WO2008064197A2

WO2008064197A2 - Systems and methods for producing power using positive displacement devices

Info

Publication number: WO2008064197A2
Application number: PCT/US2007/085181
Authority: WO
Inventors: Eric Ingersoll
Original assignee: Mechanology, Inc.
Priority date: 2006-11-20
Filing date: 2007-11-20
Publication date: 2008-05-29
Also published as: WO2008064197A3

Abstract

The present invention exploits the differences in heat capacities of working fluids to address the problem of low efficiency and low power density of energy cycles for the production of power. More specifically, the present invention relates to systems and methods of injecting a heat transfer fluid into a high pressure working fluid for the purpose of capturing and/or harnessing the energy of condensation resulting from constant volume heating and converting that energy into work to power other machines and systems.

Description

SYSTEMS AND METHODS FOR PRODUCING POWER USING POSITIVE

DISPLACEMENT DEVICES

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/860,163, filed on November 20, 2006. The entire teachings of the above application are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Heat engine design typically takes one of two approaches. In the first instance, the engine is designed such that the primary cycle captures a significant amount of energy from a fuel producing a high pressure ratio but low heat transfer. These engines typically have low efficiencies (-40% or less), less specific power and lower power density. In general, attempts at making these engines more efficient or more powerful has resulted in significant increases in size, cost and complexity of design. Alternatively, heat engines are designed such that the primary cycle operates at a lower pressure ratio and relies on a regeneration cycle to supplement and increase efficiency. The tradeoff for lost primary efficiency is the realization of increased energy return in the regeneration cycle with a higher heat transfer capacity. These engines may have an overall efficiency which exceeds 55%. The difficulties associated with obtaining significant work from a low temperature steam cycle are also well known. In the absence of condensation, most of the latent heat remains in the steam. Consequently, the amount of energy which can be produce work is small.

Information relevant to attempts to address energy conversion can be found in United States Patent numbers 4,085,591, 4,249,385, 4,387,576, and 6,202,419 issued to Bissell for example, which are incorporated herein by reference. However these references fail to address the issue of efficiency and power density in the disclosed process whereby air is added to a chamber containing steam. For example, the Bissell-type system operates by adding compressed air to a chamber of steam resulting in an increase in the temperature and pressure of the air. In order to continue raising the temperature and pressure in the chamber, the compressed source of air must continue to rise to achieve these higher values, hence more energy must be used for the additional compression and the added energy required soon overcomes the resultant work performed. Furthermore, while this system functions in a turbine system, it is not amenable to positive displacement devices.

For the foregoing reasons there is a need for a simple, efficient, adaptable, multi-configurable system for use with positive displacement devices for producing work.

SUMMARY OF THE INVENTION

The present invention exploits the differences in heat capacities of working fluids to address the problem of low efficiency and low power density of energy cycles for the production of power. More specifically, the present invention relates to systems and methods of injecting a heat transfer fluid into a high pressure working fluid for the purpose of capturing and/or harnessing the energy of condensation resulting from constant volume heating and converting that energy into work to power other machines and systems. The present invention is further directed to solving the problems of low power density and low efficiency that plague engine design.

To this end, condensation of a heat transfer fluid effectively releases the heat of vaporization into a working fluid. While condensation and heat transfer may not be complete, (as the condensate will inherently retain a certain amount of heat), the system and methods of the present invention still result in significant improvements in efficiency and power density of positive displacement devices.

ABBREVIATIONS

HTF, heat transfer fluid; WF, working fluid; T, temperature; P, pressure; V, volume; PDD, positive displacement device; TIVM, toroidal intersecting vane machine; TIVE, toroidal intersecting vane expander; TIVC, toroidal intersecting vane compressor; K, Kelvin; C, Celsius; kW, kilowatt; OVM, oscillating vane machine. BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 is a schematic representation of the system of the present invention showing Closed Working Fluid (CW) and Heat Transfer Fluid (HTF) Loops. FIG. 2 is a schematic representation of the system of the present invention showing an Open Heat Transfer Fluid (HTF) Loop.

FIG. 3 is a schematic representation of the system of the present invention showing an Open Working Fluid (CW) Loop.

