Abstract:
The present invention is a prime mover with recovered energy driven compression for stationary and motor vehicle application. Efficient low compression operation, especially beneficial to small gas turbines, is enabled with either ambient or cryogenic intake air. Recovered energy, liquefied air cooling and re-liquefaction of air by a cryogenic sink minimize motive fluid compression work of a jet compressor driving exhaust gas recirculation. Regenerative heat exchanger terminal temperature difference relative to turbine temperature drop and heat exchanger surface area are reduced.

Description:
CLAIM OF PRIORITY 
       [0001]    This application is a continuation in part and claims the benefit of priority of co-pending U.S. patent application Ser. No. 13/374,861, filed on Jan. 20, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the use of recovered energy to provide minimal compression work in low compression motor vehicle and stationary engines, and in particular to systems for exhaust gas recirculation by a jet compressor driven by motive fluid, which may be compressed by recovered energy, cooled by liquefied air and re-liquefied by a cryogenic sink to minimize motive compression work. 
       BACKGROUND 
       [0003]    A high efficiency prime mover with renewable energy storage has long been a goal of motor vehicle and stationary engine design to provide energy independence, conserve fossil fuels, and reduce emission of combustion products. While the expansion engine of the present invention is applicable to both reciprocating and rotary engines, it is especially beneficial to the gas turbine. The gas turbine offers several advantages over other engines including simplicity, reliability, low maintenance, low emissions, low weight, and ability to burn most any fuel or to run on recovered heat. It has the potential to provide a universal prime mover. It is inefficient in the motor vehicle and stationary distributed electric generation size range, however, especially with respect to variable speed operation. This is because of two factors: First, it has rotor stress limitations imposed by the pressure-speed relationship. The rotor speed is directly proportional to working fluid flow rate and compression ratio, and indirectly proportional to rotor diameter. Second, it has a high heat exchanger terminal temperature difference relative to turbine temperature drop. Both of these factors begin to adversely affect cycle efficiency at a pressure ratio less than about 3. As a result, turn-down is inefficient, exhaust temperature and rotor stresses are high with rotational speeds exceeding 100,000 rpm, and a large expensive heat exchanger is needed. 
         [0004]    Previous efforts to adapt a gas turbine to motor vehicle use, notably the Chrysler turbine have been unsuccessful. Present efforts to employ micro-turbines for distributed electric generation are proving successful, but with marginal cost advantage. In general, problems with smaller gas turbine applications are attributable to high compression work with low density ambient intake air and exhaust gas heat recovery with large and complex regenerative heat exchangers. Several cryogenic compression engines have been built and tested to reduce compression work by, in effect, transferring compression to production and storage of liquefied air or nitrogen for compression cooling. Liquefaction work is by renewable energy or other low cost means such as off-peak electricity, therefore not chargeable to cycle efficiency. Both Brayton and Rankine cycles, either fired or with fuel-less ambient heating have been tried. 
         [0005]    Consumption of the liquefied coolant has proved to be excessive, however, and high efficiency liquefaction is still sought after. A highly effective regenerative heat exchanger is also sought after. Most gas turbines have a heat exchanger for recovering exhaust heat to improve cycle efficiency. Large surface area and enhanced heat transfer features are combined to attain high effectiveness. Fixed area recuperators constructed of numerous tubes, brazed or welded in complex header arrangements and with enhanced heat transfer are difficult to manufacture and expensive. Another kind of heat exchanger, the rotary regenerator, attains higher effectiveness than recuperators by providing passage of the atmospheric and pressurized flow streams, alternately over the same heat transfer matrix. Seals to minimize leakage between the streams are difficult to maintain and application is limited to low compression systems. 
