System and method for generating electric power using heat from the inside of the earth
阅读说明：本技术 利用自地球内部的热产生电力的系统及方法 (System and method for generating electric power using heat from the inside of the earth ) 是由 西奥多·S·萨姆罗尔 于 2018-09-26 设计创作，主要内容包括：用于由地热层生产能源的系统及方法。可将热交换器安置于井内部以自地热层吸收热。可利用高导热性材料在井内部支撑热交换器。将热交换器连接至包括二级热交换器及涡轮机的有机朗肯循环引擎。选定一级及二级热传递流体以使有机朗肯循环的效率最大化。(Systems and methods for producing energy from geothermal layers. A heat exchanger may be disposed inside the well to absorb heat from the geothermal layer. The heat exchanger may be supported inside the well using a high thermal conductivity material. The heat exchanger is connected to an organic rankine cycle engine including a secondary heat exchanger and a turbine. The primary and secondary heat transfer fluids are selected to maximize the efficiency of the organic rankine cycle.)
1. A geothermal energy system comprising:
a primary heat exchanger located inside a well in contact with a geothermal component and a heat carrier inside a geothermal layer, the primary heat exchanger containing a first heat transfer fluid configured to absorb heat from the heat carrier in the primary heat exchanger;
a secondary heat exchanger in thermal communication with the primary heat exchanger, the secondary heat exchanger containing a second heat transfer fluid, wherein the first and second heat transfer fluids are maintained separate from each other, and wherein the second heat transfer fluid has a flash point below that of water; and
a turbine in fluid communication with the secondary heat exchanger, wherein the second heat transfer fluid is vaporized in the secondary heat exchanger and the vaporized second heat transfer fluid is a working fluid in the turbine; and
a generator coupled to the turbine, the generator configured to generate electricity based on movement of the turbine.
2. The geothermal energy system of claim 1, wherein the primary heat exchanger comprises a supply portion and a return portion, the supply portion comprising a housing in thermal communication with the geothermal element, and wherein the return portion is located concentrically inside the housing of the supply portion.
3. The geothermal energy source system of claim 2, wherein the return portion comprises an insulated pipe, wherein the insulated pipe is configured to isolate the hot first heat transfer fluid in the return portion from the relatively cooler first heat transfer fluid in the supply portion of the primary heat exchanger.
4. The geothermal energy source system of claim 3, wherein the insulated pipe is suspended inside the housing of the primary heat exchanger via a plurality of centralizers, the centralizers being located inside the housing of the primary heat exchanger such that the primary heat exchange fluid is in contact with the plurality of centralizers.
5. The geothermal energy source system of claim 4, wherein the plurality of centralizers are coupled to an outer surface of the insulated pipe and are not coupled to an inner surface of the housing.
6. The geothermal energy source system of claim 3, wherein the insulated tube has a first end located near a bottom portion of a housing of the supply portion and a second end connected to the secondary heat exchanger, and wherein the first end of the insulated tube is closed and includes a plurality of holes in the first end of the insulated tube to allow the first heat transfer fluid to flow from the supply portion into the insulated tube.
7. The geothermal energy source system of claim 1, wherein the housing comprises a well casing comprising a plurality of casing sections located inside the well.
8. The geothermal energy source system of claim, wherein the plurality of centralizers are connected to the inner surface of the casing at junctions between casing sections.
9. The geothermal energy source system of claim 1, wherein the primary heat exchanger is supported inside the well by cement or cement slurry having a high thermal conductivity.
10. The geothermal energy source system of claim 1, wherein the primary heat exchanger is supported inside the well by a plurality of support collars.
11. The geothermal energy system of claim 1, wherein the primary heat exchanger is suspended at or near the surface of the earth or the sea floor.
12. The geothermal energy source system of claim 1, wherein the heat carrier comprises a thermally conductive material interposed between an outer surface of the primary heat exchanger and an inner surface of the wall.
13. The geothermal energy system of claim 1, wherein the heat carrier is brine that can flow inside the geothermal layer.
14. The geothermal energy source system of claim 10, wherein each of the plurality of support collars comprises a first end and a second end, wherein the first ends of the plurality of support collars are securely connected with an inner wall of the well, and wherein the second ends of the plurality of support collars contact an outer shell of the primary heat exchanger at a point in the well above the respective first ends of the plurality of support collars.
