SYSTEMS AND METHODS FOR THE GENERATION OF ELECTRICAL ENERGY

Abstract

Power generation assemblies and related methods are described. In one embodiment, the power generation assembly includes a thermoelectric generator and a conductor configured to carry the electricity generated by the thermoelectric generator to the surface of an underground well. The power generation assembly must circulate a working fluid through a closed loop in response to the reception of geothermal energy within an underground formation, causing the thermoelectric generator to produce electricity.

Description

SYSTEMS AND METHODS FOR THE GENERATION OF ELECTRICAL POWER CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of the provisional US patent application Serial Number 62 / 785,538 filed on December 27, 2018 and entitled “Systems and Methods for Electric Power Generation”, which is incorporated herein by reference in its entirety. STATEMENT REGARDING FEDERALLY FUNDED RESEARCH OR DEVELOPMENT Not applicable. BACKGROUND This disclosure generally refers to the generation of electrical power. More specifically, some aspects of this disclosure relate to systems and methods for generating electrical power using geothermal energy accessed through a borehole extending from the surface into an underground formation. Wells are commonly drilled from the surface to access minerals or other resources (e.g., oil, gas, water, etc.) that exist within underground formations. The Earth's internal heat (e.g., residual heat from the Earth's formation, heat generated by radioactive elements beneath the Earth's surface, etc.) typically induces an increasing temperature gradient with each greater depth within such wells (e.g., at a rate of approximately -17.22°C per 21.33 vertical meters (1°F per 70 vertical feet) in some locations). The elevated temperatures within these wells are potential sources of energy that can be harnessed to provide power (e.g., electricity) at the surface. BRIEF DESCRIPTION OF THE DISCLOSURE Some of the modalities described in this document are directed to a system that includes a power generation assembly. The power generation assembly is configured to be contained within a well that extends from the surface into an underground formation along a central axis. The power generation assembly includes a thermoelectric generator and a conductor configured to carry the electricity generated by the thermoelectric generator to the surface. The power generation assembly is configured to circulate a working fluid through a closed loop in response to the reception of geothermal energy within the underground czo / nn / Lznz / E / Yii formation, causing the thermoelectric generator to produce electricity. Other embodiments described in this document include a power generation assembly. In one embodiment, the power generation assembly includes a first barrier and a second barrier spaced apart along a central axis. Furthermore, the power generation assembly includes a first chamber, a second chamber, and a third chamber. The first chamber, second chamber, and third chamber are bounded by the first and second barriers, and the second chamber is axially positioned between the first and second barriers. Additionally, the power generation assembly includes a central housing that defines a central through-hole and an annular flow path in the second chamber.Furthermore, the power generation assembly includes a thermoelectric generator arranged radially within the second chamber between the central through-hole and the annular flow path, and a working fluid arranged in each of the first, second, and third chambers. The central through-hole and the annular flow path are in fluid communication with the first and third chambers. When the first chamber is exposed to a first temperature and the second chamber is exposed to a second temperature higher than the first temperature, the working fluid flows through the central through-hole at a third temperature and through the annular flow path at a fourth temperature lower than the third temperature. Other embodiments are directed to a method for generating electrical power. In one embodiment, the method includes (a) placing a power generation assembly in a well extending into a subsurface formation, and (b) transferring heat from the formation to a working fluid disposed within the power generation assembly. The method further includes (c) circulating the working fluid within a closed loop in the power generation assembly as a result of (b). The method also includes (d) exposing a thermoelectric generator of the power generation assembly to a temperature gradient using the working fluid circulating during (c). Finally, the method includes (e) generating electrical current with the thermoelectric generator as a result of (d). The modalities described herein comprise a combination of functions and features intended to address various deficiencies associated with certain previous devices, systems, and methods. The foregoing has provided a fairly broad summary of the functions and technical characteristics of the described modalities to facilitate a better understanding of the detailed description that follows. The various features and functions described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description and referring to the accompanying drawings. It should be noted that the concept czo? nn / Lznz / E / YiAi and the specific modalities described can easily be used as a basis for modifying or designing other structures to accomplish the same purposes as the described modalities.It should also be noted that such equivalent constructions do not depart from the spirit and scope of the principles described in this