AU2010246433A1 - A power generator assembly - Google Patents

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (ORIGINAL) Name of Applicant: Roderick John Mould Actual Inventors: Roderick John Mould Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, Level 10, 301 Coronation Drive, Milton 4064, Queensland. Invention Title: "A power generator assembly" Details of Associated Provisional Application: Australian Provisional Patent Application No. 2009905816, filed 27 November 2009 The following statement is a full description of this invention, including the best method of performing it known to us: CANRPonhrlCC\SRH\3307968 DOC - 22/1 1/10 C:RPonb\DCCSE 308011 6I.DOC-i/1/i flow A POWER GENERATOR ASSEMBLY Background of the Invention This invention relates to a power generator assembly and in particular a power generator assembly including a solar water heating system. 5 Description of the Prior Art The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to 0 which this specification relates. U.S. patent no. 6,672,064 to Lawheed describes systems or combinations and methodology for converting solar energy to electrical energy and thermal energy and for converting the resultant thermal energy to electrical energy. Systems and methodology for conversion of low temperature thermal energy, wherever obtained, to electrical energy using a Rankine cycle 5 mechanism to drive an electrical generator or do other work in a cost-effective way are also disclosed. U.S. patent no. 6,981,377 to Vaynberg et al. describes the recovery of electric power from low-grade waste heat-solar energy, comprising a closed-cycle charged refrigerant loop. Pressurized refrigerant fluid is pumped at ambient temperature through a heat exchanger 20 connected to a waste heat/solar source to extract heat energy during conversion to a high pressure gas. Heated/pressurized refrigerant gas is inlet into an expander to power an output shaft during the expansion of the fluid to a cooled gas at approximately Opsig. Cooled gaseous refrigerant is condensed to a liquid at low pressure and ambient temperature, and recycled under pressure to the heat exchanger. The expander is a reverse-plumbed gas 25 compressor; the pressurized, hot refrigerant gas is inlet at what is ordinarily its outlet, and the normal inlet becomes the expander end. The refrigerant gas mass flow pressure/temperature drop spins the expander shaft for direct mechanical power take-off, or coupling to a synchronous or inductive generator to produce electricity.

CANRPonblDCCSEM10036_ DOC-I16/11/20 10 -2 W02009/034573 describes a solar electricity generation system including a solar energy-to electricity converter having a solar energy receiving surface including at least an electricity generating solar energy receiving surface and a plurality of reflectors arranged to reflect solar energy directly onto the solar energy receiving surface, each of the plurality of reflectors 5 having a reflecting surface which is configured and located and aligned with respect to the solar energy receiving surface to reflect specular solar radiation with a high degree of uniformity onto the solar energy receiving surface, the configuration, location and alignment of each of the reflectors being such that the geometrical projection of each reflecting surface is substantially coextensive with the electricity-generating solar energy receiving surface. 0 WO/2010/012491 describes an open concentrator system for solar radiation, comprising a hollow mirror and a photovoltaic module which is arranged at the focus thereof and comprises a plurality of solar cells, wherein the photovoltaic module is encapsulated by a housing. The housing is in this case designed such that it has a transparent cover at least in the area of the incident radiation reflected by the hollow mirror, and such that this transparent 15 cover is at a distance from the photovoltaic module, that is to say it is located in the cone of the incident radiation. None of the prior art systems provides a cost-effective and practical means to convert solar heat or low-grade excess heat from industrial or power generation processes into useful electrical energy. 20 Summary of the Present Invention One aspect of the invention provides for a power generator assembly including: a) a heat collector for collecting heat from a heat source; b) a Rankine cycle heat engine arranged in fluid communication with the heat collector, the heat collector configured to operatively transfer heat to the heat engine via a fluid, 25 the heat engine configured to generate electrical power; c) a heat sink arranged in fluid communication with the heat engine and configured to dissipate heat from the heat engine; and d) a controller configured to control a flow of fluid between the heat collector and the heat engine according to a predetermined temperature of the heat source.

