Dual thermodynamic cycle cryogenically fueled systems

Abstract

Systems and methods for converting thermal energy, such as solar energy, from a localized thermal energy source to another form of energy or work comprise dual thermodynamic cycle systems that utilize the liquid-to-gas phase transitions of a cryogenic fluid such as liquid nitrogen and a working fluid such as sulfur hexafluoride to drive prime movers. Heat transfer between the fluids as they undergo the phase transitions is used to increase the energy in the system and its work output, and improve system efficiency.

1 . A method of converting thermal energy comprising: 
 transferring thermal energy into a cryogenic fluid from a first portion of working fluid to expand the cryogenic fluid and create a first gas and to convert the first portion of working fluid to a working liquid;    transferring thermal energy into a second portion of the working fluid to expand the second portion of the working fluid and create a second gas;    utilizing the second gas to operate an energy conversion apparatus;    transferring additional thermal energy to the first gas from exhausted second gas from the energy conversion apparatus to increase the energy in the first gas; and    utilizing the first gas with said increased energy to operate another energy conversion apparatus.    
     
     
         2 . The method of  claim 1 , wherein said transferring of additional thermal energy to the first gas comprises substantially reducing the temperature of said exhausted second gas by a heat exchange between said first and exhausted second gasses.  
     
     
         3 . The method of  claim 2 , wherein said transferring of additional thermal energy comprises flowing said first gas and said exhausted second gas through a common heat exchanger that provides thermal communication between said gasses.  
     
     
         4 . The method of  claim 1 , wherein said cryogenic fluid comprises cryogenic fluid from a cryogenic liquid reservoir, said first portion of working fluid comprises said exhausted second gas, and wherein said transferring thermal energy into said cryogenic fluid comprises extracting said thermal energy from the exhausted second gas to create said first gas.  
     
     
         5 . The method of  claim 4 , wherein said extracting thermal energy comprises transferring heat from said exhausted second gas to condense said exhausted second gas to said working liquid.  
     
     
         6 . The method of  claim 1 , wherein said transferring thermal energy into a cryogenic fluid comprises transferring heat from said first portion of working fluid into a cryogenic liquid in a reservoir.  
     
     
         7 . The method of  claim 1 , wherein said transferring thermal energy into said second portion of working fluid comprises expanding said second portion of working fluid in an atmospheric boiler.  
     
     
         8 . The method of  claim 7  further comprising adding heat to said atmospheric boiler from a heat collector to increase the temperature of said atmospheric boiler above ambient.  
     
     
         9 . The method of  claim 1 , wherein said portions of working fluid comprise working fluid in different parts of a closed system that operates on a first thermodynamic cycle.  
     
     
         10 . The method of  claim 9  further comprising using pressure and temperature differentials in said closed system to circulate said working fluid in said closed system without using a pump.  
     
     
         11 . The method of  claim 10  further comprising moving said circulating working fluid between first and second containers by exchanging pressures in said containers and by controlling inlet and outlets of said containers.  
     
     
         12 . The method of  claim 9 , wherein said cryogenic fluid and said first gas comprise different phases of the cryogenic fluid in an open system operating on a second thermodynamic cycle.  
     
     
         13 . The method of  claim 1 , wherein one or both of said first and second energy conversion apparatus comprises a prime mover.  
     
     
         14 . The method of  claim 1 , wherein the working fluid is selected from the group consisting of sulfur hexafluoride, carbon dioxide, liquefied natural gas, and a mixture of the above.  
     
     
         15 . A method of converting thermal energy comprising: 
 expanding a portion of a working fluid in a first system operating according to a first thermodynamic cycle to create a working gas for operating first energy conversion apparatus;    expanding a portion of a cryogenic fluid in a second system operating according to a second thermodynamic cycle to create another gas for operating second energy conversion apparatus, said second system being coupled to said first system and said expanding comprising transferring heat from the working gas to said portion of cryogenic fluid to create said other gas; and    transferring additional heat from said working gas in said first system to said other gas in said second system to increase the internal energy of said other gas.    
     
     
         16 . The method of  claim 15 , wherein said transferring heat from said working gas to expand said portion of cryogenic fluid comprises substantially condensing said working gas.  
     
     
         17 . The method of  claim 15 , wherein said first-mentioned expanding to create said working gas comprises reducing the pressure and increasing the temperature of said working fluid in an atmospheric boiler.  
     
     
         18 . The method of  claim 15 , wherein said transferring additional heat to said other gas comprises passing said working gas and said other gas through a common heat exchanger.  
     
     
         19 . A method of converting thermal energy, comprising: 
 transferring heat into a working fluid in a first container to expand a portion of the working fluid to create a first gas;    operating a first prime mover using said first gas;    exhausting said first gas from said first prime mover into a second container immersed in a cryogenic fluid in a third container;    transferring heat from the exhausted first gas to said cryogenic fluid to expand a portion of said cryogenic fluid to create a second gas;    operating a second prime mover utilizing the second gas; and    swapping said first and second containers and repeating said foregoing steps.    
     
     
         20 . A system for converting thermal energy, comprising: 
 a cryogenic fluid reservoir;    a condenser for a working fluid, the condenser and the cryogenic fluid reservoir being in thermal communication for the transfer of heat to cryogenic fluid in said cryogenic fluid reservoir to expand a portion of the cryogenic fluid to a first gas;    a boiler for transferring heat to working fluid from said condenser to expand the working fluid to a second gas, the second gas operating energy conversion apparatus, and the energy conversion apparatus exhausting said second gas;    a heat exchanger receiving the first gas and the exhausted second gas for transferring thermal energy from said exhausted second gas to the first gas to increase the energy in the first gas; and    the first gas with increased energy operating another energy conversion apparatus.    
     
     
         21 . The system of  claim 20 , wherein said condenser receives exhausted second gas from the heat exchanger, said exhausted second gas comprising said working fluid, and wherein said heat transfer to the cryogenic fluid condenses said working fluid to a working liquid, said working liquid comprising said working fluid in said boiler.  
     
     
         22 . The system of  claim 21  further comprising first and second working fluid reservoirs being connected together and to said condenser and to said boiler by a plurality of lines containing control valves to enable the control of working fluid through said lines.  
     
     
         23 . The system of  claim 20 , wherein said heat exchanger comprises heat conductive pipes through which said gasses pass, the pipes being in thermal communication for the exchange of thermal energy.  
     
     
         24 . The system of  claim 23 , wherein said cryogenic reservoir, said heat exchanger and said other energy conversion apparatus comprise a first system part that operates according to an open thermodynamic cycle, and said condenser, said boiler, said heat exchanger and said first mentioned energy conversion apparatus comprise a second system part the operates according to a closed thermodynamic cycle, said system parts being coupled for the exchange of thermal energy.  
     
     
         25 . A method of operating a system that operates on a closed thermodynamic cycle to circulate fluids through the system without using a pump, the fluids comprising fluids that expand to a gas and condense to a liquid upon the transfer and removal of heat, the method comprising: 
 filling substantially the first tank with cold liquid and the second tank with hot gas;    pressurizing the first tank with the hot gas from the second tank;    flowing cold liquid into the second tank while expanding the liquid from the first tank to form a gas;    supplying the gas to a prime mover;    condensing the gas from the prime mover to said cold liquid; and    repeating said foregoing steps by swapping said filling, said pressurizing, and said flowing steps between said first and second tanks, thereby circulating said fluids through said system.