DETAILED DESCRIPTION OF THE INVENTION A description of the embodiments of the invention follows.

The present invention is directed to solving the problem of low efficiency, low power density energy systems for use in generating power. For example, if a low pressure gas is used in an energy cycle, the power density is insufficient; and if a high pressure gas is used then the system moves away from optimal thermodynamic pressure ratios with low pressure ratios producing very little work.

By using a vapor as a heat transfer fluid for heating a working fluid at constant volume, a phase change in the heat transfer fluid can be exploited and the latent heat energy can be captured by the working fluid thereby producing work for any number of systems or machines. For example in one embodiment of the present invention, steam (the heat transfer fluid) is injected into air (the working fluid) within the working volume of a positive displacement device. The positive displacement device used in the present invention may be any positive displacement device. Because the working fluid (e.g., air) is colder and at a lower pressure than the heat transfer fluid (e.g., steam) injected, the ability of the working fluid to condense the heat transfer fluid converts a portion of the heat in the vapor into temperature rise in the working fluid. Expansion of the working mixture (heat transfer fluid and working fluid) back to a first pressure results in the production of work.

Positive Displacement Devices According to the present invention, a positive displacement device is used to achieve expansion of a working mixture. As used herein a "positive displacement device" (PDD) is one having an expanding cavity in fluid communication with an inlet port and a decreasing cavity in fluid communication with a discharge port. Positive displacement devices include, but are not limited to scrolls, screws, wankle type machines, pistons, toroidal intersecting vane machines (TIVM), and oscillating vane machines.

Within a positive displacement device is contained a working volume. The "working volume of a positive displacement device" is that volume or volumes within the positive displacement device containing a working fluid or working mixture which performs work. A "working volume" can also include a chamber which is in fluid communication with the working volume of the positive displacement device, is of substantially the same volume as the working volume of the working volume of the positive displacement device, and is capable of receiving or delivering a heat transfer fluid, working fluid or working mixture to the positive displacement device.

In one embodiment of the invention, the positive displacement device is a toroidal intersecting vane machine (TIVM). TIVMs are capable of efficiently pumping, compressing and/or expanding working fluids passed through them. Their function and design are explained in United States Patent No.: 6,901,904 incorporated herein by reference in its entirety. TIVMs and TIVM improvements are also described in Chomyszak, United States Patent 5,233,954, issued August 10, 1993 and Tomcyzk, United States Patent Application Publication 2003/0111040, published June 19, 2003 as well as improvements made thereto as described in United States Patent Application 11/507,065 filed August 16, 2006 which claims the benefit of U.S. Provisional Application No. 60/709,368 filed on August 18, 2005, each of which is incorporated herein by reference in its entirety. In one embodiment of the invention, the positive displacement device is an oscillating vane machine (OVM), including those of the type disclosed in USSN 60/846,543 filed September 22, 2006 and USSN 11/858,963 filed September 21, 2007 ("DragonFly" machines) which are incorporated herein by reference in their entirety.

In one embodiment the positive displacement device, such as a TIVM or OVM, or DragonFly, may be configured as a multistage expander. Here, a plurality of fluid injectors may be employed at one or more stages to control the adiabatic process and improve efficiency. One or more communicative detection and control units may also be systematically employed.

Use of a TIVM, OVM, or DragonFly, as the positive displacement device or expander also solves the recognized problem in the art related to size. When work is extracted from an expander, it is typically the case that producing more work requires a larger machine to accomplish greater expansion. The size of the machine, especially with turbine systems, must increase substantially. The TIVM and OVM, or DragonFly, positive displacement devices used in the present invention are significantly smaller than those in the art.

Fluids The present invention is directed to the production of work using a power cycle which exploits the thermodynamic properties of fluids. According to the present invention a "fluid" is any continuous, amorphous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; a liquid or gas or combination thereof, such as air, water or steam.

As used herein a "vapor" is the gaseous form of any substance or substances. Vapors can be saturated, unsaturated or superheated. "Steam" refers to the vapor phase of water.

