Patent Publication Number: US-2007101717-A1

Title: Energy recuperation machine system for power plant and the like

Description:
FIELD OF THE INVENTION  
      The present invention relates to energy transformation and/or recuperation machines or systems, more particularly to a heat energy system operating from latent heat sources of different nature readily available and external to the system, the system including external heat motors having high heat transfer components therein for improved efficiency.  
     BACKGROUND OF THE INVENTION  
      As an example, it is well known in the art that latent heat is part of output liquids, gas, or fluids from turbines or furnaces of power plants, or even any other fluids found in the nature. Although existing systems try to lower the temperatures of these gas and/or liquids as much as possible, they still come out at temperatures high enough to enable recuperation of a significant amount of useful energy there from, although the nature of this latent energy would typically be considered useless relative to the purpose of the machine or system the energy comes from.  
      It is also known in the art to use external combustion or hot gas motors or Stirling-type (alpha, beta &amp; gamma types) motors or engines, or any modifications thereof such as Ericsson-, Martini- (generally free piston), Ringbom- (generally free displacer), etc. type motors, to generate power from a temperature differential between hot and cold sources.  
      Many documents refer to either these existing systems that typically include additional turbine cycles or the like or Stirling derived motors. Examples of such documents are: 
          U.S. Pat. No. 4,077,216 issued to Cook-Yarborough on Mar. 7, 1978 for “Stirling Cycle Thermal Devices”;     U.S. Pat. No. 4,435,959 issued to Mohr on Mar. 13, 1984 for “Hot-Gas Piston-Type Engine and Use Thereof in Heating, Cooling and Power Plants”;     U.S. Pat. No. 5,924,305 issued to Hill on Jul. 20, 1999 for “Thermodynamic System and Process for Producing Heat, Refrigeration, or Work”; and     U.S. Pat. No. 6,672,063 issued to Proeschel on Jan. 6, 2004 for “Reciprocating Hot Air Bottom Cycle Engine”.        

      These Stirling motors or the like, also often called external combustion engines, rely on the transfer of heat energy form an external hot heat source to an internal compressible fluid and from the fluid to an external cold source. Therefore, the efficiency of these motors essentially depends on the rapidity of the heat transfers as well as on the relatively short path of travel of the internal fluid between the external hot and cold sources. Such existing motors lack these characteristics, especially when these motors get larger in size, in which more than hundreds of BTUs (British Thermal Units) per minute output is looked at.  
      Accordingly, there is a need for an improved energy recuperation system, and corresponding external combustion motor, for power plant or the like that would efficiently take advantage of the available temperature differential between existing hot and cold sources.  
     SUMMARY OF THE INVENTION  
      It is therefore a general object of the present invention to provide an improved energy recuperation system, and corresponding external combustion motor, for power plant and the like, as especially applicable in any heavy-type industry, including boat engines, locomotives and the like.  
      An advantage of the present invention is that the energy recuperation system is easily customizable to the size, the vapor flow and the respective vapor and water temperatures of the power plant, or even the type of power plant.  
      Another advantage of the present invention is that the energy recuperation system is efficient and can recuperate as much as 80% of the heat that would otherwise be rejected and lost in the atmosphere, therefore as much as many megawatts or millions of BTUs (British Thermal Units) per hour or day, with improved heat capture capabilities using reduced-section fluid pipes forming a pipe network or manifold.  
      A further advantage of the present invention is that the energy recuperation system can be environmentally-friendly with reduced atmospheric pollution and reduced greenhouse effect, substantially silent and with limited vibrations.  
      Another advantage of the present invention is that the energy recuperation system recuperates heat energy that is usually lost and reduces the amount of cooling water required in power plants or the like, and more specifically in nuclear power plants.  
      Still another advantage of the present invention is that the energy recuperation system can be highly efficient, depending of the temperature differential between the hot and cold sources; the hot sources can be selected from a very wide variety such as different gas, wood, garbage combustions, solar energy, geothermal energy, enclosed hot/cold air in attics or the like areas, etc.  
      Another advantage of the present invention is that the energy recuperation system has motor(s) that are designed to have efficient and rapid heat transfer capabilities between the hot and cold sources and the internal gas; using different design features such as improved piston/cylinder designs and relatively small diameter of the internal gas conduits.  
      Another advantage of the present invention is that the energy recuperation system has motor(s) that are reliable, require relatively low maintenance, therefore have a long life duty-cycle.  
      Yet another advantage of the present invention is that the energy recuperation system is substantially autonomous, depending on the type of heat source, and easily adaptable to the nature of the hot (and cold) source.  
      A further advantage of the present invention is that the energy recuperation system allows for some adjustment of the time duration of each cycle or stroke of the motor for better efficiency thereof, depending on the type of motor.  
      Still another advantage of the present invention is that the energy recuperation system allows, when installed in a power plant, to preheat the cold water just before it enters the boiler of the power plant to save some fuel energy thereof.  
      Yet a further advantage of the present invention is that the energy recuperation system has a motor of which the different cycle durations can be adjusted to improve the overall efficiency of the system, especially to ensure a better transfer of heat from the hot gas or vapor to the closed-loop gas.  