         [0006]    Accordingly, objects of the prime mover of the present invention are to provide: 
         [0007]    high cycle efficiency in a low compression prime mover of a transport vehicle drawing ambient atmospheric working fluid, while utilizing recovery of vehicle braking energy and other recoverable energy to reduce compression work of the prime mover; 
         [0008]    high cycle efficiency throughout the speed range of a low compression prime mover of a transport vehicle, utilizing recovery of vehicle braking energy and other recoverable energy to drive the engine compressor with injected liquefied air and optionally driving a cryogenic sink for absorbing heat from and re-liquefying the working fluid to reduce compression work of the prime mover; 
         [0009]    high cycle efficiency of a low compression prime mover for distributed electric generation, drawing ambient atmospheric working fluid, while utilizing recovery of wind, solar and other recoverable energy to reduce compression work of the prime mover; 
         [0010]    high cycle efficiency of a low compression prime mover for distributed electric generation utilizing recovery of wind, solar and other recoverable energy to drive the engine compressor with injected liquefied air and optionally driving a cryogenic sink for absorbing heat from and re-liquefying the working fluid to reduce compression work of the prime mover; 
         [0011]    minimal heat transfer surface area of the regenerative heat exchanger of the prime mover of the present invention; 
         [0012]    minimal liquefied working fluid consumption of the prime mover of the present invention; and 
         [0013]    a selection of working fluid and heat sink cryo-coolant combinations for the prime mover of the present invention. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention is a gas turbine and a vehicle including the gas turbine of the present invention. The inventor&#39;s co-pending U.S. patent application Ser. No. 13/374,861 is hereby incorporated by reference. 
         [0015]    The gas turbine of the present invention involves the flow, compression, expansion, heating, and cooling of a working fluid. In its most basic form, the gas turbine of the present invention includes a turbine-generator that operates through a flow of working fluid and produces electricity from the operation; an air heater that heats working fluid and provides it to the turbine-generator; a recuperator with a recuperator atmospheric side and a recuperator pressurized side, wherein working fluid flows from the turbine-generator into the recuperator atmospheric side where heat is absorbed from the working fluid before it is vented to atmosphere and working fluid in the recuperator pressurized side absorbs heat from the recuperator atmospheric side and provides it to the air heater; and working fluid compression means for compressing and cooling the working fluid and supplying the compressed working fluid to the air heater. 
         [0016]    Preferred embodiments also include a motor-compressor. 
         [0017]    In some embodiments, the gas turbine also includes a chiller. In this embodiment, the working fluid compression means are a cryogenic cooling system, which may include a cryogenic sink to re-liquefy evaporated liquid air, a bypass valve, a liquid air dewar, and a liquid air valve. The cryogenic sink includes a cryogenic storage dewar and a slush compressor. In this embodiment of the working fluid compression means, the compressed working fluid is not supplied directly to the air heater or heat source, which may be a combustor, but travels first through the motor-compressor, the chiller, and the recuperator. 
         [0018]    In some embodiments, the working fluid compression means are a jet compressor that supplies the compressed working fluid directly to the air heater. 
         [0019]    In some embodiments including a jet compressor, the gas turbine also includes a condenser, a motive pump, and an evaporator. 
         [0020]    In some embodiments including a jet compressor, the gas turbine also includes a rotary regenerator. 
         [0021]    In some embodiments including a jet compressor, the gas turbine also includes a separator. 
         [0022]    In some embodiments, the working fluid compression means are both the cryogenic cooling system and the jet compressor. 
         [0023]    In its most basic form, the vehicle of the present invention includes a battery that powers the vehicle; wheels connected by axles; a braking generator that converts energy from the vehicle&#39;s braking into electricity; and a gas turbine of the present invention. The vehicle preferably also includes an inverter that enables the braking generator to act as an AC motor to directly power the vehicle and as a DC generator to charge the batter. It is preferable that the battery is charged by the turbine generator of the gas turbine when the vehicle is operating but not braking, and by the braking generator when the vehicle is operating and braking. 
