US20150292774A1

US20150292774A1 - System and method for geothermal heat harvesting

Info

Publication number: US20150292774A1
Application number: US14/443,891
Authority: US
Inventors: Sukhvinder S. Kang; Randolph H. Cook; Joseph Edward Nicolato; Jonathan James Hall
Original assignee: GTHERM Inc; Aavid Thermalloy LLC
Current assignee: Gtherm Geo Inc; Aavid Thermalloy LLC
Priority date: 2012-11-21
Filing date: 2013-11-21
Publication date: 2015-10-15
Also published as: WO2014081911A3; WO2014081911A2

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.

Description

BACKGROUND

Harvesting of heat energy from a geothermal well (i.e., an underground region) can be useful for various purposes, including electrical energy generation, transferring heat to above ground systems for use in space heating, industrial or other processes, or other uses.

SUMMARY OF INVENTION

Aspects of the invention provide for heat harvesting from a geothermal well (i.e., an underground region) using one or more heat pipes. In some embodiments, one or more heat pipes may be arranged in a tree-type or other configuration and used to transfer heat from portions of the geothermal well to a heat exchanger and a heat receiving component, such as a heat exchange liquid, a thermoelectric device, or other component that receives heat, e.g., for use in generating electricity.
In one aspect of the invention, a geothermal heat harvesting system includes a heat exchanger arranged to receive heat from a geothermal well for transfer to a heat receiving component. The heat exchanger may include a cylindrical body or pipe that receives heat at its outer wall and transfers that heat to a working fluid, such as water or steam, in the heat exchanger. The heated fluid may be conducted out of the heat exchanger to a heat receiving component such as a thermal storage device, a thermal storage medium, and/or one or more thermoelectric or other power conversion devices, such as a steam turbine and generator.
One or more heat pipes may be arranged in the well to transfer heat from the well to the heat exchanger, e.g., heat pipes may be arranged around the heat exchanger and extend outwardly from the heat exchanger into hot rock or other medium of the geothermal well. The heat pipes may be arranged in one or more levels, e.g., a plurality of heat pipes may be arranged around the heat exchanger and extend radially into the geothermal well (e.g., 20 to 100 feet) at one or more vertical positions in the well. The one or more heat pipes may each have an evaporator section positioned within the geothermal well and distant from the heat exchanger, and a condenser section positioned adjacent the heat exchanger. Thus, heat received at the evaporator section may be transferred to the condenser section, which relays the heat to the heat exchanger. The heat pipes may be arranged in any suitable way, and may include a thermosiphon, a loop thermosiphon, a pulsating heat pipe, and/or an osmotic heat pipe. The heat pipes may have a length of 40 to 120 feet (or other suitable length such as up to 300 feet), and may have the condenser section aligned along a length of the heat exchanger. For example, the condenser section of the heat pipes may be uniformly spaced from the heat exchanger along a length of the condenser section of 2 to 20 feet. Thus, portions of the condenser section may be spaced from the heat exchanger to achieve a defined thermal gap or thermal resistance which helps to control the heat transfer rate between the heat pipes and the heat exchanger, allowing the heat pipe to operate at an optimal or other designed working temperature.
In some embodiments, a thermal gap material may be positioned in a thermal gap between the condenser section of the one or more heat pipes and the heat exchanger. The thermal gap material may provide a thermal coupling between the one or more heat pipes and the heat exchanger such that a desired temperature drop is incurred when heat is transferred between the one or more heat pipes and the heat exchanger via the thermal gap material. The thermal gap material may have a relatively low thermal conductivity, e.g., less than about 12 W/m-K or around 0.6 W/m-K, so as to meter heat transferred to the heat exchanger in comparison to a condition in which the heat pipe(s) are coupled to the heat exchanger by a steel or other relatively highly thermally conductive metal connection. A conduction length of the thermal gap and the thermal conductivity of the thermal gap material may be arranged to define a working temperature for the at least one heat pipe, which may be elevated above the operating temperature of the heat exchanger by 10 to 40% of the temperature difference between the heat exchanger and the geothermal resource and may allow the heat pipe(s) to harvest heat from the geothermal resource more efficiently than at lower temperatures. A majority of heat transferred between the heat pipe(s) and the heat exchanger may be transferred through the thermal gap material, e.g., 60%, 70%, 90%, 95% or more of heat transferred between the two may be transmitted through the thermal gap material.
In some embodiments, a heat spreader may be provided between the at least one heat pipe and the thermal gap material to help transfer heat from the heat pipe to the thermal gap material. Thus, the heat spreader may have a relatively high thermal conductivity, e.g., above 12 W/m-K, and be in direct thermal contact with the at least one heat pipe and with the thermal gap material. While the heat spreader may be arranged in different ways, the heat spreader may generally present a relatively smaller surface area to the heat pipe(s) for receiving heat and a relatively larger surface area to the thermal gap material. For example, the heat spreader may include a sleeve positioned over the heat pipe, and/or may include a plate with a partial cylindrical shell configuration that generally conforms to the outer periphery of a heat exchanger. The heat spreader may therefore effectively increase a surface area of the heat pipes for transferring heat to the thermal gap material.
In some embodiments, the heat pipe(s) may be mechanically coupled by a collar or other mounting component which also helps define the thermal gap between the heat pipe(s) and the heat exchanger. For example, a collar may engage with one or more heat pipes and be configured to receive the heat exchanger at an inner side of the collar, i.e., the collar may extend around the heat exchanger. The collar may help to position the one or more heat pipes from the heat exchanger so as to define a thermal gap, e.g., one or more spacer elements such as protrusions extending radially inwardly from the collar inner side may help maintain a desired distance between the heat pipe(s) and the heat exchanger. Two or more relatively short collars (e.g., 1 to 2 feet long, or more or less) may be employed, and may be spaced from each other along the condenser section of one or more heat pipes, e.g., at a distance of 10 to 20 feet or more (or less), so that portions of the heat pipes extending between the collars are suitably positioned from the heat exchanger to define a thermal gap. Alternately, a collar may have a relatively long length, e.g., of 10 to 20 feet or more (or less), and be arranged as a solid cylindrical shell, e.g., to control fluid flow in the thermal gap between the heat pipes and the heat exchanger along the length of the shell. In some embodiments, the collar may include one or more openings in the shell to permit fluid flow, e.g., to allow relatively hot fluid in the geothermal well to flow into the space between the collar and the heat exchanger and allow relatively cool fluid to exit. A collar or other mounting component may, or may not function as a heat spreader.
In one aspect of the invention, a heat pipe and mounting component apparatus for use with a heat exchanger in harvesting geothermal heat includes one or more heat pipes each having two end portions and an elongated central portion, and a mounting component dimensioned to engage and thermally couple with at least one heat pipe at or near one of the said end portions. The mounting component may be dimensioned to extend at least partially around a portion of a perimeter of the heat exchanger. For example, the mounting component may include a collar or sleeve arranged to receive a portion of a heat exchanger in the central opening of the collar, and/or may include a shoe or plate that extends around only a part of the heat exchanger. The portion of the mounting component that faces the heat exchanger may be shaped to generally conform to the shape of an adjacent portion of the heat exchanger, e.g., so that a generally uniform gap may be present between the mounting component and the heat exchanger. As will be understood by those of skill in the art, a uniform gap may provide for a uniform conduction length for heat passing between the mounting component and the heat exchanger, and thus uniform and predictable heat flow.
An interface material, or thermal gap material, may be positioned between, and thermally couple, the heat exchanger and the mounting component. The interface material may have a thermal conductivity that is less than the mounting component, and thus may provide a desired thermal gap or resistance to heat flow, e.g., to allow the one or more heat pipes to operate within an optimal working temperature range. As discussed in detail below, having a heat pipe operate in an optimal working temperature range may allow for more efficient heat harvesting. Thus, the thermal conductivity of the interface material may be selected to define an optimal heat pipe working temperature for use in harvesting geothermal energy, e.g., may be 0.5 to 12 W/m-K. Other characteristics of the thermal coupling of the heat pipe(s) to the heat exchanger, such as the surface area of the mounting component that faces the heat exchanger and the conduction length of the thermal gap, may be similarly selected to define, or otherwise be consistent with, an optimal heat pipe working temperature. In some embodiments, the optimal heat pipe working temperature may be higher than the temperature of the heat exchanger by an amount between 10% and 40% of the temperature difference between the heat exchanger and the geothermal resource. In contrast to the thermal gap material, the mounting component may have a relatively high thermal conductivity that is selected to promote heat spreading from the one or more heat pipes for transfer to the thermal gap material. As a result, a surface area of contact between the thermal gap material and the mounting component, and the thermal conductivity and thickness of the thermal gap material may be the primary controlling factors in defining a working temperature of the one or more heat pipes thermally coupled to the mounting component.
A surface area of the mounting component that faces the heat exchanger may define the surface area of contact between the thermal gap material and the mounting component, and so may help define heat flow characteristics of the heat pipe/heat exchanger thermal junction. In some embodiments, the mounting component may have a surface area facing the heat exchanger (i.e., a surface area that functions to transfer a majority of heat to the heat exchanger) that is larger than a surface area presented by the at least one heat pipe to the heat exchanger. That is, the mounting component may present a larger surface area for heat transfer to the heat exchanger than the heat pipe(s) would present in the absence of the mounting component. Such an arrangement may allow for higher heat flow rates, and/or better control over the heat flow rate of the thermal junction. In one embodiment, the surface area of the mounting component facing the heat exchanger may be at least 1 to 10 times the surface area presented by the at least one heat pipe to the heat exchanger.