C :\RPonbl\DCCSEH\33111 36_I.DOC-16/11/21110 -3 Typically, the Rankine cycle heat engine includes an organic Rankine cycle heat engine. Typically, the heat source includes a solar water heating system. Typically, the heat source includes a duct or pipe. Typically, the Rankine cycle heat engine includes: 5 a) a pump for pressurizing and circulating refrigerant; b) an evaporator for converting the refrigerant to pressurized vapour; c) a turbine for expansion of the refrigerant with an associated extraction of energy to facilitate in generation of electrical energy; and d) a condenser to facilitate in cooling of the refrigerant to liquid form before re-entering t0 the pump. Typically, said refrigerant is at least one of R-134a and R-245fa. Typically, the heat sink is selected from a group consisting of: a subterranean heat exchanger, a submerged heat exchanger, a fluid reservoir, a cooling tower, and an air cooler. Typically, the heat sink is configured to dissipate heat distally from the heat engine. 5 Typically, the controller includes a temperature sensor configured to sense a temperature of the heat source, and actuators for actuating valves to control the flow of fluid between the heat collector and the heat engine. Typically, the power generator assembly forms part of a solar water heating system. Typically the heat source includes: 20 a) at least one reflector for reflecting solar radiation; and, b) at least one pipe containing fluid to be heated using the reflected solar radiation. Typically the heat source includes at least one photovoltaic cell for generating electricity using the reflected solar radiation and wherein the at least one pipe is in thermal communication with the at least one photovoltaic cell. 25 Typically the at least one reflector is a parabolic trough reflector.

C:\NRPrtnbIlCC\SEIm330M036_L DOC.61 I1/2010 -4 Typically the heat source includes: a) a frame; and, b) a plurality of elongate reflectors movably mounted to the frame to allow the reflectors to reflect the solar radiation. 5 Typically the heat source includes a cover member for protecting at least the at least one tube. Typically the cover member is a trough shaped cover member having a reflective inner surface for directing reflected radiation onto the at least one pipe. Typically the fluid is at least one of water, heat transfer fluid and thermal oil. A further aspect of the invention provides for a solar water heating system including: 0 a) a solar water heater arranged in fluid communication with a hot water tank; b) a Rankine cycle heat engine arranged in fluid communication with the solar water heater and the water tank, the heat engine configured to generate electrical power; c) a valve arrangement for regulating water flow between the heat engine and the solar water heater and water tank; 5 d) a heat sink arranged in fluid communication with the heat engine and configured to dissipate heat from the heat engine; and e) a controller configured to control the valve arrangement so that the heat engine is only active when the water in the water tank has reached a predetermined temperature. Typically, the Rankine cycle heat engine includes: 20 a) a pump for pressurizing and circulating refrigerant; b) an evaporator for converting the refrigerant to pressurized vapour; c) a turbine for expansion of the refrigerant with an associated extraction of energy to facilitate in generation of electrical energy; and d) a condenser to facilitate in cooling of the refrigerant to liquid form before re-entering 25 the pump. Typically, the refrigerant is at least one of R-134a and R-245fa. Typically, the heat sink includes a subterranean heat exchanger.

C\NRPonbPDCC\SEH\330116_ LDOC-16/11/2010) -5 Typically, the heat sink includes a heat exchanger submerged in, or arranged in thermal connection with, a swimming pool. Typically, the heat sink includes a fluid reservoir having a suitable thermal mass for dissipating heat from the heat engine. 5 Typically, the heat sink includes a heat exchanger installed underneath flooring of a house. Typically, the heat sink includes a cooling tower. Typically, the heat sink includes an air cooler. Typically, the valve arrangement is configured to operatively divert the flow of water from the solar water heater to the Rankine heat engine to the water tank. 10 Typically the solar water heater includes: a) at least one reflector for reflecting solar radiation; and, b) at least one pipe containing water to be heated using the reflected solar radiation. Typically the solar water heater includes at least one photovoltaic cell for generating electricity using the reflected solar radiation and wherein the at least one pipe is in thermal 5 communication with the at least one photovoltaic cell. Typically the at least one reflector is a parabolic trough reflector. Typically the heat source includes: a) a frame; and, b) a plurality of elongate reflectors movably mounted to the frame to allow the reflectors 20 to reflect the solar radiation. Typically the solar water heater includes a cover member for protecting at least the at least one tube. Typically the cover member is a trough shaped cover member having a reflective inner surface for directing reflected radiation onto the at least one pipe.

