Abstract:
An apparatus and method for converting a differential in thermal energy between a first thermal source having a thermal conducting fluid and a second thermal source having a thermal conducting fluid is provided. The apparatus employs a first vessel and a second vessel. Each of the vessels contain a gas under pressure The vessels contain heat exchanging coils that are connected to the thermal sources by fluid lines. A plurality of cooperating valves regulate the flow of the thermal conducting fluid from the first and second thermal sources to the first and second vessels. The valves alternate between first and second operating positions. In the first position, the valves permit a flow of thermal conducting fluid from the first thermal source to the first vessel and from the second thermal source to the second vessel and prevent a flow of thermal conducting fluid from the first thermal source to the second vessel and from the second thermal source to the first vessel. In the second position, the valves permit a flow of thermal conducting fluid from the first thermal source to the second vessel and from the second thermal source to the first vessel and prevent a flow of thermal energy from the first thermal source to the first vessel and from the second thermal source to the second vessel. A pressure driven actuator in fluid communication with the first and second vessels is driven into reciprocating motion between a first position and a second position by alternating positive pressure and negative pressure from the first and second vessels.

Description:
FIELD OF THE INVENTION 
     The invention relates to devices and methods for converting thermal energy into kinetic energy especially for the production and/or storage of electrical energy. 
     BACKGROUND OF THE INVENTION 
     Given society&#39;s ever increasing energy consumption, there is a resultant high demand for energy. Since the earth&#39;s natural energy reserves are becoming depleted and prices of oil and natural gas are relatively high, there is a demand for new sources of energy. 
     There have been attempts to convert existing forms of energy into forms of energy that can be used to satisfy our energy needs. Many of these processes harness energy sources that are replenished by natural processes. These energy sources are referred to as renewable energy sources. An example is solar energy where energy from the sun in the form of heat energy and light energy is converted into electrical energy. However, sunlight is a weak energy source compared to traditional energy sources such as fossil fuels. It is very difficult to harness sunlight efficiently for conversion into useful forms of energy. It is particularly difficult to use sunlight effectively for home energy needs. Energy requirements are usually highest when it is dark and cold. This is precisely when solar energy is least effective. Solar energy becomes much more useful when we change it to another form. Sunlight can be converted to electricity by photovoltaic cells. However, this conversion is inefficient and high in cost. Also, some types of photovoltaic solar cells contain mercury that is highly toxic. 
     Other renewable energy sources have the drawback of being environmentally unfriendly. For example, wind power plants can damage local animal populations. Also, hydroelectric dams can cause problems such as the creation of large reservoirs. This can upset the ecological balance of the surrounding environment. This has the consequences of disrupting local animal populations and their migration patterns. Dams also affect fish populations. 
     It would therefore be desirable to be able to harness existing forms of energy in an effective and environmentally friendly manner. It has been recognized that it would be desirable to convert naturally occurring heat sources into useable forms of energy. There have been a number of attempts to convert low-level heat sources into mechanical energy. These methods employ the principle of expansion and contraction of a working fluid, utilizing a heat source to add and remove heat from the working fluid. These methods have the drawback of failing to obtain a sufficient concentration of heat to activate the process in an efficient manner. Such methods to date have failed to produce an economically viable energy generation process. 
     U.S. Pat. No. 4,134,265 provides an example of such a prior art process. This patent discloses a method for developing gas pressure to drive an engine. The method involves the use of a plurality of separate containers in a closed circuit. The tanks communicate with heat exchangers that are arranged in combination with certain controls to create pressure variations on a given volume of gas by varying the gas temperatures. The tanks are used in pairs with the gas in one tank being cooled while the other gas in the other tank is heated to develop a pressure differential therebetween. Controlled communication between the tanks produces flow to one of the tanks with an increase in mass of gas therein and followed by a second development of gas differential pressure. The gas is released for communication with a piston to produce a work stroke. 