The mounting component may also function to help deploy one or more heat pipes in a well and/or perform other functions. For example, the mounting component may include an upper collar portion and a lower collar portion, with the upper collar portion having one or more heat pipes fixed to the upper collar portion and the lower collar portion defining a heat pipe guide feature to receive at least one heat pipe that is fixed to the upper collar portion. The heat pipe(s) may move in a sliding relationship in the guide feature as the upper collar portion is moved toward the lower collar portion, e.g., to help guide the heat pipe(s) into side holes formed from a main well as the heat pipes are lowered into the main well bore.
In another aspect of the invention, a heat pipe and mounting component apparatus for use with a heat exchanger in harvesting geothermal heat includes 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. The thermal gap may be filled by a thermal gap material that thermally couples the one or more heat pipes to the heat exchanger. The thermal gap material may have a thermal conductivity of 0.5 to 12 W/m-K that is less than the heat pipes, mounting component or heat exchanger outer surface, e.g., the thermal gap material may be water (including brine or water containing a variety of dissolved minerals and other substances) or a thermal grout, such as a cement-like substance with an engineered thermal conductivity. The mounting component may, or may not assist in transferring heat to the heat exchanger, e.g., may play a minor role in actual heat transfer. For example, a majority of heat transferred from a heat pipe to the heat exchanger may occur along portions of the heat pipe where no mounting component, heat spreader or other structure is located. In one embodiment, the mounting component includes an upper collar and a lower collar which are fixed to a set of heat pipes and are spaced from each other. Thus, an exposed portion of the heat pipes may extend between the collars and be spaced from the heat exchanger by a desired thermal gap. A bulk of heat transferred from the heat pipes to the heat exchanger may occur along the exposed heat pipe sections extending between the collars. In some embodiments, a heat spreader in the form of a sleeve may be arranged around the heat pipes, e.g., the heat pipes may include two concentric tubes with the outer tube functioning as a heat spreader.
In another aspect of the invention, a heat pipe deployment system may include one or more anti-buckling supports to assist in inserting one or more heat pipes in a geothermal well. For example, a geothermal well may be prepared for deployment of heat pipes by drilling or otherwise forming bores that extend radially outwardly from a main well bore. These bores may each receive at least one corresponding heat pipe, which is inserted into the bore from the main well bore and may have a length of 100 feet or more. To assist in inserting the heat pipe(s) into corresponding radial bores, one or more anti-buckling supports may be engaged with the heat pipe(s) to help keep the heat pipe(s) relatively straight when an axial load is applied to the pipe(s) to push the pipe(s) into the bore(s). The anti-buckling supports may disengage from the heat pipe(s) under particular conditions, such as when an axial force on the heat pipe(s) relative to the support exceeds a threshold. Thus, the anti-buckling supports may release from the heat pipes to allow their further insertion into a bore.
The system may additionally, or alternately include a heat pipe guide, or “kicker,” that helps to guide the heat pipe(s) into their respective bore. For example, the heat pipe guide may be arranged in the main well bore and include a flared or curved guide channel for one or more heat pipes. The guide channel may engage a heat pipe, e.g., at the distal end, and guide the heat pipe into a radially extending bore. The heat pipe guide may also be used to guide a tool that forms radially extending heat pipe bores, such as a rotary drilling tool, high pressure jet device, etc.
Thus, in one aspect of the invention, a heat pipe and mounting component apparatus for use with a heat exchanger in harvesting geothermal heat may include one or more heat pipes each having two end portions and an elongated central portion and an upper collar engaged with an end portion of the one or more heat pipes. An anti-buckling support, separate from the upper collar, may be attached to the one or more heat pipes at a location below and away from the upper collar. The anti-buckling support may be 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, e.g., in response to an axial force on the heat pipe(s) relative to the anti-buckling support that exceeds a threshold.
In some embodiments, the anti-buckling support 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. The frangible connection may fix the anti-buckling support 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. For example, as a force is applied to the upper collar and/or heat pipes to push the heat pipes downwardly and into respective radial bores, the heat pipes and attached anti-buckling support may move downwardly together. However, at a specified point, such as where the anti-buckling support reaches the radial bores, the anti-buckling support may disengage from the heat pipes. In some embodiments, when the anti-buckling support disengages from the heat pipe(s), the anti-buckling portion may slide along the heat pipes such that the upper collar and anti-buckling portion move toward each other. In other embodiments, the anti-buckling portion may completely detach from the heat pipes.
In some embodiments, a lower heat pipe guide portion may also be provided which 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. For example, the anti-buckling portion may be positioned between the upper collar and lower guide portion, and the upper collar may be movable toward the lower guide portion to deploy the one or more heat pipes in the well, e.g., into radially extending bores from a main well bore. As noted above, two or more collars may be engaged with the heat pipes at an upper end, e.g., a lower collar may be engaged with the one or more heat pipes at a location below the upper collar and above the anti-buckling support. In some embodiments, the upper and/or lower collars, the anti-buckling support and/or the lower heat pipe guide may include two or more 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. For example, the components may be arranged in a clam shell or other configuration so that the components can be assembled over and around an existing drill string at the surface of the well.
In another aspect of the invention, a method for deploying one or more heat pipes in a geothermal well for use with a heat exchanger in harvesting geothermal heat includes 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. The distal end of the one or more heat pipes may be inserted into a corresponding well bore, e.g., a bore that extends radially from a main well bore, and a force may be exerted on the one or more heat pipes so as to disengage the one or more heat pipes from the anti-buckling support. For example, the heat pipes may be forced downwardly into the main well bore such that the distal ends of the heat pipes move into a radially extending bore. The anti-buckling support may help keep the heat pipes generally straight in the main well bore (e.g., prevent buckling) until a certain point, such as when the anti-buckling support reaches a point where the heat pipes exit the main well bore and enter a radially extending bore. At this point, the heat pipes may detach from the anti-buckling support, allowing 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. The upper collar may be arranged adjacent a heat exchanger in the geothermal well, e.g., to position a condenser portion of the one or more heat pipes at a desired distance from the heat exchanger and thereby establish a desired thermal gap.
In another aspect of the invention, a geothermal heat harvesting system includes 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, a heat spreader in direct thermal contact with the condenser section of at least one heat pipe, and a thermal gap material positioned in a thermal gap between the heat spreader and the heat exchanger. The heat spreader may have a surface area and a first thermal conductivity, and the thermal gap material may have a second thermal conductivity that is less than the first thermal conductivity. As discussed above, a surface area of the heat spreader that functions to transfer a majority of heat to the heat exchanger, along with the thermal conductivity of the thermal gap material and a thickness of the thermal gap material (which defines the conduction length for heat moving between the heat spreader and the heat exchanger) may define a working temperature for the one or more heat pipes. In one embodiment, the heat spreader is metal and/or has thermal conductivity over 12 W/m-K, and the thermal gap material has a thermal conductivity of 0.5 to 12 W/m-K. The heat spreader may have a cylindrical shape, a partial cylindrical shell configuration, include a sleeve and/or a plate, etc., and may have a surface contour arranged to generally conform to a surface contour of a heat exchanger portion with which the heat spreader is thermally coupled. This arrangement may help define a uniform thermal gap between the heat spreader and the heat exchanger.
The geothermal heat harvesting system may be employed for any suitable purpose, e.g., the heat receiving component may include 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. Also, heat pipes used in this or other embodiments may include 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.
In another aspect of the invention, a method for deploying a thermal coupling for a geothermal device includes 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, providing a heat spreader thermally coupled to the condenser section of at least one heat pipe, the heat spreader having a first thermal conductivity, and providing a thermal gap material that extends between, and thermally couples, the heat spreader and the heat exchanger, the thermal gap material having a second thermal conductivity that is less than the first thermal conductivity. Components of the system, such as the heat spreader, thermal gap material, etc., may have any of those features described herein.
In yet another aspect of the invention, a method for designing a geothermal heat harvesting system includes determining an optimal working temperature range for one or more heat pipes used to transfer heat from portions of a geothermal well to a heat exchanger, determining a first surface area of a heat spreader to be thermally coupled to the heat exchanger based on the optimal working temperature range, the heat spreader being designed to provide heat to the heat exchanger via a thermal gap material having a thermal conductivity that is less than the heat spreader, and providing the heat spreader having the first surface area. The thermal conductivity of the thermal gap material and/or the thickness of the thermal gap material may also be determined based on the optimal working temperature range. In one embodiment, an optimal working temperature range may be determined by modeling fluid flow in the geothermal well in response to heat removal by the one or more heat pipes from portions of the geothermal well.
These and other aspects of the invention will be apparent from the following description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention are described with reference to the following drawings in which numerals reference like elements, and wherein:

FIG. 1 shows a schematic drawing of a geothermal heat harvesting system in an illustrative embodiment;

FIG. 2 shows a schematic drawing of a geothermal heat harvesting system having multiple heat pipes arranged at multiple levels in a well;

FIG. 3 shows a partial side view of a thermal transfer arrangement for transferring heat from one or more heat pipes to a heat exchanger in an illustrative embodiment;

FIG. 4 shows a cross sectional top view of the thermal transfer arrangement of FIG. 1 along the line 4-4 in one embodiment;

FIG. 5 shows a cross sectional top view of the thermal transfer arrangement of FIG. 1 along the line 4-4 in another embodiment;

FIG. 6 shows an arrangement for deploying thermal gap material in an illustrative embodiment;

FIG. 7 shows an arrangement for deploying thermal gap material in an embodiment in which one or more ports are used to position thermal gap material in a gap;

FIG. 8 shows a perspective view of a heat pipe deployment system prior to heat pipe deployment;

FIG. 9 shows a cross sectional view along the line 9-9 in FIG. 8;

FIG. 10 shows an anti-buckling support in an illustrative embodiment;

FIG. 11 shows a collar having a clam shell arrangement;

FIG. 12 shows a cross sectional view along the line 12-12 in FIG. 8;

FIG. 13 shows a perspective view of a heat pipe deployment system in an illustrative embodiment;

FIG. 14 shows a close up view of a heat pipe guide in the FIG. 13 embodiment;

FIG. 15 shows an illustrative embodiment including a multi-part mounting component in an assembled condition;

FIG. 16 shows the FIG. 15 embodiment in a pre-deployment condition;

FIG. 17 shows the mounting component and heat pipes of the FIG. 15 embodiment in a deployed condition;

FIG. 18 shows an illustrative embodiment of heat exchanger portions including one or more alignment features;

FIG. 19 shows a top perspective view of an upper portion of a mounting component in an illustrative embodiment;

FIG. 20 shows a cross sectional view of the FIG. 19 embodiment along the line 20-20 in FIG. 15;

FIG. 21 shows a cross sectional side view of the FIG. 19 embodiment;

FIGS. 22-25 show illustrative embodiments for saddles useable for engaging one or more heat pipes; and

FIG. 26 shows a cross sectional side view of an arrangement in which heat pipes extend into a heat exchanger space.