         [0024]    The prime mover and associated energy recovery systems of the present invention have application in a capacity range of approximately 20 kWe to 150 kWe in which speed of an expansion engine such as a gas turbine is reduced by operation in a compression ratio range of approximately 1.1 to 2.5. Problems and deficiencies of the prior art described above are improved by the present invention. A feature of the prime mover in accordance with the present invention lies in providing a jet compressor to circulate exhaust gas for increasing thermodynamic cycle efficiency in low compression operation while reducing the size and complexity of a regenerative heat exchanger. Another feature of the prime mover in accordance with the present invention lies in providing recovered energy available to a transport vehicle or a distributed electric generator to drive an ambient primary air compressor to offset motive compression work of a jet compressor. Another feature of the prime mover in accordance with the present invention lies in providing recovered energy available to a transport vehicle or a distributed electric generator to reduce motive compression work of a jet compressor by liquefying the motive fluid. Another feature of the prime mover in accordance with the present invention lies in providing a cryogenic sink with a slush compressor driven by recovered energy to provide suction pressure for solidifying a melt cryo-coolant during liquefaction of the working fluid. Another feature of the prime mover in accordance with the present invention lies in providing two parallel working fluid flow paths, a lower pressure primary working fluid path and a motive fluid path to minimize consumption of the liquefied working fluid. Another feature of the prime mover in accordance with the present invention lies in maintaining the melt cryo-coolant of a cryogenic sink between a subliming solid-vapor and a liquid state. Another feature of the prime mover in accordance with the present invention lies in providing on-stream liquefaction of boiled-off working fluid by circulation through the cryogenic sink. Another feature of the prime mover in accordance with the present invention lies in providing partial make-up of the melt cryo-coolant of a cryogenic sink by reliquefaction of vented cryo-coolant in a liquefier powered by recovered energy. Another feature of the prime mover in accordance with the present invention lies in providing make-up of the melt cryo-coolant of a cryogenic sink by dewar exchange. Another feature of the prime mover in accordance with the present invention lies in providing a selection of working fluid and melt cryo-coolant combinations for economizing coolant consumption. 
         [0025]    Accordingly, the principal object of the present invention is to provide a prime mover with high cycle efficiency and economic consumption of heat sink coolant and liquefied working fluid in vehicle and stationary application. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
         [0026]    These aspects of the present invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, accompanying drawings, and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a schematic illustrating a preferred embodiment of a gas turbine engine of the present invention with a recovered energy driven compressor with liquefied air injection for compression cooling of the working fluid. 
           [0028]      FIG. 2A  is a schematic illustrating a transport vehicle powered by a jet compression gas turbine engines of the present invention with recovered energy driven compression. 
           [0029]      FIG. 2B  is a schematic illustrating a preferred embodiment of a jet compression gas turbine engine of the present invention with recovered energy driven compression of ambient atmospheric air. 
           [0030]      FIG. 3  is a schematic illustrating an alternate preferred embodiment of a jet compression gas turbine engine of the present invention with a recovered energy driven cryogenic sink for re-liquefying evaporated liquid air. 
           [0031]      FIGS. 4A and 4B  illustrate an alternate preferred embodiment of the gas turbine of the present invention with energy recovery from a motor vehicle. 
           [0032]      FIGS. 5A and 5B  illustrate an alternate preferred embodiment of the gas turbine jet compressor of the present invention with a liquid motive fluid. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Referring first to  FIG. 1 , a schematic illustrating a preferred embodiment of a gas turbine  100  of the present invention is provided. Gas turbine  100  circulates a working fluid and creates energy through the various heating, cooling, and compression of the working fluid. The working fluid is preferably air, but may also be nitrogen, nitric oxide, argon, or neon. Gas turbine  100  includes at least turbine-generator  102 , air heater  104 , recuperator  106 , and working fluid compression means  500 . Working fluid compression means  500  are means for compressing and cooling the working fluid and supplying the compressed working fluid to air heater  104 . Several embodiments of working fluid compression means  500  are identified herein. In some embodiments of working fluid compression means  500 , the means supply the compressed working fluid to air heater  104  directly. In other embodiments of working fluid compression means  500 , there are intermediary gas turbine features through which the working fluid travels before reaching air heater  104 . 