document. BRIEF DESCRIPTION OF THE DRAWINGS For a detailed description of several exemplary forms, reference will now be made to the accompanying drawings in which: Figure 1 is a schematic view of a geothermal power generation system according to some modalities described in this document; Figure 2 is a cross-sectional side view of a power generation assembly for use within the system of Figure 1 according to some modalities described herein; and Figure 3 is a cross-sectional side view of another power generation assembly according to some modalities described in this document. DETAILED DESCRIPTION OF EXEMPLARY MODALITIES The following discussion is directed to several exemplary forms. However, a person skilled in the art will understand that the examples described herein have broad application, and that the discussion of any one form is intended only as an example of that form, and is not meant to suggest that the scope of the disclosure, which includes the claims, is limited to that form. The figures in the drawings are not necessarily to scale. Certain features and components may be shown exaggerated in scale or in a somewhat schematic form, and some details of conventional elements may be omitted for the sake of clarity and conciseness. In the following discussion and in the claims, the terms “including” and “comprising” are used broadly and should therefore be construed as meaning “including, but not limited to…”. Furthermore, the term “couples” or “couples” is intended to mean either a direct or indirect connection. Thus, if a first device couples to a second device, that connection may be through a direct connection between the two devices, or through an indirect connection established via other devices, components, nodes, and connections. Additionally, as used herein, the terms “axial” and “axially” generally mean along or parallel to a given axis (e.g., the central axis of a body or a port), whereas the terms “radial” and “radially” generally mean perpendicular to the given axis.For example, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. As used herein, the terms substantial, substantially, generally, about, approximately, and the like mean + / - 10%. Finally, any reference to "up" or "down" in the description and claims is for the sake of clarity, with "up," "above," "upward," "upward of the well," or "ascending" meaning toward the surface of the well or borehole, and with "down," "below," "downward," "bottom of the well," or "descending" meaning toward the end of the well or borehole, regardless of the orientation of the well or borehole. As described earlier, the elevated temperatures found within the lower regions of underground wells are a potential source of thermal energy that can be harnessed to generate power (e.g., electricity) for use at the surface. A common type of well that forms in an underground formation is the oil and gas well. These wells can typically be drilled to a depth of 1,524 to 3,048 meters (5,000 to 10,000 feet) below the surface (depending on the specific location) and can have a bottomhole temperature at or above 148.88°C (300°F). A large number of such wells have been drilled to access oil and gas reserves worldwide over the past two centuries. Once hydrocarbon production ceases or falls below an economic threshold, these wells are typically capped (e.g., with cement / plugs, etc.).and are abandoned. The costs of carrying out these operations can be considerable in some circumstances. However, these abandoned wells can still serve as an effective access point for geothermal energy stored within the Earth. Therefore, the methods described herein include systems and methods for generating electricity from geothermal energy emitted into an underground well, such as, for example, an abandoned oil and gas well. Furthermore, as will be described in more detail below, the systems and methods described herein can also be used to generate electricity from other sources of thermal energy (i.e., sources other than geothermal energy). Referring now to Figure 1, a geothermal power generation system is shown in several embodiments. The system (10) generally includes a well (12) extending from the surface (4) into an underground formation (6). The well (12) includes a central shaft (15), a first end or upper end (12a), and a second end or lower end (12b) opposite the upper end (12a). The upper end (12a) is located at the surface (4), and the lower end (12b) is located within the underground formation (6). In this embodiment, the well (12) is substantially vertical, so the shaft (15) is generally aligned with the vertical direction (e.g., along the direction of gravity). However, in other embodiments, one or more sections or portions of the well (12) may be oriented non-vertically (e.g., laterally).A casing (16) (or more simply casing (16)) is laid inside the well (12) and secured in place. In some embodiments, the casing (16) is cemented inside the well (12) to prevent formation fluids (e.g., oil, gas, water, etc.) from migrating to the surface (4) between the casing (16) and the wellbore wall (12). A plurality of perforations (18) extend through the casing (16) and into the formation (6) to provide a path for formation fluids to the casing (16) and ultimately to the surface (4). In this modality, the well (12) is abandoned and therefore plugged to prevent formation fluids from advancing into the casing (16) and to the surface (4). Specifically, in this modality, cement (14) fills the lower portion of the well (12), from the lower end (12b) to a point above the perforations (18). In other modality, a mechanical plug or seal may be placed inside the casing (16) above the perforations (18) to