DETAILED DESCRIPTION

Aspects of the invention are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Other embodiments may be employed and aspects of the invention may be practiced or be carried out in various ways. Also, aspects of the invention may be used alone or in any suitable combination with each other. Thus, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
FIG. 1 shows a schematic view of a geothermal heat harvesting system 100 in an illustrative embodiment. It should be appreciated, however, that this is only one example configuration for a heat harvesting system 100 and that other system types or configurations are possible for use with aspects of the invention. For example, in this embodiment, a heat receiver 6 includes a steam generator, turbine, and electricity generator coupled to the turbine (along with other suitable components, such as control systems, valves, heat and/or electricity storage systems, etc.) that use heat harvested from the geothermal well 1 to generate electricity. Heat may be delivered from the well 1 to the heat receiver 6 in the form of steam or other heated fluid. However, the heat receiver 6 may be arranged in other ways. For example, harvested heat may be used to heat a building, to heat materials used in an industrial process (such as oil shale heating to recover petroleum), to generate electricity via one or more thermoelectric devices, to provide heat for a heat pump system, and so on. Moreover, the heat receiver 6 may include components below ground, such as thermoelectric components (e.g., Peltier or similar devices) located in the well 1 that generate electricity, additional heat exchangers, and so on.
It should also be understood that a geothermal well 1, as used herein, may include any underground region from which heat is harvested. In this embodiment, the well 1 is accessed by drilling using an above-surface drilling system, but the well 1 may be accessed in other ways, such as by digging a hole, providing below-ground system 100 components in the hole, and again filling the hole, whether with soil originally dug from the hole or other materials. Also, drilling to provide components in a well 1 may be done by rotating bit, fluid jet injection and/or any other suitable techniques, or combinations of such techniques.
In this embodiment, the geothermal well 1 includes fluid (such as underground water) that has at least some ability to flow in the well 1 (i.e., in a region around the below-ground components of the system 100), and therefore move heat in the well 1 by convection. However, embodiments described herein need not exchange fluid in the well 1 (e.g., underground water or steam) with fluid used by the heat harvesting system 100 to carry heat to the heat receiver 6. Instead, any fluid used by the system 100 to transport heat from the well 1 to the heat receiver 6 is generally isolated from rock, underground water and/or other features of the well. It should also be understood that aspects of the invention are not limited to such applications, however, but may be used in “dry” well 1 conditions in which fluid is not very free to flow in the well 1, or other well conditions.
The system 100 in FIG. 1 includes a heat exchanger 2 that in this embodiment transfers heat harvested from the well 1 to fluid that flows between the heat exchanger 2 and the heat receiver 6. The fluid may be gas and/or liquid (such as steam and/or water) or any other material, such as a molten salt, glycol solution or other material. In this embodiment, the heat exchange fluid flows in a closed loop system, although open loop flow may be used in some embodiments. Flow of the heat exchange fluid may be driven by pump, gravity, capillary action and/or other driving forces. In one embodiment, the heat exchanger may include one or more “hot” pipes positioned at an outer periphery of the heat exchanger 2 that carry heated fluid upwardly, and one or more “cold” pipes positioned at an interior of the heat exchanger 2. In another arrangement, the heat exchanger 2 includes a single outer pipe (e.g., used to conduct heated fluid to the receiver 6), and a single inner pipe (e.g., used to deliver relatively cool fluid to the well 1 for heating). The heat exchanger 2 may include other features to enhance heat transfer, such as serpentine flow tubes or other pathways, finned tube segments, baffles, and other components to assist in transferring heat to the working fluid, whether by increasing a surface area of heated components presented to the working fluid, slowing or diverting flow of the working fluid in one or more sections of the heat exchanger, etc. Also, the heat exchanger 2 may be arranged to transfer heat to the working fluid over an extended length of the well 1, may be arranged to transfer heat at multiple, distinct sections or levels of the well (e.g., which are vertically displaced), or may transfer heat to the working fluid only in one well section (e.g., near a bottom of the well 1). However, other arrangements are possible.
In accordance with an aspect of the invention, one or more heat pipes 5 are coupled with a mounting component 3 (in this example a collar or other support arranged to mount one or more heat pipes) that is positioned around at least part of an outer periphery of the heat exchanger 2 and that positions the heat pipes 5 for transfer of heat to the heat exchanger 2 via a thermal gap material 4. Thus, in this example, heat is harvested by the heat pipes 5 that extend radially from the mounting component 3 into portions of the geothermal well 1 surrounding a well bore in which the heat exchanger 2 is positioned. The harvested heat from the heat pipes 5 is transmitted to the thermal gap material 4, e.g., by conduction and/or convection, which in turn transfers heat to the heat exchanger 2. In some embodiments, heat may be conducted from the heat pipes 5 to the mounting component 3 which transfers heat to the thermal gap material 4 and into an outer wall or other suitable portion of the heat exchanger 2. Accordingly, a liquid or other fluid flowing in the heat exchanger 2 picks up the heat and transports it to the heat receiver 6. Although only two heat pipes are shown, any suitable number of such heat pipes assemblies may be arrayed along the length of the heat exchanger 2 to provide the required heat harvesting rate for a particular geothermal energy system 100. For example, FIG. 2 shows an arrangement in which the heat exchanger 2 is located in a main well bore 11, and multiple heat pipes 5 extend radially into corresponding bores 12 that extend away from the main well bore 11. In this embodiment, the heat pipes 5 are arranged at three levels, or distinct vertical positions, relative to the main well bore 11, although more or fewer levels may be employed. Also, multiple heat pipes 5 may be deployed at each level, such as 3, 4, 6 or more heat pipes 5 per level. Alternately, the heat pipes 5 may be arrayed around the main well bore 12 in random or irregular ways, e.g., to accommodate particular geologic features of the well 1.
The mounting component 3 may support portions of the heat pipes 5 so that the heat pipes are spaced from the heat exchanger 2 by a thermal gap, i.e., a space of desired size and thickness to create the thermal resistance through which heat is transferred from the heat pipes 5 to the heat exchanger 2. In some embodiments, the thermal gap may be about ¼ inch to 2 inches, although other suitable spacing may be employed. Thus, the heat pipes 5 may be out of direct contact with the heat exchanger so that a majority of heat transferred to the heat exchanger is through a thermal gap material 4 located in the thermal gap, e.g., 60%, 70%, 80%, 90%, 95% or more of heat transfer may occur via the thermal gap material 4. The thermal gap material 4 may have a relatively low thermal conductivity, e.g., 0.5 to 12 W/m-K, at least as compared to a thermal conductivity of the material at the heat pipe 5 and/or heat exchanger 2 outer surface. As such, the thermal gap material 4 may meter heat transfer in a desired way, e.g., to allow the heat pipes 5 to operate at an optimal working temperature as discussed more below. The thermal gap material 4 may be or include a thermal grout, e.g., a cement-like material that is designed to have a desired thermal conductivity, or other material such as water (including water with dissolved minerals, salts and/or other material). Thus, the thermal gap material 4 may be a solid, liquid, semi-solid or other composite and may transfer heat by conduction and/or by convection.
In some embodiments, to achieve meaningful heat harvesting rates, the geothermal well should include a liquid pool or liquid-permeated porous rock so as to allow circulation of liquid within the volume of the geothermal well 1. Heat removal from the geothermal resource by the heat exchanger 2, and particularly by the heat pipes 5, cools the liquid of the well 1 and increases its density. As the denser, cool liquid sinks downwardly in the geothermal well 1, hotter liquid from below or elsewhere in or around the well 1 may move outwards and upwards to create large scale liquid circulation that may be necessary to deliver sufficient heat to the heat pipes 5 and the heat exchanger 2 for harvesting. This liquid already present in the geothermal well may itself, at least in part, function as a thermal gap material. Of course, other system 100 arrangements employing a lower heat harvesting rate need not exploit a liquid or liquid-permeated substrate and/or employ a large scale liquid circulation to operate properly. Also, although this embodiment shows the heat pipes 5 extending away from the mounting component 3 in a downward, curving arc, the heat pipes 5 may extend in a straight line and/or at any suitable angle(s) to the horizontal, including extending horizontally (or nearly so) in some embodiments.
