System and method for geothermal heat harvesting

Abstract

A system and method for deploying a heat harvesting system and for harvesting heat from a geothermal well using one or more heat pipes. A heat exchanger may receive heat from one or more heat pipes for transfer to a heat receiving component. The heat pipes may be thermally coupled to the heat exchanger via a thermal gap material having a relatively low thermal conductivity. A mounting component may engage heat pipes and define a thermal gap between the heat pipes and heat exchanger. A heat spreader, having a relatively high thermal conductivity, may be used to transfer heat from the heat pipes to the thermal gap material and help define a working temperature for the heat pipes. A heat pipe deployment system may include anti-buckling supports and/or a guide to help keep the heat pipes from buckling and to guide the heat pipes into corresponding well bores during deployment.

1 . A geothermal heat harvesting system, comprising:
 a heat exchanger arranged to receive heat from a geothermal well for transfer to a heat receiving component; and   one or more heat pipes arranged in the well to transfer heat from the well to the heat exchanger, the one or more heat pipes each having an evaporator section positioned within the geothermal well and distant from the heat exchanger and a condenser section positioned adjacent the heat exchanger.   
     
     
         2 . The system of  claim 1 , further comprising:
 a thermal gap material positioned in a thermal gap between the condenser section of the one or more heat pipes and the heat exchanger, the thermal gap material providing a thermal coupling between the one or more heat pipes and the heat exchanger such that a desired temperature drop is achieved between the one or more heat pipes and the heat exchanger when heat is transferred via the thermal gap material, the thermal gap material having a thermal conductivity less than about 12 W/m-K.   
     
     
         3 . The system of  claim 2 , wherein a conduction length of the thermal gap and the thermal conductivity of the thermal gap material are arranged to define a working temperature for the at least one heat pipe. 
     
     
         4 . The system of  claim 2 , wherein the thermal gap material includes liquid water or geothermal brine and has a thermal conductivity of about 0.6 W/m-K. 
     
     
         5 . The system of  claim 2 , further comprising a heat spreader between the one or more heat pipes and the thermal gap material and that is in direct thermal contact with the one or more heat pipes and the thermal gap material. 
     
     
         6 . The system of  claim 5 , wherein the heat spreader is metal and/or has thermal conductivity over 12 W/m-K. 
     
     
         7 . The system of  claim 5 , wherein the heat spreader includes a sleeve positioned over the heat pipe. 
     
     
         8 . The system of  claim 5 , wherein the heat spreader has a cylindrical shape, a partial cylindrical shell configuration, is a sleeve and/or is a plate. 
     
     
         9 . The system of  claim 1 , wherein the one or more heat pipes includes a plurality of heat pipes that are arranged around the heat exchanger at a vertical level in the well. 
     
     
         10 . The system of  claim 9 , wherein the one or more heat pipes includes a plurality of heat pipes that are arranged around the heat exchanger at multiple vertical levels in the well. 
     
     
         11 . The system of  claim 1 , wherein the one or more heat pipes each have a length of 40 to 300 feet. 
     
     
         12 . The system of  claim 1 , wherein the condenser section of the heat pipes is aligned along a length of the heat exchanger. 
     
     
         13 . The system of  claim 1 , wherein the condenser section of the heat pipes is uniformly spaced from the heat exchanger along a length of the condenser section of 2 to 20 feet. 
     
     
         14 . The system of  claim 1 , wherein the evaporator section of the one or more heat pipes extends radially away from the heat exchanger from 20 to 300 feet. 
     
     
         15 . The system of  claim 1 , further comprising a collar engaged to the one or more heat pipes, the collar configured to receive the heat exchanger at an inner side of the collar and to position the one or more heat pipes from the heat exchanger so as to define a thermal gap between the one or more heat pipes and the heat exchanger. 
     
     
         16 . The system of  claim 1 , further comprising a heat receiving component that includes a heat exchange fluid, one or more conduits to conduct a heat exchange fluid, a thermal storage device, a thermal storage medium, and/or one or more thermoelectric or other power conversion devices. 
     
