Organic Rankine cycle decompression heat engine

Abstract

An improved heat engine that includes an organic refrigerant exhibiting a boiling point below −35° C.; a heat source having a temperature of less than 82° C.; a heat sink; a sealed, closed-loop path for the organic refrigerant, the sealed, closed-loop path having both a high-pressure zone that absorbs heat from the heat source, and a low-pressure zone that transfers heat to the heat sink; a positive-displacement decompressor providing a pressure gradient through which the organic refrigerant in the gaseous phase flows continuously from the high-pressure zone to the low-pressure zone, the positive-displacement decompressor extracting mechanical energy due to the pressure gradient; and a positive-displacement hydraulic pump, which provides continuous flow of the organic refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone, the hydraulic pump and the positive-displacement decompressor maintaining a pressure differential between the two zones of between about 20 to 42 bar.

What is claimed is: 
     
         1 . A heat engine configured to operate an organic Rankine cycle, the heat engine comprising:
 an organic refrigerant exhibiting a boiling point below −35° C. −35° C.;   a closed-loop path for the organic refrigerant, the closed-loop path having both a high-pressure zone and a low-pressure zone, wherein the organic refrigerant is heated from a liquid phase to a gaseous phase in the high-pressure zone contains a first portion of the organic refrigerant in at least a gaseous phase, and wherein the low-pressure zone contains a second portion of the organic refrigerant in at least a liquid phase and the organic refrigerant is expanded and cooled from the gaseous phase to the liquid phase in the low-pressure zone;   a positive-displacement decompressor configured to provide a pressure gradient through which the organic refrigerant in the gaseous phase flows continuously from the high-pressure zone to the low-pressure zone such that the positive-displacement decompressor extracts mechanical energy;   an electrical generator coupled to the positive-displacement decompressor and configured to convert mechanical energy to electrical energy;   a positive-displacement hydraulic pump for providing continuous flow of the organic refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone; and   a refrigerant holding tank in the high-pressure zone and in operable communication with the positive-displacement hydraulic pump, a lower portion of the refrigerant holding tank having a larger cross-sectional area than an upper portion thereof,   wherein the heat engine is configured such that the organic refrigerant in the closed-loop path absorbs heat in the high-pressure zone from a heat source having a temperature of less than 82° C. 82° C. and transfers heat to a heat sink in the low-pressure zone; and   a vertically oriented tubular heat exchanger in the high-pressure zone, wherein the vertically oriented tubular heat exchanger includes:
 an upper portion including a fluid entrance configured to receive fluid from the heat source; 
 a lower portion including a fluid exit configured to deliver the fluid; 
 a refrigerant entrance for the organic refrigerant in the lower portion; and 
 a refrigerant exit for the organic refrigerant in the gaseous phase in the upper portion, wherein the refrigerant exit is configured to deliver organic refrigerant in the gaseous phase to an input of the positive-displacement decompressor. 
   
     
     
         2 . The heat engine of  claim 1 , further comprising a lubricating oil in the closed-loop path, the lubricating oilwherein the positive-displacement decompressor is located within a prime mover shell housing the positive-displacement decompressor. 
     
     
         3 . The heat engine of  claim 1 , wherein the positive-displacement decompressor comprises an orbital scroll claim 2 , further comprising an exhaust gas barrier ring positioned in the prime mover shell between the positive-displacement decompressor and an oil reservoir, wherein the exhaust gas barrier ring includes apertures through which a lubricating oil passes to the oil reservoir. 
     
     
         4 . The heat engine of  claim 1 , wherein the refrigerant holding tank is eccentrically shaped,includes inclined sides, and wherein the refrigerant holding tank is configured to hold the refrigerant in a vapor phase at the upper portion. 
     
     
         5 . The heat engine of  claim 1 , wherein the organic refrigerant exhibits a boiling point below −40° C −40° C. 
     
     
         6 . The heat engine of  claim 1 , wherein the organic refrigerant exhibits a boiling point below −45° C −45° C. 
     
     
         7 . The heat engine of  claim 1 , further comprising a vertically oriented refrigerant tank having a downwardly tapering and downwardly decreasing cross-sectional area in the low-pressure zone. 
     