FIG. 3 shows a cross sectional side view of the heat pipe mounting assembly of the FIG. 1 embodiment. The mounting component 3 (which in this embodiment is shaped as a collar or sleeve) extends around at least part of the outer periphery of the heat exchanger 2 and positions the heat pipes 5 to define a gap between the heat pipes 5 and the heat exchanger 2. Note that the mounting component 3 may help establish a suitable gap between the heat pipes 5 and the heat exchanger 2 in portions of the heat pipes 5 positioned below or otherwise away from the mounting component 3. The heat exchanger 2 in this embodiment includes an outer pipe 22 which carries a working fluid flow in a downward direction and an inner pipe 21 which carries an working fluid flow in an upward direction, e.g., heated working fluid may travel upwardly in the inner pipe 21 to the heat receiver 6. Thus, heat from the heat pipes 5 may be transmitted to the working fluid flowing downwardly in the outer pipe 22 in this embodiment. Of course, the flow direction may be reversed, with relatively hot working fluid flowing upwardly in the outer pipe 22 and cooler working fluid flowing downwardly in the inner pipe 21.
In the gap between the mounting component 3/heat pipes 5 and the heat exchanger 2 is a thermal gap material 4, such as a thermal grout. As is explained in more detail below, the thermal conductivity of the thermal gap material 4 may be lower than the thermal conductivity of the mounting component 3 and heat pipes 5, and generally speaking, “meters” the flow of heat from the mounting component 3/heat pipes 5 to the heat exchanger 2 so that the heat pipe(s) 5 operate at an appropriate working temperature. In some embodiments, relatively little heat may be transmitted from the heat pipes 5 to the mounting component 3, so that a bulk of heat transfer from the heat pipes 5 to the heat exchanger 2 occurs directly from the heat pipes 5 to the thermal gap material 4 and then to the heat exchanger 2. However, in other embodiments, a significant amount of heat may be transferred from the heat pipes 5 to the mounting component 3, which is then transferred from the mounting component 3 to the thermal gap material 4. In this case, the mounting component 3 may function as a heat spreader, i.e., assisting to transmit heat from a first surface area of a heat pipe having a first size to a second surface area of the mounting component 3 that has a second size greater than the first size. As discussed more below, such heat spreading may assist in desired heat transfer to the heat exchanger, and to do so, a heat spreader may have a relatively high thermal conductivity, e.g., above 12 W/m-K. In some embodiments, a surface of the mounting component 3 that faces or otherwise thermally communicates with the heat exchanger 2 may be configured to generally conform to the shape of the heat exchanger portion that receives heat from the thermal gap material 4, e.g., so that a conduction length across the thermal gap material 4 may be maintained constant or otherwise controlled.
Many heat pipes are closed systems that rely on the counter flow of “liquid” and “vapor” phases of the “working fluid” within a sealed interior volume of the pipe to transport heat along the pipe. At the hot or “evaporator” end, heat is absorbed by evaporating or boiling the liquid inside the heat pipe into its vapor phase while at the cold or “condenser” end the vapor phase condenses back into a liquid and releases heat into the walls of the heat pipe. Vapor travels automatically from the hot end to the cold end by the pressure difference caused by small temperature differences between the hot and cold ends. Other forces, such as gravity, are used to return the condensed liquid from the cold to the hot end. Heat pipes that depend on gravity as the primary means to return condensed liquid from the cold end to the hot end are also called thermosiphons. Liquid and vapor flow in opposite directions in the heat pipe.
Because heat transport in heat pipes is mediated by the physical movement of liquid and vapor phases of the working fluid, the heat transport rate that can be achieved in heat pipes is limited by many mechanisms that apply to fluid flows. Some common limiting mechanisms are entrainment limit, flooding limit, sonic limit, boiling limit etc., but in short, the heat transport limit of heat pipes is strongly dependent on the temperature of the working fluid inside the heat pipe. (The liquid and vapor phases inside a heat pipe exist in near thermodynamic equilibrium so, for the purpose of this description, a single temperature is used to refer to both phases.)
In accordance with an aspect of the invention, the thermal gap (i.e., the conduction length or distance from the mounting component 3 (or other heat spreader) and/or the heat pipe 5 to the heat exchanger 2) and the thermal gap material 4 in the gap between the heat spreader/heat pipe 5 and the heat exchanger 2 may be arranged to conduct heat such that the heat pipe(s) 5 operate at a desired working temperature, and enable substantial heat harvesting from the geothermal resource via the heat pipe(s) 5. For example, if the heat pipes 5 were to be placed in direct and very intimate thermal contact with the heat exchanger 2, the operating temperature of the heat pipes would be low, close to the cold fluid temperature in the heat exchanger 2. Such cold heat pipes extending into the hot rock or other well 1 substrate could create a “high heat demand” from the well 1. However, at the “cold operating temperature,” the heat pipes 5 would have a “low heat transport capability” and would not be able to carry the heat that would want to flow into the heat pipe 5 from the hot rock or other well substrate.
On the other hand, if the thermal connection between the heat pipes 5 and the heat exchanger 2 is poor (such as if the heat pipes 5 are simply inserted into the holes drilled into hot rock around a main well bore and not thermally coupled to the heat exchanger 2 in any particular way), the heat pipe temperature would be high, closer to the high temperature of the hot rock. Such “hot heat pipes” would create a “low heat demand” from the rock even though the heat pipes 5 would have a “high heat transport capability” due to their high operating temperature. In both the above scenarios, the heat pipes 5 would not provide a suitably high heat harvesting rate, at least for some applications. By providing a suitable thermal gap characteristics (conduction length and thermal conductivity) between the heat pipes 5/heat spreader and the heat exchanger 2, the heat pipes 5 may operate at the desirable “in between” temperature such that a “relatively high heat demand” is placed on the hot rock and is well balanced against the “relatively high heat transport capability” of the heat pipes 5.
A further benefit of the “balanced high heat harvesting” rate of the heat pipes 5 is that more well fluid may be cooled to a higher density to drive a larger total convective circulation in the geothermal resource. In this way, embodiments configured in accordance with an aspect of the invention may operate such that the heat content of the geothermal well, or “reservoir,” is replenished at the same rate that heat is harvested for efficient and cost effective energy production over long term operation. Computer modeling of a geothermal well 1 having its heat harvested using three thermal transfer components (i.e., heat pipe/heat spreader/thermal gap material assemblies) positioned along the length of a vertical heat exchanger arrangement like that in FIG. 2 have shown that the thermal transfer components are effective in increasing convective flow in the geothermal well 1, and that additional thermal transfer assemblies are expected to improve convective flow over systems with fewer thermal transfer assemblies.
FIG. 4 shows a top cross sectional view of the mounting component 3 along the line 4-4 in FIG. 1 in an illustrative embodiment. In this example, the mounting component 3 has the form of a continuous annular collar or sleeve that extends around the heat exchanger 2. Also, in this embodiment, four heat pipes 5 pass through openings in the wall of the collar 3, thereby thermally coupling the heat pipes 5 to the collar 3 and allowing the collar 3 to function as a heat spreader. Of course, fewer or more heat pipes 5 may thermally couple with the mounting component 3 if desired. Other configurations for a mounting component 3 are possible, such as that shown in FIG. 5 in which the mounting component 3 includes four “shoes” or curved plates that each thermally couple with a corresponding heat pipe 5. The shoes may be physically attached to each other, or not, as desired, and may be thermally coupled with each other, or not. Note also that the mounting component 3 need not necessarily be thermally coupled with a heat pipe 5, but instead may mechanically support the heat pipe 5 in a desired orientation and distance from a heat exchanger 2, e.g., to define a desired thermal gap. Thus, the mounting component 3 need not function as a heat spreader or otherwise transmit significant heat from the heat pipes 5 to the thermal gap material 4. Also, a heat spreader may be used in conjunction with a mounting component 3 that serves to physically support the heat pipe(s) 5, but does not function as a heat spreader.
While the surface area of the heat pipes 5 and/or heat spreader is an important design consideration when arranging the system to operate such that the coupled heat pipe(s) 5 function at a desired working temperature, the distance between the heat pipes 5 and/or heat spreader and the heat exchanger 2 (or conduction length) may be another important factor. As noted above, the surface of the heat pipes 5 or heat spreader that faces the heat exchanger 2 may be shaped or contoured to match or conform with a counterpart surface of the heat exchanger 2. Thus, if the heat exchanger 2 has a cylindrically-shaped outer surface, the mounting component 3 or other heat spreader may include a corresponding cylindrically-shaped inner surface that faces the heat exchanger 2. Alternately, if the heat exchanger 2 includes a dimpled, grooved, or other shaped surface, the mounting component 3 or other heat spreader may have a corresponding shape. This arrangement may help maintain a thermal gap between the heat spreader and the heat exchanger 2 at a constant or otherwise known value, e.g., to help ensure that a conduction length of the thermal gap material 4 is constant or otherwise known across the thermal junction. In some embodiments, the distance between the mounting component 3 and the heat exchanger 2 may be defined in different ways, such as by standoffs, tabs, pins, annular rings or other structures that extend from the mounting component 3 toward the heat exchanger 2. These gap-defining elements may help ensure that there is a minimum (or maximum) distance between the mounting component 3/heat pipes 5 and the heat exchanger 2. The gap-defining elements may be made small enough or otherwise configured to contribute minimally to heat transfer between the heat spreader and the heat exchanger, or alternately, these gap-defining spacer elements may function as a non-trivial part of the heat transfer. If so, the gap between the heat spreader and the heat exchanger (conduction length), the thermal conductivity of the thermal gap material and/or the surface area of the heat spreader (i.e., the surface area facing the heat exchanger or that meaningfully contributes to heat transfer to the heat exchanger) may be designed to provide the desired heat transfer rate along with the gap-defining elements.
