel reactant to enter the reactant-flow passageway, and thus contact the fuel electrode.

As illustrated, the sealer material 60A is disposed about the input oxidizer manifold 17, forming an effective reactant flow barrier about the oxidizer manifold 17.

The sealer material helps maintain the integrity of the fuel reactant contacting the fuel electrode side 20B of the electrolyte plate 20, as well as maintain the integrity of the spent fuel exhausted through the spent fuel manifold 19.

The top 3 OA of the interconnector plate 30 has the sealer material 60B disposed about the fuel input manifolds 18 and the spent fuel manifold 19. The top of the interconnector plate 30A contacts the oxidizer coating 20B' of an opposing electrolyte plate 20'. Consequently, the junction at the input oxidizer manifold 17 is devoid of WO 02/37587 PCT/USOO/29895 -24sealer material, thereby allowing the oxidizer reactant to enter the reactant-flow passageways. The sealer material 60B that completely surrounds the fuel manifolds 18 inhibits the excessive leakage of the fuel reactant into the reactant-flow passageways, thus inhibiting the mixture of the fuel and oxidizer reactants. Similarly, the sealer material 60C that completely surrounds the spent fuel manifold 19 inhibits the flow of spent oxidizer reactant into the spent fuel manifold 19. Hence, the purity of the spent fuel that is pumped through the manifold 19 is maintained.

Referring again to FIG. 7, the oxidizer reactant can be introduced to the electrochemical converter through axial manifold 17 that is formed by the apertures 22, 32, and 22' of the electrolyte and interconnector plates, respectively. The oxidizer is distributed over the top of the interconnector plate 30A, and over the oxidizer electrode surface 20A' by the reactant-flow passageways. The spent oxidizer then flows radially outward toward the peripheral edge 31A, and is finally discharged along the converter element periphery. The sealer material 60C inhibits the flow of oxidizer into the spent fuel manifold 19. The flow path of the oxidizer through the axial manifolds is depicted by solid black arrows 26A, and through the oxidizer cell unit by the solid black arrows 26B.

The fuel reactant is introduced to the electrochemical converter 10 by way of fuel manifold 18 formed by the aligned apertures 24, 34, and 24' of the plates. The fuel is introduced to the reactant-flow passageways and is distributed over the bottom of the interconnector plate 30B, and over the fuel electrode coating 20B of the electrolyte plate Concomitantly, the sealer material 60A prevents the input oxidizer reactant from entering the reactant-flow passageways and thus mixing with the pure fuel/spent fuel reactant mixture. The absence of any sealer material at the spent fuel manifold 19 allows spent fuel to enter the manifold 19. The fuel is subsequently discharged along the annular edge 31A of the interconnector plate 30. The flow path of the fuel reactant is illustrated by the solid black arrows 26C.

The dimples 40 of the interconnector surface have an apex 40A that contact the electrolyte plates, in assembly, to establish an electrical connection therebetween.

A wide variety of conductive materials can be used for the thin electroconnector plates of this invention. Such materials should meet the following requirements: (1) high strength, as well as electrical and thermal conductivity; good oxidation WO 02/37587 PCT/US00/29895 resistance up to the working temperature; chemical compatibility and stability with the input reactants; and manufacturing economy when formed into the textured plate configuration exemplified by reactant-flow passageways.

The suitable materials for interconnector fabrication include nickel alloys, nickel-chromium alloys, nickel-chromium-iron alloys, iron-chromium-aluminum alloys, platinum alloys, cermets of such alloys and refractory material such as zirconia or alumina, silicon carbide and molybdenum disilicide.

The textured patterns of the top and bottom of the interconnector plate can be obtained, for example, by stamping the metallic alloy sheets with one or more sets of matched male and female dies. The dies are preferably prefabricated according to the desired configuration of the interconnector plate, and can be hardened by heat treatment to withstand the repetitive compressing actions and mass productions, as well as the high operating temperatures. The stamp forming process for the interconnectors is preferably conducted in multiple steps due to the geometrical complexity of the gas passage networks, the dimpled interconnector plate surface. The manifolds formed in the interconnector plates are preferably punched out at the final step. Temperature annealing is recommended between the consecutive steps to prevent the overstressing of sheet material. The stamping method is capable of producing articles of varied and complex geometry while maintaining uniform material thickness.

Alternatively, corrugated interconnectors can be formed by electro-deposition on an initially flat metal plate using a set of suitable masks. Silicon carbide interconnector plates can be formed by vapor deposition onto pre-shaped substrates, by sintering of bonded powders, or by self-bonding processes.

The oxidizer and fuel reactants are preferably preheated to a suitable temperature prior to entering the electrochemical converter. This preheating can be performed by any suitable heating structure, such as a recuperative heat exchanger or a radiative heat exchanger, for heating the reactants to a temperature sufficient to reduce the amount of thermal stress applied to the converter.

A significant feature of the present invention is that the hybrid power systems illustrated in FIGS 1 and 12-17 operate at system efficiencies that exceed any that were previously known. Another significant feature of the present invention is that the extended heating surfaces 31D and 31C heat the reactants contained within the oxidizer WO 02/37587 PCT/US00/29895 -26and fuel manifolds 17 and 18 to the operating temperature of the converter.

Specifically, the extended surface 31D that protrudes into the oxidizer manifold 17 heats the oxidizer reactant, and the extended surface 31C that protrudes into the fuel manifold 18 heats the fuel reactant. The highly thermally conductive interconnector plate facilitates heating of the input reactants by conductively transferring heat from the fuel cell internal surface, the middle region of the conductive interconnector plate, to the extended surfaces or lip portions, thus heating the input reactants to the operating temperature prior to traveling through reactant flow passageways. The extended surfaces thus function as a heat fin. This reactant heating structure provides a compact converter that is capable of being integrated with an electricity generating power system, and further provides a highly efficient system that is relatively low in cost.

Electrochemical converters incorporating fuel cell components constructed according to these principles and employed in conjunction with a gas turbine provides a power system having a relatively simple system configuration.

In an alternate embodiment, the electrolyte and interconnector plates can have a substantially tubular shape and have an oxidizer electrode material disposed on one side and a fuel electrode material disposed on the opposing side. The tubes can then be stacked together in a like manner.

With reference to FIGS. 1 and 8-11, the thermal control stack 116 of FIG. 1 can be operated to heat and/or cool the fuel cell 112 during use. The foregoing Figures illustrate various embodiments of the thermal control stack 116, using different reference numbers for purposes of clarity. The term thenrmal control stack as used herein is intended to include any suitable structure capable of functioning either or both as a heat source or a heat sink relative to the fuel cell 112. The thermal control stack can also preferably function as an isothermal surface to decrease or eliminate temperature nonuniformities along the axial length of the fuel cell 112. This preserves or enhances the structural integrity of the electrochemical converter system 72 of the present invention.

During use, the thermal control stack is disposed within the pressure vessel 120 and is in thermal communication with the fuel cell. The thermal control stack can be mounted relative to the fuel cell in any selected arrangement to achieve the appropriate system thermal management. One particular arrangement suitable for this purpose is to interdigitate the fuel cells and thermal control stacks to form a single collection of units WO 02/37587 PCT/US00/29895 -27that achieves the desired thermal management. This arrangement can form a rectangular or hexagonal pattern, or any other suitable two-dimensional or three-dimensional arrangement. For example, as illustrated in FIGS. 19A-19E, the components of the electrochemical converter system 72, such as the fuel cell 112 and the thermal control stack 116, can have a quadrilateral arrangement, such as a square or rectangular interdigitated arrangement as shown in FIGS. 14A and 14B. Alternatively, the components of the electrochemical converter system 72 can be arranged in a hexagonal shape, as shown in FIGS. 14C-14E. The foregoing interdigitated arrangements are merely examples of the various types of arrangements that can be used. Those of ordinary skill will also recognize that although he fuel cell and thermal control stack are illustrated as having a cylindrical shape, other shapes can also be used.

According to one embodiment, as shown in FIG. 8, the thermal control stack 116 can be formed as an isothermal structure (heat exchanger) 27 having a porous structure 28, which receives radiated heat from its environment from a nearby fuel cell). A working fluid 44, such as the oxidizer reactant, flows in an inner passageway or reservoir 42 and permeates radially outward from an inner surface 28A to the outer face 28B. The working fluid 44 can be collected by any suitable structure, such as by the pressure vessel 120, and can be conveyed to other parts of the hybrid power system To ensure the axial and azimuthal uniformity of the working fluid 44 flow rate, the radial pressure drop as the working fluid permeates through the structure 28 is maintained to be substantially greater than the pressure of the working fluid 44 as it flows through the reservoir 42. An inner flow distribution tube may be mounted within the structure 28 to enhance the flow uniformity. The working fluid 44 can also be discharged from either axial end.

According to another embodiment, the thermal control stack according to the present invention can also employ a plurality of thermally conductive plates, as depicted in FIG. 9. The thermal control stack 29 includes a series of plates 46 that are stacked on top of each other, as shown. The plates 46 can be formed of any suitable thermally conductive material, such as nickel and other materials typically used with fuel cells. A central fluid passageway or reservoir 42 connects the plates, while spaces are provided between the plates to allow a working fluid 44 to flow from an inner surface 62A to an outer surface 62B. The working fluid 44 flows through the reservoir 42 connecting the WO 02/37587 PCT/US00/29895 -28plates 62. The plates 62 can have a substantially cylindrical configuration as shown, or can have any other suitable geometric shape, such as a tubular shape. The embodiment of FIG. 9 is particularly useful in the construction of isothermal fuel cells. For example, by using spacing elements between cell units, a uniform flow of reactants can be achieved.