      According to an aspect of the present invention, there is provided a heat energy reclaim system for providing output power from input latent heat energy of a hot source fluid, said system comprises: means for capturing the latent heat energy from the hot source fluid, said capturing means including an input distribution pipe network for distributing the hot source fluid along a plurality of paths with reduced flow and flow rate; and a respective external heat motor operatively connected to each one of said reduced flow paths for providing a portion of the output power.  
      Conveniently, the network includes a plurality of main input pipes for receiving the hot source fluid therein, each said main input pipe being in fluid communication with a plurality of respective secondary input pipes, all said secondary input pipes connected downstream of one of said main input pipes being said reduced flow paths and having corresponding said external heat motors connected to an output shaft for delivering said output power portions thereto.  
      In one embodiment, the external heat motor includes: a piston axially slidably and reciprocally engaging a corresponding cylinder between an extended position in which said piston and said cylinder define a gas chamber with a first volume therebetween and a retracted position in which said gas chamber has a second volume less than said first volume, said piston having a head partially defining said gas chamber and generally axially facing said cylinder, said piston head having a shaped head surface with a plurality of head protrusions extending substantially outwardly axially therefrom so as to enable increased turbulences of a gas located within said gas chamber when said piston is being displaced relative to said cylinder; said cylinder being exposable to the hot source fluid for receiving latent heat therefrom and transmitting the received latent heat to the turbulent gas inside the gas chamber for actuation of said piston; and an output shaft operatively connected to said piston for transmitting said displacement thereof, thereby providing the motor output power.  
      In one embodiment, the external heat motor includes: a piston axially slidably and reciprocally axially engaging a corresponding cylinder between an extended position in which said piston and said cylinder define a gas chamber therebetween; a displacer dividing said gas chamber into first and second chamber sections being located adjacent and away from said piston, respectively, said displacer being axially displaceable within said gas chamber for selectively controlling volumes of said first and second chamber sections, said displacer including a plurality of rod spaced and parallel from one another, said plurality of rod connecting to each other for simultaneous displacement thereof in respective gas chamber portions of reduced cross-section area for increased heat exchange between said cylinder and the gas inside said gas chamber portions; a gas conduit being in fluid communication with said first and second chamber sections to allow an internal gas to flow therethrough between first and second chamber sections; a section of said cylinder adjacent one of said first and second chamber sections being exposable to the hot source fluid for receiving latent heat therefrom and transmitting the received latent heat to the gas inside gas chamber portions of corresponding said chamber section with increased heat exchange therebetween for displacement thereof and actuation of said piston; and an output shaft operatively connected to said piston for transmitting said displacement thereof, thereby providing the motor output power.  
      According to another aspect of the present invention, there is provided a method for providing output power from input latent heat energy of a hot source fluid, said method comprises the steps of: a) distributing a flow of the hot source fluid through an input distribution pipe network into a plurality of paths with reduced flow and flow rate; and b) operatively connecting a respective external heat motor to each one of said reduced flow paths for providing a portion of the output power.  
      According to a further aspect of the present invention, there is provided an external heat motor for providing output power from input latent heat energy of a hot source fluid connected thereto, said motor comprises: a piston axially slidably and reciprocally engaging a corresponding cylinder, said cylinder defining a plurality of generally cylindrical gas chambers spaced apart from one another and extending generally axially and in a generally parallel relationship relative to one another, said piston having a plurality of piston heads generally spaced apart from one another and extending generally axially and in a generally parallel relationship relative to one another, each said piston heads axially slidably and reciprocally engaging a corresponding said gas chambers; said cylinder being exposable to the hot source fluid for receiving latent heat therefrom and transmitting the received latent heat to the gas inside the gas chambers for displacement of respective said piston heads and said piston relative to said cylinder; and an output shaft operatively connected to said piston for transmitting said displacement thereof, thereby providing the motor output power.  
      According to another aspect of the present invention, there is provided an external heat motor for providing output power from input latent heat energy of a hot source fluid connected thereto, said motor comprises: a piston axially slidably and reciprocally engaging a corresponding cylinder between an extended position in which said piston and said cylinder define a gas chamber with a first volume therebetween and a retracted position in which said gas chamber has a second volume less than said first volume, said piston having a head partially defining said gas chamber and generally axially facing said cylinder, said piston head having a shaped head surface with a plurality of head protrusions extending substantially outwardly axially therefrom so as to enable increased turbulences of a gas located within said gas chamber when said piston is being displaced relative to said cylinder; said cylinder being exposable to the hot source fluid for receiving latent heat therefrom and transmitting the received latent heat to the turbulent gas inside the gas chamber for actuation of said piston; and an output shaft operatively connected to said piston for transmitting said displacement thereof, thereby providing the motor output power.  
      According to another aspect of the present invention, there is provided an external heat motor for providing output power from input latent heat energy of a hot source fluid connected thereto, said motor comprises: a piston axially slidably and reciprocally engaging a corresponding cylinder between an extended position in which said piston and said cylinder define a gas chamber therebetween, said cylinder having an internal chamber wall partially defining said gas chamber, said internal chamber wall having a fin network extending outwardly therefrom, said fin network being exposable to the hot source fluid for receiving latent heat therefrom and conductively transmitting the received latent heat to the internal chamber wall for transfer to the gas inside the gas chamber so as to displace said piston relative to said cylinder; and an output shaft operatively connected to said piston for transmitting said displacement thereof, thereby providing the motor output power.  