Deployment of a thermal gap material 4 in the space or gap between the mounting component 3/heat pipes 5 and the heat exchanger 2 may be done in a variety of ways. For example, the thermal gap material 4 may take the form of a flowable grout that can flow when deployed, and then may optionally harden after deployment. The grout may be pumped into place after the mounting component 3 and heat exchanger 2 are positioned relative to each other in the well 1, or may be applied to the heat exchanger 2 and/or to the mounting component 3 prior to positioning of the elements relative to each other. In other embodiments, the thermal gap material 4 may be present in the well 1 at or after the time of installing the heat exchanger 2 and/or heat pipes 5. For example, the thermal gap material 4 may be or include water (such as brine) in the well 1 that occurs naturally or is introduced, e.g., by pumping the water into the well 1. Thus, in some embodiments, the thermal gap material may include a liquid that can flow so as to accommodate convective heat transfer, as well as conductive heat transfer, between the heat pipes 5 and the heat exchanger 2.
FIG. 6 shows an illustrative embodiment in which thermal gap material 4 is contained in one or more reservoirs 42 as introduced into the well 1. In FIG. 6, the portion of the image to the left of the heat exchanger 2 shows the thermal gap material 4 before deployment, while the portion of the image on the right of the heat exchanger 2 shows the thermal gap material 4 after deployment. A shaped charge (e.g., an explosive device), a plunger or piston, a clamp or other mechanism 41 may deform the reservoir 42, or otherwise force the thermal gap material 4 to flow from the reservoir 42 into the gap between the heat exchanger 2 and the heat pipes 5 and/or heat spreader. FIG. 7 shows another illustrative embodiment in which the mounting component 3 has an attached thermal gap material reservoir 42 that includes one or more ports 43 arranged to expel thermal gap material 4 in the gap when the thermal gap material is caused to flow. In this embodiment, the reservoir 42 that is squeezed by a clamp 41 that includes a collar or sleeve with a conical lower surface that bears on the reservoir 42 as the collar is moved downwardly toward the mounting component 3. (As in FIG. 6, the portion of the image to the left of the heat exchanger 2 in FIG. 7 shows the thermal gap material 4 before deployment, while the portion of the image on the right of the heat exchanger 2 shows the thermal gap material 4 after deployment.) Of course, other arrangements are possible for deploying a thermal gap material 4, such as a pump that pumps thermal gap material 4 via a conduit to the gap between a heat pipe and the heat exchanger. Also, while in the FIGS. 6 and 7 embodiments the thermal gap material 4 flows generally downwardly and radially inwardly, the material 4 may flow in any suitable way, e.g., the material 4 may flow only radially inwardly from one or more reservoirs to a thermal gap between a heat spreader and/or heat pipe and the heat exchanger.
In accordance with an aspect of the invention, one or more heat pipes may be engaged with a mounting component so that the assembled heat pipes and mounting component may be lowered into a well bore and the heat pipes deployed into corresponding well bores. For example, FIG. 8 shows an illustrative arrangement in which four heat pipes 5 are attached to a mounting component 3 that includes upper and lower collars 3 a, although more collars 3 a may be used if desired. The upper and lower collars 3 a may be spaced from each other, e.g., at a distance of 5, 10, 20 or more feet along the length of the heat pipes 5, which in this embodiment may be up to 120 to 300 feet long or more. In other embodiments, the upper and lower collars 3 a may be replaced with a single collar that spans along a desired length of the heat pipes 5, e.g., 5, 10 or 20 feet or more in length. The single collar 3 a may be arranged as a cylindrical shell, e.g., to prevent flow into/out of a space within the collar 3 a, or may have openings to permit flow. In the illustrated embodiment, the portion of the heat pipes 5 between the collars 3 a are exposed and a gap between the heat pipes 5 and a heat exchanger 2 positioned within the heat pipes (not shown) may be defined by the collars 3 a. Given the relatively long length of the heat pipes 5 positioned adjacent the heat exchanger 2, a majority of heat transferred from the heat pipes 5 to the heat exchanger 2, e.g., 90%, 95% or more, may be transmitted directly from the heat pipes 5 to the heat exchanger via a thermal gap material 4. Thus, the collars 3 a may play a minor role in heat transfer in this embodiment, but in other embodiments may serve to transfer a much larger amount of heat.
FIG. 9 shows a cross sectional view of a collar 3 a along the line 9-9 in FIG. 8. This embodiment is similar to that shown in FIG. 4, with one difference being that the collar 3 a (a mounting component) engages the heat pipes 5 at an outer surface of the collar 3 a. Also, the collar 3 a is shown including one or more spacer elements 34, such as a protrusion, rib, pin, etc. that extends radially inwardly from an inner side of the collar 3 a. The spacer elements 34 may assist in defining a suitable thermal gap between the heat pipes 5 and the heat exchanger 2, not only in areas at or near the collar 3 a, but also for portions of the heat pipes 5 between the upper and lower collars 3 a. Note also that the heat pipes 5 in this embodiment each include a heat spreader 51 in the form of a sleeve 51 that is positioned over the outer surface of the heat pipe 5. In one embodiment, the heat pipe 5 may be formed by a copper tube or pipe, and the heat spreader 51 may be arranged as a stainless steel sleeve that extends over a portion of, or the entire, heat pipe 5. The heat spreader 51 may serve to not only increase a surface area for heat transfer from the heat pipe 5, but also may provide the heat pipe 5 with mechanical support (e.g., to resist crushing and/or bursting of the pipe 5), corrosion resistance, and/or other characteristics. The collars 3 a may engage the heat spreaders 51 by welding, an adhesive, clamping, an interference fit or other suitable arrangement.
In accordance with an aspect of the invention, the assembly may include one or more anti-buckling supports which may help support the heat pipes before and/or during deployment in the well 1. For example, as shown in FIG. 8, anti-buckling supports 3 c may be attached to the heat pipes 5 below the collars 3 a, e.g., to help keep the heat pipes 5 from bending or buckling during deployment or to otherwise support the heat pipes 5. A distance between each anti-buckling supports 3 c and an adjacent anti-buckling support 3 c or collar 3 a may be arranged to be equal to or less than a maximum unsupported length of heat pipe for loading in compression without buckling. So, for example, if a particular force is needed to be applied to the heat pipes 5 for deployment of the heat pipes into the well 1, one or more anti-buckling supports 3 c may be provided at suitable locations along the length of the heat pipes 5 to help prevent buckling of the pipes 5 during deployment. The heat pipes 5 may be attached to the anti-buckling supports 3 c in a way that maintains the anti-buckling supports 3 c in place relative to the heat pipes 5 during deployment of the heat pipes 5 into the well 1, but that releases the heat pipes 5 relative to the anti-buckling supports 3 c once a force exerted on the heat pipes 5 relative to the anti-buckling support 3 c exceeds a threshold. For example, with reference to FIG. 3, as the collars 3 a and heat pipes 5 are moved downwardly in the main well bore 11, the heat pipes 5 may be deployed into their respective bores 12 of the well 1. As the anti-buckling supports 3 c reach the point where the heat pipes 5 exit the main well bore 11, the anti-buckling supports 3 c may disengage from the heat pipes 5, e.g., via a frangible or other releasable connection.
For example, FIG. 10 shows one illustrative embodiment of an anti-buckling support 3 c. Heat pipes 5 may be engaged at openings 37 of heat pipe engagement portions 35, and the heat pipes may be fixed to the portions 35 by welding, solder, an adhesive, a clamp, or other arrangement. Frangible links 36 may permit the engagement portions 35 and heat pipes 5 to disengage from a central portion 38 of the anti-buckling support 3 c, e.g., when a suitable force is applied to the heat pipes 5 relative to the support 3 c whether in shear and/or tension. As will be understood, and is discussed more below, the heat pipes 5 may be releasably attached to the anti-buckling support(s) 3 c in other ways, such as by an adhesive that breaks or fails in the presence of a suitable force, rubber sleeves on the heat pipes 5 that hold the anti-buckling supports 3 c in place relative to the heat pipes 5, but allow the heat pipes 5 move along their length relative to the anti-buckling supports in the presence of a suitable force, and others.