FIG. 10 shows a cross-sectional end view of another embodiment of the thermal control stack 25 for use in the hybrid power system of FIG. 1. The stack 25 includes three concentric tubular structures that are preferably axially spaced as shown. The inner lumen 64 has a plurality of passageways 66 that extend between an inner face 68A and an outer face 68B of a sleeve or tube 68. A porous sleeve structure 28 surrounds inner tube 68 and has an inner surface 28A and an outer surface 28B. The inner surface 28A is in intimate facing contact with the outer surface of the inner tube 68, such that the transverse passageways 66 are in fluid communication with the porous sleeve 28.

The transverse passageways 66 are evenly spaced apart.

An outer tube 69 or wall element is disposed about the porous sleeve 28 and the inner tube 68, thereby forming a substantially co-axial geometry. The outer tube 69 has an internal surface 69A and an external surface 69B. The interior lumen of inner tube 68 forms an elongate central passageway 64 that serves as a reservoir for the working fluid 44 as shown in FIG. 11. The interior space between the internal surface of the outer tube 69A and the porous sleeve outer face 28B forms an elongate second passageway 67 that is substantially parallel to the central passageway 64.

The inner tube 68 and the outer tube 69 are preferably made of the same material, such as metal or ceramics. The porous sleeve structure 28 can be ceramic and serves to diffuse the flow of the working fluid from the inner lumen to the outer lumen.

Referring to FIG. 11, the working fluid 44 flows through the elongate central lumen or passageway 64 that serves as a reservoir and which extends along a longitudinal axis 41. As the working fluid 44 flows through the reservoir 64, the working fluid is forced through the transverse passageways 66. The sleeve 28 overlies the transverse passageways 66 so as to receive that portion of the working fluid 44 that flows through the passageways 66. The working fluid 44 permeates radially outward through the porous sleeve 28 into the outer lumen 67 where the fluid is heated by an external heat source, a fuel cell assembly or other system which requires cooling, or WO 02/37587 PCT/US00/29895 -29is cooled by other structure. The working fluid 44 contained within the outer lumen 67 flows along the internal surface of the outer tube 69, and absorbs heat conductively transferred thereto from the external surface 69B. The outer tube's external surface 69B can be heated by being placed in direct contact with the fuel cell assembly 112, or by being radiantly coupled to the fuel cell 112. The distribution of the working fluid 44 along the internal surface 69A of the outer tube 69 provides for the effective transfer of heat between the working fluid 44 and the external environment. By selectively spacing the transverse passageways 66 along the inner tube 68, the working fluid 44 collected within the second passageway 67 maintains a constant temperature. The uniform distribution of the isothermic working fluid 44 along the inner surface 69A creates an isothermal condition along the external surface of the outer tube 69B. The passageway size and spacing are dependent upon the outer tube 69 and the inner tube 68 diameters.

The foregoing description describes the thermal control stack 25 as operating as a heat sink. Those of ordinary skill will realize that the thermal control stack 25 can also operate as a heat source. For example, the working fluid 44 can comprise a heated fluid rather than a coolant. As the heated fluid flows through the reservoir 34, heat is transferred from the external surface of the outer tube 69B to an external environment.

It should also be appreciated that the principles of the present invention can also be applied to construct isothermal fuel cells (and other electrochemical converters) by employing similar structures which distribute the reactants uniformly along the length of a fuel cell stack. The temperature of the stacks as a whole can be regulated and, when desired, rendered isothermal.

Other embodiments of the thermal control stack would be obvious to the skilled artisan in light of the teachings herein, and include employing a hollow porous cylinder that has various shaped surface structures disposed therein. The surface structures can be composed of metal or ceramic, and the porous cylinder can be composed of any suitable material, including a wire mesh screen.

With reference again to FIG. 1, upon start-up operation of the fuel cell 112, the thermal control stack 116 functions as a start-up heater for the electrochemical converter system 72. In order to initiate start-up operation of the hybrid power system 70, the compressor 76 of the gas turbine assembly 74 is actuated by a separate motor (not shown) or the generator which functions as a motor. The air 84 passing through the WO 02/37587 PCT/US00/29895 compressor is eventually introduced to the thermal control stack 116 and is exhausted inside the pressure vessel 120. The exhaust 124 from the pressure vessel passes through the combustor 144, where it is further heated prior to introduction to the gas turbine assembly 74 or to the heat exchanger 88. Subsequent to passing air through the thermal control stack 116, a suitable fuel is introduced to the thermal control stack 116, as illustrated in FIG. 1. The air and fuel inputs of the thermal control stack 116 are controlled by the controller 140 to attain a prescribed fuel cell heating rate, such as 250 'C/hr. The exothermic heat generated by the thermal control stack 116 serves to heat the adjacent fuel cell 112. The thermal control stacks heat the fuel cell 112 until it attains a fuel self ignition temperature. If desired, the hybrid power system 70 can be maintained in this thermal stand-by mode until it is necessary to bring the fuel cell up to an appropriate operating temperature.

The controller 140 can continue to adjust the fuel and air introduced to the thermal control stack 116, as well as operation of the combustor 144, in order to continue heating the fuel cell 112 up to or near the operational temperature thereof.

Once the fuel cell. 112 attains a temperature close to the normal operational temperature, typically 1000 the fuel 85 and air 84 are introduced to the fuel cell in order to generate the required power output. Once the electrochemical converter system 72 is operational, the fuel supplied to the thermal control stack can be terminated, since the thermal control stack is no longer operating as a heat source. By passing only air through the stack at this juncture, the thermal control stack can operate as a heat collector or heat sink by removing waste heat from the fuel cell 112.

As described above, the illustrated electrochemical converter system 72 produces high temperature exhaust gas which is introduced to the turbine expander 78 of the gas turbine assembly 74. The turbine expander 78 adiabatically expands the high temperature fuiel cell exhaust and then generates a turbine exhaust for subsequent use by the hybrid power system 70. The turbine converts the thermal energy of the drive gas into rotary energy, which in turn rotates shaft 85 to generate alternating current electricity by the generator 80. This electricity can be combined with the electricity generated by the electrochemical converter system 72 for subsequent commercial or residential use.

WO 02/37587 PCT/US00/29895 -31- During steady state operation, the primary air supply 84 sequentially passes through the compressor 76, and if desired the heat exchanger 88, into the fuel cell 112, for subsequent introduction to the gas turbine assembly 74. The turbine exhaust is then dispelled from or vented to the ambient environment. In order to achieve selected operational control and temperature regulation of one or more system components, the controller 140 can actuate one or more of the fluid regulating devices in order to regulate one or more operational parameters of the hybrid power system 70. For example, fluid regulating elements 100 and 104 can be controlled so as to allow a selected amount of air to pass through the thermal control stack 116 to effect temperature regulation of the fuel cell 112. Further, the fluid regulating device 108 can be actuated in order to mix relatively cool air passing through conduit 107 with the high temperature exhaust passing through conduit 124 prior to introduction to the gas turbine assembly 74.

Controlling the amount of cool and hot exhaust gases that are mixed allows a selected degree of control over one or more parameters, such as the power output or exhaust temperature of the turbine expander 78 of the gas turbine assembly 74. Hence, selectively controlling the fluid regulating device 108 enables the hybrid power system to regulate the temperature of the gas turbine assembly 74.

According to another operational feature of the illustrated system 70, the controller 140 can actuate fluid regulating device 142 in order to vent some or all of the exhaust of the electrochemical converter system 72 to the ambient environment. By controlling the fluid regulating device 142, the system achieves significant control over the speed or power output of the gas turbine assembly 74.

Those of ordinary skill will further recognize that additional control over the power output of the fuel cell 112 can be achieved by regulating the flow of the air or fuel input reactants. This attains a wide dynamic range of control of the overall hybrid power system. The fuel flow controls the power output of the fuel cell, while concomitantly maintaining a constant operational temperature. Moreover, by controlling the amount of air that by-passes the electrochemical converter system 72, the system 70 controls the gas turbine and the fuel cell power output.

The system can also operate as a high efficiency system by passing the turbine exhaust through the heat exchanger 88 in order to recoup the thermal energy present within the turbine exhaust. The thermal energy in the turbine exhaust preheats the WO 02/37587 PCT/US00/29895 -32reactant passing through the heat exchanger. For example, passing the air 84 through the heat exchanger 88 preheats the air by reclaiming waste heat present within the turbine exhaust. The fluid regulating device 96 can also be controlled by the controller 140 to determine whether some or all of the air passing through the fluid conduit 90 is to be preheated by the heat exchanger 88.

The exhaust exiting the electrochemical converter system 72 and passing through fluid regulating device 142 can be further heated by an optional secondary combustor 144 disposed along fluid conduit 124. The secondary combustor 144 further heats the exhaust in order to provide a drive gas that is compatible with the input temperature requirements of the gas turbine assembly 74.

The turbine exhaust generated by the gas turbine assembly 74 is further introduced to a fluid regulating device 148 that is disposed in fluid conduit 146. The fluid regulating device 148 regulates the amount of turbine exhaust that passes through the fluid conduit 146 of the gas turbine assembly 74. For example, the fluid regulating device 148 regulates the amount of drive gas that by-passes the turbine expander and which can be mixed with the turbine exhaust.

The fluid regulating devices 150 and 154 can be controlled by the controller 140 to regulate the amount of turbine exhaust that is introduced to the heat exchanger 88. In this way, the controller 140 can control the temperature of the air passing through the heat exchanger 88, and hence control the temperature of the fuel cell 112.The fluid regulating device 154 further regulates the amount of external fluid which can be introduced to the fluid passing through the heat exchanger in order to provide an additional degree of temperature control over the air reactant. The system can control the temperature of the air reactant and thus the power of the fuel cell 112. Conversely, the fluid regulating devices 150 or 154 can regulate the amount of turbine exhaust exiting the heat exchanger 88 which is introduced or vented to the ambient environment.