      Other objects and advantages of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Further aspects and advantages of the present invention will become better understood with reference to the description in association with the following Figures, in which similar references used in different Figures denote similar components, wherein:  
       FIG. 1  is a simplified schematic diagrammatic layout of a typical power plant with a heat energy recuperation system in accordance with an embodiment of the present invention;  
       FIG. 2  is an enlarged view of a heat energy recuperation system similar to the one of  FIG. 1  that could be used with any other application producing available latent heat source;  
       FIG. 2   a  is an enlarged perspective view of a heat energy recuperation system of  FIG. 1 , showing the fluid pipe network or manifold distributing the flow of hot fluid to individual external heat motors for efficient capture or transfer of the latent heat energy from the fluid;  
       FIG. 3  is a simplified top perspective view of a motor, namely an alpha-type Stirling motor with regenerator, of the embodiment of  FIG. 1  for recuperation of heat energy;  
       FIG. 4  is a simplified enlarged section view taken along line  4 - 4  of  FIG. 3 ;  
       FIG. 4   a  is a simplified enlarged sectioned top perspective view similar to  FIG. 4 , showing an embodiment of a motor with multi-conduit heat exchangers inside hot and cold source fluid pipes;  
       FIG. 5  is a simplified broken top perspective section view of a piston head region of the block engine of the embodiment of  FIG. 2 ;  
       FIG. 5   a  is a simplified top perspective section view of a piston head with corresponding gas circulation pipes of the embodiment of  FIG. 2 ;  
       FIG. 6  is a simplified top perspective section view of a regenerator of the motor of  FIG. 3 ;  
       FIG. 6   a  is a simplified broken top perspective section view of the regenerator of  FIG. 6  with its insulating cover;  
       FIG. 7  is a view similar to  FIG. 5   a , showing a second embodiment of a piston head;  
       FIG. 8  is a simplified top perspective section view of a third embodiment of a piston head;  
       FIGS. 9 and 9   a  are simplified schematic layouts of another embodiment of a motor in accordance with the present invention, namely an Ericsson-type motor, showing one-way gas circulation pipes and corresponding heat exchanger arrangement between hot and cold double-acting cylinders shown in a back-to-back configuration, being displaced in the opposite first and second displacement directions;  
       FIG. 10  is a view similar to  FIG. 5   a , showing the one-way gas circulation conduits;  
       FIG. 11  is a simplified front elevation section view, taken along line  11 - 11  of  FIG. 12 , of an embodiment of the motor shown in  FIG. 2   a  with some parts taken away, namely a beta-type Stirling motor, with a displacer restraint mechanism used in the energy recuperation system of  FIG. 2   a ; and  
       FIG. 12  is a simplified top plan section view taken along line  12 - 12  of  FIG. 11  with some parts taken away. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      With reference to the annexed drawings the preferred embodiments of the present invention will be herein described for indicative purpose and by no means as of limitation.  
      Referring to  FIG. 1 , there is shown a schematic layout of a conventional power plant  20  in which a boiler  22  fed with some combustibles  24  burned through a burner  25  is used to heat up cold input water  26  into vapor  28  that feed a turbine  30  and generate electrical power  32  from alternators  34 . Hot gas outputs from the combustion and rejected into the atmosphere via chimneys  36  while output vapors from the turbine  30  enter a condenser (not shown). From the condenser, water returns back and mix with the cold input water  26  while residual vapor is also rejected into the atmosphere via cooling towers  38 . The rejections from both the chimneys  36  and the towers  38  have temperatures high enough such that useful latent heat energy could still be recuperated there from.  
      In addition, there is shown a heat energy recuperation or reclaim system  40  in accordance with an embodiment of the present invention for use with a conventional power plant  20  or the like. The system  40  of the present invention essentially replaces the condenser to recuperate a large amount of latent heat energy from the power plant vapor and hot gas rejections via a means for capturing the latent heat energy there from.  
      The energy recuperation system  40  includes two groups of motor  42 , typically external combustion motors such as Stirling-type motors or the like, in which the heat or hot source  44  is provided by the hot pressurized vapor coming out from the turbine  30  and the cold source  46  or sink is provided by the cold input water  26  or the like of the power plant  20 . A similar additional motor group  42   a  has its heat source  44   a  provided from the hot gases coming out from the boiler  22 . Each motor group  42 ,  42   a  includes a plurality, four being shown in  FIG. 3 , of simple motors  48  connected to a same output shaft  50  connected to a corresponding alternator  52  (see  FIG. 1 ) to generate additional electrical power. In order to better control the temperature of the hot source  44 , a portion of the vapor exiting the boiler  22  could flow through a turbine bypass conduit  23 , the access of which being controlled by a flow control valve  23 ′ or the like, and mix with the vapor coming out of the turbine  30  before entering the energy recuperation system  40 , as shown in  FIGS. 1 and 2   a.    
      As shown in  FIG. 2 , the system  40  could be installed in any other type of locations adjacent any hot source  44  and cold source  46  which could simply be the ambient air or the like, and could ultimately include only one motor  48 , depending on the available amount of heat and the specific application. For example, the hot source  44  could be heat generated by an internal combustion engine or boiler, hot air found in the attics of domestic housings, solar energy, air heated by underground pipes in winter time, hot surface water of oceans, etc. while the cold source  46  could be the ambient air (especially in winter time), ocean deep water, etc.  