As used herein the term "working fluid" can include one or more fluids hich can be compressed and is, preferably, not substantially consumed during the cycle or the production of work in the positive displacement device. Preferably, the working fluid is a vapor that does not condense or combust during the method and/or during the production of work in the positive displacement device. Examples include air, nitrogen, inert gases or other pure or mixed gases.

In one embodiment the working fluid may be caused to change phase (e.g., evaporate) through the delivery of heat through the walls of the positive displacement device. This could be a cryogenic fluid such as liquid nitrogen.

As used herein the term "heat transfer fluid" can include one or more fluids which have a high heat capacity, a rapid heat transfer capacity and/or a pressure which is greater than the pressure of the working fluid into which the heat transfer fluid is to be mixed or injected. As used herein, "heat capacity" is an amount of heat required to raise the temperature of a quantity of a substance.

A heat transfer fluid is considered to have a "high heat capacity" when the heat capacity of the heat transfer fluid is greater than that of the working fluid into which the heat transfer fluid is to be mixed or injected. Heat transfer fluids can be vapors, liquids or gases and preferably can readily undergo phase changes under the conditions of the method. For example, water is considered to have a high heat capacity relative to air. Because the ratio of latent heat to sensible heat in such phase change fluids can be great, they are particularly beneficial heat transfer fluids. For example, water may serve as a heat transfer fluid in either its vapor phase or as a mixture of liquid or vapor phases. Heat transfer fluids may also comprise combinations or mixtures of different species or substances or may contain multiple phases of the same or different substance. For example, a heat transfer fluid may comprise steam and ammonia.

The methods and systems of the present invention can be operated with the heat transfer fluid loop open or closed. When closed it may be advantageous to reject a portion of the heat from the working fluid to reduce its temperature so as to improve heat transfer from the expanded working fluid.

The methods and systems of the present invention can be run with a working fluid loop open or closed. Conducting the method at a high pressure can increase the power density of the power recovery device. This is because the working fluid can absorb more heat. Injection

According to the present invention a heat transfer fluid is injected into a working fluid. Injection of the heat transfer fluid may be effected by any number of ways. Injection may be effected by, but is not limited to, misting, spraying, atomizing, pulsing or flashing. Injection may be through a wall of a chamber of the positive displacement device, from underneath the chamber, into the chamber via a port or duct in positive displacement expander such as through a secondary vane in a toroidal intersecting vane expander with timing of the injection being accomplished via the moving vane. The present invention also contemplates mixing or combining the heat transfer fluid and the working fluid prior to addition into the working volume of the positive displacement device. A variety of ratios of HTF:WF can be adopted.

In general, heat is transferred from the HTF to the WF. In one embodiment, the heat transfer fluid is a condensable vapor and is injected into a gaseous working fluid. In another embodiment, the heat transfer fluid is a condensable vapor and is injected into a liquid working fluid, whereby the working fluid evaporates. Injection may also be done where the heat transfer fluid is a liquid and the working fluid undergoes a phase change to a vapor due to the heat contained in the heat transfer fluid. One method of injection contemplated by the present invention involves configuring a heat transfer fluid injector at the injection passage to the positive displacement device so as to regulate, atomize and spray a fine mist of heat transfer fluid into the working volume of the positive displacement device. The injector is preferably a pulse-width type injector wherein the frequency and duration of the pulses can control the amount of heat transfer fluid injected in a given period of time. The heat transfer fluid for the injector may be optionally pumped along a heat transfer fluid supply conduit. The heat transfer fluid may also be pumped via conduit to other equipment in the system.

According to the present invention, the heat transfer fluid may be flashed into the working volume of the positive displacement device. As used herein the term "flashing" or "vapor flashing" means the process of producing a vapor by discharging a fluid into a region of pressure lower than the saturation pressure that corresponds to the fluid temperature.