     
         17 . The system of  claim 1 , wherein the one or more heat pipes includes a thermosiphon, a loop thermosiphon, a pulsating heat pipe, and/or an osmotic heat pipe. 
     
     
         18 . A heat pipe and mounting component apparatus for use with a heat exchanger in harvesting geothermal heat, comprising:
 one or more heat pipes each having two end portions and an elongated central portion; and   a mounting component arranged and dimensioned to engage with an end portion of the one or more heat pipes and to position the end portion within a specified distance of a perimeter of the heat exchanger to define a thermal gap between the one or more heat pipes and the heat exchanger to be filled by a thermal gap material that thermally couples the one or more heat pipes to the heat exchanger.   
     
     
         19 . The apparatus of  claim 18 , further comprising the thermal gap material positioned in the gap between, and thermally coupling, the heat exchanger and the one or more heat pipes. 
     
     
         20 . The apparatus of  claim 19 , wherein a size of the gap and a thermal resistance of the thermal gap material are configured to permit the one or more heat pipes to operate at an optimal heat pipe working temperature for use in harvesting geothermal energy. 
     
     
         21 . The apparatus of  claim 20 , wherein the optimal heat pipe working temperature is higher than the temperature of the heat exchanger by an amount between 10% and 40% of the temperature difference from the heat exchanger to the geothermal resource. 
     
     
         22 . The apparatus of  claim 18 , wherein the thermal gap material has a thermal conductivity of 0.5 to 12 W/m-K that is less than a thermal conductivity of the mounting component. 
     
     
         23 . The apparatus of  claim 18 , wherein the mounting component has a contact area with the one or more heat pipes and a thermal conductivity selected to promote heat spreading from the one or more heat pipes that are thermally coupled to the mounting component. 
     
     
         24 . The apparatus of  claim 23 , further comprising the thermal gap material which includes water. 
     
     
         25 . The apparatus of  claim 18 , wherein the mounting component has a surface area facing the heat exchanger that is larger than a surface area presented by the at least one heat pipe to the heat exchanger. 
     
     
         26 . The apparatus of  claim 25 , wherein the surface area of the mounting component facing the heat exchanger is at least 1 to 10 times the surface area presented by the at least one heat pipe to the heat exchanger. 
     
     
         27 . The apparatus of  claim 18 , wherein the mounting component includes a collar arranged to extend around the perimeter of the heat exchanger, the collar including a plurality of spacer elements extending radially inwardly from the collar to define, at least in part, the gap between the one or more heat pipes and the heat exchanger. 
     
     
         28 . The apparatus of  claim 18 , wherein the mounting component includes an upper collar and a lower collar, the upper and lower collars being spaced from each other and having the one or more heat pipes fixed to the upper and lower collar and arranged to define a gap between the one or more heat pipes and the heat exchanger in areas between the upper and lower collars. 
     
     
         29 . The apparatus of  claim 28 , further comprising an anti-buckling support engaged with the one or more heat pipes below the lower collar and arranged to move relative to the one or more heat pipes in the presence of a force over a threshold. 
     
     
         30 . The apparatus of  claim 18 , wherein the one or more heat pipes each include an evaporator section and a condenser section, the one or more heat pipes being thermally coupled with the mounting component at the condenser section. 
     
     
         31 . The apparatus of  claim 18 , further comprising a heat exchanger positioned adjacent the mounting component, wherein the thermal gap is present between the heat exchanger and the mounting component. 
     
     
         32 . The apparatus of  claim 31 , further comprising a thermal gap material positioned between the mounting component and the heat exchanger, the thermal gap material having a thermal conductivity that is less than a thermal conductivity of the mounting component. 
     
     
         33 . The apparatus of  claim 32 , wherein the thermal gap material includes liquid water. 
     
     
         34 . The apparatus of  claim 18 , further comprising a heat pipe guide including a guide channel to guide movement of a heat pipe into a bore in a geothermal well. 
     