15. The geothermal energy source system of claim 14, wherein the plurality of support collars support an outer shell of the primary heat exchanger at a location above a bottom of the well.
16. The geothermal energy source system of claim 14, wherein the plurality of support collars are located inside the well such that the plurality of support collars are in contact with the heat carrier in the geothermal layer, and the heat carrier is capable of flowing around the plurality of support collars to contact the primary heat exchanger.
17. The geothermal energy source system of claim 1, wherein the housing comprises a scale resistant coating on a well-facing surface of the housing, the coating comprising a non-metallic material that is extremely smooth, prevents formation of ionic bonding sites, thereby preventing scale formation and also inhibiting corrosion.
18. The geothermal energy source system of claim 1, wherein the housing comprises a fouling resistant coating on a well facing surface of the housing, the coating comprising a non-metallic material, such as carbon or boron applied via chemical vapor deposition or vapor deposition alloying.
19. The geothermal energy source system of claim 1, wherein the housing comprises an anti-fouling coating on a well-facing surface of the housing, the coating comprising a coating having a plurality of sp3Amorphous carbon materials that hybridize carbon to inhibit corrosion and fouling.
20. The geothermal energy source system of claim 1, wherein the housing comprises an anti-fouling coating on a well-facing surface of the housing, the coating comprising carbon nitride, boron nitride to prevent or minimize fouling and corrosion.
21. The geothermal energy source system of claim 1, wherein the housing comprises an anti-fouling coating on a well-facing surface of the housing, the coating comprising a highly thermally conductive ceramic that is resistant to fouling and corrosion.
22. The geothermal energy source system of claim 1, wherein the first heat transfer fluid is a nanofluid.
23. A method of generating electricity from geothermal energy, comprising:
moving a first heat transfer fluid into a primary heat exchanger located inside a well in contact with a geothermal component and a heat carrier inside a geothermal layer;
absorbing heat from a heat carrier in the well in the first heat transfer fluid;
removing the first heat transfer fluid from the primary heat exchanger and from the well and into a secondary heat exchanger;
transferring heat from the first heat transfer fluid to a second heat transfer fluid inside the secondary heat exchanger, vaporizing the secondary heat transfer fluid in the secondary heat exchanger;
flowing the vaporized secondary heat transfer fluid into a turbine, the turbine being connected to a generator and the vaporized secondary heat transfer fluid moving the turbine; and
generating electrical power in the generator using the motion of the turbine.
24. The method of claim 23, wherein moving the first heat transfer fluid into the primary heat exchanger comprises:
moving the first heat transfer fluid down to a supply portion of the primary heat exchanger; and
contacting a surface of a housing of the primary heat exchanger and a return tube concentrically disposed inside the housing of the primary heat exchanger with the first heat transfer fluid.
25. The method of claim 23, wherein moving the first heat transfer fluid out of the primary heat exchanger and out of the well comprises flowing the first heat transfer fluid through a return tube disposed concentrically inside a housing of a supply portion of the primary heat exchanger, wherein the return tube is thermally isolated to minimize heat transfer between the first heat transfer fluid inside the return tube and the first heat transfer fluid in the supply portion of the primary heat exchanger.
26. The method of claim 23, wherein the primary heat exchanger inside the well is supported via a hot cement or cement slurry with high thermal conductivity.
27. The method of claim 23, wherein the primary heat exchanger is supported inside the well via a plurality of support collars.
28. The method of claim 27, further comprising flowing the heat carrier between an inner surface of the well and an outer surface of the primary heat exchanger and around the plurality of support collars.
29. The method of claim 23, further comprising:
inserting the primary heat exchanger into the well, the primary heat exchanger having attached thereto a plurality of support collars, a first end of each of the plurality of support collars being movably attached with an outer surface of the primary heat exchanger, and a second end of each of the plurality of support collars being temporarily connected with the outer surface of the primary heat exchanger via a degraded connection; and
degrading the temporary connection such that a second end of each of the plurality of support collars extends to contact an inner surface of the well.