       FIG. 2   a  refers to a typical system  40  of the present invention in which the fluid of the hot source  44  is directed to the different motor groups  42 , each having eight motors  248  of a different embodiment as shown, as an example. In order to efficiently capture the latent heat energy from the hot source  44 , which is a key feature of the present invention, the system  40  includes a means for capturing the latent heat energy from the hot source fluid  44 . This capturing means is typically located in each one of the motor groups  42  and includes an input distribution pipe network  41  (or manifold) to distribute the hot source fluid  44  along a plurality of paths  49  with reduced flow and flow rate to maximize the amount of heat transferred from the hot source  44  to the motors  248  (as further described hereinbelow in relation with  FIGS. 11 and 12 ). A reduced flow and flow rate of hot source fluid  44  is one of the best way to increase the heat capture efficiency by capturing as much heat energy as possible there from since the heat energy is located at every location of the hot source fluid  44 . A respective external heat motor  248  is operatively connected to each reduced flow path  49  to provide a portion of the output power of the system  40 .  
      Typically, the pipe network  41  includes a plurality of main hot input pipes  53 , one per motor group  42 , to receive the hot source fluid  44  therein that are in fluid communication with a plurality of respective secondary hot input pipes  54  located downstream thereof and forming the different reduced flow paths  49 . Each secondary hot input pipe  54  is connected to a corresponding external heat motor  248 . In opposite, using large hot input pipes connecting to large motors would not enable efficient heat recuperation and would be too costly in relation to the amount of energy that would be recuperated.  
      Now referring more specifically to the embodiment of the motor  48  shown in  FIGS. 3 and 4 , the vapor of the hot side of all motors  48  is fed via a hot input pipe  54  through hot sleeves or jackets  56  surrounding and connecting to the respective hot cylinder  58  and to a hot output pipe  60 . Similarly, the cold water of the cold side of all motors  48  is fed via a cold input pipe  62  through cold sleeves or jackets  64  surrounding and connecting to the respective cold cylinder  66  and to a cold output pipe  68 , as also shown in  FIG. 2   a  in which the main cold input pipe  61  feeds the secondary cold input pipes  62 . Ultimately, the water from both the hot and cold output pipes  60 ,  68  could be mixed together before returning to the boiler  22 , as partially shown in  FIGS. 11 and 12 . At the same time, some residual low temperature vapor from the hot output pipe  60  is redirected toward the cooling towers  38  via the vapor output pipe  70 , as shown in  FIG. 1 . The hot and cold jackets  56 ,  64 , typically made out of a network or trellis of highly efficiently designed fins or the like and made out of a highly heat conductive material and coarsely represented with a specific hashed pattern for pictorial purposes only, are used to rapidly heat up and cool down the temperature of the respective hot and cold cylinders  58 ,  66  exposed to the hot and cold sources  44 ,  46  by efficient heat transfer such that the internal gas inside the hot  72  and cold  74  gas chambers is quickly and better uniformly heated up and cooled down respectively.  
      In each simple motor  48 , the internal gas circulating between the hot and cold gas chambers  72 ,  74  flows through respective hot  76  and cold  78  gas pipes that typically at least partially extend through the respective jacket  56 ,  64  and a regenerator  80  located there between. The regenerator  80  (see  FIGS. 6 and 6   a ) is typically a sort of highly efficient heat exchanger  81 , typically made out of a metallic mesh or the like, used to further cool down the gas flowing from the hot gas chamber  72  to the cold gas chamber  74  and heat up the gas when flowing in the opposite direction from the cold  74  to the hot gas chamber  72 . Obviously, the amount of dead gas volume flowing inside the hot and cold gas pipes  76 ,  78  located between the two hot and cold jackets  56 ,  64  (and outside the regenerator  80  if present) is kept to a minimum since the internal gas is not being warmed or cooled when flowing therein therefore being thermally inefficient pipe sections that unnecessarily further increase the head loss inside the internal gas conduits  76 ,  78 .  
      As it is for an alpha-type Stirling motor/engine  48 , both the hot  82  and cold  84  pistons are connected to the same output shaft  50  with a cycle delay between the two typically varying between about thirty and about hundred-and-twenty degrees (30°-120°) depending on the specific use, and preferably about ninety degrees (90°). Accordingly, there is a detent (expansion) phase (at essentially constant temperature) of the closed-loop or internal gas just after the heating phase (at essentially constant volume), then a cooling phase (at essentially constant volume) of the gas occurs followed by a compression phase (at essentially constant temperature) thereof. Although an alpha-type Stirling motor/engine  48  is illustrated herein, it would be obvious to one skilled in the art to consider any other type of external combustion or hot gas engine/motor without departing from the scope of the present invention.  
      In order to minimize heat losses and to isolate the hot and cold cylinders  58 ,  66  from one another, both the hot and cold jackets  56 ,  64  are externally insulated by a respective hot  86  and cold  88  insulation sleeve. Similarly, the regenerator  80  is typically well externally covered by a good temperature insulator  89 , as shown in  FIG. 6   a , as well as having the hot  90   a  and cold  90   b  gas inputs insulated from each other by an insulating interface  91  (see  FIGS. 6 and 6   a ). Typically, the insulating material is ceramic or the like.  