Another feature shown in FIG. 10 is that the anti-buckling support 3 c may be arranged with a clam shell or other suitable configuration that allows the support 3 c to be assembled around an existing drill string and/or heat exchanger 2. That is, when installing a thermal energy harvester in a well 1, a drill string used to form one or more bores 11, 12 may be in place when the heat pipes 5 and mounting component(s) 3 are installed. By making the anti-buckling support 3 c and/or the collars 3 a in a clam shell configuration (see FIG. 11 regarding a collar 3 a having a clam shell arrangement), the support 3 c and/or collars 3 a may be assembled around a drill string or heat exchanger 2. That is, bolts or other fasteners used to secure the support 3 c and/or collar 3 a sections together may be removed so the sections can be placed around the drill string or heat exchanger 2 and then fastened together. FIG. 12 shows a cross sectional view along the line 12-12 in FIG. 8 and shows another illustrative embodiment for an anti-buckling support 3 c. In this embodiment, the heat pipes 5 are engaged by sleeve-shaped engagement portions 35 of the anti-buckling support 3 c as opposed to a plate shaped element as in FIG. 10. The frangible links 36 are formed as rib-shaped elements that extend along a length of the heat pipes 5, although other arrangements are possible. FIG. 12 also shows an embodiment of a collar 3 a like that in FIG. 9, except that in FIG. 12 the collar 3 a is formed in two sections. The sections may be joined together by bolts or other fasteners, welding, etc. This embodiment also incorporates a spacer element 34 at the joint between the two collar sections.
In accordance with another aspect of the invention, a heat pipe deployment system may include a heat pipe guide, or “kicker,” that helps to guide the heat pipe(s) into their respective bore in a well. For example, the heat pipe guide may be arranged in the main well bore and include a flared or curved guide channel for one or more heat pipes. The guide channel may engage a heat pipe, e.g., at the distal end, and guide the heat pipe into a radially extending bore. The heat pipe guide may also be used to guide a tool that forms radially extending heat pipe bores, such as a rotary drilling tool, high pressure jet device, etc. For example, FIG. 13 shows an assembly including four heat pipes 5, upper and lower collars 3 a, an anti-buckling support 3 c and a heat pipe guide 3 b. FIG. 14 shows a close up view of the heat pipe guide 3 b. The guide 3 b may include a plurality of guide grooves 39, e.g., one for each heat pipe 5, that is curved or otherwise arranged to guide movement of the distal end of the heat pipes 5 into a corresponding radial bore 12 as the heat pipes 5 are lowered into a well 1. The radius of curvature of the grooves 39 may be any suitable distance, such as 10-30 ft. Although in this embodiment, the guide 3 c is shown arranged as a solid part with no through hole, e.g., through which a heat exchanger 2 may pass, the guide 3 c may be arranged to receive a drill string, heat exchanger 2 or other element in an opening in the center of the guide 3 c. Moreover, the guide 3 b may be made in a clam shell configuration or other multi-part arrangement that permits assembly of the guide 3 b around a drill string. In some embodiments, the guide 3 b may be used to guide a drill bit or other device that is used to form the bores 12 for heat pipes. This may help ensure that the grooves 39 are aligned with corresponding bores 12 for insertion of the heat pipes 5. Alternately, the bores 12 may be made without the use of the guide 3 b, and the grooves 39 may be suitably aligned with the bores 12 prior to heat pipe insertion.
In accordance with another aspect of the invention, a portion of a mounting component, anti-buckling support and/or heat pipe guide may form part of the heat exchanger. That is, in the embodiments above, a portion of the mounting component is adjacent to, and spaced from, a portion of the heat exchanger and a thermal gap material serves to conduct heat from the heat spreader to the heat exchanger. However, in some embodiments, one or more portions of the heat pipe deployment system may function as part of the heat exchanger, and any thermal gap or other thermal link between heat pipes and the heat exchanger may be provided as part of the system. For example, FIG. 15 shows an embodiment in which a mounting component 3 a, heat pipe guide 3 b, and anti-buckling support 3 c serve as part of the heat exchanger 2. In this embodiment, the heat exchanger 2 includes an inner pipe 21 that extends downwardly within an outer pipe 22. The inner pipe 21 carries cool working fluid to near a bottom of the well 1, and heated working fluid is conducted upwardly in the space between the inner and outer pipes 21, 22. Although the inner pipe 21 extends downwardly to near a bottom of the well 1, the outer pipe 22 is connected to the mounting component 3 a, and from that point downward, the assembly of the mounting component 3, anti-buckling support 3 c and heat pipe guide 3 b defines the “outer pipe” of the heat exchanger 2. To contain the working fluid in the heat exchanger 2, the portions 3 a, 3 b and 3 c may be joined together to define a water tight conduit around the inner pipe 21, e.g., by the use of o-rings, adhesives, threaded connections, clamps and/or other components. Any thermal gap provided between the heat pipes 5 and the working fluid in the heat exchanger 2 may be provided as part of the portions 3 a, 3 b and 3 c.
FIG. 16 shows the heat spreader arrangement of FIG. 15 in an “expanded” state prior to deployment in the FIG. 12 configuration. That is, the mounting component 3 may include an upper portion 3 a that is fixed to the heat pipes 5 and a lower portion 3 b that includes heat pipe guides to guide deployment of the heat pipes 5 into corresponding bores 12 in the well 1 as the upper portion 3 a is moved toward the lower portion 3 b. However, this embodiment additionally includes one or more middle portions 3 c (e.g., an anti-buckling portion) that may be attached to the heat pipes 5, e.g., to help keep the heat pipes 5 from bending or buckling during deployment or to otherwise support the heat pipes 5. A distance L between each middle portion 3 c and an adjacent middle portion 3 c, upper portion 3 a or lower portion 3 b may be arranged to be equal to or less than a maximum unsupported length of heat pipe for loading in compression without buckling. So, for example, if a particular force is needed to be applied to the heat pipes 5 by the upper portion 3 a for deployment, one or more middle portions 3 c may be provided at a suitable length L along the heat pipes 5 to help prevent buckling of the pipes 5 during deployment. The heat pipes 5 may be attached to the middle portions 3 c in a way that maintains the middle portions 3 c in place relative to the heat pipes 5 during deployment of the heat pipes 5 into the well 1, but that releases the heat pipes 5 relative to the middle portion 3 c once the middle portion reaches the lower portion 3 b or an adjacent middle portion 3 c below. For example, as the upper portion 3 a is moved toward the lower portion 3 b in the well 1, the heat pipes 5 will be deployed into their respective bores 12 of the well 1 and the middle portion 3 c will move downwardly toward the lower portion 3 b. When the middle portion 3 c contacts the lower portion 3 b, a connection between the middle portion 3 c and the heat pipes 5 will be released so that the heat pipes 5 can slide relative to the middle portion 3 c. For example, the heat pipes 5 may be joined to the middle portion 3 c by a frangible joint (e.g., a tin soldered connection, an adhesive, etc.) that is capable of supporting the middle portion 3 c on the heat pipes 5, but that breaks away once the middle portion 3 c contacts the lower portion 3 b. This allows the upper portion 3 a to be moved downwardly, further deploying the heat pipes 5 in the well 1 until the upper portion 3 a meets the middle portion 3 c.
As a result, the portions 3 a, 3 b, 3 c may be stacked onto each other when the heat pipes 5 are fully deployed into the well 1. As mentioned above, the portions 3 a, 3 b, 3 c may be joined together, as shown in FIG. 17, to form a water tight seal at an inner portion such that the portions 3 a, 3 b, 3 c may define an outer conduit of the heat exchanger 2. For example, as shown in FIG. 18, the portions 3 a, 3 b, 3 c may engage each other such that one portion (the middle portion 3 c in this example) includes a protruding conical section that engages with a conical receiver opening in the other portion (the lower portion 3 b in this example). These conical sections may be tightly forced together, forming a water tight seal, by threaded engagement, one or more clamps, etc. The conical engagement surfaces of the middle portion 3 c and the lower portion 3 b (a male conical engagement surface of the middle portion 3 c, and female engagement surface of the lower portion 3 b) may also help align the portions 3 c, 3 b relative to each other in a radial direction. For example, if the heat pipes 5 and middle portion 3 c are lowered to the lower portion 3 b as shown in FIG. 18, the middle and lower portions 3 c, 3 b may need to be aligned with each other radially to form a suitable water tight joint. In addition, or alternately, the heat pipe 5 ends may need to be aligned with guide grooves in the lower portion 3 b, and the radial alignment feature provided by the conical engagement surfaces may also serve to align the heat pipes 5 with the guide grooves.
Furthermore, the middle and lower portions 3 c, 3 b may include features that help align the portions in a rotational direction. For example, the lower portion 3 b may include two heat pipe guide grooves located at 180 degrees from each other. To help align the heat pipes 5 with their respective guide grooves, the conical engagement surfaces may include complementary slots and protrusions that interact to align the middle and lower portions 3 c, 3 b rotationally. For example, the lower portion 3 b may include one or more V-shaped slots in the conical engagement surface (with the wide end of the “V” facing upwardly) that received complementary V-shaped protrusions on the conical engagement surface (with the narrow end of the “V” facing downwardly) of the middle portion 3 c. The complementary slots and protrusions may engage with each other to rotate the middle and lower portions 3 c, 3 b relative to each other, as necessary, so that the heat pipe 5 ends are suitably located relative to the guide grooves of the lower portion 3 b. Those of skill in the art will appreciate that other engagement surface arrangements are possible to provide radial and/or rotational alignment of the middle and lower portions 3 c, 3 b. Moreover, such alignment features may be provided between adjacent middle portions 3 c, and/or between a middle portion 3 c and the upper portion 3 a.