     
         8 . The heat engine of  claim 1 , wherein the high-pressure zone comprises a vertically oriented tubular heat exchanger having:
 a fluid entrance configured to receive fluid from the heat source in an upper portion thereof;   a fluid exit configured to deliver the fluid in a lower portion thereof;   a refrigerant entrance for the organic refrigerant in the gaseous phase in the lower portion thereof; and   a refrigerant exit for the organic refrigerant in the gaseous phase in the upper portion thereof, wherein the refrigerant exit is configured to deliver organic refrigerant in the gaseous phase to an input of the positive-displacement decompressor.   
     
     
         9 . The heat engine of  claim 8   claim 1 , wherein the vertically oriented tubular heat exchanger is configured to maintain a temperature gradient at least partially based onassisted by gravity. 
     
     
         10 . The heat engine of  claim 1 , wherein the closed-loop path further comprises at leastincludes two oil separators connected in seriesin the low-pressure zone. 
     
     
         11 . The heat engine of  claim 1 , wherein the low-pressure zone of the closed-loop path further comprises at least one refrigeration coilincludes a first cooling coil and a second cooling coil configured to receive cool, pressurizedthe organic refrigerant from the high-pressure zone. 
     
     
         12 . A method of generating electricityoperating a heat engine using an organic Rankine cycle, the method comprising:
 circulating an organic refrigerant in a closed-loop path, the organic refrigerant exhibiting a boiling point below −35° C. −35° C., the closed-loop path having both a high-pressure zone and a low-pressure zone, wherein the organic refrigerant is heated from a liquid phase to a gaseous phase in the high-pressure zone contains a first portion of the organic refrigerant in at least a gaseous phase, and wherein the low-pressure zone contains a second portion of the organic refrigerant in at least a liquid phase and the organic refrigerant is expanded and cooled from the gaseous phase to the liquid phase in the low-pressure zone;   operating a positive-displacement decompressor to continuously flow the organic refrigerant in the gaseous phase from the high-pressure zone to the low-pressure zone and extract mechanical energy;   operating an electrical generator to convert mechanical energy to electrical energy, wherein the electrical generator is coupled to the positive-displacement decompressor;   operating a positive-displacement hydraulic pump to provide continuous flow of the organic refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone, the organic refrigerant flowing through a refrigerant holding tank in the high-pressure zone between the positive-displacement hydraulic pump and the positive-displacement decompressor, wherein a lower portion of the refrigerant holding tank has a larger cross-sectional area than an upper portion thereof;   absorbing heat from a heat source to the organic refrigerant in the high-pressure zone of the closed-loop path, the heat source having a temperature of less than 82° C.; and 82° C.;   transferring heat from the organic refrigerant to a heat sink in a the low-pressure zone of the closed-loop path with a refrigerant cooling heat exchanger, wherein the positive-displacement hydraulic pump is between the refrigerant holding tank and the refrigerant cooling heat exchanger; and   removing lubricating oil from the gaseous phase of the organic refrigerant at a pourous oil separator covering exhaust ports of the positive-displacement decompressor.   
     
     
         13 . The method of  claim 12 , further comprising circulating apumping the lubricating oil in the closed-loop pathfrom an oil reservoir to an intake port of the positive-displacement decompressor. 
     
     
         14 . The method of  claim 13 , further comprising heating at least a portion of the lubricating oil in a the oil reservoir. 
     
     
         15 . The method of  claim 13 , further comprising separating at least a portion ofpassing the removed lubricating oil from a gaseous phase of the organic refrigerantthrough apertures in an exhaust gas barrier ring. 
     
     
         16 . The method of  claim 12 , wherein absorbing heat from a heat source to the organic refrigerant comprisesincludes transferring heat from water to the organic refrigerant in a vertically oriented heat exchanger that is a fin-tube heat exchanger. 
     
     
         17 . The method of  claim 16 , further comprising causing a temperature gradient assisted by gravity in the vertically oriented heat exchanger. 
     
     
       18. A heat engine configured to operate an organic Rankine cycle, the heat engine comprising:
 a closed-loop path for an organic refrigerant, the closed-loop path including a high-pressure zone and a low-pressure zone;   a high-pressure vapor enhancer within the high-pressure zone configured to heat the organic refrigerant to a superheated vapor within the high-pressure zone with a heat source;   a vapor expansion chamber connected to an expansion chamber extension in the low-pressure zone;   a sub-cooling coil within the expansion chamber extension configured to begin condensing the organic refrigerant to a liquid phase in the low-pressure zone;   a refrigerant cooling heat exchanger configured to receive the organic refrigerant from the expansion chamber extension, the refrigerant cooling heat exchanger configured to continue condensing the organic refrigerant to the liquid phase in the low-pressure zone with a heat sink;   a positive-displacement decompressor configured to receive the superheated vapor and provide a pressure gradient between the high-pressure zone and the low-pressure zone;   a positive-displacement pump for providing continuous flow of the organic refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone; and   a refrigerant holding tank in the high-pressure zone in operable communication with the positive-displacement pump and positioned between the high-pressure vapor enhancer and the positive-displacement pump, a lower portion of the refrigerant holding tank having a larger cross-sectional area than an upper portion thereof, wherein the positive-displacement pump is between the refrigerant holding tank and the refrigerant cooling heat exchanger.   
     