Those of ordinary skill will readily recognize that the electrochemical converter system 72, and in particular the fuel cell 112, can function as the combustor for the gas turbine assembly 74. However, alternate embodiments are also contemplated by the present invention wherein the gas turbine assembly 74 can include a combustor replacement and/or a recuperator as part of the gas turbine assembly. In system designs where the gas turbine assembly 74 includes its own internal combustor, a different start- WO 02/37587 PCT/US00/29895 -33up procedure is necessary in order to actuate the hybrid power system 70. For example, the gas turbine assembly 74 can be actuated by any suitable start-up motor (not shown).

The compressor 76 can therefore establish an air flow through the gas turbine assembly.

The combustor of the gas turbine then receives fuel which reacts with the air according to a prescribed rate of heating. A fluid regulating element, such as a diverter valve, can be placed at the exit of the gas turbine assembly recuperator to gradually introduce heated air to the thermal control stack 116 of the electrochemical converter system 72.

The thermal control stack is also configured to receive fuel from a fuel source, and to preheat the fuel cell 112 close to its operating temperature. The remaining operational functions of this alternate system arrangement are the same as for the hybrid power system shown and described in FIG. 1.

Those of ordinary skill will also recognize that any selected combination of fluid regulating devices can be provided in the illustrated hybrid power system Consequently, each fluid regulating device and/or fluid pathway can be deemed an optional feature or part of the system.

Those of ordinary skill will also recognize that the temperature of the fuel cell 112 can be controlled with selected ones of the fluids flowing in the hybrid power system. In particular, the fuel cell temperature can be controlled with the fluids exiting the compressor and the gas turbine assembly when passing through an intermediate recuperator. Different heating regimens can thus be implemented to control or regulate one or more operational parameters, such as the temperature and/or power output, of the fuel cell. For example, if maximum fuel cell cooling is desired, the fluid exiting the compressor can by-pass the recuperator and is directly introduced to the fuel cell. In this manner, no pre-heating of the compressed fluid occurs.

According to another thermal regimen, the relatively cool compressed fluid bypasses the recuperator and is introduced to the thermal control stack. The thermal control stack operates to cool the fuel cell as set forth above.

According to another thermal regimen, some percentage of the compressor fluid by-passes the recuperator and is introduced to the thermal control stack (such as and the remainder of the fluid passes through the recuperator and is then introduced to the fuel cell.

WO 02/37587 PCT/US00/29895 -34- According to still another thermal regimen, most or all of the compressor fluid passes through the recuperator, where it is heated, and then introduced to the fuel cell or thermal control stack. Alternatively, some percentage of the pre-heated fluid can be introduced to the fuel cell and the remainder to a secondary heating source, such as a combustor, prior to introduction to the gas turbine assembly. Those of ordinary skill will recognize that fluid heating occurs in these latter regimens.

FIG. 12 illustrates an alternate embodiment of the hybrid power system of FIG.

1. The illustrated hybrid power system 200 controls the power output of the gas turbine assembly 193. The description of this embodiment is similar in some respects to the system 70 described above. The system 200 introduces air 190 from an air source to the compressor 192 by way of any suitable fluid conduit, where it is compressed, pressurized and heated, and then discharged therefrom. The heated, pressurized air can be introduced to a heat exchanger 206, such as a recuperator, by the fluid conduit 202, where it is pre-heated by exhaust discharged from the gas turbine assembly 193, as described in more detail below.

A fuel 208 can be introduced to an electrochemical converter system 212 after optionally passing through the heat exchanger 206, where it is also preheated by the gas turbine exhaust. The heated air 190 and fuel 208 function as input reactants and are introduced to an electrochemical converter system 212 through appropriate manifolding.

The electrochemical converter system 212 can be identical to the electrochemical converter system 72 of FIG. 1. The electrochemical converter system 212 processes the fuel and oxidizer reactants and generates, in one mode of operation, electricity and waste heat associated with the high temperature exhaust. This electricity is direct current which can be converted to alternating current by an alternator (not shown). The exhaust produced by the electrochemical converter system 212 is coupled, and optionally directly coupled, to the gas turbine expander 196 by a suitable fluid conduits or manifolding 214. The turbine expander 196 adiabatically expands the exhaust produced by the electrochemical converter system, and converts this thermal energy into rotary energy for subsequent transfer to the electric generator 198. The generator 198 produces electricity that can be used for both commercial and residential purposes. In this arrangement, the electrochemical converter system 212 functions as the combustor for the gas turbine assembly 193 and the gas turbine functions as a bottoming cycle plant.

WO 02/37587 PCT/US00/29895 One benefit of utilizing the electrochemical converter system 212 as the gas turbine combustor is that the converter system functions as an additional electric generator. The illustrated electrical connections 222 extract electricity from the system 212. The gas turbine and generator components are art known and commercially available. Those of ordinary skill will readily understand the manner in which the electrochemical converter and gas turbine are coupled, especially in light of the present description and illustrations.

The gas turbine assembly further produces hot exhaust which can be captured and ducted for subsequent use by the fluid manifolding 218. According to one practice, the turbine exhaust is passed through the heat exchanger 206. The fuel 208 and heated air are also passed through the heat exchanger 206. The waste heat associated with the turbine exhaust serves to pre-heat the air and the fuel prior to introduction to the electrochemical converter system 212. Preferably, the sensible heat exchange between the incoming reactants and the outgoing exhaust are such that the convective heat exchanged between the gases is either optimized, or some specific amount of heat is recuperated. For example, waste heat associated with the exhaust that would otherwise be transferred out of the system is absorbed by the incoming reactant gases. The effect is to continuously recover at least a portion of the waste heat used to heat the reactants, and which is carried in the exhaust flow. By employing this heat exchange mechanism, the amount of heat lost by the system is decreased, thereby improving the overall system efficiency.

The electrochemical converter system 212 is operated at an elevated temperature at an elevated pressure. The electrochemical converter is preferably a fuel cell system that can include an interdigitated heat exchanger, similar to the type shown and described in U.S. Patent No. 4,853,100, which is herein incorporated by reference.

The illustrated electrochemical converter system 212 can include a fuel cell (as shown in FIG. 1 and which operates at a selected operating temperature, and an optional thermal control stack. According to a preferred embodiment, the fuel cell is a solid oxide fuel cell that has an operating temperature of about 1000 and thus generates exhaust having a temperature at about this level. Certain gas turbines, such as small turbine units, require an input fluid having a temperature below 1000 and usually about 900 This fluid temperature requirement thus mandates that the high WO 02/37587 PCT/US00/29895 -36temperature exhaust emitted by the electrochemical converter system 212 be regulated to temperature levels compatible with the input temperature requirements of the gas turbine assembly 193. The present invention addresses this temperature incompatibility by providing a number of methods suitable for effectuating a selected degree of temperature control over the converter system exhaust.

Referring again to FIG. 12, the hybrid power system 200 further includes multiple fluid regulating devices and a controller 220 for regulating the amount of fuel introduced to the system 200, as well as regulating the temperature of the exhaust introduced to the gas turbine assembly 193. The illustrated hybrid power system 200 includes a first fluid regulating device 204 that spans between the compressor fluid conduit 202 and the exhaust fluid conduit 214. The fluid regulating device selectively allows a portion of the heated air discharged from the compressor 192 to be directly intermingled or mixed with the further heated exhaust of the electrochemical converter system 212 prior to introduction to the gas turbine expander As is known in the art, conventional gas turbines tolerate input work fluids up to a certain maximum temperature. The gas turbine assembly 193 can operate at lower temperatures, but the power output of the turbine is decreased accordingly. Hence, if the gas turbine 14 has an input maximum temperature requirement of 900 the high temperature exhaust of the electrochemical converter system should be cooled to at least this temperature level or below in order to comply with this gas turbine operational requirements. In this scenario, the temperature of the air discharged from the compressor 192 is typically below the exhaust temperature of the electrochemical converter system 212. The by-pass valve 204 can be controlled by the controller 220 to allow some or all of the air to pass through the by-pass conduit 224 to mix with and cool the high temperature exhaust of the electrochemical converter system 212. By regulating the amount of air mixed with the exhaust, the resultant fluid temperature of the exhaust can be adjusted to desired levels. According to one practice, the exhaust temperature is regulated to a temperature at or below the maximum turbine temperature, according to a user selected or prestored temperature condition. In the example set forth above, the high temperature exhaust from the electrochemical converter system 212 can be cooled to about 900 'C or even less.

WO 02/37587 PCT/US00/29895 -37- With further reference to FIG. 12, the fluid regulating device 204 can be coupled to a controller 220 by any suitable communication link. The controller 220 can include appropriate storage that has stored thereon program instructions for operating the fluid regulating device 204 according to a user defined or preselected sequence. The controller 220 can selectively open or close the device according to the stored sequence to allow a predetermined amount of air to mix with the high temperature exhaust generated by the electrochemical converter system 212. The amount of air flowing through the fluid regulating device 204 can be a function of the desired power output of the electrochemical converter system 212, the gas turbine assembly 193, and a desired system efficiency which may necessitate operating the gas turbine at a desired power output while modulating the fluid amount and temperature introduced to the expander 196.

The illustrated hybrid power system 200 further includes a fuel adjustment fluid regulating device 210 that regulates the amount of fuel introduced to the electrochemical converter system 212. The fluid regulating device 210 is in feedback communication with the controller 220 via any suitable communication link. The controller 220 and the device 210 regulate the amount of fuel introduced to the electrochemical converter system, and thus regulate the power output thereof without inducing a corresponding decrease in operational temperature of the hybrid power system 200. This allows the electrochemical converter system 212 to continue operation at or near optimum system efficiency. Furthermore, regulating the power output of the electrochemical converter system 212 enables the controller 220 to regulate the power output of the gas turbine, and thus of the entire system 200.