C:WPonbDCC\SEH\13I0J36_L1 DOC-1611/2010 -6 Brief Description of the Drawings An example of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a schematic representation of an example of a power generator assembly; 5 Figure 2 shows a schematic representation of the power generator assembly as part of a solar heating arrangement; Figures 3A and 3B are schematic end and plan views of a first example of a heat source; and, Figures 4A and 4B are schematic end and plan views of a second example of a heat source. Detailed Description of the Preferred Embodiments 10 With reference now to Figure 1 of the accompanying drawings, there is shown one example of a power generator assembly 10 which includes a heat collector 12, a Rankine cycle heat engine 14, a heat sink 16, and a controller 18. The heat collector 12 is for collecting heat 26 from a heat source 20. Typically, the heat source 20 includes a solar heating system, such as a solar water heating 5 system (described in more detail below). However, the heat source 20 can include any low grade heat from industrial or power generation processes and typically includes a duct or pipe used for transporting a working fluid used in such industrial or power generation processes, e.g. hot air from blowers or compressors, or the like. For example, the heat collector 12 may include copper tubing coiled around the outside of the duct or pipe; or a fin-coil type heat 20 collector used for motor-vehicle radiators, or a shell-and-tube or plate heat collector, or the like. The assembly 10 also includes the Rankine cycle heat engine 14 which is arranged in fluid communication with the heat collector 12 by means of suitable conduits or ducts 24, as shown. The heat collector 12 is configured to operatively transfer heat to the heat engine 14 25 via a fluid in these ducts 24. The fluid is typically water, however any suitable fluid can be used, such as thermal oil, or the like. In this regard, the efficiency of the Rankine cycle engine 14 typically depends on a temperature differential between the heated fluid and a heat dissipation mechanism, such as a heat sink 16, as will be described in more detail below.

C.\NRPorbl\DCC\SEH\330N1036_ IDOC.16/11/20 10 -7 Accordingly, the use of thermal oil can be desirable as this has a higher boiling point than water, thereby allowing a greater temperature differential to be established. The Rankine cycle heat engine 14 generally includes an organic Rankine cycle heat engine using an organic, high molecular mass fluid with a liquid-vapour phase change occurring at a 5 lower temperature than a conventional water-steam phase change heat engine. Accordingly, the heat engine 14 is configured to generate electrical power by means of a generator (shown at 46 in Figure 2). As shown in Figure 2, the Rankine cycle heat engine 14 typically includes a pump 40 for pressurizing and circulating a suitable refrigerant, an evaporator or boiler 42 for converting 10 the refrigerant to pressurized vapour, a turbine 44 for expansion of the refrigerant with an associated extraction of energy via generator 46 to facilitate in generation of electrical energy, and a condenser 48 to facilitate in cooling of the refrigerant to liquid form before re entering the pump 40. In this manner, the Rankine heat engine 14 operates as a closed refrigerant cycle to generate electrical energy due to a temperature differential between the 5 evaporator 42 and the condenser 48. In one example, the refrigerant is typically one of R 134a and R-245fa, with this being selected depending on the intended operating temperature range. It will be appreciated however that any suitable refrigerant can be used having a suitable liquid-vapour phase change temperature. The assembly 10 also incorporates a heat sink 16 arranged in fluid communication with the 20 heat engine 14 by means of conduits 24, as shown, with the heat sink 16 configured to dissipate heat 27 from the heat engine 14. The heat sink 16 is typically a subterranean heat exchanger, a submerged heat exchanger, a fluid reservoir, a cooling tower, or an air cooler. In general, the heat sink 16 is arranged to dissipate the heat 27 distally from the heat engine 14. The heat sink 16 is typically placed inside, or in thermal connection with, some medium 22 to 25 facilitate in the dissipation of heat 27 from the heat engine 14. For example, the heat sink may be submerged in a swimming pool or stream or process water, fluid from a fluid reservoir may be circulated through the heat sink to carry heat away, installed underneath flooring of a house, or buried underground. The heat sink 16 may also include a cooling tower or an air cooler to facilitate in the dissipation of heat 27.