In flashing, the heat transfer fluid, either alone or in combination with another fluid, is maintained as a liquid until entry into the working volume. For example, water may be mixed with ammonia. This allows for addition of a greater amount of heat into the working volume and hence greater power output. Flashing is accomplished in one embodiment through the use of a regenerative heat exchanger acting to approximate a counterflow heat exchanger in order to exploit thermodynamic "glide." In one embodiment, multiple heat transfer fluid injections from different sources may be used to exploit the differing grades of heat (heat at different temperatures) within the system. For example, it is contemplated that a low temperature heat transfer fluid (e.g., with capacity to raise a working fluid to 27 atm) may be first injected into the working fluid to raise the pressure to 27 atmospheres followed by injection of a lesser amount of a high temperature heat transfer fluid (e.g., with capacity to raise a working fluid to 40 atmospheres), thereby raising the working fluid pressure to 40 atmospheres. This represents an efficient use of different grades of heat available in the system (e.g. waste heat) whereby a low cost heat (low temperature) is used first and a lesser amount of a high cost heat (high temperature) is used sparingly. This approach also allows addition of the higher cost heat at the higher temperature. It will be understood by those of skill in the art that heat additions in this fashion may be optimized to produce the desired result through selection of mixing proportions in light of the application.

The current invention also provides a solution and strategy for controlling unwanted elements within the working volume of the positive displacement device. In this embodiment, a secondary heat transfer fluid injection unit is used. Often times the compression or expansion of working fluids introduces undesirable elements into the system such as NOx or SOx compounds or some particulate matters, for example. Appropriate secondary heat transfer fluids can be injected into the positive displacement device that will not only improve thermodynamic efficiencies but also capture and collect these undesirable elements. Closed loop configuration

A significant advantage and solution presented by a preferred embodiment of the present invention lies in maintaining the fluids in a high pressure closed loop configuration. A closed loop cycle means that a working fluid of high pressure can be used and the system can operate in the absence of compression. This advantageously increases the power density of the preferred embodiment.

One problem with low pressure ratio cycles is that they are limited by the amount of heat which can be added to the working fluid. With a low pressure ratio, the working fluid has a low density and hence any machine operating on such a cycle has a low power density. If the density of the working fluid can be increased, it can accept more heat which increases pressure ratio and power density. This problem is solved by the present invention by exploiting a cycle which may have a low pressure ratio but incorporating a regenerative heat exchanger to improve overall efficiency coupled with a high pressure closed loop to overcome the low power density.

The closed loop system operates with a working fluid at a predetermined pressure (high density) and heat is used to increase produce power. This heat is derived directly from the heat transfer process.

A closed loop system is not typically exploited in combustion type scenarios as combustion depletes the available working fluid (oxygen in the air) during the fuel burning process. The canonical example is a car engine, which must compress air at the beginning of the cycle and continually receive replenishment of the working fluid.

While it is possible to achieve high power densities in closed loop turbines, these systems suffer from, among other disadvantages, that condensation of steam in a turbine because the condensate (water) has extreme detrimental effects on the turbine components.

In the closed loop cycle of the present invention, the system is charged with a predetermined working fluid at a predetermined temperature and pressure as the system is assembled. Absent any leakage the system need not be disturbed to receive additional working fluid. However it will be understood that it may be prudent for the configuration to contain valves or ports which allow replenishment of the working fluid or exchange of the working fluid with a different working fluid. An advantage of the instant invention is the improvement of the power density of any system operating on this cycle. By simply altering the operating pressure of the closed loop the power density can be improved, thereby improving both the efficiency of the system and resulting in lower cost.

Heat addition

In one embodiment of the present invention, the working fluid is heated at substantially constant volume and the increase in temperature causes an increase in pressure which enables a cycle without compression.

In one embodiment, heat addition and removal of waste heat occurs at the highest possible temperature (e.g.., at the top of the cycle). The waste heat, advantageously, can be recycled back to the heat source. While condensation of the prior art systems occurs at low temperature, here the condensing can occur at the front of the cycle resulting in a significant portion of the heat being transferred.

It is understood that the most effective type of heat addition to a system is isothermal heat addition. Therefore, in an effort to approximate isothermal or quasi- isothermal expansion, the heat transfer fluid may be injected during the entire process of expansion (approximating true isothermal expansion; with the temperature at beginning being equal to the temperature at end of cycle). To this end, the rate of initial injection may differ from the rate of additional heat injection in order to continually raise the temperature of the system to the temperature of maximum heating. The present invention, when undergoing heat transfer fluid addition (heat addition) during expansion can be combined with a regenerative heat exchanger functioning to provide heat to make more steam or heat transfer fluid. This can be arranged in a counter flow arrangement resulting in effective transfer of the sensible heat from the expanded working mixture to the working fluid — cool air and hot steam. Heat exchange and regeneration

In another embodiment, there is a regenerative heat exchanger to recover heat from the expanded working mixture. Because the latent heat in the heat transfer vapor has been transformed into sensible heat in the working fluid, it can be easily transferred out of the working fluid by means of a heat exchanging process. This process is accomplished via a heat exchanger or regenerative heat exchanger.