      As shown in  FIGS. 4, 5  and  5   a , each piston  82 ,  84  includes a piston head  92  having a shaped head surface  94  with a plurality of head protrusions  96  extending substantially outwardly axially there from to enable increased turbulences of the internal gas located within the gas chamber  72 ,  74  when the piston  82 ,  84  is in movement relative to the cylinder  58 ,  66 , for increased heat transfer between the gas and the cylinder  58 ,  66 . In the opposite, each cylinder  58 ,  66  has a bottom wall  98 , generally axially facing the piston head  92 , that has a shaped wall surface  100  with a plurality of wall recesses  102  extending substantially inwardly axially therein such that each head protrusion  96  selectively engages a respective wall recess  102  when the piston  82 ,  84  moves from an extended position in which the piston  82 ,  84  and the cylinder  58 ,  66  define the gas chamber  72 ,  74  with a first volume there between toward a contracted position in which the gas chamber  72 ,  74  has a second volume less than the first volume. Typically, the shaped cylinder wall surface  100  is substantially a complementary image of the shaped piston head surface  94  such that the head protrusions  96  almost entirely fill the corresponding wall recesses  102  when the piston  82 ,  84  is in the contracted position, with a second volume substantially null. In the latter configuration, the cylinder wall recesses  102  define respective gas chamber portions  72   a  spaced apart, typically equally, and generally parallel relative to one another such that they form a plurality of individual sub-cylinders  58   a  of reduced cross-section area for increased heat exchange between cylinder wall  98  and the gas inside the gas chamber portions  72   a.    
      Furthermore, each cylinder wall recess  102  defines a bottom region  104  thereof, via which the wall recess  102  is in fluid communication with at least one, typically all, of the adjacent wall recesses  102 .  
      Now referring more specifically to  FIGS. 5 and 5   a , there is shown the hot piston head protrusions  96  typically having a blade shape to maximize the overall chamber surface area over volume ratio and enable a relatively rapid heating up of the gas filling the hot gas chamber  72 , including the space between the blades  96 , from the hot vapor flowing inside the jacket  56 , through the cylinder wall  98 . To improve a relatively uniform flow distribution of the gas between the hot gas chamber  72  and the corresponding hot gas pipes  76  and to facilitate the heating (heat transfer) of the gas flowing therethrough from vapor inside the jacket  56 , the hot gas pipes  76  includes a plurality of generally parallel hot gas conduits  106  of a smaller diameter. Although the hot side has been described hereinabove, the description, including cold gas conduits  108 , also applies to the cold side which might be different in size and configuration depending on the required heat transfer between the internal gas and the respective hot source  44  or cold sink  46 .  
      As shown in  FIGS. 1 and 2 , in order to control the flow of hot vapor or gas  44  flowing into the hot jackets  56  of a same motor group  42 ,  42   a  and coming out there from, input  110 ,  110   a  and output  112  hot valves connected to the corresponding pipes  53 ,  60 . Similarly, the flow of cold water flowing into the cold jackets  64  of a same motor group  42 ,  42   a  and coming out there from is controlled with input  114  and output  116  cold valves connected to the corresponding pipes  61 ,  68 . The input and output hot and cold valves  110 ,  110   a ,  112 ,  114 ,  116  are also used to isolate any motor group  42 ,  42   a  from the others for maintenance thereof or the like.  
      Many types of gas or refrigerant could be used as a compressible working fluid inside the closed-loop or internal gas network between the hot and cold gas chambers  72 ,  74  and through the regenerator  80  depending on the heat requirements of the specific application, such as the thermodynamics characteristic of the gas, safety (toxicity, explosiveness, etc.), and environmental, technical and economic considerations. For examples, the gas categories could include CFCs (chlorofluorocarbons), HCFCs (hydro-chlorofluorocarbons), HFCs (hydro-fluorocarbons), low green-house-effect gas such as ammonia (NH 3 ), HCs (hydrocarbons), CO 2  (carbon dioxide), and water (vapor), as well as typical efficient gases such as helium, hydrogen, nitrogen or simply air. In order to increase the temperature difference between the hot and cold sources  44 ,  46 , and/or to improve the efficiency of the motor group  42 ,  42   a , one could consider the use of artifices of external devices, such as the use of cold ambient air (in winter, when and where applicable) to further cool down the cold source  46  (as illustrated in  FIG. 2  with heat exchanger  29 ), or the use of a sodium based solution or mixture  84   a  (schematically represented in  FIG. 8 ) inside weight relief chambers  84   b  of the cold piston  84  to increase the piston capacity to dissipate the heat extracted from the internal gas, etc.  
      Inside the regenerator  80 , it would be preferable to have a phase change material (PCM), such as ammonia (NH3) or carbon dioxide (CO2), to increase its heat capacity and heat transfer efficiency.  
      Operation  
      Although the following example specifically refers to a power plant with hot pressurized vapor, any other type of heat source (especially the hot one) from any other location could be considered for the system of the present invention as long as there is sufficient temperature difference between the hot and cold sources  44 ,  46  as further detailed hereinafter.  