     U.S. Pat. No. 3,995,429 provides another example of a prior art process that fails to produce an economically viable energy generation system. The patent discloses a system of generating electric power derived from the energy of the sun, the atmosphere, the ground or the heat stored in ground water, whichever provides the greatest temperature differential with another adjacent source of energy. The apparatus generates a fluid vapour pressure for the operation of a vapour engine and includes at least three heat sources. One of the sources is a solar absorber for absorbing the heat from the sun. A second source is a heat exchanger which dissipates the heat of the fluid to the atmosphere. A third source is a radiator positioned in the ground water. A fourth source for transforming ground or geothermal heat to the fluid also for transferring the heat of the ground water to the fluid is provided. Other well-known heat sources may be substituted where available. Valve connecting means are operated to connect any two of the four heat sources in a closed cycle system for the transfer of heat from one source to another. Pumping means are provided for forcing fluid through the system to a source where the fluid is vaporized. A transducer such as a turbine or piston engine connected to the heat source vaporizes the fluid that produces the mechanical power. 
     There have been attempts to harness naturally occurring temperature gradients. An example is Ocean Thermal Energy Conversion. A significant amount of financial resources have been invested in pilot plants to harness the surface heat of the world&#39;s oceans by making use of temperature gradients between the warm surface and cold depths. This has not yielded an economically viable method for energy production. 
     There is therefore a need for an apparatus and method for converting thermal energy into mechanical and electrical energy in an environmentally friendly efficient, and economically viable manner. There is a need for such an apparatus and method that can utilize a very low temperature differential to produce energy efficiently. 
     SUMMARY OF THE INVENTION 
     The invention provides a method of extracting a differential in thermal energy between a first thermal source and a second thermal source and converting this energy into mechanical energy that can be used to generate electrical energy for energy storage or direct use or to feed into a power grid. The thermal sources are put in fluid communication with two vessels containing a gas under pressure. The thermal sources have thermal values that are different than the thermal values of the vessels. The thermal sources are used to alternately increase the temperature and pressure in one of the vessels and decrease the temperature and pressure in the other vessel. A pressure driven actuator is moved in a single direction by the resultant pressure released by the first vessel and suction from the second vessel. 
     According to another aspect of the invention, there is provided an apparatus for extracting a differential in thermal energy between a first thermal source and a second thermal source and converting this energy into mechanical energy is provided. The apparatus has first and second vessels that include a gas under pressure. The thermal sources are in fluid communication with the two vessels. The thermal sources have thermal values that are different than the thermal values of the vessels. The thermal sources are adapted to alternately increase the temperature and pressure in one of the vessels while decreasing the temperature and pressure in the other vessel. A pressure driven actuator coupled to the vessels and is moved in a single direction by pressure released by the first vessel and suction from the second vessel. The pressure driven actuator may be coupled to a piston and cylinder assembly or a rotary actuator in order to transfer mechanical energy thereto. 
     An apparatus for converting a differential in thermal energy between a first thermal source having a thermal conducting fluid and a second thermal source having a thermal conducting fluid, the apparatus comprising:
         a first vessel for containing a gas under pressure, the first vessel being in fluid communication with said first and second thermal sources;   a second vessel for containing a gas under pressure, the second vessel being in fluid communication with said first and second thermal sources;   a plurality of cooperating valves for alternately regulating a flow of thermal conducting fluid from the first and second thermal sources to the first and second vessels, the plurality of cooperating valves alternating between first and second operating positions, the plurality of cooperating valves permitting a flow of thermal conducting fluid from the first thermal source to the first vessel and from the second thermal source to the second vessel in first operating position, the plurality of cooperating valves preventing a flow of thermal conducting fluid from the first thermal source to the second vessel and from the second thermal source to the first vessel in the first operating position, the plurality of cooperating valves permitting a flow of thermal conducting fluid from the first thermal source to the second vessel and from the second thermal source to the first vessel in the second operating position, the plurality of cooperating valves preventing a flow of thermal conducting fluid from the first thermal source to the first vessel and from the second thermal source to the second vessel in the second operating position;   a pressure driven actuator in fluid communication with the first and second vessels whereby the actuator is driven into reciprocating motion between a first position and a second position by alternating positive pressure and negative pressure from the first and second vessels wherein positive pressure from the first vessel coupled with negative pressure from the second vessel when the plurality of cooperating valves is in the first operating position drives the actuator to the first position and negative pressure from the first vessel coupled with positive pressure form the second vessel when the plurality of cooperating valves is in the second operating position drives the actuator to the second position.       