     
       19. The heat engine of  claim 18 , wherein the pressure gradient is between about 20 bar and about 42 bar. 
     
     
       20. The heat engine of  claim 18 , wherein the positive-displacement decompressor is located within a prime mover shell. 
     
     
       21. The heat engine of  claim 18 , further comprising a lubricating oil pump configured to inject lubricating oil at an intake port of the positive-displacement decompressor. 
     
     
       22. The heat engine of  claim 18 , wherein the refrigerant holding tank is configured to operate as a pulsation dampener to mitigate fluid hammer. 
     
     
       23. The heat engine of  claim 18 , wherein the upper portion of the refrigerant holding tank is configured to hold the organic refrigerant in a gaseous phase. 
     
     
       24. The heat engine of  claim 18 , wherein the vapor expansion chamber is in operable communication with an exhaust portion of the positive-displacement decompressor. 
     
     
       25. A heat engine configured to operate an organic Rankine cycle, the heat engine comprising:
 a closed-loop path for an organic refrigerant, the closed-loop path including a high-pressure zone and a low-pressure zone;   a high-pressure vapor enhancer within the high-pressure zone configured to heat the organic refrigerant to a gaseous phase within the high-pressure zone with a heat source;   a vapor expansion chamber connected to an expansion chamber extension in the low-pressure zone;   a sub-cooling coil within the expansion chamber extension configured to begin condensing the organic refrigerant to a liquid phase in the low-pressure zone;   a refrigerant cooling heat exchanger configured to receive the organic refrigerant from the expansion chamber extension, the refrigerant cooling heat exchanger configured to continue condensing the organic refrigerant to the liquid phase in the low-pressure zone with a heat sink;   a positive-displacement decompressor configured to provide a pressure gradient through which the organic refrigerant in the gaseous phase flows continuously from the high-pressure zone to the low-pressure zone such that the positive-displacement decompressor extracts mechanical energy;   a positive-displacement pump for providing continuous flow of the organic refrigerant in the liquid phase from the low-pressure zone to the high-pressure zone; and   a refrigerant holding tank in the high-pressure zone and in operable communication with the positive-displacement pump and having inclined sides, a lower portion of the refrigerant holding tank having a larger cross-sectional area than an upper portion thereof, wherein the positive-displacement pump is between the refrigerant holding tank and the refrigerant cooling heat exchanger.   
     
     
       26. A method of operating a heat engine using an organic Rankine cycle, the method comprising:
 circulating an organic refrigerant in a closed-loop path, the closed-loop path having both a high-pressure zone and a low-pressure zone;   operating a positive-displacement hydraulic pump to provide continuous flow of the organic refrigerant in a liquid phase from the low-pressure zone to the high-pressure zone, the organic refrigerant flowing through a refrigerant holding tank in the high-pressure zone between the positive-displacement hydraulic pump and a positive-displacement decompressor, wherein a lower portion of the refrigerant holding tank has a larger cross-sectional area than an upper portion thereof, wherein the positive-displacement hydraulic pump is between the refrigerant holding tank and a refrigerant cooling heat exchanger in the low-pressure zone;   absorbing heat from a heat source to the organic refrigerant in the high-pressure zone of the closed-loop path to superheat the organic refrigerant;   operating the positive-displacement decompressor to continuously flow the organic refrigerant from the high-pressure zone to the low-pressure zone:   begin condensing the organic refrigerant in an expansion chamber extension that has a sub-cooling coil therein, wherein the expansion chamber extension is connected to an expansion chamber that receives the organic refrigerant from the positive displacement decompressor; and   transferring heat from the organic refrigerant to a heat sink in the refrigerant cooling heat exchanger to continue condensing the organic refrigerant when the refrigerant cooling heat exchanger receives the organic refrigerant from the expansion chamber extension.