FIG. 19 shows a perspective view and FIG. 20 shows a cross sectional view of the upper portion 3 a along the line 20-20 in FIG. 15. As can be seen, the inner pipe 21 extends within an inner wall 31 of the upper portion 3 a. The inner wall 31 is joined to the outer pipe 21 of the heat exchanger 2, and so forms an outer conduit of the heat exchanger 2 in this embodiment. An outer wall 32 is also provided, but may function only as a well bore liner pipe. As such, the outer wall 32 may be made of a less robust or corrosion resistant material than other parts of the upper portion 3 a since the outer wall 32 may be needed only during installation of the upper portion 3 a, e.g., to prop up the walls of a well hole. The upper portion 3 a couples to four heat pipes 5 in this embodiment, though more or fewer heat pipes 5 could be used. The upper portion 3 a includes saddles 33 that join to a respective heat pipe 5, and may provide physical support for the pipe 5 relative to the upper portion 3 a. The saddles 33 may be arranged in different ways, such as by a block of material having a hole formed in it, as a two-part clamshell device that clamps onto the heat pipe outer surface, a plate with a hole formed in it, etc. The saddles 33 may be directly joined to the inner wall 31, and the joint may be arranged (e.g., of suitable cross sectional area) to provide a desired (e.g., to create a suitable thermal gap) thermal coupling between the heat pipe 5 and the inner wall 31. For example, if the heat pipe 5 is directly in contact with the saddle 33, a joint between the saddle 33 and the inner wall 31 may be suitably sized (e.g., of suitable cross sectional area and joint thermal conductivity) to provide a suitable thermal coupling between the heat pipe 5 and the inner wall 31 to balance the heat pipe temperature and the heat harvesting rate as earlier described. Alternately, the junction of the saddles 33 to the inner pipe 31 may be of such relatively small cross sectional area and/or low thermal conductivity as to be ineffective in transferring heat to the working fluid, and instead a thermal gap material 4, e.g., filling a space between the inner and outer walls 31, 32, provides the bulk of thermal coupling between the heat pipe 5 and the inner wall 31, similar to that in the FIG. 3 embodiment.
In another embodiment, if the saddles 33 are joined to the inner wall 31 with higher than desired thermal transfer capacity, a junction between the saddles 33 and the heat pipes 5 may be arranged to provide the desired thermal junction. For example, as shown in the close up view of the saddle 33 at the 9 o'clock position in FIG. 20, a joint between the heat pipes 5 and the saddles 33 may include a thermal gap material 4 that provides the desired thermal coupling between the heat pipes 5 and the inner wall 31. This arrangement may have the advantage of being constructed outside of the well 1, e.g., a thermal gap material 4 such as a grout, polymer material, etc., may be provided between the heat pipe 5 outer surface and the saddle 33 when the heat pipes 5 are attached to the saddle 33. This may allow for easier, less expensive and possibly more accurate control of the thermal gap thickness between the heat pipe 5 and the saddle 33.
FIG. 21 shows a cross sectional side view of the upper section 3 a of the FIG. 15 embodiment and illustrates that the inner wall 31 of the upper section 3 a may be joined to the outer pipe 22 of the heat exchanger 2. This joint may be formed in any suitable way, such as by welding, a threaded connection, a clamp, etc. Also, this view shows a saddle 33 arrangement in which the saddle 33 is joined directly to the inner wall 31 only, e.g., by brazing, welding, an adhesive, etc.
FIGS. 22-25 show different saddle arrangements for connecting a heat pipe 5 to the inner wall 31 or other portion of a mounting component 3. Note that all, or at least some, of these saddle arrangements may be used with a middle portion (or anti-buckling support) 3 c of a mounting component 3. In FIG. 22, the saddles 33 are arranged to have two parts 33 a, 33 b that are joined together at a seam 33 c that is oriented radially relative to the inner wall 31. Thus, to mount a heat pipe 5 to the inner wall 31, a first part 33 a or 33 b may be attached to the inner wall 31, e.g., via welding at a joint 33 d. With the heat pipe 5 positioned against the first part 33 a or 33 b, the other part may be positioned adjacent the heat pipe 5 and attached to the inner wall 31 to capture the heat pipe 5 in place. FIG. 23 shows a similar arrangement to that of FIG. 22, except that the saddle portions 33 a, 33 b do not extend completely around the heat pipe 5. In fact, the saddle 33 need not surround all or part of the heat pipe 5, but may engage just a portion of the heat pipe, as shown for example in FIG. 24. In an arrangement like that in FIG. 24, the heat pipe 5 may be attached to the saddle 33 by welding, brazing, an adhesive, or other suitable arrangement. In fact, a heat pipe 5 may be secured to any type of saddle, including those of FIGS. 22 and 23, by welding, brazing, an adhesive or other arrangement, and the connection of the heat pipe 5 to the saddle 33 may be made permanent (e.g., so the heat pipe 5 will not detach from the saddle 33 without damage or deformation of the heat pipe 5 or saddle 33) or made frangible or otherwise releasable. For example, a heat pipe 5 may be attached to a saddle 33 so that the heat pipe 5 can detach from the saddle 33 in certain conditions, such as where more than a threshold level of force is applied to the heat pipe 5 relative to the saddle 33. However, one possible advantage of attaching a heat pipe 5 to a saddle 33, yet allowing the heat pipe 5 to freely slide, e.g., like that in FIGS. 22 and 23, is that the heat pipe 5 may be attached to the inner wall 31 yet allowed to slide along its length relative to the saddle 31, which may be desirable in circumstances where a temperature of the heat pipe may cycle between high and low temperatures. This feature may also be exploited when used with a middle portion (anti-buckling support) 3 c of the mounting component 3. For example, the heat pipe 5 may be passed through the opening of a saddle 33 so that the heat pipe 5 can slide freely relative to the saddle 33. To support the middle portion 3 c relative to the heat pipe 5, rubber sleeves may be positioned on the heat pipe 5 above and below the saddle 5 that engage the heat pipe 5 with a suitable amount of friction to support the weight of the middle portion 3 c, but allow the heat pipe 5 to slide relative to the saddle 33 with forces over a threshold level. Alternately, the rubber sleeves may be replaced with a frangible or releasable connection (e.g., a brazed or solder joint, adhesive, etc.), a break-away collar or other component that releases the heat pipe 5 from the saddle 33 when the force on the heat pipe 5 relative to the saddle 33 exceeds the threshold level. Thus, the arrangement of FIG. 24 may also be used with a middle portion 3 c, and if so, a connection of the heat pipe 5 to the saddle 33 may be made frangible so as to give way once force over a threshold level is applied to the heat pipe 5 relative to the saddle 33. One type of frangible connection may be provided by a tin soldered joint, an adhesive of suitable bonding strength, etc.
FIG. 25 shows another arrangement similar to that in FIG. 22, except that the seam 33 c between the saddle portions 33 a, 33 b is oriented circumferentially rather than radially as in FIG. 22. This may allow a first portion 33 a of the saddle 33 to be attached to the inner wall 31, and the second portion 33 b to be attached to the first portion 33 a to capture the heat pipe 5. The first and second portions 33 a, 33 b may engage in any suitable way, such as by welding, one or more screws or other fasteners, etc. In one arrangement, the first and second portions 33 a, 33 b may be joined by a hinge at one seam portion 33 d, so that the second portion 33 b may be pivoted to an open position to allow a heat pipe 5 to be positioned in a receiving groove of the first portion 33 a. Thereafter, the second portion may be pivoted to a closed position and secured to the first portion 33 a to capture the heat pipe 5. As with other saddle embodiments, the heat pipe 5 may be secured to the saddle via a permanent or frangible connection as well.
While in the embodiments above, a thermal gap material or other component is provided to control (e.g., limit) heat transfer between a heat pipe and a working fluid of the heat exchanger 2, such material is not always required, especially when the well temperature is low. For example, FIG. 26 shows an embodiment in which a condensing portion of a heat pipe 5 extends through the inner wall 31 to directly contact the working fluid in the heat exchanger 2. (The opening in the inner wall 31 through which the heat pipe 5 passes may be sealed closed, e.g., welded or brazed, to prevent leakage of working fluid.) The condensing portion of the heat pipes 5 may be a relatively long length, e.g., 5 meters or more, and may extend from near a bottom end of the heat exchanger 2 upwardly. A similar result may be achieved as well by having the heat pipes in direct thermal contact with the inner wall 31, such as by having the heat pipes 5 in direct contact with saddles 33, that are in direct contact with the inner wall 31, where the saddles 33 and the wall 31 are formed of, or include, a highly thermally conductive material, such as steel. As noted above, such an arrangement may reduce the temperature and the heat transport capability of the heat pipes, but such a result may be acceptable for some applications.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified.
The use of “including,” “comprising,” “having,” “containing,” “involving,” and/or variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
While aspects of the invention have been described with reference to various illustrative embodiments, such aspects are not limited to the embodiments described. Thus, it is evident that many alternatives, modifications, and variations of the embodiments described will be apparent to those skilled in the art. Accordingly, embodiments as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit of aspects of the invention.

Claims

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.