      In a typical power plant application wherein turbines are activated with vapor, that vapor, when at substantially zero relative pressure at the outlet of the turbines, is at the temperature range between about 200° C. (390° F.) and about 250° C. (480° F.), being the temperature of the hot source  44 . After the heat has been transferred to the gas inside the hot gas chamber  72  and hot gas pipes  76  while flowing through the hot jacket  56 , the vapor temperature drops down to about 95-100° C. (203-212° F.) in the hot output pipe  60 , essentially in water state. For the cold source  46 , the water is typically available at about 15° C. (60° F.) to enter the cold input pipe  62 . After the heat has been transferred from the gas inside the cold gas chamber  74  and cold gas pipes  78  while flowing through the cold jacket  64 , the water temperature increases up to about 80-90° C. (176-194° F.) in the cold output pipe  68 . The water from both hot and cold output pipes  60 ,  68  are mixed together before going to the boiler  22  were it is vaporized again, and therefore saving the amount of energy that would have been required to heat it up from 15° C. (60° F.) to that temperature of about 95° C. (203° F.). As seen in dotted lines in  FIG. 1 , when the ambient outside temperature is below 15° C. (60° F.), the cold water  26  can even be further cooled down via the cold ambient atmospheric air via a heat exchanger  29 ; this would further increase the efficiency of the system  40 .  
      As mentioned hereinabove, other types of hot and cold sources  44 ,  46  could also be considered as well as any other temperature ranges. For example, the hot vapor temperature could vary between about 50° C. (122° F.) and about 550° C. (1020° F.) while a hot gas temperature could as high as about 750° C. (1380° F.). In any case, and without limitation, a hot-cold temperature difference (between the hot and cold source temperatures) as low as about 30° C. (54° F.) could typically be considered as sufficient to generate a significant amount of power there from for power plants or the like, and even as low as about 10° C. (18° F.) for domestic size applications in which smaller size external heat motors would be considered.  
      Alternatives  
      In the example hereinabove described, instead of having a motor group  42   a  fed with the hot gas coming out from the boiler  22  and/or the burner  25 , there simply could be a heat exchanger  27  (as shown in dotted lines in  FIG. 1 ) between these hot gases and the cold input water  26  to cool down the hot gases before rejection thereof and pre-warm-up of the water  26  before entering the boiler  22 .  
      In order to increase the uniformity of the heating or cooling of the gas inside the respective hot or cold gas chamber  72 ,  74 , by inducing vortex motion to the gas during filing thereof, the piston heads  92   a ,  92   b  could have surfaces  94   a ,  94   b  with protrusions  96  of different shapes such as radial pyramids  96   a  of a tapered star-shaped head  92   a  or tapered blades  96   b , as shown in  FIGS. 7 and 8  respectively.  
      Now referring more specifically to  FIGS. 4   a  and  10 , the hot and cold gas conduits  106 ,  108  of the motor  48 ″ could follow different path between the gas chambers  72 ,  74  and therefore would typically include a plurality of respective inlet gas conduits  120 ,  122  and a plurality of respective outlet gas conduits  124 ,  126  to allow the gas to enter and exit the corresponding gas chamber  72 ,  74  there through, respectively. Each inlet and outlet gas conduit  120 ,  122 ,  124 ,  126  typically has a one-way flow control valve  128  for controlling the flow of gas there through, the valves  128  being typically electronically controlled valves or spring-loaded type, or simple one-way flaps to prevent backflow of the internal gas.  
      In order to improve the heat transfer between the hot or cold source  44 ,  46  and the gas inside the inlet gas conduits  120 ,  122 , a conduit heat exchanger  130 ,  132 , typically a serpentine or the like, in fluid connection with a respective inlet gas conduit  120 ,  122 . Typically, the conduit heat exchangers  130 ,  132  are exposable to the respective hot and cold source  44 ,  46  either for receiving latent heat from the hot source  44  and transmitting the received latent heat to the gas inside the conduit heat exchangers  130  for heating the gas flowing therein or for receiving latent heat from the gas flowing inside the conduit heat exchangers  132  and transmitting the received latent heat to the cold source  46  for heating the same.  
      Typically, the fin network of the jackets  56 ,  64  extend outwardly around the bottom region  104  of the cylinder recesses  102 , the hot and cold gas conduits  106 ,  108  there around and typically the inlet gas conduits  120 ,  122  with their serpentines  130 ,  132  such that the latter are all exposed to the respective hot and cold sources  44 ,  46  for further increased heat transfer efficiency of the system  40  with the internal gas.  
      As schematically shown in  FIGS. 9 and 9   a , to further enhance efficiency of the system  40 , the hot and cold circulation gas pipes  76 ,  78  of an Ericsson-type motor  48 ′ as illustrated herein typically includes multiple parallel small gas conduits  120 ,  122 ,  124 ,  126  with respective one-way flow control valves  128 , as partially illustrated between the two cylinders  58 ′,  66 ′. The motor  48 ′ shown in  FIGS. 9 and 9   a  includes double-acting pistons  82 ′,  84 ′ typically assembled in a back-to-back configuration with shaped head surfaces  94 ′ on both sides thereof. During the displacement of the pistons  82 ′,  84 ′ in a first direction of the reciprocation movement illustrated in  FIG. 9 , the internal gas, with one-way flow valves  128   a  opened and one-way flow valves  128   b  closed, flows via the hot serpentines  130  and the hot inlet small gas conduits  120 ,  120   a , all typically exposed to the hot source  44 , into the first hot gas chamber  72   a , and from the second hot gas chamber  72   b  into the hot outlet small gas conduits  124 ,  124   a . Then the hot gas could enter a heat exchanger  80 ′ such as a regenerator or the like and preferably cold serpentines  132  to get cooler by the cold source  46 . Thereafter, the cold internal gas flows via the cold inlet small gas conduits  122 , typically exposed to the cold source  46 , into the first cold gas chamber  74   a , and from the second cold gas chamber  74   b  into the cold outlet small gas conduits  126 .  