     According to another aspect of the present invention there is provided a method for converting a differential in thermal energy to kinetic energy comprising the following steps:
         providing first and second vessels containing a gas under pressure, the gas under pressure being of a temperature T;   providing a first thermal source and a second thermal source, the first thermal source housing a thermal transfer fluid of a temperature above T and the second thermal source housing a thermal transfer fluid of a temperature below T.   delivering the thermal transfer fluid from the first thermal source to the first vessel thereby raising the pressure of the gas in the first vessel;   delivering the thermal transfer fluid from the second thermal source to the second vessel thereby lowering the pressure of the gas in the second vessel;   delivering gas under pressure from the first vessel to a pressure activated actuator and applying suction from the second vessel to the pressure activated actuator thereby causing the pressure activated actuator to move in a first direction.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In drawings which illustrate by way of example only a preferred embodiment of the invention, 
         FIG. 1  is a schematic illustration of a preferred embodiment of the present invention; 
         FIG. 2  is a longitudinal cross-sectional view taken along lines  2 - 2  of  FIG. 1  of a first vessel of the present invention; 
         FIG. 3  is a longitudinal cross-sectional view taken along lines  3 - 3  of  FIG. 1  of a second vessel of the present invention; 
         FIG. 4  is a front view of a first thermal source of the present invention; 
         FIG. 5  is a front view of a second thermal source of the present invention; 
         FIG. 6  is a front view with portions cut away showing a pneumatic cylinder of the present invention; 
         FIG. 7  is a schematic illustration of a first side of reversing transmission of the present invention; 
         FIG. 8  is a schematic illustration of a second side of a reversing transmission of the present invention; and 
         FIG. 9  is a schematic illustration of an alternate embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an apparatus for converting a differential in thermal energy between two thermal sources into mechanical energy that can be used for a wide range of applications known to a person skilled in the art including the generation and storage of electrical energy. The invention also relates to a method of converting a differential in thermal energy between two thermal sources into mechanical energy. The method can be carried out with the apparatus of the present invention. 
     A preferred embodiment of the present is shown in  FIG. 1 . Apparatus  1  includes a first vessel  2  and a second vessel  4 . Each of the two vessels is preferably a sealed container that defines a chamber therein for containing a gas under pressure. As shown in  FIGS. 2 and 3 , the first vessel  2  defines a chamber  3  and the second vessel  4  defines a chamber  5 . The vessels contain the gas under pressure in the chambers. The vessels are shown in lateral cross section in  FIG. 1  and in longitudinal cross-section in  FIGS. 2 and 3 . Each of the vessels preferably has an insulating jacket  72  for preventing thermal exchange with the ambient environment. 
     The first vessel  2  has heat exchange conduit  10  located in the chamber  3 . The conduit  10  is preferably coiled copper tubing that is adapted to conduct a fluid. Other conduits known in the art to have favourable heat exchanging properties may also be employed in alternate embodiments. The conduit  10  has a first end  30  that communicates with the exterior of the vessel  2  through an opening  31  defined by the vessel  2 . The conduit  10  has a second end  32  that communicates with the exterior of the vessel  2  through an opening  33  defined by the vessel  2 . Similarly, the second vessel  4  has heat exchange conduit  12  located in the chamber  5 . The conduit  12  is also preferably coiled copper tubing that is adapted to conduct a fluid. Again, other conduits known in the art to have favourable heat exchanging properties may also be employed in alternate embodiments. The conduit  12  has a first end  34  that communicates with the exterior of the vessel  4  through an opening  35  defined by the vessel  4 . The conduit  12  has a second end  36  that communicates with the exterior of the vessel  4  through an opening  37  defined by the vessel  12 . Vessel  2  has a pressure sensor  102 . Vessel  4  has a pressure sensor  104 . 
     The apparatus  1  further includes a first thermal unit  6  and a second thermal unit  8 . The thermal units are shown in  FIGS. 1 ,  4  and  5 . Each of the thermal units is preferably a container that can receive a thermal delivery fluid. Preferably, the container is an insulated container that is of metal, plastic or fibreglass construction. Preferably, each of the thermal units defines a channel running therethrough for passage of the thermal conducting fluid. The thermal delivery fluid is preferably an environmentally suitable fluid of the type required in ground source closed loop heat pumps. However, other fluids with good thermal conductivity properties known in the art may also be used in other embodiments. 