C:\NRPonblOCC\SEHU30016_ .DOC-16/1 l2010 -8 In another example, the heat sink 16 includes a fluid reservoir, such as a water storage tank or other fluid reservoir, which has a suitable thermal mass for dissipating heat from the heat engine 16. For example, the fluid reservoir, such as a water storage tank, may form part of the closed fluid cycle of the assembly 10, wherein water is pumped into the tank and extracted 5 therefrom for return to the heat engine 14. Alternatively, water from a swimming pool or similar reservoir may be circulated through the heat sink to carry heat from the heat engine back to the reservoir, or the like. It is to be appreciated that the larger the temperature differential between the evaporator 42 and the condenser 48 of the heat engine, the more energy can be extracted by the heat engine 10 14. In one example, the heat sink 16 includes condensing fluid pump 50 and a length of tubing 52 to facilitate in dissipating the heat 27 from the heat engine 14. The pump 50 also assists in dumping the heat 27 away or distally from the heat engine 14. The power generator assembly 10 further includes a controller 18 which is configured to control the flow of fluid between the heat collector 12 and the heat engine 14 according to a 15 predetermined temperature measured at the heat source 20. Accordingly, the controller 18 generally includes a temperature sensor (not shown) configured to sense a temperature of the heat source 20, and actuators for actuating valves (shown at 38 in Figure 2) to control the flow of fluid between the heat collector 12 and the heat engine 14. In use, as generally shown in Figure 1, the power generator assembly 10 extracts excess heat 20 26 from the heat source 20. As mentioned above, this heat 26 can be produced by any suitable process. The heat 26 is then transferred by the fluid in the conduits 24 to the Rankine heat engine 14 where, due to the liquid-vapour phase change temperature characteristics of the refrigerant in the heat engine 14, the heat 26 can be converted to electrical energy 28. The heat sink 16, typically placed inside a medium having a below-ambient temperature, extracts 25 excess heat from the condenser of the heat engine 14 to assist in cooling the refrigerant. The current arrangement can be used to generate electrical power cost-effectively, in conjunction with existing industrial systems or as a stand-alone system. The assembly 10 is able to utilise low-grade excess heat from industrial or power generation processes to generate electrical power cost-effectively. In addition, by utilising a below-ambient or C \NRPonb \DCC\SEI\1308016_l.DOC.16/11/2010 -9 cooling media 22, such as a geothermal subterranean installation of the heat sink 16, or submersion in, or other suitable transfer of heat to, natural or man-made water bodies, or using the heat sink 16 as underfloor heating, or a cooling tower or air-cooler or similar arrangements in which the excess heat can be dissipated, the arrangement is able to scavenge 5 excess heat energy for conversion to electrical energy. Although the assembly 10 can be used as a stand-alone system, the assembly 10 finds particular application when used in conjunction with a conventional solar water heating system. Figure 2 shows an example of a solar water heating system 30 including the power generator assembly 10. 0 In such an example, the power generator apparatus 10 forms part of the solar water heating system, which typically includes a solar water heater 12 arranged in fluid communication with a hot water tank 32. In such an example, the solar water heater functions as the heat collector 12. The system 30 also includes a circulating pump 34 for distributing water from the tank 32 to a hot water supply 36. 5 Conventional solar water heaters, such as a Solar Premier Hiline - 52H180, supplied by Rheem Australia, and other similar products generally include a number of tubes arranged on a surface for collecting solar heat energy. The number of tubes is determined according to a placement of the solar water heater, for example, a larger number of tubes are required in climates having less direct sunlight hours per day than a climate having a lot of direct 20 sunlight hours per day. One example of the current arrangement can be easily integrated with existing conventional solar water heating systems, and its power generation capacity can be increased by including additional tubes in the solar water heater. The system 30 also includes a valve arrangement 38 for regulating water flow between the heat engine 14 and the solar water heater 12 and water tank 32. The valve arrangement 38 is 25 configured to operatively divert the flow of water from the solar water heater 12 to the Rankine heat engine 14 to the water tank 32, i.e. include the heat engine 14 in a flow loop when the valves 38 are actuated. The controller 18 is generally configured to control the valve arrangement 38 so that the heat engine 14 is only active when the water in the water tank 32 has reached a predetermined temperature.