         [0034]    Preferred embodiments of gas turbine  100 , such as that shown in  FIG. 1 , also include chiller  118  and motor-compressor  120 . In  FIG. 1 , working fluid compression means  500  is cryogenic cooling system  114  and jet compressor  148 . Cryogenic cooling system  114  includes liquid air dewar  126 , liquid air valve  128 , and coolant  134 , which is preferably liquid air. In this embodiment of working fluid compression means  500 , the working fluid compressed by cryogenic cooling system  114  does not flow directly into air heater  104 , but flows first through chiller  118 , recuperator  106 , and jet compressor  148 . Cryogenic cooling system  114  includes liquid air dewar  126 . Liquefied working fluid air for start-up and boil-off replacement is imported to liquid air dewar  126 . Liquid air valve  128  is disposed between liquid air dewar  126  and motor-compressor  120  and controls a flow of liquid air  134  from liquid air dewar  126  to motor-compressor  120 . As discussed below, a portion of combustion working fluid from chiller atmospheric side  119  is drawn into motor-compressor  120 . This combustion working fluid combines with liquid air from liquid air dewar  126  that has travelled through the open liquid air valve  128 . 
         [0035]    Turbine-generator  102  is fired from air heater  104 , which is fueled by fuel  103 . Air heater  104  may be any type of heater commonly used in the art, such as a combustor. Air heater  104  is not fueled by fuel  103  in all embodiments of the present invention. Together with recuperator  106 , turbine-generator  102  provides electrical power to electrical controller  108  for distribution. Recuperator  106  is an energy recovery heat exchanger that removes heat from the exhaust working fluid. Recuperator  106  has recuperator atmospheric side  105  and recuperator pressurized side  107 . Working fluid expelled from turbine-generator  102  flows into recuperator atmospheric side  105 . The products of combustion  110  of the working fluid in the air heater  104  continue through recuperator atmospheric side  105  and exhaust to atmosphere. Heat from the exhaust working fluid is absorbed by recuperator pressurized side  107 . 
         [0036]    Chiller  118  has chiller atmospheric side  119  and chiller pressurized side  117 . Atmospheric intake combustion air  116  is drawn into chiller atmospheric side  119  is drawn into motor-compressor  120 . Liquid air is mixed into the atmospheric intake air at the motor-compressor intake. The working fluid is compressed by motor-compressor  120  and flows back into chiller pressurized side  117 . This compression cools the working fluid and heat generated from the compression is absorbed by the liquid air. Within the chiller working fluid side  117 , the working fluid is further cooled when its heat is absorbed by cryogenic intake combustion air  116  in chiller atmospheric side  119 . Cold, compressed working fluid then flows into recuperator pressurized side  107 . The working fluid in recuperator pressurized side  107  absorbs heat from the heat absorbed by recuperator atmospheric side  105  and begins to expand. The working fluid then flows into jet compressor  148  and then air heater  104  where it is further heated. The resulting expansion of the working fluid operates turbine-generator  102 . Working fluid from turbine-generator  102  also flows into jet compressor  148  through valve  156 . 
         [0037]    Gas turbine  100  may also include an electric generator that provides electricity to storage battery  132 . This electric generator may be a vehicle&#39;s braking generator  244 , as shown in  FIG. 2A , or one or more photovoltaic panels. 