similarly prevent the flow of formation fluids to the surface (4) through the casing (16). In still other modality, a combination of mechanical plugs and cement may be used to plug and abandon the well (12). With reference to Figure 1, as previously described, the internal temperature gradient of the Earth's crust results in an increasing temperature gradient as it moves along axis (15) from the surface (4) into the well (12), from the upper end (12a) to the lower end (12b). Therefore, the temperature inside the well (12) can be higher near the lower end (12b) than near its upper end (12a). Therefore, system (10) also includes a power generation assembly (100) installed inside the well (12) (specifically within the casing (16)) and configured to utilize the temperature difference within the well (12) to generate electrical power.Once generated, electrical energy can be conducted to the surface (4) through a conductor (52) (or a plurality of conductors) and delivered to a final location (50), which may include a local power grid, one or more batteries, capacitors, or other energy storage assemblies. It should be noted that the power generation assembly (100) is contained or encapsulated within the well (12). Therefore, in this configuration, each component of the power generation assembly (100) is arranged at the bottom of the well (e.g., inside well (12)) such that only the electric current (e.g., through conductor (52)) returns to the surface (4). As a result, the power generation assembly (100) may require little or no surface space. The details of one configuration of the power generation assembly (100) will now be discussed in more detail below. With reference to Figure 2, one embodiment of the power generation assembly (100) installed within the casing (16) of the well (12) is shown (see Figure 1). The power generation assembly (100) includes a first barrier or upper barrier (110), a second barrier or lower barrier (122), and a third barrier or intermediate barrier (120). Each of the barriers (110), (122), (120) is axially spaced from the others along the axis (15) and each is watertightly coupled to the inner wall of the casing (16). In this embodiment, the lower barrier (122) is close to, and axially above, the cement (14) and the perforations (18), and the intermediate barrier (120) is axially positioned between the upper barrier (110) and the lower barrier (122).Therefore, the upper barrier (110) is above the well of the middle barrier (120) and the lower barrier (122), the middle barrier (120) is at the bottom of the well of the upper barrier (110) and above the well of the lower barrier (122), and the lower barrier (122) is at the bottom of the well of each of the upper barrier (110) and the middle barrier (120). A first chamber or upper chamber (112) is defined between the upper barrier (110) and the intermediate barrier (120), a second chamber or lower chamber (114) is defined between the lower barrier (122) and the cement (14), and a third chamber or intermediate chamber (150) is defined between the intermediate barrier (120) and the lower barrier (122). Therefore, the upper chamber (112) is above the well of the intermediate chamber (150) and the lower chamber (114), the intermediate chamber (150) is at the bottom of the well of the upper chamber (112) and above the well of the lower chamber (114), and the lower chamber (114) is at the bottom of the well of each of the upper chamber (112) and the intermediate chamber (150). In this mode, because the power generation assembly (100) is installed and incorporated within the casing well (12) (16), the barriers (110), (120), (122) comprise plugs that are installed within the casing (16). The upper chamber (112) may be disposed within an axial section or portion of the well (12) at a first temperature, and the lower chamber (114) may be disposed within an axial section or portion of the well (12) at a second temperature that is higher than the first. For example, in some embodiments, the first temperature around the upper chamber (112) may range from 21.11°C (70°F) to 48.88°C (120°F), and the second temperature around the lower chamber (114) may range from 82.22°C (180°F) to 178.88°C (300°F). The axial length of the chambers (112), (114), and (150) may be adjusted to position the upper and lower chambers (112) and (114), respectively, at predetermined depths to achieve a desired temperature difference between them. czo? nn / Lznz / E / YiAi Referring again to Figure 2, the intermediate barrier (120) includes a central orifice (121) extending axially through it. Furthermore, the lower barrier (122) includes a first end or upper end (122a), a second end or lower end (122b) opposite the upper end (122a), a first port (124) extending axially between the ends (122a) and (122b), and a second port (126) also extending axially between the ends (122a) and (122b) that is separate from the first port (124). A first conduit (127) extends axially from the lower end (122b) into the cement (14) (i.e., the first conduit (127) extends axially downward or to the bottom of the well) and is in fluid communication with the first port (124).A second conduit (128) extends axially from the upper end (122a) into the intermediate barrier (120) (i.e., the second conduit (128) extends axially upward or upward) and is in fluid communication with the second port (126). Thus, the first conduit (127) and the first port (124) define a first flow path through the lower barrier (122) from the intermediate chamber (150) to the lower chamber (114), and the second conduit (128) and the second port (126) define a second flow path through the lower barrier (122) from the intermediate chamber (150) to