      During the displacement of the pistons  82 ′,  84 ′ in an opposite second direction of the reciprocation movement illustrated in  FIG. 9   a , the internal gas, with one-way flow valves  128   a  closed and one-way flow valves  128   b  opened, flows via the hot serpentines  130  and the hot inlet small gas conduits  120 ,  120   b , all typically exposed to the hot source  44 , into the second hot gas chamber  72   b , and from the first hot gas chamber  72   a  into the hot outlet small gas conduits  124 ,  124   b . Then the hot gas could similarly enter the heat exchanger  80 ′ and preferably cold serpentines  132  and the cold inlet small gas conduits  122  to get cooler by the cold source  46 . At the cold end of the engine  48 ′, to further cool the compressed internal gas before it gets redirected towards the hot cylinder  58 ′ in the following phase (first displacement direction of the pistons  82 ′,  84 ′), the cold internal gas flows from the first cold gas chamber  74   a  into the second cold gas chamber  74   b  via cold by-pass conduits  134 , with one-way valves  128   b , that include by-pass heat exchanger  136  or serpentines exposed to the cold source  46 . The second cold gas chamber  74   b  is smaller than the first cold gas chamber  74   a  because the internal gas is further compressed due to its colder temperature.  
      The cold inlet small gas conduits  122  and the cold serpentines are shown in dotted lines in  FIGS. 9 and 9   a  because instead of having a closed-loop internal gas, the latter could eventually be rejected out from the hot outlet small conduits  124  of the motor  48 ′ after actuation of the hot piston  82 ′, and have new cold gas (such as air or the like) entering the cold cylinder  66 ′ of the motor  48 ′ via the cold inlet small gas conduits  122 .  
      In  FIGS. 9 and 9   a , although both the hot and cold pistons  82 ′,  84 ′ are connected to the output shaft  50 , the cold piston  84 ′ could be disconnected there from and acting as a displacer  142  which displacement could be controlled by a displacer actuating means  151 , shown in dotted lines in  FIGS. 9 and 9   a , as further explained hereinbelow with reference to  FIGS. 11 and 12 . The same approach could eventually be considered with the motor  48  of  FIG. 4  without departing from the scope of the present invention. The hot piston  82 ′ could have its displacement helped or operated by a typically magnetic displacer actuating means  151 ′ that would have at least one controllable electromagnet  153 ′ acting on a magnetic piston  152 ′ or the like connected to the hot piston  82 ′.  
      The large quantity (only duplication shown in  FIG. 4   a ) of small gas conduits  120 ,  122 ,  124 ,  126  as well as heat exchangers  130 ,  132  enable to keep them relatively small to increase the heat exchange all along their respective path. Such increased heat transfer capability of the motor of the present invention is further enhanced by the shaped gas chambers  72 ,  72   a ,  72   b ,  74 ,  74   a ,  74   b  as explained hereinabove. The heat exchangers  130 ,  132  could also be any type of heating or cooling mechanism such as an electrical heating coil or a liquid nitrogen cooling coil, respectively. Obviously, having the outlet small conduits  124 ,  126  running outside of the respective jacket  56 ,  64  could also apply even if the small conduits  124 ,  126  are free of one-way valves  128 ,  128   a ,  128   b  or the like.  
      The motor  48 ′ of  FIGS. 9 and 9   a  is obviously well suited for Bourke and Wiseman type engines in which single-acting pistons with fixed connecting rods would run at approximately in opposed cycles (compression/expansion), namely at about one-hundred-and-eighty degrees (180°) from each other in a back-to-back relationship. Although not specifically illustrated herein, it would be obvious to one skilled in the art to have the motor  48 ′ be modified into a motor with a rotary piston having multiple gas chambers there around without departing from the scope of the present invention.  
      Referring now more specifically to  FIGS. 11 and 12 , instead of using an alpha-type Stirling motor  48  shown in  FIGS. 3, 4  and  5  to  6   a , the system  40  could also use a plurality of beta-type Stirling motors  248  in connection with both hot and cold sources  244 ,  246 . The beta (as well as gamma-type) motor  248  has only one piston  140  and a displacer  142  located inside the gas chamber and in-between the hot and cold gas chamber sections  272 ,  274  divided thereby that forces the closed-loop internal gas to be alternately displaced between the hot and cold gas chamber sections  272 ,  274  via the hot and cold gas pipes  276 ,  278  and the regenerators  280  which are also covered with insulating ceramic material  289  or the like, upon axial displacement of the displacer  142  that selectively control the volumes of the two chamber sections  272 ,  274  exposed to the hot and cold sources  244 ,  246 .  