         [0038]    An open cycle fired system is selected to illustrate design point performance of an 8 kW (10.7 HP) gasoline fired turbine-generator for vehicle or stationary application. Cycle efficiency is 54% at 50,000 rpm with the turbine compression ratio of 1.5; turbine inlet gas temperature of 825° C. (1515° F.); air compressor inlet temperature of −172° C. (−280° F.); and recuperator effectiveness of 95%. Under these conditions fuel consumption is 33 km/L 1.2 kg/hr (2.7 lb/hr); liquefied air consumption is 44 kg/hr (97 lb/hr); and excess air ratio is 24. For comparison, a typical reciprocating engine in the same application has a cycle efficiency of 18% at 5,000 rpm and compression ratio of 10, and efficiency of a typical micro-turbine is 28% at 96,000 rpm with a compression ratio of 3.6. 
         [0039]    A small [e.g., 28 kWe (21 HP) peak] recuperated gas turbine, which can be modified to incorporate cryogenic features of the present invention, is available from the Capstone Corporation of Chatsworth, Calif. Cryogenic components including chiller, compressor, and dewar are available from Chart Industries of Garfield Heights, Ohio, Barber-Nichols of Arvada, Colo. and Technifab Products of Brazil, Ind., respectively. 
         [0040]    Now referring to  FIG. 2A , a side elevation view illustrating a preferred embodiment of a transport vehicle  240  of the present invention is provided. Vehicle  240  operates by propulsion provided to two motorized wheels  242  an 8 kWe (10.8 HP) jet compression gas turbine  200 , which are discussed in detail below with reference to  FIG. 2B . An electrical controller  208  distributes recovered energy from a storage battery  232 . Storage battery  232  is charged by a braking generator  244  for pressurization of the gas turbines  200 . A regenerative braking system, which can be adapted to the vehicle of the present invention, is available from the Ford Motor Company of Dearborn, Mich. 
         [0041]    Now referring to  FIG. 2B , a schematic illustrating a preferred embodiment of a gas turbine  200  of the present invention is provided. Regardless of reference number, features with the same name are substantially the same feature throughout the FIGS. In addition, similar features that include reference numbers in some but not all FIGS., should be considered to be substantially similar features. Turbine-generator  202  is fired from a fueled air heater  204 . Combined with a recuperator  206 , turbine-generator  202  provides electrical power to an electrical controller  208  for distribution. The working fluid of gas turbine  200  consists of a motive combustion air portion  246  that drives a jet compressor  248 , a circulated exhaust portion  250  that is entrained into the motive air, and an emission portion  210  that continues to atmosphere through recuperator  206 . A motor-compressor  252  provides combustion air through recuperator  206  to a motive nozzle  254  which entrains and circulates exhaust working fluid by suction of high velocity motive fluid from compressor  252  through a sonic nozzle, under control of an exhaust valve  256 , for delivery through a discharge nozzle  258  to air heater  204 . In the gas turbine  200  shown in  FIG. 2B , working fluid compression means  500  is jet compressor  248 . In this embodiment of working fluid compression means  500 , the compressed working fluid flows directly from jet compressor  248  to air heater  204 . 
         [0042]    An open cycle fired system is selected to illustrate performance of a gasoline fired gas turbine as prime mover in a compact car operating at an 80 km/hr (50 mph) design point requiring 8 kW (10.7 HP). Compression work, normally provided by turbine-generator output, is supplemented by 33% recovered vehicle braking energy. Cycle efficiency is 44% at 50,000 rpm with motive compression ratio of 5; turbine inlet gas temperature of 825° C. (1515° F.); air compressor inlet temperature of 20° C. (68° F.); and recuperator effectiveness of 95%. Under these conditions fuel economy is 33 km/L (78 mpg) and excess air ratio is 22. High excess air ratio associated with the low turbine pressure ratio obviates the effect of combustion products in the recirculating suction flow. For comparison, a typical reciprocating engine in the same application has a cycle efficiency of 18% at 5,000 rpm and compression ratio of 10, and efficiency of a typical micro-turbine is 28% at 96,000 rpm with a compression ratio of 3.6. 