C \NRPonbl\DCOSEHOfI'NIr_36 I.DOC-16/II/2110 - 10 To this end, the controller 18 is typically configured to actuate the valves 38 so that the solar water heater or heat collector 12 heats the water in the tank 32 to a predetermined temperature, e.g. 60'C. Once the water in the tank 32 reaches the predetermined temperature, the controller 18 actuates the valves 38 so that the flow of water from the solar water heater is 5 diverted to the heat engine 14 before returning to the water tank 32. The controller 18 typically includes a controlling and metering part 18.1 and an electrical inverter and synchroniser part 18.2. The heated water allows the heat engine 14 to function to generate electrical energy which can be exported to an electrical grid 28 via the inverter and synchroniser part 18.2 and 0 metered by the controlling and metering part 18.1. Water exiting the evaporator 42 is typically controlled by the controlling and metering part 18.1 to be at around 60'C, maintaining this temperature in the hot water tank 32. In general, the controller 18 is configured to monitor the various temperatures, pressures and other parameters throughout the system 30 to control the water and refrigerant flows and the 5 electrical energy generation to match any input heat 26 available from the solar water heater 12. It will be appreciated from the above that the apparatus can be used with any system that is capable of heating a working fluid, such as water, and therefore has particular beneficial applications with solar water heating systems. 20 An example of a particular solar water heating system that can be used is described in WO09/34573. In particular, this document describes apparatus for the co-generation of electricity and heated water, which in one example includes a substantially parabolic dish reflector that is used to reflect sunlight onto photovoltaic (PV) cells, which are in turn used to generate electricity. A heat exchanger is also provided to allow water received via a cold 25 water inlet to be heated and returned via a hot water outlet. The heated water supplied via the hot water outlet can be provided to the Rankine cycle heat engine 14, with cooled water being recirculated to the cold water inlet of the solar water heating system.

C NRPonb\DCCSEHon10)X016_ .DOC.16/I /24110 - 11 The reflector of W009/34573 is a parabolic dish shaped reflector. However, this is not essential, and an alternative arrangement can use a parabolic trough reflector, an example of which is shown in Figures 3A and 3B. In this example a parabolic trough reflector 60 is supported by a support 62. One or more 5 arms 64, which are coupled to the trough reflector 60 via a mounting 66, are used to support an elongate PV cell(s) 68, which can be positioned substantially at the focal point of the trough reflector 60. This allows solar radiation to be focused onto the PV cell(s) 68, thereby allowing electricity to be generated. A cooling pipe 70 is provided in thermal communication with the PV cell(s) 68, typically by having the cooling pipe extend along a rear surface of the 0 PV cell(s) 68, allowing water to be used to cool the PV cell(s) 68. In this example, the cooling pipe 70 is connected to the conduits or ducts 24 allowing water to be circulated through the cooling pipe 70 and the Rankine cycle engine 14. This allows heat to be recovered from the PV cell(s) 68, with heated water being supplied to the Rankine cycle engine 14 allowing energy to be extracted and used for generating electricity. The cooled 5 water output from the Rankine cycle engine 14 is then returned to the cooling tube 70 to allow further cooling of the PV cell(s) 68 to be performed. Thus, it will be appreciated that this allows electricity to be generated both using the PV cell(s) 68 and the Rankine cycle engine 14. In one particular example, the support 62 is adjustable, thereby allowing the reflector 60 to be 20 directed towards the sun. In one example, a tracking system can be used to automatically control the positioning of the reflector 60, so that exposure of the PV cell(s) 68 to sunlight is maximised. With such tracking systems it is typical to align the trough in a North-South direction, with the tracking system being used to track the sun as it moves across the sky during the day. 25 However, as an alternative to this, in one example the trough is arranged aligned in an East West direction. This means that the sun will be incident on the trough throughout the day, with the trough positioning