      The hot and cold gas chamber sections  272 ,  274  and their respective hot and cold gas conduits  276 ,  278  are located inside the hot and cold fluid input pipes  254 ,  262 , upstream of respective hot and cold fluid output pipes  260 ,  268 ; the hot output pipe  260  being subdivided into a main vapor pipe  260   a  or gas output pipe and a smaller water pipe  260   b  or liquid output pipe collecting condensed vapor. In order to maximize the heat transfer, the hot and cold gas chamber sections  272 ,  274  are preferably composed of a plurality of parallel gas chamber cylinder portions  144  of a smaller diameter (reduced cross-section area). Accordingly, the displacer  142  includes a plurality of generally cylindrical rods  146  generally equally spaced apart and parallel from each other and adapted to axially tightly and reciprocatingly slide into the respective cylinder hot and cold chamber portions  144 . The cylindrical rods  146  are secured to one another via link bars  148  that reciprocatingly slide inside an insulating spacer  150 , typically made out of ceramic material or the like. Obviously, both longitudinal ends of each cylindrical rod  146  could have a different shape such as a hemispherical end or any other shape to increase the turbulences of the gas flowing inside the portions  144  of the hot and cold chamber sections  272 ,  274 .  
      As known in the art and not shown, although the displacer  142  could be either free or connected to the shaft  250 , freely extending through the piston  140 , with any angle a ninety-degree (90°) cycle delay relative to the piston varying between about thirty and about hundred-and-twenty degrees (30°-120°) depending on the specific use, it could also have its displacement being controlled and actuated by a displacer actuating means  151  such as an external actuator (electric, magnetic  151 ′, electromagnetic, pneumatic, hydraulic, etc.) or a passively resisting pressure mechanism including a piston  152  displaced by a pressurized volume  154  and connected to the displacer  142  by a connecting rod  156 , as schematically shown in  FIG. 11 , or as a helical spring as represented in  FIGS. 9 and 9   a . As the hot vapor lost most of its heat to the closed-loop gas before entering the reduced diameter hot output pipe  260 , it is mostly transformed into hot water by condensation; accordingly, the hot output pipe  260  is slightly angled, although not specifically shown, to ensure the flow of water away from the motor  248 , through the water pipe  260   b.    
      From  FIG. 12 , it can be seen that the hot source  244  surrounds the hot gas chamber  272  and the corresponding hot gas pipes  276 . To ensure a good heat transfer, the hot input pipe  254  typically forms a generally 180° curve or spiral shape (not shown) to force formation of turbulences in the hot vapor flow. To control the flow of hot vapor thereto and to allow maintenance of each motor  248 , independently of each other, the motor  248  is typically isolable from the others with input and output control and purge valves  210 ′,  212 ′ or the like, the latter output valve  212 ′ being typically located upstream of the hot output pipe  260  split into vapor and water pipes  260   a ,  260   b ; similar valves (not shown) are mounted on the cold side of the motor  248 .  
      Now referring more specifically to  FIG. 11 , the motor  248  could alternatively have the displacer  142  movably linked to a piston extension  140   a , as shown in dotted lines, such that the displacer actuating means  151  is a displacer retarding mechanism  151   a  connecting the displacer  142  to the piston  140 . The displacer connecting rod  156   a , or displacer bar, has a pin end  160  slidably and reciprocatingly mounted into a corresponding slot  162  of the piston extension  140   a . Coil springs  164  or the like are mounted at both ends  166  of the slot  162 , or limit positions of the displacer connecting rod  156   a  relative to the piston extension  140   a , to damper the contact abutment of the pin end  160  with the piston extension  140   a  at the respective slot end  166 . This displacer retarding mechanism  151   a  allow the displacer  142  to be substantially free while allowing slightly longer detent and compression cycle durations which increase the heat transfer efficiency, up to two or three times more heat transfer, especially in the hot source  244  side.  
      As it would be obvious to one skilled in the art, it could be possible to control the flow of the working gas flowing through the regenerator  80  by adding control valves or the like (not shown) to the hot and/or cold gas pipes  76 ,  78  without departing from the scope of the present invention.  
      Furthermore, one skilled in the art would easily understand that any type (alpha, beta, gamma) of Stirling motor/engine, variation thereof or the like could be considered for use with the system of the present invention without departing from the scope of the present invention.  
      The present invention also refers to a method for providing output power from input latent heat energy of a hot source fluid  44 . The method comprises the steps of: 
          a) distributing (or networking) a flow of the hot source fluid  44  through an input distribution pipe network  41  into a plurality of paths  49  with reduced flow and flow rate; and     b) operatively connecting a respective external heat motor  48  to each one of the reduced flow paths  49  for providing a portion of the output power.        

      Typically, the method further comprises the step of: 
          c) connecting the external heat motors  48  corresponding to all secondary input pipes  54  connected downstream of one of the main input pipes  53  to an output shaft  50  for delivering the output power portions thereto.        

      Conveniently, above step b) further includes controlling a flow of the hot source fluid flowing through each secondary input pipe  54  with a corresponding flow control valve  110 .  
      Furthermore, the method comprises the step of: 
          d) subdividing each secondary input pipe  54 , downstream of its respective motor  48 , into a gas output secondary pipe  260   a  and a liquid output secondary pipe  260   b  for receiving a gas portion and a liquid portion of the hot source fluid  44  therein, respectively.        

      Although the present invention has been described with a certain degree of particularity, it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiments described and illustrated herein, but includes all variations and modifications within the scope and spirit of the invention as hereinabove described.