The fluids of the invention (e.g., heat transfer fluid or working fluid or working mixture) may be directed to a heat exchanger after expansion. Here, thermal energy is efficiently scavenged from the expansion process and further utilized in the system or rejected. Rejection may simply involve venting to the atmosphere. Regeneration of heat greatly improves the efficiency and use of the positive displacement device in industrial applications requiring compression.

In one embodiment the heat is transferred to, or is part of, the process of generating the vapor. In this manner some or substantially all of the heat remaining in the expanded working fluid can be recaptured to reduce to heat addition required to power the cycle. The cycle can also supply heat to another process or machine.

Applications and technologies

The present invention has applications in many industries and technologies including, but not limited to all areas involving the generation of power, transportation, automotives, aeronautics, maritime and desalination.

For use in transportation, and in particular passenger vehicles, the present system and methods may be used in cars, trucks, buses, boats, ships, tractors, trains, planes, UAVs, airships, munitions vehicles, or any other type of vehicle. The systems and methods of the present invention also find utility in applications such as generators, engines, turbines etc., as well as in machine using an internal combustion engine (gasoline or diesel) and generator to produce AC or DC electricity. These applications may be combined with other generators or power generator methods including with those that act to or facilitate cooling, heating. They may also be staged such that heating may occur prior to cogeneration, generation may occur first followed by cogeneration and all may occur with varying ratios of heating/cooling/power outputs. Staging may occur in one or more stages with heating and cooling being involved.

Use of the instant invention affords operation at comparable efficiencies of typical systems (power plants) in the art but at significantly lower temperatures. Use of the present invention in power plants which usually operate at supercritical temperatures of working fluids, would allow comparable efficiency at temperatures at least 200 degrees lower. For example, 600K is a moderate steam temperature, while 900K is a very high steam temperature. Typical cycled power plants operate at approximately 870K. Referring now to the drawings wherein the showings are for purposes of illustrating preferred and alternate embodiments of the invention only and not for purposes of limiting same. While the system of the present invention is one which exploits and harnesses heat transfer, it will be appreciated that the overall inventive concept involved could be adapted for use in many other machine or system environments and in any technology where generation of power is critical. Reference is now made to the figures. Figure 1 shows a schematic representation of the system of the present invention showing Closed Working Fluid (CW) and Heat Transfer Fluid (HTF) Loops.

In this embodiment, the working volume of the positive displacement device 10 (PDD) is charged with a working fluid (WF) along the line 11 at a first pressure (P_I-_WF) ^and temperature (T_1-WF) or WF Loop 12, which may be at the same first pressure and temperature. A heat or a heat transfer fluid (HTF) is supplied in a separate line 21 and loop 22. Heat is added to the HTF using a heat source such as a boiler 23 configured to add heat to the HTF and to receive preheated HTF along from a heat exchanger 30, using an optional pump 25. The boiler 23 may be fueled by any source of energy, conventional (e.g., combustible fuels, etc.) or non- conventional (e.g., solar, wind, geothermal, etc.).

On injection of a heat transfer fluid (HTF) at a second pressure (P_1-HTF), which is higher than the pressure of the working fluid, heat in the HTF is transferred to the working fluid and the temperature and the pressure within the working volume of the positive displacement device (PDD) 10 rises. If the heat transfer occurs at constant volume, constant volume heating occurs. It is known that constant volume heating is more efficient than constant pressure heating.

Within the working volume of the PDD 10, the mixture of HTF and WF is then expanded to a third pressure (P₂-_WF-_HTF)- The third pressure may be substantially equivalent to the first pressure. In this embodiment, no compression of the WF is required during the cycle, eliminating the drain of energy needed by conventional systems to supply the energy for the compression.