     The thermal units  6 ,  8  preferably have a heat exchanger that is in thermal communication with the thermal fluid in order to transfer the temperature of the thermal unit to the thermal fluid. The thermal source can be any medium that is capable of storing or transferring thermal energy. Examples of acceptable thermal sources for the purposes of the present invention include ambient outside air, outside soil, water heated by energy produced by natural gas combustion, wood combustion, solar energy or energy provided by a thermal heat pump. The first thermal unit preferably has a plurality of thermal sources  77 , 78 , 79  while the second thermal unit thermal unit preferably has a plurality of thermal sources  82 , 83 , 84 . As shown in  FIG. 4 , the thermal source  77  can be outside air with a heat exchanger coil in direct contact with the air. The thermal source  78  in such a case could be a hot water tank heated by natural gas, wood combustion, solar energy or a geothermal heat pump. In this case, there would be two heat exchangers in the tank. 
     A first heat exchanger would transfer heat to the thermal fluid and a second heat exchanger would be connected to the heat source. Thermal source  79  could be direct contact heat exchanger embedded in soil or a body of water. As shown in  FIG. 5 , thermal source  82  can be outside air with a heat exchanger coil in direct contact with the ambient air. The thermal source  83  could be a cool water tank cooled by a geothermal heat pump operating in reverse by extracting heat from the thermal fluid, The thermal source  84  could be a direct contact heat exchanger thermal source embedded in soil or a body of water. 
     Preferably, the first thermal unit  6  uses thermal sources that provide a warm thermal source while the second thermal unit  8  preferably uses thermal sources that provide a cold thermal source. In other embodiments, it is possible that the thermal unit  8  contains the warm thermal sources while thermal unit  6  contains the cold thermal sources. A controller  70  controls from which of the compartments thermal conducting fluid will be dispensed. 
     A thermal fluid conducting conduit  42  communicates between the thermal source  6  and the first vessel  2 . The conduit  42  further communicates between thermal unit  6  and the second vessel  4 . A fork  43  in the conduit  42  separates the conduit into a first branch leading to the first vessel  2  and a second branch leading to the second vessel  4 . The conduit  42  is received by in-pipe  86  that leads into the first end  30  of the thermal exchange conduit  10 . The conduit  42  is also received by in-pipe  94  that leads into the first end  34  of the heat exchange conduit  12 . A thermal fluid-conducting conduit  44  communicates between the thermal source  8  and the second vessel  4 . The conduit  44  further communicates between thermal unit  8  and the first vessel  2 . A fork  45  in the conduit  44  separates the conduit into a first branch leading to the first vessel  2  and a second branch leading to the second vessel  4 . The conduit  44  is received by in-pipe  96  that leads into the first end  34  of the heat exchange conduit  12 . The conduit  44  is also received by in-pipe  88  that leads into the first end  30  of the heat exchange conduit  10 . 
     A thermal fluid-conducting conduit  38  communicates between the first vessel  2  and the thermal source  8 . The conduit  38  further communicates between the second vessel  4  and the thermal source  8 . A fork  39  in the conduit  38  separates the conduit into a branch leading from the first vessel  2  and another branch leading from the second vessel  4 . The conduit  38  is received by out-pipe  92  that leads from the second end  32  of the heat exchange conduit  10 . The conduit  38  is also received by out-pipe  100  that leads from the second end  36  of the heat exchange conduit  12 . A thermal fluid-conducting conduit  40  communicates between the first vessel  2  and the thermal source  6 . The conduit  40  further communicates between the second vessel  4  and the thermal source  6 . A fork  41  in the conduit  40  separates the conduit into a branch leading from the first vessel  2  and another branch leading from the second vessel  4 . The conduit  40  is received by out-pipe  90  that leads from the second end  32  of the heat exchange conduit  10 . The conduit  40  is also received by out-pipe  98  that leads from the second end  36  of the heat exchange conduit  12 . 
     The thermal fluid conducting conduits are preferably made of insulated synthetic polymer or metal tubing which meets the standards of local building codes. 