         [0043]    Now referring to  FIG. 3 , a schematic illustrating an alternate preferred embodiment  300  of gas turbine  200  is provided. This gas turbine  300  may also be used with vehicle  240 , shown in  FIG. 2A . Like the gas turbine  100  shown in  FIG. 1 , working fluid compression means  500  include both jet compressor  348  and cryogenic cooling system  314 . In this embodiment, however, cryogenic cooling system  314  includes bypass valve  322 , cryogenic sink  312 , liquid air dewar  326 , and liquid air valve  328 . Bypass valve  322  is disposed below chiller atmospheric side  118 . When bypass valve  322  is closed, all working fluid feeds into motor-compressor  320 , as described above. When bypass valve  322  is open, some or all of the working fluid flows into cryogenic storage dewar  324 . 
         [0044]    Cryogenic sink  312  includes cryogenic storage dewar  324  and slush compressor  330 . Cryogenic sink  312  provides liquefaction of the portion of cryogenic intake combustion air  316  drawn in through chiller atmospheric side  318  that comes through bypass valve  322 . Cryogenic storage dewar  324  includes dewar working fluid side  323  and shell side  325 . As described below, coolant  334  flows through shell side  325  so that working fluid flowing through dewar working fluid side  323  is cooled. In this embodiment, coolant  334  is preferably liquid nitrogen, but may liquid air or other commonly used coolants. Slush compressor  330  circulates the coolant  334 , preferably nitrogen slush, through shell side  325 . The portion of working fluid that flowed through bypass valve  322  enters dewar working fluid side  323 . Condensed, frozen nitrogen  334  therefore enters cryogenic sink  312  and alternately melts in shell side  325  due to heat of absorption from the working fluid flowing through dewar working fluid side  323 , and solidifies due to suction pressure of slush compressor  330 . Nitrogen vapor is vented through vent  327  out of shell side  325 . It is preferred that slush compressor  330  is powered by storage battery  332 . 
         [0045]    The working fluid is cooled to cryogenic temperature by a cryogenic sink  312  of a cryogenic cooling system  314 . The sink  312  is powered by recovered braking energy of vehicle  240 . A turbine-generator  302  fired from air heater  304  fueled by fuel  303  with a recuperator  306  provides electrical power to an electrical controller  308  for distribution. The working fluid of gas turbine  300  consists of a combustion air portion  316  following two parallel flow paths, a circulated exhaust portion  350  that is entrained into the motive air, and an emission portion  310  that continues to atmosphere through recuperator  306 . The first combustion air path provides primary air from a cryogenic motor-compressor  320 , drawing air through the atmospheric side of a chiller  318  and discharging to air heater  304  via recuperator  306 . The second path provides motive air, which is drawn through chiller  318  and a bypass valve  322  for liquefaction and storage in a liquid air dewar  326 . The liquid is discharged, as required, back through chiller  318  to recuperator  306  and jet compressor  348 . A motive nozzle  354  entrains the circulated exhaust into the motive air, under control of an exhaust valve  356 , for delivery through a discharge nozzle  358  to air heater  304 . 
         [0046]    In sink  312 , a slush compressor  330  powered by a battery  332 , circulates a two phase melt cryo-coolant  334  through the shell side of cryogenic storage dewar  324  wherein entering cryo-coolant alternately melts due to heat absorption and solidifies due to suction pressure of compressor  330 . Condensed melt cryo-coolant is imported into the shell side of dewar  324  and liquefied air is imported into liquefied air dewar  326  for boil-off replacement. As described above with reference to other embodiments, gas turbine  300  also includes vent  325  of dewar  324 , liquefied fluid air intake  336 , and liquid air valve  328 . 