Depending on the selection of HTF, the HTF may condense in the expansion process. The WF/HTF mixture or working mixture is then ported to a heat exchanger 30 (e.g. a regenerative heat exchanger) where the fluids are regenerated. Use of a heat exchanger reduces the amount of heat addition required to sustain the system.

During regeneration of the fluids, pumps may be used. According to the present invention, pumps may be used within the loops, such as pump 25 and/or 26, or as external devices to supply or move fluids.

Surplus heat of the system (typically referred to as waste heat) may also be recycled or rejected. Heat rejection device(s) 18 may be incorporated into the WF loop 12 from the heat exchanger. Heat rejection may be used to cool the WF in the WF loop. A heat rejection device 28 can be used within the HTF Loop 22 as well. Rejected heat from the heat exchanger may be used as a heat source to supply additional heat to the HTF in the HTF loop 22.

Figure 2 is a schematic representation of the system of the present invention showing an Open Heat Transfer Fluid (HTF) Loop. Here, the heat transfer fluid is being shown as supplied via line 27, the remaining elements having been described above with respect to Figure 1.

Open systems, as the name implies, are those that are open to external systems such as the atmosphere. Here, the HTF loop is open. While this embodiment operates on the same principle as that described for the embodiment of Figure 1, the HTF loop is configured to allow external supply of HTF and does not recycle or redirect any rejected heat from the heat exchanger to the HTF supply.

Figure 3 is a schematic representation of the system of the present invention showing an Open Working Fluid (WF) Loop. In this embodiment, the WF loop is open to an external system (the atmosphere). Here, the WF is supplied from an external source via line 22 and is not recycled.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A method of producing work comprising: (a) providing a working fluid at a first pressure and a heat transfer fluid at a second pressure which is greater than the first pressure; (b) injecting the heat transfer fluid into the working fluid thereby creating a working mixture at a higher pressure than the first pressure and optionally condensing the heat transfer fluid; and (c) reducing the pressure of the working mixture within a working volume of a positive displacement device to a third pressure, thereby producing work.

2. The method of claim 1 wherein the third pressure is equal to the first pressure.

3. The method of claim 2 wherein the working fluid is contained within a closed loop preferably at higher than atmospheric pressure.

4. The method of claim 3 further comprising the step of separating the working fluid and heat transfer fluid after step (c).

5. The method of claim 4 wherein a heat exchanger is used to transfer the heat remaining in the working fluid mixture to preheat heat transfer fluid.

6. The method of claim 5 wherein the separation of the fluids occurs in a heat exchanger.

7. The method of claim 6 wherein the heat exchanger is a counterflow heat exchanger.

8. The method of claim 6 wherein the working fluid is cooled via expansion and/or the heat transfer fluid is heated by compression.

9. The method of claim 8 further comprising the step of further heating the heat transfer fluid with a boiler.

10. The method of claim 9 further comprising a generator operably connected to the positive displacement device.

11. The method of claim 7 further wherein additional heat transfer fluid or fluids are added during expansion of the working fluid mixture.

12. The method of claim 11 wherein said additional HTFs are at lower temperature(s) than the first HTF.

13. The method of claim 11 wherein the lower pressure HTFs are injected before the higher pressure HTFs.

14. The method of Claim 3 wherein during step (c), an additional amount of heat transfer fluid is injected into the working volume of the positive displacement device.

15. The method of Claim 12 wherein the rate of injection of the additional amount of heat transfer fluid is the same or different.

16. The method of Claim 12 wherein the additional amount of heat transfer fluid is added in a rate and amount to approximate an isothermal expansion.

17. The method of claim 3 wherein the step (c) is conducted after the injection step (b) is substantially complete.

18. The method of claim 3 wherein step (b) is conducted in a chamber separate from the positive displacement device.

19. The method of claim 3 wherein step (b) is conducted within the working volume of the positive displacement device.

20. The method of claim 1 wherein the heat transfer fluid is provided in liquid phase and is converted to a vapor phase and subsequently condenses to release its latent heat of vaporization to the working fluid.