     
         35 . A geothermal heat harvesting system, comprising:
 a heat exchanger arranged to transfer heat from a geothermal well to a heat receiving component;   one or more heat pipes arranged in the well to transfer heat from the well to the heat exchanger, the one or more heat pipes having an evaporator section and a condenser section; and   a thermal gap material positioned in a thermal gap between the one or more heat pipes and the heat exchanger, the thermal gap material providing a thermal coupling between the one or more heat pipes and the heat exchanger such that more than 60% of heat transferred between the one or more heat pipes and the heat exchanger is transferred via the thermal gap material, the thermal gap material having a thermal conductivity less than about 12 W/m-K.   
     
     
         36 . The system of  claim 35 , wherein a conduction length of the thermal gap and the thermal conductivity of the thermal gap material are arranged to define a working temperature for the at least one heat pipe. 
     
     
         37 . The system of  claim 36 , wherein the thermal gap material includes liquid water and has a thermal conductivity of about 0.6 W/m-K. 
     
     
         38 . The system of  claim 35 , further comprising a heat spreader between the at least one heat pipe and the thermal gap material and that is in direct thermal contact with the at least one heat pipe and the thermal gap material. 
     
     
         39 . The system of  claim 38 , wherein the heat spreader is metal and/or has thermal conductivity over 12 W/m-K. 
     
     
         40 . The system of  claim 39 , wherein the heat spreader includes a sleeve positioned over the heat pipe. 
     
     
         41 . The system of  claim 38 , wherein the heat spreader has a cylindrical shape, a partial cylindrical shell configuration, is a sleeve and/or is a plate. 
     
     
         42 . The system of  claim 35 , wherein the heat receiving component includes a heat exchange fluid, one or more conduits to conduct a heat exchange fluid, a thermal storage device, a thermal storage medium, and/or one or more thermoelectric or other power conversion devices. 
     
     
         43 . The system of  claim 35 , wherein the heat pipe includes a thermosiphon, a loop thermosiphon, a pulsating heat pipe, osmotic heat pipe and/or other possible specific configurations driven by other forces such as electro-osmotic, acoustic, electrical, and/or magnetic. 
     
     
         44 . A method for deploying a thermal coupling for a geothermal device, comprising:
 providing a heat exchanger in a geothermal well;   providing one or more heat pipes in the geothermal well, each of the heat pipes including a condenser section located nearer the heat exchanger than an evaporator section of the heat pipe; and   providing a thermal gap material that extends between, and thermally couples, the one or more heat pipes and the heat exchanger such that more than 60% of heat transferred between the one or more heat pipes and the heat exchanger is transferred via the thermal gap material, the thermal gap material having a thermal conductivity less than about 12 W/m-K.   
     
     
         45 . The method of  claim 44 , wherein a conduction length of the thermal gap and the thermal conductivity of the thermal gap material are arranged to define a working temperature for the at least one heat pipe. 
     
     
         46 . The method of  claim 44 , wherein the thermal gap material includes liquid water and has a thermal conductivity of about 0.6 W/m-K. 
     
     
         47 . The method of  claim 44 , further comprising providing a heat spreader between the at least one heat pipe and the thermal gap material and that is in direct thermal contact with the at least one heat pipe and the thermal gap material. 
     
     
         48 . The method of  claim 47 , wherein the heat spreader is metal and/or has thermal conductivity over 12 W/m-K. 
     
     
         49 . The method of  claim 48 , wherein the heat spreader includes a sleeve positioned over the heat pipe. 
     
     
         50 . The method of  claim 47 , wherein the heat spreader has a cylindrical shape, a partial cylindrical shell configuration, is a sleeve and/or is a plate. 
     
     
         51 . The method of  claim 44 , further comprising transferring heat from the heat exchanger to a heat receiving component that includes a heat exchange fluid, one or more conduits to conduct a heat exchange fluid, a thermal storage device, a thermal storage medium, and/or one or more thermoelectric or other power conversion devices. 
     