The illustrated controller can also be coupled to the air and fuel reservoirs to control the amount of air and fuel delivered to the hybrid power system 200. The controller 220 thus functions as a modular computing center for the system and can be programmed in a variety of ways to control the reactant flow to corresponding control the power output of the system 200.

The system 200 further can employ an optional combustor 216 disposed between the converter system 212 and the turbine expander 196 to additionally heat the exhaust prior to introduction to the turbine. The combustor 216 provides an additional level of temperature control over the drive gas for the turbine expander 196.

WO 02/37587 PCT/US00/29895 -38- A significant advantage of the illustrated hybrid power system 200 is that it allows electricity to be produced in a high efficiency system by the integration of a high efficiency, compact electrochemical converter with a bottoming plant constituent components. The integration of the electrochemical converter system 212 with the gas turbine assembly 193 produces a hybrid power system that has an overall power efficiency of about 70% or even higher. This system efficiency represents a significant increase over the efficiencies achieved by prior art gas turbine systems and prior art electrochemical systems. The illustrated hybrid power systems incorporates an electrochemical converter to provide high grade thermal energy and electricity, while utilizing the benefits of electrochemical converters. For example, the converter operates as a low NO x thermal source, thereby improving environmental performance relative to conventional gas turbine generating plants.

A significant advantage of the control portion of the illustrated hybrid power system 200, which includes the fluid regulating devices 204 and 210 and the controller 220, is that the system can attain further increases in overall system efficiency by regulating certain system components to maximize, optimize, increase or decrease the power output of the system 200. Furthermore, the illustrated energy system 10 achieves full control of the power output of the electrochemical converter system 12 and the gas turbine assembly 14.

FIG. 13 illustrates an alternate embodiment of the hybrid power systems of FIGS. 1 and 12. The illustrated hybrid power system 230 controls the power output of the gas turbine assembly 258. The description of this embodiment is similar in some respects to the system 70 described above. The system 230 introduces air 232 from an air source to the compressor 234 by way of any suitable fluid conduit, where it is compressed, pressurized and heated, and then discharged therefrom. The heated, pressurized air can be introduced to a heat exchanger 244, such as a recuperator, by the fluid conduit 242, where it is pre-heated by exhaust discharged from the gas turbine assembly 258, as described in more detail below.

A fuel 246 can be introduced to an electrochemical converter system 250 after optionally passing through the heat exchanger 244, where it is also preheated by the gas turbine exhaust. The heated air 232 and fuel 246 function as input reactants to an WO 02/37587 PCT/US00/29895 -39electrochemical converter system 250. The electrochemical converter system 250 can be identical to the electrochemical converter system 72 and 212 of FIGS. 1 and 12.

The electrochemical converter system 250 processes the fuel and oxidizer reactants and generates, in one mode of operation, electricity and waste heat associated with the high temperature exhaust. The electricity is typically direct current electricity which can be converted to alternating current by an alternator (not shown). The exhaust produced by the electrochemical converter system 250 passes through another heat exchanger 248 for additional heating the air (or fuel) entering the electrochemical converter system 250. The high temperature exhaust exiting the electrochemical converter system 250 can have a temperature higher than the air introduced to the heat exchanger 248. In this arrangement, the system recoups waste heat from both the electrochemical converter system 250 and the gas turbine assembly 258 in order to control the system efficiency.

The exhaust exiting the heat exchanger 248 can be coupled, and optionally directly coupled, to the gas turbine expander 238 by fluid conduit 254. The turbine expander 238 adiabatically expands the exhaust produced by the electrochemical converter system 250, and converts this thermal energy into rotary energy for subsequent transfer to the electric generator 240. The generator 240 produces electricity that can be used for both commercial and residential purposes. In this arrangement, the electrochemical converter system 250 functions as the combustor for the gas turbine assembly 258 and the gas turbine functions as a bottoming cycle plant.

One benefit of utilizing the electrochemical converter system 250 as the gas turbine combustor is that the converter system functions as an additional electric generator. The illustrated electrical connections 252 extract electricity from the system 230. The gas turbine and generator components are art known and commercially available. Those of ordinary skill will readily understand the manner in which the electrochemical converter and gas turbine are coupled, especially in light of the present description and illustrations.

The gas turbine assembly 258 further produces heated exhaust which can be captured and ducted for subsequent use by the fluid manifolding 256. According to one practice, the turbine exhaust is passed through the heat exchanger 244. The fuel 246 and/or the heated air can also pass through the heat exchanger 244. The waste heat WO 02/37587 PCT/US00/29895 associated with the turbine exhaust serves to pre-heat the fuel and air prior to introduction to the electrochemical converter system 250. Preferably, the sensible heat exchange between the incoming reactants and the outgoing turbine exhaust are such that the convective heat exchanged between the gases is either optimized, or some specific amount of heat is recuperated. For example, waste heat associated with the exhaust that would otherwise be transferred out of the system is absorbed by the incoming reactant gases. The effect is to continuously recover at least a portion of the waste heat used to heat the reactants, and which is carried in the turbine exhaust flow. By employing this heat exchange mechanism, the amount of heat lost by the system is decreased, thereby improving the overall system efficiency. The illustrated hybrid system further recaptures waste heat by employing the heat second heat exchanger 248 to pre-heat one or more of the reactants passing therethrough with the exhaust of the converter system 250.

The electrochemical converter system 250 is operated at an elevated temperature and at an elevated pressure. The electrochemical converter is preferably a fuel cell system that can include an interdigitated heat exchanger, similar to the type shown and described in U.S. Patent No. 4,853,100, which is herein incorporated by reference.

The illustrated electrochemical converter system 250 can include a fuel cell (as shown in FIGS. 1 and which operates at a selected operating temperature, and an optional thermal control stack. According to a preferred embodiment, the fuel cell is a solid oxide fuel cell that has an operating temperature of about 1000 and thus generates exhaust having a temperature at about this level. Certain gas turbines, such as small turbine units, require an input fluid having a temperature at or below 1000 'C.

This fluid temperature requirement thus mandates that the high temperature exhaust emitted by the electrochemical converter system 212 be regulated to temperature levels compatible with the input temperature requirements of the gas turbine assembly 258.

The present invention addresses this temperature need or incompatibility by providing selected degree of temperature control over the converter system exhaust.

As is known in the art, conventional gas turbines tolerate input work fluids up to a certain maximum temperature. The gas turbine assembly 258 can operate at lower temperatures, but the power output of the turbine is decreased accordingly. Hence, if the gas turbine 258 has an input maximum temperature requirement of between about 800 WO 02/37587 PCT/US00/29895 -41- 'C and about 900 the high temperature exhaust of the electrochemical converter system should be cooled to at least this temperature level in order to comply with this gas turbine operational requirements. In this scenario, the temperature of the air discharged from the electrochemical converter system 250 can be used to pre-heat the incoming reactant, thereby reducing the overall temperature of the exhaust. By regulating the amount of heat exchange, the resultant fluid temperature of the exhaust can be adjusted to a desired level. According to one practice, the exhaust temperature can be regulated or controlled to a temperature at or below the maximum turbine temperature, according to a user selected or prestored temperature condition. In the example set forth above, the high temperature exhaust can be cooled to about 900 'C or less.

A significant advantage of the illustrated hybrid power system 230 is that it allows electricity to be produced in a high efficiency system by the integration of a highly efficient, compact electrochemical converter with a gas turbine bottoming plant.

The integration of the electrochemical converter system 250 with the gas turbine assembly 258 produces a hybrid power system that has an overall power efficiency of about 70% or even higher. This system efficiency represents a significant increase over the efficiencies achieved by prior art gas turbine systems and prior art electrochemical systems.

FIG. 14 illustrates an alternate embodiment of the hybrid power systems of FIGS. 1, 12 and 13. The illustrated hybrid power system 260 controls the power output of the gas turbine assembly 286. The description of this embodiment is similar in some respects to the systems 70, 200 and 230 described above. The illustrated hybrid power system 260 introduces air 262 from an air source to the compressor 264 by way of any suitable fluid conduit, where it is compressed, pressurized and heated, and then discharged therefrom. The heated, pressurized air can be introduced to a heat exchanger 272, such as a recuperator, by the fluid conduit 270, where it is pre-heated by exhaust discharged from the gas turbine assembly 286, as described in more detail below.

A fuel 274 can be introduced to an electrochemical converter system 278 after optionally passing through the heat exchanger 272, where it is also preheated by the gas turbine exhaust. The heated air and fuel function as input reactants to the WO 02/37587 PCT/US00/29895 -42electrochemical converter system. The converter system 278 can be identical to the electrochemical converter system 72, 212 and 250 of FIGS. 1, 12 and 13.

The electrochemical converer system 278 processes the fuel and oxidizer reactants and generates, in one mode of operation, electricity and waste heat associated with high temperature exhaust. The electricity is typically direct current electricity which can be converted to alternating current by an alternator (not shown). The exhaust produced by the electrochemical converter system 278 can be coupled, and optionally directly coupled, to the gas turbine expander 266 by fluid conduit 282. The turbine expander 266 adiabatically expands the exhaust produced by the electrochemical converter system 278, and converts this thermal energy into rotary energy for subsequent transfer to the electric generator 268. The generator 268 produces electricity that can be used for both commercial and residential purposes. In this arrangement, the electrochemical converter system 278 functions as the combustor for the gas turbine assembly 286 and the gas turbine functions as a bottoming cycle plant.

One benefit of utilizing the electrochemical converter system 278 as the gas turbine combustor is that the converter system functions as an additional electric generator. The illustrated electrical connections 280 extract electricity from the system 260. The gas turbine and generator components are art known and commercially available. Those of ordinary skill will readily understand the manner in which the electrochemical converter and gas turbine are coupled, especially in light of the present description and illustrations.