     A first valve  14  controls the flow of fluid from the thermal unit  6  to the conduit  10 . A second valve  26  controls the flow of fluid from the thermal unit  6  to the conduit  12 . A third valve  22  controls the flow of fluid from the thermal unit  8  to the conduit  10 . A fourth valve  18  controls the flow of fluid from the thermal unit  8  to the conduit  12 . A fifth valve  16  controls the flow of fluid from the conduit  10  to the thermal unit  6 . A sixth valve  24  controls the flow of fluid from the conduit  10  to the thermal unit  8 . A seventh valve  28  controls the flow of fluid from the conduit  12  to the thermal unit  6 . An eighth valve  20  controls the flow of fluid from the conduit  12  to the thermal unit  8 . Preferably the valves are solenoid valves although other valves known in the art may also be employed. Controller  70  is operatively connected to the valves for opening and closing the valves as required to carry out the method of the present invention. The eight valves described herein together with the controller comprise a plurality of cooperating valves for alternately regulating a flow of thermal energy from the first and second thermal sources to the first and second vessels. 
     Preferably, pump  46  and pump  48  pump the thermal fluid through the thermal fluid conducting conduits. The pumps  46 ,  48  are preferably circulating pumps of the type used in solar or geothermal applications. 
     Vessel  2  further defines an opening  53 . A pressure conduit  54  is received in the opening  53  and communicates between the chamber  3  and the exterior of the vessel  2  for delivering gas from the chamber  3  to the exterior and vice versa. Similarly vessel  4  further defines an opening  55 . A pressure conduit  56  communicates between the chamber  5  and the exterior of the vessel  4  for delivering gas from the chamber to the exterior and vice versa. 
     As shown in  FIG. 6 , each of the pressure conduits  54 , 56  preferably communicates with pneumatic cylinder  58  and pneumatic cylinder  60 . The pneumatic cylinder  58  has a piston  74  moveably received therein while the pneumatic cylinder  60  has a piston  76  moveably disposed therein. The pneumatic cylinder  58  defines a first chamber  106  and a second chamber  108 . Similarly, the pneumatic cylinder  60  defines a first chamber  110  and a second chamber  112 . The piston  74  has a piston rod  73  while the piston  76  has a piston rod  75 . Both piston rods are attached to a connecting member  80  as shown in  FIG. 5 . A valve  50  is located in the pressure conduit  54  between the vessel  2  and the pneumatic cylinders for regulating gas flow. Similarly, valve  52  is located in the pressure conduit  56  between the vessel  4  and the pneumatic cylinders for regulating gas flow. 
     Connecting member  80  is preferably coupled to a reversing transmission known in the art. The reversing transmission can be coupled to a generator according to methods well known in the art. 
     An example of a basic reversing transmission is shown in  FIGS. 7 and 8 . These Figures show opposite sides of a flywheel  64  coupled to sprockets  116  and  126  respectively. The transmission includes sprocket pulleys  118  and  128 . Transmission chains  120  and  130  are attached to the sprockets  116  and  146  and to the pulleys  118  and  128  respectively. The flywheel  64  is coupled to drive pulley  122  of a generator  124  by way of drive belt  126 . 
     An alternate embodiment of the invention is shown in  FIG. 9 . Vessel  2  is connected to the pressure conduit  54 . Pressure conduit  54  feeds into pressure conduits  130  and  132 . Valve  50  is located between conduit  54  and the conduits  130  and  132 . Similarly, vessel  4  is connected to the pressure conduit  56 . Pressure conduit  56  feeds into pressure conduits  134  and  136 . Valve  52  is located between conduit  56  and the conduits  134  and  136 . Valve  138  is located at a junction between conduit  130  and conduit  134 . Similarly, valve  140  is located at a junction between conduit  132  and conduit  136 . Conduit  130  and conduit  134  join to form conduit  152  that preferably leads to the ports of a double rack rotary actuator. Similarly, conduit  132  and conduit  136  join to form conduit  150  that preferably leads to the ports of the double rack rotary actuator. 
     In its operation, the apparatus reciprocates between a first operating position and a second operating position thereby driving the pressure-activated actuator into reciprocal motion. This reciprocal motion can be translated into various forms of energy. For example, when the pressure-activated actuator is a pneumatic cylinder the motion can be converted into mechanical or kinetic energy that can in turn be converted into electric potential energy by way of coupling the pneumatic cylinder to a generator. 