the lower chamber (114). A central housing (152) is arranged within the intermediate chamber (150). In particular, the central housing (152) is arranged axially between the upper barrier (110) and the lower barrier (122) and extends axially through the central through-hole (121) in the intermediate barrier (120). The housing (152) includes a first end or upper end (152a), a second end or lower end (152b) opposite the upper end (152a), and a central through-hole (154) extending axially between the ends (152a) and (152b). The upper end (152a) is arranged within the upper chamber (112), and the lower end (152b) is arranged within the intermediate chamber (150) near the lower barrier (122). Therefore, the second conduit (128) coupled to the lower barrier (122) extends into the through hole (154) of the central housing (152). An annular cavity (158) is defined within the housing (152), which is formed radially between a radially inner annular wall (156) and a radially outer annular wall (159). The radially inner annular wall (156) forms a portion of the central through-hole (154). A thermoelectric generator (180) is arranged within the cavity (158) radially between the annular walls (156) and (159). This generator is configured to generate electric current when exposed to two different temperatures. Specifically, the generator (180) generates electric current when a radial temperature gradient is applied to it via the Seebeck effect.The construction of a thermoelectric generator (e.g., such as generator (180)) is well known and therefore the details of such construction are not described in detail in this document; however, in general, the electric generator (180) includes different metallic materials that are exposed (during the operation of the power generating assembly (100)) to different temperatures through radial annular walls (156), (159) to thereby generate electric current that is conducted to the surface (4) (e.g., through the conductor (52) shown in Figure 1). An annular flow path (160) is defined radially between the lining (16) and the radially outer annular wall (159) that extends axially from the intermediate barrier (120) to a collector region (162) within the intermediate chamber (150) that is axially arranged between the lower end (152b) of the central housing (152) and the lower barrier (122). The collector region (162) is also in fluid communication with the central through-hole (154) of the housing (152) through the lower end (154b) of the central housing (152) and with the lower chamber (114) through the first port (124) and the first conduit (127). Therefore, the annular flow path (160) is in fluid communication with the lower chamber (114) through the collector region (162).Furthermore, the annular flow path (160) is in fluid communication with the upper chamber (112) through a flow path (164) defined between the upper barrier (120) and the central housing (152). The flow path (164) is an annular flow path that includes a U-bend (166). As will be described in more detail below, the U-bend (166) prevents or restricts gases from flowing or advancing axially upward from the annular flow path (160) into the upper chamber (112) during operations. Referring again to Figure 2, during operation, a working fluid, such as a coolant, is circulated within the power generation assembly (100) to expose the thermoelectric generator (180) to two different temperatures. As a result, the thermoelectric generator (180) can generate an electric current that is supplied to the surface (e.g., surface (4)) through a suitable conductor or conductors (e.g., conductor (52) shown in Figure 1). In particular, in this embodiment, the working fluid circulating within the power generation assembly (100) may comprise a multicomponent fluid, such as, for example, a two-component fluid. Therefore, the working fluid may comprise a first fluid and a second fluid. The first fluid may have a first boiling point, and the second fluid may have a second boiling point that is higher than the first boiling point. In the following example, the fluid circulating within the power generation assembly comprises a mixture of ammonia and water; however, it should be appreciated that other fluid combinations may be used in other embodiments, and the ammonia-water mixture discussed below is merely a potential example of a multicomponent working fluid that may circulate within the power generation assembly (100). Furthermore, the annular flow path (160) can initially be charged with a gas different from the working fluid components. In some embodiments, the gas charged into the annular flow path (160) can be inert. In the following particular example, the gas charged into the annular flow path (160) is helium; however, it should be noted that other gases can be used in other embodiments. It should also be noted that the gas charged into the annular flow path (160) (e.g., helium in the following example) pressurizes the working fluid within the power generation assembly (180) so that, during subsequent operations, the circulating working fluid is maintained at a substantially constant pressure. In some embodiments, the pressure of the working fluid circulating within the power generation assembly (180) can be maintained within the range of -14.7 psig (-1 bar) to 150 psig (10 bar) during operations. In other words, the circulation of the working fluid within the power generation assembly (180) (which is described in more detail below) is achieved by changes of state (e.g., from liquid to gas or from gas to liquid) and by the transfer of thermal energy, and not from an induced differential pressure (e.g., from a mechanical pump, compressor, or the like). With