         [0047]    An open cycle fired system is selected to illustrate performance of a gasoline fired gas turbine as prime mover in a compact car operating at an 80 km/hr (50 mph) design point requiring 8 kW (10.7 HP). Compression work for combustion air is provided by turbine-generator output and cryo-coolant compression work is provided by recovered vehicle braking energy, which is limited to 33% of turbine-generator shaft power. Cycle efficiency is 70% at 46,000 rpm with primary air compression ratio of 1.4; motive compression ratio of 20; turbine inlet gas temperature of 825° C. ( 1515 ° F.); air compressor inlet temperature of −172° C. (−280° F.); and recuperator effectiveness of 95%. Under these conditions, fuel economy is 60 km/L (140 mpg); liquefied air consumption is 40 kg/hr (88 lb/hr); and excess air ratio is 27. High excess air ratio associated with the low turbine pressure ratio obviates the effect of combustion products in the recirculating suction flow. For comparison, a typical reciprocating engine in the same application has a cycle efficiency of 18% at 5,000 rpm and compression ratio of 10, and efficiency of a typical micro-turbine is 28% at 96,000 rpm with a compression ratio of 3.6. 
         [0048]    The sink is filled with solidified nitrogen coolant and maintained at below the boiling point of −196° C. (−325° F.). Reduction of vapor pressure from 0.7 to 0.1 atmospheres by the slush compressor provides circulation of the melting and solidifying nitrogen. Recovered vehicle braking energy to the slush compressor is 2.4 kW (3.2 HP), equal to 30% of turbine-generator shaft power, while the cryogenic storage dewar provides required working fluid reliquefaction of 35 kg/hr (76 lb/hr). A continuous and sufficient supply of liquefied air is maintained as recovered energy charges the battery to drive the slush compressor. A high temperature jet compressor suitable for exhaust gas recirculation in the present invention is available from the Fox Company of Dover, N.J. Other components to enable features of the present invention are available as discussed with reference to  FIG. 1 , above. 
         [0049]    Now referring to  FIG. 4A , a schematic diagram of a chassis  650  of a motor vehicle is provided. The vehicle has typically four wheels  652 , a rear axle  654 , a front trans-axle  656 , and gas turbine  600  of the present invention as prime mover. A battery  658  is charged by a turbine-generator  618  of gas turbine  600  when the vehicle is under power and by a motor-generator  660  during regenerative braking, as required. An inverter  663  enables the motor-generator  660  to act as an AC motor to power the vehicle, and as a DC generator to charge the battery  658 . 
         [0050]    Now referring to  FIG. 4B , a schematic illustrating a preferred embodiment of gas turbine  600  based on a Brayton thermodynamic cycle is provided. A motor-compressor  624  powered by battery  658  provides motive pressure of atmospheric air via a motive air valve  662  to a jet compressor  614  for re-circulating a portion of turbine exhaust gas to an air heater  616  while remaining exhaust gas enters a rotary regenerator  634 . Rotary regenerator  634  includes a rotating wheel with metallic heat absorbing elements and transfers exhaust heat to pre-heat motive air. A working-fluid bypass valve  664  opens for turbine-generator operation above a selected speed. In this embodiment, working fluid compression means  500  are jet compressor  614 . 
         [0051]    During operation of the gas turbine of  FIGS. 4A and 4B , the compressor requires electrical input of about 50% of turbine output at an average cruising speed of 80 km/hr (50 mph). Regenerative braking at this speed is estimated to provide 65% of required compressor power with the remaining 35% from a charged battery. During infrequent driving situations when regenerative braking is insufficient, there are several supplementary compressor power options, such as those disclosed in U.S. Pat. No. 7,854,278. These include vehicle draft resistance and rolling resistance, estimated to provide 15% and 10% of turbine output, respectively. At higher speeds, recoverable vehicle draft resistance increases exponentially with respect to rolling resistance. At cruising speed, estimated gasoline mileage is 64 km/L (150 mpg) for a vehicle with a curb weight of 1600 kg (3500 lb) and drag coefficient times frontal area of 0.64 m 2  (7 ft 2 ). At this speed, the estimated driving range with a 136 kg (300 lb) lithium-ion battery is 485 km (300 mi). For comparison, an electric vehicle requires about (2000 lb) of lithium-ion batteries. 