     The controller  70  controls the opening and closing of the valves of the plurality of cooperating valves. To begin the cycle whereby the apparatus moves to the first operating position, the controller opens valve  14  and closes valve  26  so that warm thermal fluid from the thermal unit  6  flows through thermal fluid conduit  42  to in-pipe  86  and into the heat exchange conduit  10  of the vessel  2 . As the warm thermal fluid flows through the conduit  10  in the chamber  3 , heat is transferred from the conduit to the surrounding gas in the chamber  3 . This causes the pressure of the gas to increase. An acceptable pressure range for the purposes of the invention of the gases is approximately 10 p.s.i to 500 p.s.i. The controller opens valve  16  and closes valve  24  so that the thermal fluid can flow through the out-pipe  90  through the thermal fluid conduit  42  and back to the thermal unit  6  where the thermal fluid is re-heated. 
     In addition to opening valve  14  and closing valve  26 , the controller simultaneously opens valve  18  and closes valve  22  so that cool thermal fluid from the thermal unit  8  flows through thermal fluid conduit  44  to in-pipe  96  and into the heat exchange conduit  12  of the vessel  4 . As the cool thermal fluid flows through the conduit  12  in the chamber  5 , heat is transferred from the surrounding gas in the chamber  5  to the conduit. This causes the pressure of the gas to decrease. The controller opens valve  20  and closes valve  28  so that the thermal fluid can flow through the out-pipe  100 . The thermal fluid flows through thermal fluid conduit  38  and back to the thermal unit  8  where the thermal fluid is re-cooled. 
     When maximum thermal transfer has occurred, in the two vessels after about three seconds, the controller  70  will open the pressure valve  50 . The increased pressure in the vessel  2  will cause the gas from the chamber  3  to flow through the pressure conduit  54  and into the first chamber  106  of the pneumatic cylinder  58  and the first chamber  110  of the pneumatic cylinder  60 . At the same time, the controller opens the pressure valve  52 . The decreased pressure in the vessel  4  will cause the gas from the second chamber  112  of the pneumatic cylinder  60  and the second chamber  108  of the pneumatic cylinder  58  to flow through the pressure conduit  56  and into the chamber  5  of the vessel  4 . 
     In both cases, the gas flow will be in the same direction thereby causing the pistons  74 ,  76  to move in the same direction. The movement of the pistons causes the piston rods and the connecting member  80  to move in the same lateral direction. The movement of the connecting member  80  causes the transmission chain  120  to move. The transmission chain  120  in turn drives the sprocket  116  and the flywheel  64 . Energy from the turning of the flywheel can be transferred to the generator  124 . 
     When the pistons  74 ,  76  have reached their maximum travel, a sensor at the front of the cylinder  58  will cause the valves  50 ,  52  to close. The pressure conduits have large enough diameters so as not to restrict the flow to and from the vessels  2 , 4  which would reduce efficiency. For example, in an embodiment that has a diameter of 1.5 inches for cylinders  58 ,  60 , the pressure conduits would preferably have a minimum diameter of about 0.75 inch. 
     The cycle whereby the apparatus moves to the second operating position is the direct reverse of the cycle whereby the apparatus moves to the first operating position. To begin the cycle whereby the apparatus moves to the second operating position, the controller opens valve  26  and closes valve  14  is so that warm thermal fluid from the thermal unit  6  flows through thermal fluid conduit  42  to in-pipe  94  and into the heat exchange conduit  12  of the vessel  4 . As the warm thermal fluid flows through the conduit  12  in the chamber  5 , heat is transferred from the conduit to the surrounding gas in the chamber  5 . This causes the pressure of the gas to increase. The controller opens valve  28  and closes valve  20  so that the thermal fluid can flow through the out-pipe  98 . The thermal fluid flows through thermal fluid conduit  40  and back to the thermal unit  6  where the thermal fluid is re-heated. 