only needing to be adjusted periodically to account for seasonal variations in sun latitude. By avoiding the need to track movements of the sun on a daily basis, this allows adjustment to be performed on a weekly or monthly basis, thereby making 30 manual adjustment feasible. Whilst this will result in a slight decrease in exposure to sunlight C:\NRPobl\DCC\SEu DOC-V3/201 f 0in - 12 and hence the efficiency of the apparatus, it does vastly reduce the expense of the apparatus as compared to systems in which automated tracking is implemented. An alternative arrangement is shown in Figures 4A and 4B. In this example, the parabolic reflector trough 60 is replaced by a number of elongate reflector elements 82. The reflector 5 elements 82 are typically pivotally mounted to a frame 80 via axles 84, which allow the reflectors 82 to pivot with respect to the frame. However, any suitable mounting arrangement may be used, and in one example, a system similar to that used to support and link window louvres may be used. By suitable orientation of the reflector elements 82 this allows solar radiation to be focussed on to the PV cell(s) 68 in a manner substantially similar to that 0 described above with respect to the parabolic trough reflector. In this example, the straight cooling tube 70 is replaced with a U-shaped cooling tube 90. This allows the conduits 24 on one side of the apparatus, making connection of the conduits easier, as well as allowing additional heat to be recovered. It will be appreciated from this that the straight or U-shaped cooling tubes 70, 90 could be used interchangeably depending 5 on the preferred implementation. In the current example, a shield member 92 is positioned above the cooling tube 90 and PV cell(s) 68 to provide protection for example from hail or the like. Whilst protection is not afforded to the reflector elements 82 it will be appreciated that these can be rotated to protect the reflective surface, and can be manufactured as flat mirrors, and are therefore not 20 expensive to replace, unlike the PV cell(s) 68. Additionally, an inner surface of the shield 92 can also be reflective, to thereby further increase the radiation incident on the cooling tube 90, which in turn maximises heating of the water contained therein. In any event, it will be appreciated that the above described arrangements can be used for the co-generation of electricity and heated water, with the heated water being used to generate 25 further electrical power via the Rankine cycle engine 14. It will be appreciated that this can therefore operate to increase the efficiency of electricity generation still further. Whilst the above described examples use water as the working fluid, this is not essential, and alternatively a thermal oil or other heat transfer medium may be employed, largely depending on the degree of heating expected. Thus, whilst the description has focused on use of the C:NRPortblDCCSEH\33R036_I DOC-16/11/20 10 - 13 solar energy in heating water, allowing dual use as a water heater, this is not essential, and instead the solar system could be used to heat a thermal oil or other heat transfer medium depending on the expected operating temperatures. Thus, it will be appreciated that the solar reflector arrangements could be used with a thermal oil in the energy generating apparatus, 5 and are not restricted to implementation in a solar water heating system. Many modifications or variations will be apparent to those skilled in the art without departing from the scope of the present invention. All such variations and modifications should be considered to fall within the spirit and scope of the invention broadly appearing and described in more detail herein. 0 It is to be appreciated that reference to "one example" or "an example" of the invention is not made in an exclusive sense. Accordingly, one example may exemplify certain aspects of the invention, whilst other aspects are exemplified in a different example. These examples are intended to assist the skilled person in performing the invention and are not intended to limit the overall scope of the invention in any way unless the context clearly indicates otherwise. 5 Features that are common to the art are not explained in any detail as they are deemed to be easily understood by the skilled person. Similarly, throughout this specification, the term "comprising" and its grammatical equivalents shall be taken to have an inclusive meaning, unless the context of use clearly indicates otherwise.