30. The method of claim 23, wherein the well comprises a casing extending along only a portion of the well, the method further comprising:
drilling a portion of the well in which the casing does not extend to increase a diameter of the well with an extended reamer; and
positioning the primary heat exchanger in a portion of the well having an increased diameter.
31. A heat exchanger for use in geothermal applications, comprising:
a casing disposed inside the well, the casing having an anti-fouling and/or anti-corrosion layer thereon configured to contain a heat transfer fluid, the casing forming a housing to contain the heat transfer fluid;
a plurality of support collars disposed inside the well, the plurality of support collars supporting the casing inside the well, the plurality of support collars disposed at an angle generally upward from an inner surface of the well toward the casing;
a return tube coaxially disposed inside a cylindrical housing, wherein the arrangement of the sleeve and the return tube forms an annular space between the return tube and the cylindrical housing, an interior volume of the return tube being thermally isolated from the annular space;
a plurality of centralizers disposed inside the annulus, each of the plurality of centralizers comprising a first end and a second end, the first ends of the plurality of centralizers connected with an inner surface of the housing and the second ends of the plurality of centralizers connected with an outer surface of the return pipe, the centralizers having a low profile to minimize resistance to water flow flowing inside the annulus; and
wherein the plurality of support collars are configured to allow a heat carrier to flow between an inner surface of the well and the casing.
Background
Conventional systems for generating electricity for public consumption and utilization include nuclear power, fossil fuel powered steam generation facilities, and hydroelectric power. These systems are expensive to operate and maintain and use a large amount of natural resources, and in some cases result in excessive contamination via hydrocarbon combustion or spent nuclear fuel rod processing. Furthermore, even renewable energy resources such as solar and wind powered systems are only operable in some locations in an average of only a few hours per day, while geothermal systems may operate on an approximate 24/7 basis as needed.
Accordingly, there is a need in the art for systems and methods for inexpensively generating clean electrical power that are available on an approximately 24/7 basis and that do not rely on the import of petroleum materials or the construction of billions of dollars of power plants. There is a further need for systems and methods for utilizing heat from the earth's interior to generate electricity.
Disclosure of Invention
In one aspect described herein, a geothermal energy system includes a primary heat exchanger located inside a well, the well in contact with a geothermal component (geothermal heat) and a heat carrier inside a geothermal layer (geothermal format), the primary heat exchanger containing a first heat transfer fluid configured to absorb heat from the heat carrier in the primary heat exchanger; a secondary heat exchanger in thermal communication with the primary heat exchanger, the secondary heat exchanger containing a second heat transfer fluid, wherein the first and second heat transfer fluids are maintained separate from each other, and wherein the second heat transfer fluid has a flash point below that of water; and a turbine in fluid communication with the secondary heat exchanger, wherein the second heat transfer fluid is vaporized in the secondary heat exchanger and the vaporized second heat transfer fluid is a working fluid in the turbine; and a generator connected to the turbine, the generator configured to generate electrical power based on the motion of the turbine.
In some embodiments, the primary heat exchanger comprises a supply portion and a return portion, the supply portion comprising a shell in thermal communication with the geothermal member, and wherein the return portion is located concentrically inside the shell of the supply portion.
In some embodiments, the return portion comprises an insulated tube, wherein the insulated tube is configured to isolate the hot first heat transfer fluid in the return portion from the relatively cooler first heat transfer fluid in the supply portion of the primary heat exchanger.
In some embodiments, the insulated tube is suspended inside the housing of the primary heat exchanger via a plurality of centralizers, the centralizers being located inside the housing of the primary heat exchanger such that the primary heat exchange fluid is in contact with the plurality of centralizers.
In some embodiments, the plurality of centralizers are coupled to the outer surface of the insulated pipe and are not coupled to the inner surface of the housing.
In some embodiments, the insulated return tube has a first end located near a bottom of the housing of the supply portion and a second end connected to the secondary heat exchanger, and wherein the first end of the insulated return tube is closed and includes a plurality of holes therein to allow the first heat transfer fluid to flow from the supply portion into the insulated return tube.
In some embodiments, the housing comprises a well casing comprising a plurality of casing sections located inside the well.
In some embodiments, a plurality of centralizers are connected with the inner surface of the casing at the junctions between casing sections.
In some embodiments, the primary heat exchanger is supported inside the well by cement or cement slurry having a high thermal conductivity.