21. The method of claim 3 wherein the heat transfer fluid is provided by combining two heat transfer fluids that are characterized by two different temperatures and/or pressures.

22. A system for producing work comprising:

(a) a working fluid source for providing a working fluid;

(b) a heat transfer fluid source for providing a heat transfer fluid; (c) a heat transfer fluid injection unit;

(d) a positive displacement device configured to receive a working fluid from (a) and a heat transfer fluid from (b) and to manage a condensation step;

(e) a heat exchanger configured to receive the working fluid and heat transfer fluid or optionally a working mixture thereof from said positive displacement device; and to separate said working fluid and said heat transfer fluid;

(f) a detection unit for detecting the mass flow rate, temperature, density or humidity of the working fluid;

(g) a controlling unit for controlling a quantity of the heat transfer fluid to be injected from the fluid injection unit on the basis of a signal from the detection unit;

(h) an optional fueled boiler configured to receive and heat said heat transfer fluid; and

(i) a generator configured to receive work from said positive displacement device.

23. The system of claim 22 wherein the working fluid source is utilized on initial configuration of the system thereby, in the absence of leakage, requiring no further addition of working fluid.

24. The system of claim 22 wherein the positive displacement device is selected from the group consisting of scrolls, screws, wankle type machines, all types of pistons, star rotor (Jirnov), quasiturbines, toroidal intersecting vane machines (TIVM), and oscillating vane machines.

25. The system of claim 24 wherein the positive displacement device is a toroidal intersecting vane machine.

26. The system according to claim 25, wherein the toroidal intersecting vane machine is configured as a multistage expander.

27. The system of claim 24 wherein the positive displacement device is an oscillating vane machine.

28. The system of claim 27 wherein the oscillating vane machine is an oscillating vane machine.

29. The system of claim 22 wherein the heat transfer fluid receives heat from a heat source.

30. The system of claim 29 wherein said heat source is supplied with energy from a member selected from the group consisting of combustion, solar thermal energy, geothermal energy, nuclear energy, and a product of a bottoming cycle.

31. The system of claim 30 where geothermal energy is derived from hot dry rock or wet steam.

32. The system of claim 30 where bottoming cycle product is generated by an internal combustion engine or combustion turbine.

33. The system of claim 30 wherein nuclear energy is generated by fusion or fission.

34. The system of claim 30 wherein combustion is effected using a boiler or heat recovery steam generator.

35. The system of claim 22 wherein the fuel used to power the boiler is selected from the group consisting of gas, liquid, solid, and combinations thereof.

36. The system of claim 35 wherein the fuel is a gas and is selected from synthetic gas or natural gas.

37. The system of claim 35 wherein the fuel is a liquid and is selected from the group consisting of hydrocarbons, alcohols, ammonia and combinations thereof.

38. The system of claim 35 wherein the fuel is a solid and is selected from the group consisting of coal, biomass, waste products or combinations thereof.

39. The system of claim 35 wherein the fuel is biomass and is selected from the group consisting of wood, straw, agricultural wastes, corn stover and combinations thereof.

40. The system of claim 23 which operates in 2-cycles or 4-cycles.

41. The system of claim 23 operating as a closed cycle.

42. The system of claim 41 wherein the closed cycle is a regenerated injected closed loop power cycle whereby some or all of the heat added to the HTF is from preheating by the expanded working fluid before entering the working volume of the positive displacement device.

43. The system of claim 22 wherein the working fluid is selected from the group consisting of air, a gas, and combinations thereof.

44. The system of claim 22 wherein the heat transfer fluid is selected from the group consisting of organics, ammonia, water, a refrigerant, and combinations thereof.

45. The system of claim 22 wherein the working fluid and the heat transfer fluid comprise the same compound or substance.

46. The system of claim 45 wherein the compound or substance is water or an isotope thereof.

47. The system of claim 22 further comprising a secondary fluid injection unit, constructed such that a secondary heat transfer fluid is injected into a fluid injection passage to decrease the temperature of the working fluid.

48. The system of claim 22 wherein the fluid injector unit operates at high pressure creating a spray of heat transfer fluid.

49. The system according to claim 22 whereby the fluid injection unit is further utilized to control non-desirable elements within the working fluid.