reference to Figure 2, during the operation of a specific implementation, a mixture of ammonia and water (as described above) is placed inside the lower chamber (114) as the working fluid. As described above, the lower chamber (114) is located at a shallower depth within the well (12) and is therefore exposed to relatively high geothermal temperatures. As a result, geothermal energy is transferred from the formation (e.g., formation (6) in Figure 1), through the casing (16), and into the lower chamber (114) (see, for example, arrows (170) in Figure 2), causing the ammonia-water mixture inside the lower chamber (114) to boil and emit ammonia-water vapors. The ammonia-water vapors then flow (e.g., by natural convection) axially upwards through the second port (126) and the second conduit (128) and are emitted into the through-hole (154) of the central housing (152) (see, e.g., arrows (172) in Figure 2). The expansion of the ammonia-water vapors in the through-hole (154) and the relatively lower temperature inside the through-hole (154) (e.g., compared to the lower chamber (114)) cause the water component of the vapors to condense within the through-hole (154) and settle axially downwards in the collector region (162) (see, e.g., arrows (174) in Figure 2).Conversely, the ammonia vapors emitted from the second conduit (128) (which have a lower boiling point than water) continue upwards in a gaseous state and are emitted from the through-hole (154) into the upper chamber (112) through the upper end (152a) of the central housing (152) (see, for example, arrows (176) in Figure 2). Therefore, during operations, the radially inner wall (156) of the annular cavity (158) within the central housing (152) is exposed to the relatively high temperatures of the ammonia and water vapors flowing through the through-hole (154). In some modalities, the radially interior wall (156) may be exposed to temperatures ranging from 82.22°C (180°F) to 148.89°C (300°F) during these operations. With reference to Figure 2, upon entering the upper chamber (112), the heated ammonia vapors are exposed to the relatively lower temperatures of the upper chamber (112), which result from the relatively lower temperature of the formation (e.g., formation (6) in Figure 1) at the lower depth of the chamber (112). Consequently, upon entering the upper chamber (112), thermal energy is transferred from the ammonia vapors back to the formation (see, for example, arrows (171) in Figure 2), causing the ammonia vapors to cool and condense into a liquid that then flows through the flow path (164) into the annular flow path (160). As described above, the annular flow path (160) is filled with a gas, which in this example comprises helium.The helium is prevented from flowing back through the flow path (164) into the upper chamber (112) by the liquid ammonia that is arranged within the U-bend (166) of the flow path (164). Upon entering the annular flow path (160), the liquid ammonia is exposed to the helium gas and thus expands (e.g., evaporates) or diffuses back to a gaseous state, as it generally flows or progresses axially downwards through the annular flow path (160) towards the collector region (162) (see, e.g., arrows (178) in Figure 2). The evaporation of liquid ammonia into gas within the annular flow path (160) significantly cools the ammonia, so the annular wall (159) defining the flow path (160) is exposed to relatively low temperatures. For example, in some embodiments, the radially outer wall (159) may be exposed to temperatures ranging from -4.44°C (-40°F) to 0°C (0°F) during these operations. Therefore, the thermoelectric generator (180) is exposed to a relatively large temperature difference or gradient between the radially inner wall (156) and the radially outer wall (159) of the annular cavity (158). For example, in some embodiments, the temperature difference between the radially inner wall (156) and the radially outer wall (159) may range from 79.44°C (175°F) to 171.11°C (340°F).Because the electric current generation of the thermoelectric generator (180) can be directly proportional to the applied temperature difference, this relatively large temperature difference can allow the thermoelectric generator (180) to generate a relatively large amount of electric current. Furthermore, thermoelectric generators (e.g., generator (180)) can also operate with higher efficiencies in lower temperature environments. Therefore, by further cooling the working fluid (e.g., ammonia) as it flows through the annular flow path (160), the overall temperature exposed to the thermoelectric generator (180) can be reduced so that the generator (180) can operate with improved efficiency. With reference to Figure 2, as the evaporated ammonia vapors flow axially downwards into the collector region (162), they condense back into a liquid so that the liquefied ammonia can mix with the liquid water inside the collector region (162) (which condensed from the through-hole (154) as described above – see, for example, arrows (174)). From then on, the ammonia-water mixture can flow from the collector region (162) back to the lower chamber (114) through the first port (124) and the first conduit (127) (see, for example, arrows (179) in Figure 2) so that the cycle described above can be repeated. As a result, during operations with the power generation assembly (100), a working fluid (e.g., a coolant such as the ammonia-water mixture described above) is continuously circulated in a closed loop at a relatively constant pressure to expose the thermoelectric generator to a large temperature gradient. Consequently, by utilizing the geothermal temperature gradient along the axis (15) of the well (12), the power generation assembly (180) can generate electric current that is conducted to the surface (4) through a suitable conductor or conductors (e.g., conductor (52) in Figure 1). In the embodiment described above, the power generation assembly (100) (see Figure 2) is incorporated within the casing (16) of an underground well (12). However, in other embodiments, the power generation assembly (e.g., assembly (100)) may be a self-contained unit or assembly that is constructed on the surface (e.g., surface (4) in Figure 1) and lowered into the well (e.g., well (12)). For example, referring now to Figure 3, a power generation assembly (200) is shown.The power generation assembly (200) is generally the same as the power generation assembly (100), and therefore the components of the power generation assembly (200) that are shared with the power generation assembly (100) are identified by similar reference numbers, and the following description will focus on the features of the power generation assembly (200) that are different from the power generation assembly (100). czo? nn / Lznz / E / YiAi Primarily, the power generation assembly (200) omits the upper barrier (110) and instead includes an outer housing (202) having a central axis (205) and surrounding each of the intermediate barrier (120) and the lower barrier (122). As a result, the outer housing (202) also partially defines each of the chambers (110), (114), and (150) described above. In particular, the outer housing (202) includes a first end or upper end (202a) and a second end or inner end (202b) opposite the upper end (202a). The upper chamber (110) is defined within the housing (202) between the upper end (202a) and the intermediate barrier (120), and the lower chamber (114) is defined within the housing (202) between the lower end (202b) and the lower barrier (122).Furthermore, the intermediate chamber (150) is defined within the housing (202) axially between the intermediate barrier (120) and the lower barrier (122). Additionally, because the barriers (120) and (122) are arranged within the housing (202), they can be mechanical plugs that engage with the inner wall of the housing (202) or they can be incorporated or integrated within the walls of the housing (202) itself. With reference still to Figure 3, the operations with the power generation assembly (200) are substantially the same as those described above for the power generation assembly (100), and therefore their details are not repeated here for the sake of brevity. However, because the power generation assembly (200) is a self-contained unit, the assembly (200) is first lowered into a shaft (for example, shaft (12) in Figure 1) so that the upper and lower chambers (110) and (114), respectively, are positioned at appropriate depths to be exposed to a desired temperature difference due to the geothermal temperature gradient of an underground shaft.Once the desired temperature difference between the upper and lower chambers (110) and (114), respectively, is achieved, operations with the power generation assembly (200) (in particular, fluid circulation within it) can be carried out substantially in the same manner as described above for the generation of electrical current by the thermoelectric generator (180). After the cessation of operations (e.g., at the end of the power generation operation or during maintenance periods), the power generation assembly (200) can simply be lowered to the surface (e.g., surface (4)) using suitable lifting equipment. Furthermore, because the power generation assembly (200) is a self-contained unit within the external housing (202), it can be operated to generate electrical power in environments that include a temperature gradient, other than an underground well (e.g., well (12)). For example, the power generation assembly (200) can be placed in any location or apparatus that exposes the chambers (110), (114) to different temperatures, thereby driving the circulation of the working fluid contained therein (e.g., ammonia and water as described above) to generate electrical power via the thermoelectric generator (180) as described above. For example, the power generation assembly (200) can be operated in an industrial facility (e.g., chemical plant, refinery, manufacturing facility, etc.).) where fluids or materials are circulated at various temperatures in support of other manufacturing or chemical processing operations. By using the power generation assemblies described herein (e.g., power generation assemblies (100), (200)), electrical current can be generated from an existing temperature gradient. In some embodiments, the existing temperature gradient may be one located within an underground shaft (e.g., such as that associated with an oil and gas well) generated by geothermal energy extracted from the Earth's interior. Consequently, these existing temperature gradients can be harnessed to generate electricity for use in other processes or locations. Although exemplary embodiments have been shown and described, a person skilled in the art may make modifications to them without departing from the scope or teachings of this document. The embodiments described herein are by way of example only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is limited only by the claims that follow, the scope of which shall include all subject-matter equivalents of the claims. Unless expressly stated otherwise, the steps of a method claim may be performed in any order.The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before the steps in a method claim is not intended or specified in any particular order for the steps, but is used to simplify subsequent reference to those steps.