In some embodiments, the primary heat exchanger is supported inside the well by a plurality of support collars.
In some embodiments, the primary heat exchanger is suspended at or near the surface of the earth or the seafloor.
In some embodiments, the heat carrier comprises a thermally conductive material interposed between an outer surface of the primary heat exchanger and an inner surface of the wall.
In some embodiments, the heat carrier is brine that can flow inside the geothermal layer.
In some embodiments, each of the plurality of support collars comprises a first and second end, wherein the first ends of the plurality of support collars are securely connected with an inner wall of the well, and wherein the second ends of the plurality of support collars contact an outer shell of the primary heat exchanger at a point in the well above the respective first ends of the plurality of support collars.
In some embodiments, a plurality of support collars support the outer shell of the primary heat exchanger at a location above the bottom of the well.
In some embodiments, a plurality of support collars are located inside the well such that the plurality of support collars are in contact with a heat carrier in the geothermal layer, and the heat carrier is capable of flowing around the plurality of support collars to contact the primary heat exchanger.
In some embodiments, the housing includes a scale resistant coating on the well-facing surface of the housing, the coating comprising a very smooth non-metallic material that prevents the formation of ion bonding sites, thus preventing scale formation and also inhibiting corrosion.
In some embodiments, the housing comprises a fouling resistant coating on a well-facing surface of the housing, the coating comprising a non-metallic material, such as carbon or boron applied via chemical vapor deposition or vapor deposition alloying.
In some embodiments, the housing comprises an anti-fouling coating on a well-facing surface of the housing, the coating comprising a coating having a plurality of sp' s3Amorphous carbon materials that hybridize carbon to inhibit corrosion and fouling.
In some embodiments, the housing includes an anti-fouling coating on the well-facing surface of the housing, the coating comprising carbon nitride, boron nitride to prevent or minimize fouling and corrosion.
In some embodiments, the housing includes an anti-fouling coating on a well-facing surface of the housing, the coating comprising a high thermal conductivity ceramic that is resistant to fouling and corrosion.
In some embodiments, the first heat transfer fluid is a nanofluid.
In another aspect described herein, a method of generating electricity from a geothermal energy source includes moving a first heat transfer fluid into a primary heat exchanger located inside a well, the well being in contact with a geothermal component and a heat carrier inside the geothermal layer; absorbing heat from a heat carrier in the well in a first heat transfer fluid; removing the first heat transfer fluid from the primary heat exchanger and out of the well and into the secondary heat exchanger; transferring heat from the first heat transfer fluid to a second heat transfer fluid inside the secondary heat exchanger, vaporizing the secondary heat transfer fluid in the secondary heat exchanger; flowing the vaporized secondary heat transfer fluid into a turbine, the turbine being connected to a generator and the vaporized secondary heat transfer fluid moving the turbine; and the motion of the turbine is used to generate electricity in a generator.
In some embodiments, moving the first heat transfer fluid into the primary heat exchanger comprises moving the first heat transfer fluid downward into a supply portion of the primary heat exchanger; and contacting the housing of the primary heat exchanger and a surface of the return tube concentrically disposed inside the housing of the primary heat exchanger with the first heat transfer fluid.
In some embodiments, moving the first heat transfer fluid out of the primary heat exchanger and out of the well comprises flowing the primary heat transfer fluid through a return tube concentrically disposed inside a housing of the supply portion of the primary heat exchanger, wherein the return tube is insulated to minimize heat transfer between the primary heat transfer fluid inside the return tube and the primary heat transfer fluid in the supply portion of the primary heat exchanger.
In some embodiments, the primary heat exchanger inside the well is supported via a hot cement or grout having a high thermal conductivity.
In some embodiments, the primary heat exchanger is supported inside the well via a plurality of support collars.
In some embodiments, the method further comprises flowing a heat carrier between an inner surface of the well and an outer surface of the primary heat exchanger and around the plurality of support collars.
In some embodiments, the method further comprises inserting a primary heat exchanger into the well, the primary heat exchanger having a plurality of support collars attached thereto, a first end of each of the plurality of support collars being movably attached with an outer surface of the primary heat exchanger, and a second end of each of the plurality of support collars being temporarily connected with the outer surface of the primary heat exchanger via a degraded connection; and degrading the temporary connection such that the second end of each of the plurality of support collars extends to contact an inner surface of the well.