The gas turbine assembly 286 further produces heated exhaust which can be captured and ducted for subsequent use by the fluid manifolding 284. According to one practice, the turbine exhaust is passed through the heat exchanger 272. The fuel and/or the heated air can also pass through the heat exchanger 272. The waste heat associated with the turbine exhaust serves to pre-heat the fuel and/or air prior to introduction to the electrochemical converter system 278. Preferably, the sensible heat exchange between the incoming reactants and the outgoing turbine exhaust are such that the convective heat exchanged between the gases is either optimized, or some specific amount of heat is recuperated. For example, waste heat associated with the exhaust that would otherwise be transferred out of the system is absorbed by the incoming reactant gases. The effect is to continuously recover at least a portion of the waste heat used to heat the reactants, WO 02/37587 PCT/US00/29895 -43and which is carried in the turbine exhaust flow. By employing this heat exchange mechanism, the amount of heat lost by the system is decreased, thereby improving the overall system efficiency.

The electrochemical converter system 278 is operated at an elevated temperature and at an elevated pressure. The electrochemical converter is preferably a fuel cell system that can include an interdigitated heat exchanger, similar to the type shown and described in U.S. Patent No. 4,853,100, which is herein incorporated by reference.

The illustrated electrochemical converter system 278 can include a fuel cell (as shown in FIGS. 1 and which operates at a selected operating temperature, and an optional thermal control stack. According to a preferred embodiment, the fuel cell is a solid oxide fuel cell that has an operating temperature of about 1000 and thus generates exhaust having a temperature at about this level. Certain gas turbines, such as small turbine units, require an input fluid having a temperature below 1000 such as between 800 'C and 900 This fluid temperature requirement thus mandates that the high temperature exhaust emitted by the electrochemical converter system 278 be regulated to temperature levels compatible with the input temperature requirements of the gas turbine assembly 286. The present invention addresses this temperature need or incompatibility by providing a selected degree of temperature control over the exhaust of the electrochemical converter system.

As is known in the art, conventional gas turbines tolerate input work fluids up to a certain maximum temperature. The gas turbine assembly 258 can operate at lower temperatures, but the power output of the turbine is decreased accordingly. Hence, if the gas turbine 258 has an input maximum temperature requirement of between about 800 'C and about 900 the high temperature exhaust of the electrochemical converter system should be cooled to at least this temperature level in order to comply with this gas turbine operational requirements. In this scenario, the temperature of the exhaust discharged from the converter system 278 is above the required range. Hence, the system must dissipate a requisite amount of heat prior to introduction to the turbine expander. According to one practice, the fluid conduit is sized and dimensioned to dissipate through convection, conduction or radiation the required amount of heat from the exhaust. The fluid conduit 282 can be sized and dimensioned in any desired manner, and can be configured in a straight, curved, serpentine, and other suitable manners. By WO 02/37587 PCT/US00/29895 -44regulating the amount of heat exchange between the exhaust in the fluid conduit and the ambient or other environment, the resultant temperature of the exhaust can be adjusted to a desired level. According to one practice, the exhaust temperature can be regulated or controlled to a temperature at or below the maximum turbine temperature, according to a user selected or prestored temperature condition.

The illustrated system 260 is particularly useful with relatively small power systems, such as those less than 100kW, and where the surface to volume ratio of the system is high and the heat loss dominates the heat balance of the system.

A significant advantage of the illustrated hybrid power system 260 is that it allows electricity to be produced in a high efficiency system by the integration of a highly efficient, compact electrochemical converter with a gas turbine assembly. The integration of the electrochemical converter system 278 with the gas turbine assembly 286 produces a hybrid power system that has an overall power efficiency of higher than This system efficiency represents a significant increase over the efficiencies achieved by prior art gas turbine systems and prior art electrochemical systems.

FIG. 15 illustrates an alternative embodiment of the hybrid power system of FIGS. 1 and 12-14. The illustrated hybrid power system 290 controls the power output of the gas turbine assembly 193. The description of this embodiment is similar in at least some respects to the hybrid power systems 70, 200, 230 and 260 described above.

The system 290 introduces air 292 from an air source to the compressor 294 by way of any suitable fluid conduit, where it is compressed, pressurized and heated, and then discharged therefrom. The heated, pressurized air can be introduced to a heat exchanger 302 along fluid conduit 300, where it is heated by waste heat generated from the electrochemical converter system 320. The heated air is then introduced to the turbine expander 296 of the gas turbine assembly 306 where it functions as the expander drive gas.

A fuel 310 can be introduced to an electrochemical converter system 320 after optionally passing through the heat exchanger 314, where it is preheated by the system exhaust. Likewise, air 312 can be passed through the exchanger 314 and then introduced to the electrochemical converter system 320. The heated air 312 and fuel 310 function as input reactants for the electrochemical converter system. The amount of air and fuel introduced to the electrochemical converter system 320 can be regulated at WO 02/37587 PCT/US00/29895 the input end by the fluid regulating elements 310 and 312. The fluid regulating elements 310 and 312 control the power output of the electrochemical converter system, and hence the system 290, by regulating the amount of reactants introduced thereto. The electroehemical converter system 320 can be identical to the electrochemical converter system 72 of FIG. 1.

The electrochemical converter system 320 processes the fuel and oxidizer reactants and generates, in one mode of operation, electricity and waste heat associated with the high temperature exhaust. The exhaust produced by the electrochemical converter system 320 can be optionally coupled with the turbine exhaust to form the system exhaust which is then conveyed to the heat exchanger 314 along conduit 308 to pre-heat the incoming fuel and air reactants. The exhaust of the system 320 can be directly coupled to heat exchanger, or can be mixed with the gas turbine or system exhaust. According to another practice, the turbine exhaust and the electrochemical converter system exhaust can be separately connected to the heat exchanger 314 to preheat the incoming reactants. The waste heat associated with the system exhaust serves to pre-heat the air and the fuel prior to introduction to the electrochemical converter system 320. Preferably, the sensible heat exchange between the incoming reactants and the outgoing exhaust are such that the convective heat exchanged between the gases is either optimized, or some specific amount of heat is recuperated. For example, waste heat associated with the exhaust that would otherwise be transferred out of the system is absorbed by the incoming reactant gases. The effect is to continuously recover at least a portion of the waste heat used to heat the reactants, and which is carried in the exhaust flow. By employing this heat exchange mechanism, the amount of heat lost by the system is decreased, thereby improving the overall system efficiency.

The electrochemical converter system 320 operates as a heat source by conveying heat to the heat exchanger 302 either radiatively (as shown), conductively or convectively. The compressed air passing through conduit 300 passes through the exchanger 302 and is heated by the waste heat generated by the electrochemical converter system 320. The amount of air passing through the heat exchanger 302 and introduced to the turbine expander 296 is regulated by the fluid regulating element 304.

The fluid regulating element 304 can allow some or all of the heated air to be introduced to the turbine 296 or to be transferred to the fluid conduit 308. In this way, the WO 02/37587 PCT/US00/29895 -46controller 326 can control the amount of drive gas heated air) that is introduced to the turbine, and hence can control the power output of the turbine expander 296.

The turbine expander 296 adiabatically expands the exhaust produced by the electrochemical converter system 320, and converts this thermal energy into rotary energy for subsequent transfer to the electric generator 298. The generator 298 produces electricity that can be used for both commercial and residential purposes. In this arrangement, the electrochemical converter system 320 functions as the combustor for the gas turbine assembly 306 and the gas turbine functions as a bottoming cycle plant for the electrochemical converter system 320. Moreover, the electrochemical converter system 320 is operated at an elevated temperature and at ambient pressure. The heat exchanger 302 which heats the compressed air, on the other hand, is generally an elevated pressure operation component. The compressed and heated air is then utilized as the drive gas for the gas turbine assembly 306. The illustrated system 290 hence employs a low pressure subsystem for heating the compressed air to a temperature compatible with the gas turbine assembly 306 utilizing waste heat from an ambient pressure subsystem. This interoperation of disparate pressure subsystems can be employed in a system arrangement, and hence relaxes design configuration and tolerances of the overall system 290.

Those of ordinary skill will also recognize that the amount of waste heat exchanged in the heat exchanger 302 effects the overall system operation and efficiency.

The system 290 can regulate or adjust the power output of the gas turbine assembly 306 by regulating the input temperature of the drive gas. Moreover, the fluid regulating devices 310 and 312 regulate the amount of reactants introduced to the electrochemical converter system 320, and hence regulate the power output of the fuel cell.

FIG. 16 illustrates an alternative embodiment of the hybrid power system of FIGS. 1 and 12-15. The illustrated hybrid power system 330 controls the power output of the gas turbine assembly 340 and of the electrochemical converter system 358. The description of this embodiment is similar in some respects to the hybrid power systems 200, 230, 260, and 290 described above. The illustrated hybrid system 330 introduces air 332 from an air source to the compressor 334 by way of any suitable fluid conduit, where it is compressed, pressurized and heated, and then discharged therefrom.

The heated, pressurized air can be introduced to a heat exchanger 350 along fluid WO 02/37587 PCT/US00/29895 -47conduit 344, where it is heated by waste heat generated from the electrochemical converter system 358. The heated air is then introduced to the turbine expander 336 of the gas turbine assembly 340 where it functions as the expander drive gas.

A fuel 346 can be introduced to an electrochemical converter system 358 after optionally passing through the heat exchanger 350, where it is preheated by the system exhaust. The heated air and fuel function as input reactants to the electrochemical converter system. The converter system 358 can be identical to the electrochemical converter systems described above.

