Geothermal well using graphite as solid conductor

Abstract

A closed loop geothermal system and apparatus is provided comprising a piping system inside a main well to create a closed circulation of thermal fluid to a target temperature zone underground. The piping system may have an inner pipe is inserted inside an outer pipe/casing in a concentric arrangement to allow thermal fluid to flow downward between inner pipe and outer pipe/casing and upward inside inner pipe by entering inner pipe near the bottom of the well. A heat conducting filler comprising graphite may be packed in a space between the well and piping system in the target temperature zone. The system and apparatus may further include an extended portion of the main well and/or heat conducting channels each comprising graphite converging on a heat exchange zone of the well, which may further include a heat exchanger. Methods for constructing and operating the apparatus are also provided

1 . A closed loop geothermal apparatus comprising:
 a. a main well comprising a hole in the earth;   b. a piping system comprising one or more pipes;   c. one or more heat conducting channels; and   d. a heat conducting filler,   wherein the piping system is inside the main well, such that a bottom portion of the piping system reaches a target temperature zone underground,   wherein the one or more heat conducting channels each comprise a wellbore filled and packed with graphite,   wherein the one or more heat conducting channels converge to contact a heat exchange zone of the main well at or near the bottom of the piping system;   and   wherein the heat conducting filler consisting essentially of graphite is packed in a space between the main well and the piping system in the target temperature zone.   
     
     
         2 . The apparatus of  claim 1 , wherein the piping system comprises an inner pipe and an outer pipe in a concentric arrangement. 
     
     
         3 . The apparatus of  claim 2 , wherein the inner pipe and the outer pipe are configured such that a thermal fluid traveling downward in the space between the inner pipe and the outer pipe can enter the inner pipe at or near the bottom of the outer pipe and travel upward within the inner pipe. 
     
     
         4 . The apparatus of  claim 2 , wherein the inner pipe is made of a heat conducting material in the target temperature zone. 
     
     
         5 . The apparatus of  claim 2 , wherein the outer pipe is made of a heat conducting material in the target temperature zone. 
     
     
         6 . The apparatus of  claim 1 , wherein the heat conducting filler packed in the space between the main well and the outer pipe comprises graphite rods, graphite powder, and/or graphite flakes. 
     
     
         7 . The apparatus of  claim 1 , wherein the heat conducting filler packed in the space between the main well and the outer pipe is pure or nearly pure graphite. 
     
     
         8 . The apparatus of  claim 1 , wherein the heat conducting filler has a thermal conductivity in a range from about 100 W/m·K to about 5780 W/m·K. 
     
     
         9 . The apparatus of  claim 10 , wherein the heat conducting filler comprising graphite has a thermal conductivity from about 100 W/m·K to about 450 W/m·K. 
     
     
         10 . The apparatus of  claim 1 , wherein the heat conducting filler comprising graphite has a thermal conductivity from about 120 W/m·K to about 300 W/m·K. 
     
     
         11 . The apparatus of  claim 1 , further comprising an extended portion of the main well below the bottom of the piping system, wherein the extended portion of the main well is filled and packed with graphite. 
     
     
         12 . The apparatus of  claim 11 , wherein the graphite of the extended portion of the main well is pure or nearly pure graphite. 
     
     
         13 . The apparatus of  claim 11 , wherein the piping system has a closed bottom, and wherein the graphite in the extended portion of the main well contacts the closed bottom of the piping system. 
     
     
         14 . The apparatus of  claim 11 , wherein the graphite in the extended portion of the main well includes multiple graphite rods stacked in the extended portion of the main well, wherein the graphite rods contact the closed bottom of the piping system. 
     
     
         15 . The apparatus of  claim 1 , wherein a portion of each of the one or more heat conducting channels comprises graphite that interfaces and contacts the graphite of the heat conducting filler to provide a continuous flow of thermal energy from the one or more heat conducting channels to the heat exchange zone of the main well through the graphite of the one or more heat conducting channels and the heat conducting filler. 
     
     
         16 . The apparatus of  claim 15 , wherein the graphite filled and packed in the one or more heat conducting channels comprises graphite rods, graphite powder, and/or graphite flakes. 
     
     
         17 . The apparatus of  claim 15 , wherein the graphite filled and packed in the one or more heat conducting channels is pure or nearly pure graphite. 
     
     
         18 . The apparatus of  claim 15 , wherein the one or more heat conducting channels extend horizontally through a sedimentary layer of the earth. 
     
     
         19 . The apparatus of  claim 1 , further comprising an outer casing positioned between the main well and the piping system, wherein the heat conducting filler is packed in a space between the main well and the outer casing in the target temperature zone. 
     
     
         20 . The apparatus of  claim 3 , further comprising a heat exchanger positioned in a heat exchange zone of the main well at or near the bottom of the inner and outer pipes. 
     
     
         21 . The apparatus of  claim 20 , wherein the heat exchanger comprises one or more supporting sections between the inner and outer pipes. 
     
     
         22 . The apparatus of  claim 20 , wherein the heat exchanger comprises a thermally conducting object inside the inner pipe. 
     
     
         23 . The apparatus of  claim 1 , wherein the piping system is configured such that a thermal fluid travels downward toward the bottom portion of the piping system and heated, before traveling upward toward the surface of the earth. 
     
     
         24 . A closed loop geothermal apparatus comprising:
 a. a main well comprising a hole in the earth;   b. a piping system comprising one or more pipes;   c. an extended portion of the main well below the bottom of the piping system; and   d. a heat conducting filler,   wherein the piping system is inside the main well, such that a bottom portion of the piping system reaches a target temperature zone underground,   wherein the piping system is configured such that a thermal fluid traveling downward toward the bottom of the piping system and heated before traveling upward toward the surface of the earth,   wherein the heat conducting filler consisting essentially of graphite is packed in a space between the main well and the piping system in the target temperature zone, and   wherein the extended portion of the main well is filled and packed with graphite.   
     
     
         25 . The apparatus of  claim 24 , wherein the graphite of the extended portion of the main well is pure or nearly pure graphite. 
     
     
         26 . The apparatus of  claim 24 , wherein the piping system has a closed bottom, and wherein the graphite in the extended portion of the main well contacts the closed bottom of the piping system. 
     
     
         27 . The apparatus of  claim 24 , wherein the graphite in the extended portion of the main well includes multiple graphite rods stacked in the extended portion of the main well, wherein the graphite rods contact the closed bottom of the piping system. 
     
     
         28 . A method comprising:
 (a) providing a closed loop geothermal apparatus comprising a main well having a hole in the earth, a piping system having one or more pipes, one or more heat conducting channels; and a heat conducting filler;   wherein the piping system is inside the main well, such that a bottom portion of the piping system reaches a target temperature zone underground, wherein the one or more heat conducting channels each comprise a wellbore filled and packed with graphite, wherein the one or more heat conducting channels converge to contact a heat exchange zone of the main well at or near the bottom of the piping system; and wherein the heat conducting filler consisting essentially of graphite is packed in a space between the main well and the piping system in the target temperature zone; and (b) causing a thermal fluid to flow downward toward the bottom portion of the piping system and heated, before traveling upward toward the surface of the earth.