     In addition to opening valve  26  and closing valve  14 , the controller simultaneously opens valve  22  and closes valve  18  so that that cool thermal fluid from the thermal unit  8  flows through thermal fluid conduit  44  to in-pipe  88  and into the heat exchange conduit  10  of the vessel  2 . As the cool thermal fluid flows through the conduit  10  in the chamber  3 , heat is transferred from the surrounding gas in the chamber  3  to the conduit  10 . This causes the pressure of the gas to decrease. The controller opens valve  24  and closes valve  16  so that the thermal fluid can flow through the out-pipe  92 . The thermal fluid flows through thermal fluid conduit  38  and back to the thermal unit  8  where the thermal fluid is re-cooled. 
     When maximum thermal transfer has occurred, in the two vessels after about three seconds, the controller  70  will open the pressure valve  52 . The increased pressure in the vessel  4  will cause the gas from the chamber  5  to flow through the pressure conduit  56  and into the second chamber  112  of the pneumatic cylinder  60  and the second chamber  108  of the pneumatic cylinder  58 . At the same time, the controller opens the pressure valve  50 . The decreased pressure in the vessel  2  will cause the gas from the first chamber  110  of the pneumatic cylinder  60  and the first chamber  106  of the pneumatic cylinder  58  to flow through the pressure conduit  54  and into the chamber  3  of the vessel  2 . 
     Once again, in both cases, the gas flow will be in the same direction thereby causing the pistons  74 ,  76  to move in the same direction. In this case the pistons will move in the opposite direction to the direction of their motion in the previous cycle. The movement of the pistons again causes the piston rods and the connecting member  80  to move in the same lateral direction as the direction of the gas flow. The movement of the connecting member  80  causes the transmission chain  120  to move. This drives the sprockets  116  and  126  and the flywheel  64 . Energy from the turning of the flywheel can be transferred to the generator  124 . 
     When the pistons  74 ,  76  have reached their maximum travel, a sensor at the front of the cylinder  56  will cause the valves  50 ,  52  to close. This cycle continues continuously to cause continuous reciprocation of the pistons. 
     As will be evident from the description of the preferred embodiment, in its operation, the embodiment shown in  FIG. 9  is preferably employed when there is a significant pressure differential between the pressure vessels  2 ,  4 . The additional diversionary valve system shown in  FIG. 9  may be used to obtain multiple cycles of the pneumatic cylinders or rotary actuator before initiating the second stage of the process. 
     At the beginning of the cycle, valves  50  and  52  will be closed. When vessel  2  is heated from one of the heat sources and vessel  4  is cooled from one of the cold sources, valves  50  and  52  will be opened. In the first cycle, valve  138  will be open to pressure conduit  130  and closed to pressure conduit  134 . Valve  140  will be open to pressure conduit  136  and closed to pressure conduit  132 . Pressure conduits  142  and  144  will deliver the higher-pressure working fluid to first and second ports respectively of cylinders or a rotary actuator. Pressure conduits  146  and  148  will receive the lower pressure working fluid from third and fourth ports respectively of the cylinders or the rotary actuator. 
     In the second cycle, the valves  50  and  52  will close, and valves  138  and  140  will open to the pressure conduits  132  and  134  respectively. Valves  50  and  52  will then re-open. Pressure conduits  146  and  148  will then deliver higher-pressure working fluid to the third and fourth ports of the cylinders or the rotary actuator. 
     During the cycles of this alternate embodiment, the mass of the working fluid contained in the cylinders is re-distributed to the lower pressure vessel of the stage. When the pressure equalizes and no additional cycles can be obtained, the process will revert to the second stage. Pressure vessel  4  will then become the high-pressure source and vessel  2  will become the low-pressure receiver of the working fluid. 
     In an alternate embodiment, the pressure-activated actuator can be a rotary actuator. Other pressure activated actuators known to a person skilled in the art can be used for the purposes of the present invention. 
     In an alternate embodiment where several pressurized vessels are used, the time for maximum thermal transfer among the vessels to occur can be significantly minimized to the point that this occurs almost instantaneously. 
     While various embodiments and particular applications of this invention have been shown and described, it is apparent to those skilled in the art that many other modifications and applications of this invention are possible without departing from the inventive concepts herein. It is, therefore, to be understood that, within the scope of the appended claims, this invention may be practiced otherwise than as specifically described, and the invention is not to be restricted except by the scope of the claims.