In some embodiments, the well comprises a casing extending along only a portion of the well, and the method further comprises drilling a portion of the well with an extended reamer (under diameter) in which the casing does not extend to increase the diameter of the well; and the primary heat exchanger is positioned in the portion of the well having the increased diameter.
In another aspect described herein, a heat exchanger for use with geothermal applications includes a casing disposed inside a well having an anti-fouling and/or anti-corrosion layer configured to contain a heat transfer fluid thereon, the casing forming a housing to contain the heat transfer fluid; a plurality of support collars disposed inside the well, the plurality of support collars supporting the casing inside the well, the plurality of support collars disposed at an angle generally upward from an inner surface of the well toward the casing; a return tube coaxially disposed inside the cylindrical housing, wherein the arrangement of the sleeve and the return tube forms an annular space between the return tube and the cylindrical housing, the internal volume of the return tube being thermally isolated from the annular space; a plurality of centralizers disposed inside the annulus, each of the plurality of centralizers comprising a first end and a second end, the first ends of the plurality of centralizers connected with the inner surface of the housing and the second ends of the plurality of centralizers connected with the outer surface of the return pipe, the centralizers having a low profile to minimize hydraulic resistance to flow inside the annulus; and wherein the plurality of support collars are configured to allow flow of a heat carrier between the inner surface of the well and the casing.
Brief description of the drawings
Fig. 1 is a diagram illustrating the seebeck effect for a thermoelectric system according to an exemplary embodiment.
FIG. 2 illustrates a thermopile of a thermoelectric system in accordance with an exemplary embodiment.
FIG. 3 illustrates a thermoelectric generator in accordance with an exemplary embodiment.
Fig. 4 is an explanatory diagram of a thermoelectric generation system according to an exemplary embodiment.
FIG. 5 is an illustrative graph of temperature inside the Earth's surface in accordance with an exemplary embodiment.
Fig. 6 is an illustration of an example tube structure including an inner tube and an outer tube according to an example embodiment.
Fig. 7 is an explanatory diagram of a thermoelectric generation system according to an exemplary embodiment.
Fig. 8 is an explanatory diagram of a thermoelectric generation system according to an exemplary embodiment.
FIGS. 9A and 9B are illustrative diagrams of a pipe system in accordance with an exemplary embodiment.
Fig. 10 is an explanatory diagram of a thermoelectric generation system according to an exemplary embodiment.
Fig. 11 is an explanatory diagram of a thermoelectric generation system according to an exemplary embodiment.
Fig. 12A is a system diagram of an embodiment of a geothermal energy production system.
Fig. 12B is a cross-sectional view of an embodiment of a heat exchanger inside a well.
Figure 12C is a cross-sectional view of an embodiment of a heat exchanger inside a well.
Fig. 12D is a top view of a portion of a heat exchanger.
Detailed Description
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, this embodiment is provided so that this disclosure will be thorough and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
Some embodiments of the present invention use deep wells (e.g., abandoned or unused oil, natural gas, and geothermal wells) that are available with little investment and that are equipped with a media recirculation type system to provide sufficient thermal energy for power generation, direct heating, and/or water condensation. For example, the power generation components may include thermoelectric generators, stirling engines, rankine engines, matenal energy cycle engines (Matteran energy cycle engines), flash power plants, dry steam power plants, binary organic rankine cycle power plants, flash/binary combined cycles, and the like. Deep wells may produce a source of thermal energy, while a separate cryogenic source may provide a source of cold, heat sink, or the like for creating a temperature differential, as utilized by the various power generation components described herein. For example, the independent cryogenic source may be provided by water obtained from a variety of sources including the ocean, sea, bay, river, brook, lake, spring, or from any underground source such as a subterranean well or from a public water system. The power-generating means may be used to power public, private and government consumption.