     
         52 . The method of  claim 44 , wherein the one or more heat pipes includes a thermosiphon, a loop thermosiphon, a pulsating heat pipe, and/or an osmotic heat pipe. 
     
     
         53 . A heat pipe and mounting component apparatus for use with a heat exchanger in harvesting geothermal heat, comprising:
 one or more heat pipes each having two end portions and an elongated central portion;   an upper collar arranged and dimensioned to engage with an end portion of the one or more heat pipes and to position the end portion within a specified distance of a perimeter of the heat exchanger located inside of the collar to define a thermal gap between the one or more heat pipes and the heat exchanger; and   an anti-buckling portion separate from the upper collar and attached to the one or more heat pipes at a location below and away from the upper collar, the anti-buckling portion being releasably attached to the one or more heat pipes to allow movement of the one or more heat pipes relative to the anti-buckling portion in a direction along a length of the one or more heat pipes.   
     
     
         54 . The system of  claim 53 , wherein the anti-buckling portion is attached to the one or more heat pipes by a frangible connection, such as a metallurgical joint or adhesive, that fixes the heat pipes relative to the anti-buckling portion until a force applied to the one or more heat pipes exceeds a threshold value. 
     
     
         55 . The system of  claim 54 , wherein the frangible connection fixes the anti-buckling portion relative to the heat pipes and the upper collar until a force moving the upper collar toward the anti-buckling portion exceeds the threshold value. 
     
     
         56 . The system of  claim 53 , wherein the upper collar and the anti-buckling portion are movable toward each other so as to contact each other. 
     
     
         57 . The system of  claim 56 , further comprising a lower guide portion that includes one or more heat pipe guides arranged to guide the one or more heat pipes in deployment in the geothermal well in directions away from the heat exchanger. 
     
     
         58 . The system of  claim 57 , wherein the anti-buckling portion is positioned between the upper collar and lower guide portion, and the upper collar is movable toward the lower guide portion to deploy the one or more heat pipes in the well. 
     
     
         59 . The system of  claim 58 , further comprising a lower collar engaged with the one or more heat pipes at a location below the upper collar and above the anti-buckling portion. 
     
     
         60 . The system of  claim 53 , wherein the upper collar and/or the anti-buckling portion include two parts that are engagable with each other so as to receive a drill string or a portion of the heat exchanger between the two parts. 
     
     
         61 . The system of  claim 53 , wherein the heat pipe includes a thermosiphon, a loop thermosiphon, a pulsating heat pipe, and/or osmotic heat pipe. 
     
     
         62 . A method for deploying one or more heat pipes in a geothermal well for use with a heat exchanger in harvesting geothermal heat, comprising:
 providing one or more heat pipes each having a first portion engaged with an upper collar and a second portion engaged with an anti-buckling portion separate from the upper collar and attached to the one or more heat pipes at a location below the upper collar and above a distal end of the one or more heat pipes;   inserting the distal end of the one or more heat pipes into a corresponding well bore;   exerting a force on the one or more heat pipes so as to disengage the one or more heat pipes from the anti-buckling portion and allow the one or more heat pipes to move in a direction along a length of the one or more heat pipes relative to the anti-buckling portion; and   arranging the upper collar adjacent a heat exchanger in the geothermal well.   
     
     
         63 . The method of  claim 62 , wherein the anti-buckling portion is releasably attached to the one or more heat pipes by a frangible connection. 
     
     
         64 . The method of  claim 62 , wherein the step of arranging the upper collar includes positioning a portion of the one or more heat pipes within a specified distance of a perimeter of the heat exchanger to define a thermal gap between the one or more heat pipes and the heat exchanger. 
     
     
         65 . The method of  claim 62 , further comprising providing a lower guide portion that includes one or more heat pipe guides arranged to guide the one or more heat pipes in deployment in the geothermal well in directions away from the heat exchanger; and
 using the lower guide to guide movement of the one or more heat pipes into respective bores during the inserting step.