Claims

1. A system comprising: a power generation assembly configured to be contained within a well extending from a surface into an underground formation along a central axis and comprising: a thermoelectric generator; and a conductor configured to conduct the electricity generated by the thermoelectric generator to the surface; wherein the power generation assembly is configured to circulate a working fluid through a closed loop in the power generation assembly in response to the reception of geothermal energy within the underground formation, to cause the thermoelectric generator to generate electricity, wherein the closed loop of the working fluid is entirely disposed within the well.

2. The system according to claim 1, wherein the working fluid pressure is substantially the same throughout the closed circuit of the power generation assembly.

3. The system according to claim 1, wherein the power generation assembly comprises: a first barrier and a second barrier, wherein the first barrier is up the well from the second barrier; a first chamber, a second chamber, and a third chamber, wherein the first chamber, the second chamber, and the third chamber are bounded by the first and second barriers, and wherein the second chamber is down the well from the first chamber and up the well from the third chamber; and a central housing defining a central through-hole and an annular flow path in the second chamber; wherein the central through-hole and the annular flow path are in fluid communication with the first and third chambers; and wherein the thermoelectric generator is located radially between the central through-hole and the annular flow path.

4. The system according to claim 3, wherein the annular flow path contains a gas, wherein the working fluid is configured to flow through the gas as it flows through the annular flow path.