         [0052]    Now referring to  FIG. 5A , a schematic diagram illustrating an alternate preferred embodiment of a gas turbine  700  based on a Rankine thermodynamic cycle is provided. A pump  724  provides motive pressure of motive fluid via a motive fluid valve  762  to a jet compressor  714  for circulation of the working fluid. Motive fluid from pump  724  is pre-heated by radiation from solar panel  768  in a solar heated evaporator  769  and further heated by exhaust working fluid in recuperator  706 , before recombining with suction fluid in jet compressor  714 . The exhaust working fluid is then liquefied in a water-cooled condenser  770  and returned to the inlet of pump  724 . Air heater  716  is a heater in this embodiment. As with all embodiments, gas turbine  700  also includes turbine-generator  718 . 
         [0053]    Now referring to  FIG. 5B , a schematic diagram illustrating an alternate embodiment of the gas turbine of  FIG. 5A  is provided. In this embodiment, the working fluid consists of separate motive fluid and suction fluid components to reduce the motive fluid flow requirement. A separator  766  receives turbine exhaust working fluid and discharges the motive fluid portion to a recuperator  706  for heat recovery to pressurized motive fluid while the working fluid portion is circulated via suction of jet compressor  714  to a heater  716 . A gas turbine (micro-turbine) suitable for conversion to independent electric powered compression is available from Capstone Turbine Corp. of Chatsworth, Calif. A vacuum tube solar heater suitable for evaporating motive fluid is available from Apricus North America of Los Angeles, Calif. In the embodiments shown in  FIGS. 5A and 5B , working fluid compression means  500  are jet compressor  714 . 
         [0054]    Operating performance of the gas turbine of  FIG. 5A , with water/steam as motive and suction components of the working fluid, is exemplified by output of 30 kWh during 8 hours of overcast atmospheric conditions. Turbine conditions are 3.7 kW (5.0 HP) at 100,000 rpm, inlet gas temperature 850 C (1560 F), and 5 recuperator effectiveness 90%. High pressure of the liquid motive fluid requires a recuperator rather than rotary regenerator, which would be pressure limited due to leakage. The ratio of suction to motive mass flow may be increased by adjustment of motive fluid temperature and molecular weight relative to the suction fluid. This ratio is proportional to the square root of motive fluid temperature to suction fluid temperature, and of the square root of suction fluid molecular weight to motive fluid molecular weight. Performance results for the configuration shown in  FIG. 5A  are: solar panel area=28 m 2  (300 ft 2 ); pressure ratio=1.3; ratio of suction fluid to motive fluid=5; thermal efficiency=13%; and fuel efficiency (not including solar)=65%. In the configuration shown in  FIG. 6B , a change of suction fluid to helium improves performance results as follows: solar panel area=12 m 2  (125 ft 2 ); pressure ratio=1.1; ratio of suction fluid to motive fluid=4; thermal efficiency=25%; and fuel efficiency (not including solar)=70%. 
         [0055]    Accordingly, it is shown that the recovered energy driven compression engine of this invention improves cycle thermal efficiency in both motor vehicle and stationary applications. In particular, it overcomes problems of the gas turbine in small low pressure applications. 
         [0056]    Although the description above contains many specific details, these should not be construed as limiting the scope of the invention but as merely providing illustration of some of the preferred embodiments of this invention. For example, turbines, either radial or axial types having either electrical or mechanical output, can be connected in series to lower expansion ratio and speed, or connected in parallel to increase power. In addition, the motive compressor, motive pump, primary compressor, and liquefier may be powered by recovered energy of vehicle braking or draft loss, as well as by solar radiation and wind. The heating source may be solar radiation as well as combustion in either open or closed working fluid systems. The cryogenic sink may absorb compression heat from within the compressor and from the compressor outlet, as well as absorbing heat from the working fluid at the compressor inlet. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. 
         [0057]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the description should not be limited to the description of the preferred versions contained herein.