The electrochemical converter system 358 processes the fuel and oxidizer reactants and generates, in one mode of operation, electricity and waste heat associated with high temperature exhaust. The exhaust produced by the electrochemical converter system 358 can be coupled, and optionally directly coupled, to the gas turbine expander 336 by fluid conduit 360. The turbine expander 336 adiabatically expands the exhaust produced by the electrochemical converter system 358, and converts this thermal energy into rotary energy for subsequent transfer to the electric generator 338. The generator 338 produces electricity that can be used for both commercial and residential purposes.

The compressed air flowing through the conduit 344 pass directly through the heat exchanger 350 or can selectively by-pass the heat exchanger and be intermingled with the air exiting the heat exchanger 350 by the fluid regulating element 354. The fluid regulating element 354 selectively regulates the amount of compressed air that is intermingled with the heated air exiting the heat exchanger 350. Likewise, the fluid regulating element 356 regulates the amount of heated, compressed air that enters the electrochemical converter system 358. According to one practice, the fluid regulating element 354 regulates the amount of air that is introduced to the thermal control stack that is housed within a pressure vessel. The fluid regulating element 356 in turn can regulate the amount of air introduced to the fuel cell that can also be mounted within the pressure vessel. In combination, the fluid regulating elements 356 and 354 can regulate the power output and/or the temperature of the electrochemical converter system 358.

The gas turbine assembly 340 further produces heated exhaust which can be captured and ducted for subsequent use by the fluid manifolding 342. According to one practice, the turbine exhaust is passed through the heat exchanger 350. The waste heat associated with the turbine exhaust serves to pre-heat the fuel and/or air prior to WO 02/37587 PCT/US00/29895 -48introduction to the electrochemical converter system 358. The illustrated hybrid power system 330 can employ a fluid regulating element 352 for regulating the amount of heated turbine exhaust that is passed through the heat exchanger 350. By regulating the amount of exhaust passing through the heat exchanger 350, the fluid regulating element 352 regulates the temperature of the input reactants, and hence the thermal condition of the electrochemical converter system 358.

Those of ordinary skill will readily recognize that a controller can be employed to regulate one or more components of the hybrid power system 330.

FIG. 17 illustrates an alternate embodiment of the hybrid power system of FIGS.

1 and 12-16. In the illustrated hybrid power system 370, one or more fluid regulating devices are employed to controls the power output of the gas turbine assembly 380. The description of this embodiment is similar in some respects to the hybrid power systems described above. The system 370 introduces air 372 from an air source to the compressor 374 by way of any suitable fluid conduit, where it is compressed, pressurized and heated, and then discharged therefrom. The heated, pressurized air can be introduced to a heat exchanger 390, such as a recuperator, by the fluid conduit 382, where it is pre-heated by exhaust discharged from the gas turbine assembly 380, as described in more detail below.

A fuel 386 can be introduced to an electrochemical converter system 396 after optionally passing through the heat exchanger 390, where it is also preheated by the gas turbine exhaust. The heated air and fuel function as input reactants and are introduced to the electrochemical converter system through appropriate manifolding. The electrochemical converter system 396 can be similar or identical to the electrochemical converter systems described above. The electrochemical converter system 396 processes the fuel and oxidizer reactants and generates, in one mode of operation, electricity and waste heat associated with the high temperature exhaust. The exhaust produced by the electrochemical converter system 396 is coupled to the gas turbine expander 376 by a suitable fluid conduits or manifolding 399. The turbine expander 376 adiabatically expands the exhaust produced by the electrochemical converter system, and converts this thermal energy into rotary energy for subsequent transfer to the electric generator 378. The generator 378 produces electricity that can be used for both commercial and residential purposes. In this arrangement, the electrochemical converter WO 02/37587 PCT/US00/29895 -49system 396 functions as the combustor for the gas turbine assembly 380 and the gas turbine functions as a bottoming cycle plant.

The gas turbine assembly 380 further produces hot exhaust which can be captured and ducted for subsequent use by the fluid manifolding 406. According to one practice, the turbine exhaust is passed through the heat exchanger 390. The fuel and heated air are also passed through the heat exchanger 390. The waste heat associated with the turbine exhaust serves to pre-heat the air and the fuel prior to introduction to the electrochemical converter system 396. Preferably, the sensible heat exchange between the incoming reactants and the outgoing exhaust are such that the convective heat exchanged between the gases is either optimized, or some specific amount of heat is recuperated. For example, waste heat associated with the exhaust that would otherwise be transferred out of the system is absorbed by the incoming reactant gases. The effect is to continuously recover at least a portion of the waste heat used to heat the reactants, and which is carried in the exhaust flow. By employing this heat exchange mechanism, the amount of heat lost by the system is decreased, thereby improving the overall system efficiency.

The illustrated electrochemical converter system 396 can include a fuel cell (as shown in FIGS. 1 and which operates at a selected operating temperature, and an optional thermal control stack (as shown in FIGS. 8-11). According to a preferred embodiment, the fuel cell is a solid oxide fuel cell that has an operating temperature of about 1000 and thus generates exhaust having a temperature at about this level.

Certain gas turbines, such as small turbine units, require an input fluid having a temperature below 1000 and usually about 900 This fluid temperature requirement thus mandates that the high temperature exhaust emitted by the electrochemical converter system 396 be regulated to temperature levels compatible with the input temperature requirements of the gas turbine assembly 380. The present invention addresses this temperature incompatibility by providing a number of methods suitable for effectuating a selected degree of temperature control over the converter system exhaust.

Referring again to FIG. 17, the hybrid power system 370 further includes multiple fluid regulating devices and a controller 410 for regulating the amount of fuel introduced to the electrochemical converter system 396, as well as regulating the WO 02/37587 PCT/US00/29895 temperature of the exhaust introduced to and exiting the gas turbine assembly 380. The illustrated hybrid power system 370 includes a first fluid regulating device 384 that spans between the compressor fluid conduit 382 and the electrochemical converter system exhaust fluid conduit 399. The fluid regulating device 384 selectively allows a portion of the compressor air discharged from the compressor 374 to be directly intermingled or mixed with the further heated exhaust of the electrochemical converter system 396 prior to introduction to the gas turbine expander 376.

As is known in the art, conventional gas turbines tolerate input work fluids up to a certain maximum temperature. The gas turbine assembly 380 can operate at lower temperatures, but the power output of the turbine is decreased accordingly. Hence, if the gas turbine has an input maximum temperature requirement of 900 0 C, the high temperature exhaust of the electrochemical converter system can be cooled to at least this temperature level or below in order to comply with this gas turbine operational requirements. In this scenario, the temperature of the air discharged from the compressor 374 is typically below the exhaust temperature of the electrochemical converter system 396. The by-pass valve 384 can be controlled by the controller 410 to allow some or all of the air to pass through the by-pass conduit 385 to mix with and cool the high temperature exhaust of the electrochemical converter system 396. By regulating the amount of air mixed with the exhaust, the resultant fluid temperature of the exhaust can be adjusted to desired levels. According to one practice, the exhaust temperature is regulated to a temperature at or below the maximum turbine temperature, according to a user selected or prestored temperature condition. In the example set forth above, the high temperature exhaust from the electrochemical converter system 396 can be cooled to about 900 'C or even less.

The illustrated hybrid power system 370 further includes a fuel adjustment fluid regulating device 388 that regulates the amount of fuel introduced to the electrochemical converter system 396. The fluid regulating device 388 is in feedback communication with the controller 410 via any suitable communication link. The controller 410 and the fluid regulating device 388 regulate the amount of fuel introduced to the electrochemical converter system 396, and thus regulate the power output thereof.

WO 02/37587 PCT/US00/29895 -51- The illustrated hybrid power system 370 further can employ an optional combustor 398 disposed between the electrochemical converter system 396 and the turbine expander 376 to additionally heat the exhaust and/or the compressed air prior to introduction to the turbine. The combustor 398 provides an additional level of temperature control over the drive gas for the turbine expander 376.

The compressed air passing through the conduit 382 can be selectively intermingled with the air exiting the heat exchanger 390 by the fluid regulating element 392. The fluid regulating element 392 selectively regulates the amount of compressed air that is intermingled with the heated air exiting the heat exchanger 390. Likewise, the fluid regulating element 394 regulates the amount of heated, compressed air that enters the electrochemical converter system 396. According to one practice, the fluid regulating element 392 regulates the amount of air that is introduced to the thermal control stack of the electrochemical converter system 396. The fluid regulating element 394 in turn regulates the amount of air introduced to the fuel cell component of the electrochemical converter system 396. In combination, the fluid regulating elements 392 and 394 regulate the temperature and/or power output of the electrochemical converter system 358, and hence of the entire system 370.

Th exhaust of the electrochemical converter system 396 can be directly introduced to the turbine expander 376 of the gas turbine assembly 380, or can by-pass the expander and be intermingled with the turbine exhaust. A fluid regulating element 404 regulates the amount of exhaust of the electrochemical converter system 396 in the by-pass conduit 400 that is intermingled with the turbine exhaust flowing in conduit 402.

The fluid regulating element 404 hence controls the power output of the gas turbine by selectively regulating the amount of drive gas introduced thereto.

FIG. 18 illustrates a gas turbine assembly 450 suitable for use with the hybrid power systems of the present invention. The illustrated gas turbine assembly 450 includes an outer housing 452 that has an air inlet 454 formed therein. The air inlet is adapted to receive an oxidizer reactant, such as air, which is utilized by the gas turbine assembly 450. The air passing through air inlet 454 is introduced to a compressor 456 for compressing the air. The compressed air exits the compressor 456 and passes through an intermediate portion 458 of an outer chamber 460. Those of ordinary skill will readily recognize that the outer chamber 460 can function as a heat exchanger WO 02/37587 PCT/US00/29895 -52similar to the recuperator 88 of FIG. 12, for preheating the compressed for subsequent use by the gas turbine assembly 450. The outer chamber 460 is formed by a bulkhead portion of the outer housing 452 disposed at an outer portion or region of the gas turbine assembly. The bulkhead portion of the gas turbine outer housing 452 employs a dome cap 462 that is adapted to transfer or convey one or more internal fluids during operation of the gas turbine assembly 450.