5. The system according to claim 4, wherein the gas comprises helium. czo? nn / Lznz / E / YiAi 6. The power generation assembly according to claim 4, further comprising a U-shaped elbow in fluid communication between the first chamber and the annular flow path, wherein the U-shaped elbow is configured to retain liquid inside it to prevent gas from flowing from the annular flow path into the first chamber.

7. The system according to claim 1, wherein the working fluid comprises ammonia and water.

8. The system according to claim 3, further comprising an outer housing having a first end and a second end opposite the first end, wherein the first chamber is defined within the outer housing between the first end and the first barrier, and wherein the third chamber is defined within the outer housing between the second end and the second barrier.

9. The system according to claim 3, further comprising a third barrier above each of the first and second barriers, and wherein each of the first, second, and third barriers comprises plugs installed within a well casing pipe.

10. A power generation assembly for use within an underground well, the power generation assembly comprising: a first barrier and a second barrier spaced apart within the well along a central axis; a first chamber, a second chamber, and a third chamber, wherein the first chamber, the second chamber, and the third chamber are bounded by the first barrier and the second barrier, and wherein the second chamber is arranged axially between the first barrier and the second barrier; a central housing defining a central through-hole and an annular flow path in the second chamber; a thermoelectric generator arranged within the second chamber radially between the central through-hole and the annular flow path; and a working fluid disposed in each of the first chamber, the second chamber, and the third chamber;wherein the central through-hole and the annular flow path are in fluid communication with the first chamber and the third chamber; and wherein when the first chamber is exposed to a first temperature and the second chamber is exposed to a second temperature that is higher than the first temperature, the working fluid flows through the central through-hole at a third temperature czo? nn / Lznz / E / YiAi and flows through the annular flow path at a fourth temperature that is lower than the third temperature.

11. The power generation assembly according to claim 10, wherein the annular flow path contains a gas.

12. The power generation assembly according to claim 11, wherein the gas is an inert gas.

13. The power generation assembly according to claim 12, wherein the gas comprises helium.

14. The power generation assembly according to claim 11, further comprising a U-shaped elbow in fluid communication between the first chamber and the annular flow path, wherein the U-shaped elbow is configured to retain liquid inside to prevent gas from flowing from the annular flow path into the first chamber.

15. The power generation assembly according to claim 10, wherein the second barrier comprises: a first flow path extending through the second barrier that is in fluid communication with the central through-hole and the third chamber; and a second flow path extending through the second barrier separately from the first flow path, wherein the second flow path is in fluid communication with the annular flow path and the third chamber.

16. A method of generating electrical power, the method comprising: (a) placing a power generation assembly in a well extending into a subsurface formation; (b) transferring heat from the formation to a working fluid disposed within the power generation assembly; (c) circulating the working fluid within a closed loop in the power generation assembly as a result of (b), wherein the closed loop is entirely disposed within the well; (d) exposing a thermoelectric generator of the power generation assembly to a temperature gradient using the circulating working fluid during (c); and (e) generating electric current with the thermoelectric generator as a result of (d).

17. The method according to claim 16, wherein (c) comprises: (c1) boiling the working fluid in a first chamber of the power generation assembly to produce heated steam; (c2) flowing the heated steam through a first side of the thermoelectric generator; (c3) condensing the heated steam into a condensed liquid in a second chamber of the power generation assembly after (c2); and (c4) flowing the condensed liquid along an annular flow path extending along a second side of the thermoelectric generator.

18. The method according to claim 17, wherein (c4) comprises: (c4i) flowing the condensed liquid into a gas that fills the annular flow path; and (c4ii) vaporizing the condensed liquid into a vapor cooled during (c4i).

19. The method according to claim 18, further comprising: (c5) condensing the cooled vapor into a liquid during (c4); and (c6) returning the liquid from (c5) to the first chamber.

20. The method according to claim 18, further comprising: (f) retaining the liquid within a fluidly coupled U-elbow between the second chamber and the annular flow path; and (g) preventing the gas filling the annular flow path from flowing into the first chamber with the liquid retained within the U-elbow.

21. The system according to claim 1, wherein the well is covered.

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