The compressed air flows through the outer chamber 460 and is connected to a penetrating fluid conduit 464 which penetrates the dome cap portion 462 of the outer housing 452. The penetrating conduit 464 is in fluid communication at one end with an external heat source, such as the electrochemical converter systems described above, and communicates at another end with the outer chamber 460. The penetrating fluid conduit 464 conveys the heated compressed air exiting the outer annular chamber 460 to the external heat source. A connector or adapter 466 can be employed to connect the penetrating fluid conduit 464 to the internal portion of the gas turbine assembly 450.

The illustrated connector 466 can be any suitable mechanical coupling sufficient to connect a duct or conduit to one or more internal components of the gas turbine assembly 450. According to one embodiment, the connector 466 can be a bellows that allows the fluid conduit 464 to couple and selectively axially move relative to the gas turbine assembly 450, although other connectors are also contemplated by the present invention to alleviate the thermal stresses that arise from components operating at different temperatures, or having different coefficients of expansion.

The compressed air is heated by the external heat source, and is returned to the gas turbine assembly along a return fluid conduit 468. The return fluid conduit 468 is coupled to a middle chamber 470 by a connector 472. The exhaust from the external heat source passes through the middle chamber 470 and is introduced to a turbine expander 474. The turbine expander adiabatically expands the exhaust, which then passes through an inner chamber 476. The turbine exhaust passing through the inner chamber 476 is collected by the dome cap 462 to the outer chamber 460, where the exhaust exchanges heat with the compressed air to preheat the air prior to introduction to the external heat source along fluid conduit 464. The turbine exhaust is then vented or exhausted from the gas turbine assembly 450 through vent aperture 478.

WO 02/37587 PCT/US00/29895 -53- Those of ordinary skill will readily recognize that fluid regulating structure can be employed in connection with the gas turbine assembly 450 in order to effectuate certain selected control over one or more parameters of the gas turbine assembly 450.

By way of example, apertures can be disposed in the return fluid conduit 468 in order to selectively mix or intermingle the exhaust of the heat source with the gas turbine exhaust flowing through the inner annular chamber 476. Similarly, apertures can be formed in the dome cap 462 in order to vent the turbine exhaust to the ambient environment.

Those of ordinary skill will readily recognize that the illustrated gas turbine assembly 450 can include other conventional components such as the shaft 480. The foregoing illustration of the gas turbine assembly 450 is merely one representation, and those of ordinary skill will readily recognize that other configurations can be employed in keeping with the present invention. Specifically, the present invention contemplates providing one or more penetrating fluid conduits sufficient to extract the compressed air for subsequent delivery to an external heat source, and then delivering the exhaust of the heat source to the gas turbine assembly. Those of ordinary skill will also recognize that any selected number of penetrating fluid conduits can be employed in any particular arrangement, such as axially symmetric patterns, in order to effectuate the extraction of a fluid from the gas turbine assembly, or the delivery of a fluid to the gas turbine assembly.

Those of ordinary skill will also recognize that various system fluid flow configurations and fluid regulating element arrangements can be employed in addition to the different system configurations set forth above, while concomitantly controlling the temperature of the fuel cell and the power output of one or more system components, subsystems or assemblies.

It will thus be seen that the invention efficiently attains the objects set forth above, among those made apparent from the preceding description. Since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

WO 02/37587 PCT/US00/29895 -54- Having described the invention, what is claimed as new and desired to be secured by Letters Patent is:

Claims

2. The hybrid power system of claim 1, wherein said regulation means comprises means for combining the remainder portion of the exhaust of the electrochemical converter systems with the turbine exhaust to form an exhaust mixture for controlling an operational parameter of the turbine.
3. The hybrid power system of claim 1, wherein said regulation means comprises a regulation element disposed between said electrochemical converter system and said turbine, or in fluid communication with both, for regulating the amount of exhaust from said electrochemical converter system that by-passes said turbine.
4. The hybrid power system of claim 1, wherein said regulation means comprises a regulation element disposed between said electrochemical converter system and said turbine, and in fluid communication with both, for regulating the amount of exhaust from said electrochemical converter system that is introduced to said turbine. The hybrid power system of claim 1, further comprising cooling means for cooling the electrochemical converter system exhaust prior to introduction to the turbine. WO 02/37587 PCT/US00/29895 -56-
6. The hybrid power system of claim 5, wherein said cooling means comprises a fluid conduit in communication with the electrochemical converter system and the turbine for conveying said electrochemical converter system exhaust to the turbine, and wherein said fluid conduit is adapted to radiatively, conductively, or convectively transferring heat away from the electrochemical converter system exhaust prior to introduction to said turbine.
7. The hybrid power system of claim 1, wherein said operational parameter comprises turbine speed, turbine power output, or turbine temperature.
8. The hybrid power system of claim 1, wherein said regulation means comprises means for regulating the amount of electrochemical converter system exhaust introduced to the turbine.
9. The hybrid power system according to any of the preceding claims, further comprising a fluid regulating element in fluid communication with the electrochemical converter system and the turbine for regulating the amount of electrochemical converter system exhaust entering the turbine and by-passing the turbine, said by-pass portion being combined with the turbine exhaust or being exhausted to ambient. The hybrid power system of claim 8, wherein said fluid regulating element comprises a valve, shuttle element, rotating sphere, or diaphragm.
11. The hybrid power system of claim 8, wherein the fluid regulating element comprises a three way valve.
12. The hybrid power system according to any of the preceding claims, wherein the turbine receives only a portion of the electrochemical converter system exhaust. WO 02/37587 PCT/US00/29895 -57-
13. The hybrid power system according to any of the preceding claims, further comprising a heat exchanging element disposed between the turbine and the electrochemical converter system and adapted to receive at least one of the first medium, the second medium, the turbine exhaust, the exhaust of the electrochemical converter system, and the combined exhaust.
14. The hybrid power system of claim 13, further comprising means for introducing the exhaust mixture to the heat exchanging element, wherein said exhaust mixture selectively heats at least one of said first and second mediums when passing through the heat exchanging element. The hybrid power system of claim 14, further comprising means for introducing the compressed first medium to the electrochemical converter system after passing through the heat exchanging element.
16. The hybrid power system of claim 13, wherein said heat exchanging element comprises at least one of a heat exchanger and a recuperator.
17. The hybrid power system according to any of the preceding claims, further comprising a second fluid regulating element disposed between the compressor and the electrochemical converter system for regulating the amount of compressed first medium that is intermingled with the exhaust of the electrochemical converter system.
18. The hybrid power system of claim 17, further comprising means for controlling the operational parameter of the turbine by controlling the amount of compressed first medium intermingled with the exhaust of the electrochemical converter system.
19. The hybrid power system according to any of the preceding claims, further comprising a third fluid regulating element for regulating the amount of the second mediumn introduced to the electrochemical converter system, thereby controlling the power generated by the electrochemical converter system. WO 02/37587 PCT/US00/29895 -58- The hybrid power system according to any of the preceding claims, further comprising a heating source disposed between the electrochemical converter system and the turbine for heating the exhaust of the electrochemical converter system to a selected elevated temperature prior to introduction to the turbine.
21. The hybrid power system of claim 20, wherein said heating source comprises a combustor.
22. The hybrid power system according to any of the preceding claims, wherein said electrochemical converter system comprises a electrochemical converter and at least one of a thermal control stack and a vessel, wherein said vessel is sized for housing the fuel cell and optionally the thermal control stack.
23. The hybrid power system of claim 22, further comprising means for collecting the exhaust of the thermal control stack and the fuel cell to form the electrochemical converter system exhaust, and means for discharging the electrochemical converter system exhaust from the vessel for use external thereto.
24. The hybrid power system of claim 22, further comprising a fourth fluid regulating element for regulating the amount of first medium introduced to the thermal control stack. The hybrid power system of claim 24, wherein said fourth fluid regulating element is positioned between the compressor and one of the heat exchanging element and the thermal control stack for regulating the amount of compressed first medium from the compressor or first medium from the heat exchanging element which is introduced to the thermal control stack.
26. The hybrid power system according to any of the preceding claims, further comprising means for introducing the first medium to the electrochemical converter system from multiple different sources. WO 02/37587 PCT/USOO/29895 -59-
27. The hybrid power system of claim 26, wherein said multiple different sources comprise compressor and the heat exchanging element.
28. The hybrid power system of claim 25, further comprising means for introducing at least a portion of the first medium discharged from the compressor to the fourth fluid regulating element prior to introduction to the heat exchanging element.
29. The hybrid power system of claim 25, further comprising a fifth fluid regulating element positioned between the heat exchanging element and the electrochemical converter system for regulating the amount of first medium passing through the heat exchanging element and entering the fuel cell. The hybrid power system of claim 1, further comprising a recuperator positioned between the electrochemical converter system and the compressor and adapted to receive the exhaust mixture and at least one of the first and second mediums for heating the medium with the exhaust mixture, and a counterflow heat exchanger disposed between the electrochemical converter system and at least one of the turbine and the recuperator, and adapted to receive the electrochemical converter system exhaust and one of the first and second mediumns, for heating one of the first and second mediums with the electrochemical converter system exhaust.
31. The hybrid power system of claim 28, further comprising means for mixing the compressed first medium with the heated compressed first medium from the heat exchanging element prior to introduction to the thermal control stack.
32. The hybrid power system of claim 22, further comprising means for introducing the first and second mediums to the thermal control stack. WO 02/37587 PCT/USOO/29895
33. The hybrid power system according to any of the preceding claims, further comprising a generator associated with the turbine and adapted to receive the rotary energy thereof, wherein the generator produces electricity in response to the turbine rotary energy.
34. The hybrid power system according to any of the preceding claims, wherein the electrochemical converter system includes a fuel cell, and wherein said fuel cell comprises an electrochemical converter assembly having a plurality of stacked converter elements which include a plurality of electrolyte plates having an oxidizer electrode material on one side and a fuel electrode material on the opposing side, and a plurality of interconnector plates for providing electrical contact with the electrolyte plates, wherein the stack of converter elements is assembled by alternately stacking interconnector plates with the electrolyte plate.
35. The hybrid power system of claim 34, wherein the stacked converter elements comprise a plurality of manifolds axially associated with the stack and adapted to receive the first and second mediums, and medium heating means associated with the manifold for heating at least a portion of the first and second mediums to the operating temperature of the converter.
36. The hybrid power system of claim 35, wherein the interconnector plate comprises a thermally conductive connector plate. 37 The hybrid power system of claim 35, wherein the medium heating means comprises a thermally conductive and integrally formed extended surface of the interconnector plate that protrudes into the axial manifolds.
38. The hybrid power system of claim 35, wherein the stack of converter elements further comprises a plurality of spacer plates interposed between the electrolyte plates and the interconnector plates. \O c 39. The hybrid power system according to any of the preceding claims, o wherein the electrochemical converter system comprises a fuel cell, and wherein the power system further comprises means for maintaining the operating temperature of the fuel cell between about 20 0 C and about 1500 0 C. kn 5 40. The hybrid power system according to any of the preceding claims, wherein said electrochemical converter system comprises a fuel cell selected c from the group consisting of a solid oxide fuel cell, molten carbonate fuel cell, 0phosphoric acid fuel cell, alkaline fuel cell, and proton exchange membrane fuel C cell.
41. The hybrid power system according to any of the preceding claims, wherein the electrochemical converter system is placed serially in-line or off-line of the compressor and the turbine.
42. A method for producing electricity with a hybrid power system, comprising the steps of compressing a first medium, providing one or more electrochemical converter systems for electrochemically reacting the first with a second mediums and to produce exhaust, providing one or more turbines to receive a portion of the electrochemical converter system exhaust, said exhaust operating as a drive fluid for the turbine, wherein said turbine produces turbine exhaust, and regulating an operational parameter of the turbine with the exhaust from the electrochemical converter system.
43. A hybrid power system (290) for producing electricity, comprising one or more compressors for compressing at least a portion of a first medium to produce a compressed medium, one or more electrochemical converter systems adapted to receive the first medium and a second medium, the electrochemical converter system being configured to allow electrochemical reaction between the first and second mediums and to produce electricity and fuel cell exhaust, one or more heat exchangers in thermal communication with the electrochemical converter system and adapted to receive the compressed IND O medium, said heat exchanger exchanging heat with the electrochemical converter Ssystem to condition the compressed medium when passing through the heat o exchanger,and Sone or more turbines configured to receive the compressed medium exiting the heat exchanger, said compressed medium operating as a drive fluid for the turbine for electricity generation.
44. The hybrid power system of claim 43, further comprising a fluid regulating 1 element for regulating the amount of compressed medium introduced to the Sturbine to control an operational parameter thereof.
45. The hybrid power system of claim 43, further comprising a fluid regulating element disposed in communication with the heat exchanger, the turbine or the electrochemical converter system exhaust for combining at least a portion of the compressed medium from the heat exchanger with the exhaust of the electrochemical converter system for controlling an operational parameter of the turbine.
46. The hybrid power system of claim 45, wherein said operational parameter comprises speed, power output, or turbine temperature.
47. The hybrid power system according to any of claims 43 46, further comprising a counterflow heat exchanger adapted to receive a first medium and/or a second medium, and further comprising an additional fluid regulating element for regulating the amount of said first or second medium exiting the counterflow heat exchanger that is introduced to the electrochemical converter system.
48. The hybrid power system according to claim 43, wherein said electrochemical converter system includes a thermal control stack and one or more fuel cells disposed within a vessel, said system further comprising a counterflow heat exchanger, O a first fluid regulating element for regulating the amount of said first c medium exiting the counterflow heat exchanger that is introduced to the thermal o control stack, and/or a second fluid regulating element for regulating the amount of said first medium exiting the heat exchanger that is introduced to the fuel cell. n 49. The hybrid power system according to claim 43, further comprising a counterflow heat exchanger adapted to receive at least one of the first medium, N the second medium, the turbine exhaust, and the exhaust of the electrochemical Sconverter system.
50. The hybrid power system of claim 43, wherein said turbine comprises a recuperator disposed between the turbine and the heat exchanger and adapted to receive at least one of the first medium, the second medium, the turbine exhaust, and the exhaust of the electrochemical converter system, for heating at least one of said first and second mediums when passing through the recuperator.
51. The hybrid power system according to any of claims 43-50, wherein said electrochemical converter system comprises a fuel cell, at least one thermal control stack, and a vessel, wherein said vessel is sized for housing the fuel cell and the thermal control stack.
52. The hybrid power system according to claim 51, further comprising means for collecting the exhaust of the thermal control stack and the fuel cell to form the electrochemical converter system exhaust, and means for discharging the electrochemical converter system exhaust from the vessel for use external thereto.
53. The hybrid power system according to any of claims 43 52, further comprising a first fluid regulating element for regulating the amount of the second medium introduced to the electrochemical converter system, thereby controlling the power generated by the electrochemical converter system. O 54. The hybrid power system (450) of claim 1, further comprising N a gas turbine assembly having a housing mounting the compressor, and a c turbine expander, and 0 one or more penetrating fluid conduits adapted to penetrate the housing for communicating with an interior portion of the housing, said fluid conduit being adapted for delivering a fluid from the gas turbine assembly to an external heat source or from the external heat source to the gas turbine assembly. The hybrid power system of claim 54, further comprising a connector coupled to the fluid conduit for coupling the fluid conduit to the gas turbine assembly.
56. The hybrid power system of claim 55, wherein the connector comprises a bellows.
57. The hybrid power system of claim 54, further comprising an electrochemical converter system coupled to the gas turbine assembly and to the fluid conduit for heating a fluid or medium of the gas turbine assembly.
58. The hybrid power system of claim 54, wherein the gas turbine assembly comprises an outer chamber formed in the housing for communicating with a first penetrating fluid conduit for delivering a compressed medium to the external heat source.
59. The hybrid power system of claim 58, wherein the gas turbine assembly comprises an intermediate chamber formed in the housing and a second penetrating fluid conduit coupled to the housing for introducing the exhaust of the external heat source to the intermediate chamber, wherein said intermediate chamber is in communication with said outer chamber. A hybrid power system for controlling the temperature of a fuel cell and for producing electricity, comprising one or more compressors for compressing a first medium, IND O one or more electrochemical converter systems for allowing c electrochemical reaction between the first medium and a second medium to c produce electricity and fuel cell exhaust, one or more turbines in fluid communication with the electrochemical converter system for producing turbine exhaust, one or more heat exchangers positioned between the electrochemical Sconverter system and the compressor and adapted to receive at least a portion of the turbine exhaust or one of the first and second mediums, and _one or more controllers for controlling the flow of one of the first and second mediums or the turbine exhaust for controlling one or more operational parameters of the electrochemical converter system.
61. The hybrid power system of claim 60, further comprising one or more fluid regulating elements for regulating the flow of one of the first and second mediums to the electrochemical converter system, the turbine or the heat exchanger.
62. The hybrid power system of claim 60 wherein said operational parameter comprises power output or temperature.
63. The hybrid power system according to claim 1, 43 and 60, wherein said electrochemical converter system comprises multiple components having a two- dimensional or three-dimensional arrangement.
64. A hybrid power system of claim 1, further comprising a gas turbine assembly comprising a generator for generating the electricity, a fluid regulating element positioned relative to the gas turbine assembly and the electrochemical converter system for regulating the amount of the exhaust introduced to the gas turbine assembly, and a controller coupled to the fluid regulating element and to the generator for controlling the fluid regulating element to regulate the amount of exhaust introduced to the gas turbine assembly based on an output signal generated by the generator. IND O 65. The method of claim 42, further comprising the steps of c initiating start-up of a gas turbine assembly by introducing a selected O amount of a fluid thereto, Sheating the fluid prior to introduction to the gas turbine assembly, and initiating start-up heating of an electrochemical converter system independently of the start-up of the gas turbine assembly.
66. The method of claim 42, further comprising the steps of a) controlling start-up of a gas turbine assembly by controlling the introduction of a fluid thereto, b) controlling the amount of heating of the fluid prior to introduction to the gas turbine assembly, and c) controlling the amount of heating of an electrochemical converter system during start-up independently of the start-up of the gas turbine assembly.
67. The method of claim 66, wherein step further comprises the step of bypassing an expander of the gas turbine assembly with the fluid.
68. The method of claim 66, wherein step further comprises the step of heating the fluid with a combustor or with a thermal control stack.
69. The method of claim 66, wherein step further comprises the step of heating the fuel cell with a thermal control stack or with a heated fluid. The hybrid power system substantially as hereinbefore described with reference to the accompanying drawings.
71. The method for producing electricity substantially as hereinbefore described with reference to the accompanying drawings. INO O 72. The method of operating a hybrid power system substantially as cI hereinbefore described with reference to the accompanying drawings. o C.) DATED this 13th day of October 2006 ZTEK CORPORATION N WATERMARK PATENT TRADE MARK ATTORNEYS S 290 BURWOOD ROAD 0HAWTHORN VICTORIA 3122 AUSTRALIA P22725AU00