The method and system of the present invention have a number of inherent advantages resulting from an efficient design that utilizes available energy sources and limits the physical and ecological footprint and the waste resulting from its utilization. For example, designed as a closed-loop or substantially closed-loop approach, some disclosed embodiments may be utilized to reduce unwanted introduction of contaminants and non-natural materials into the surrounding environment, including into the earth's surface, subsurface, and into the earth's atmosphere. Furthermore, the closed loop nature and dependence on existing energy sources reduces the generation of additional waste or undesirable by-products that are typically produced with current geothermal energy production systems. By utilizing thermal energy already present inside the earth, embodiments of the present invention may additionally provide an undeveloped alternative energy source, overcoming many of the fuel dependency problems currently faced. Embodiments of the present invention may also be augmented by including multiple energy generation components and multiple heat sources, providing alternate energy sources for local utilization and/or for contributing to larger private or public grids. In addition, scalability can be achieved by economically prudent system construction, avoiding excessive construction cost, time and space. Finally, embodiments of the present invention create opportunities to take full advantage of existing energy already available from non-producing wells, such as depleted wells or exploratory wells, that might otherwise be unutilized or in use.
A first exemplary embodiment described herein may include a thermoelectric generator including a thermopile, a hot junction, and a cold junction. The thermal interface of the thermopile may be coupled to a high temperature source including heat from within the earth's surface. Additionally, the cold junction of the thermopile may be coupled to a low temperature source from the body of water that may be geographically separated from the cold junction. The high and low temperature sources may thus create a temperature gradient at the thermopile for generating electricity.
As illustrated in fig. 1, a continuously flowing current may be generated when a first wire 12 of a first material is joined with a second wire 14 of a second material and subsequently heated at one of the junction ends 16. This is known as the seebeck effect. The seebeck effect has two main applications: temperature measurement (thermocouple) and power generation. Thermoelectric systems are thermoelectric systems that operate on circuits that incorporate thermal and electrical effects to convert thermal energy into electrical energy or electrical energy to reduce temperature gradients. The combination of two more or more wires creates a thermopile 10 integrated into a thermoelectric system. The voltage generated when employed for power generation purposes is a function of the temperature difference and the materials of the two wires utilized. Thermoelectric generators have a power cycle closely related to a heat engine cycle with electrons acting as a working fluid and can be used as power generators. Heat is transferred from a high temperature source to a thermal interface and then rejected to a low temperature receiver from the thermal interface or directly to the atmosphere. The temperature gradient between the temperature of the hot junction and the temperature of the cold junction generates a voltage potential and the generation of electricity. Semiconductors can be used to significantly increase the voltage output of thermoelectric generators.
Fig. 2 illustrates a thermopile 20 constructed with n-type semiconductor material 22 and p-type semiconductor material 24. For increased current, n-type material 22 is heavily doped to create excess electrons, while p-type material 24 is used to create insufficient electrons.
Thermoelectric generator technology is a functional, practical and continuous long-term power source. Due to the accessibility of temperature gradients that occur in natural and man-made environments, thermoelectric generators can provide a continuous power supply in the form of electricity. One of the most abundant, common and available sources of energy is ambient heat, especially the heat contained inside the shell.
Fig. 3 illustrates an embodiment of a thermoelectric generator.
Any system that provides a heat sink that interfaces with a thermopile is contemplated herein, including naturally occurring sources such as heat absorption by a fluid. In an exemplary embodiment, the fluid is water. For purposes of this application, water may be obtained from any source including the ocean, sea, bay, river, brook, lake, spring, or from any underground source such as a subterranean well or from public water systems. Since water is used to absorb heat, water from a public water system used as a radiator herein can be used to preheat water to reduce the power required by public, government or industrial heating water for any desired purpose. Water or any fluid as a cryogenic source provides a technical benefit over air or natural gas by having a higher heat transfer coefficient and thus providing better heat transfer in the case of cold junctions.
Fig. 4 illustrates an exemplary embodiment of a thermoelectric generation system 400. Thermoelectric generators may be used in thermoelectric generation systems to produce electricity from a temperature gradient between a low temperature source and a high temperature source. The thermoelectric generation system 400 may be located in or near a body of water 402 including, but not limited to, an ocean, bay, sea, lake, river, spring, stream, or any other relatively cold body of water. The thermoelectric generation system 400 uses a body of water 402 as a low temperature source for the thermoelectric generator.
The body of water 402 may provide a significantly lower temperature for the thermoelectric generator to increase the temperature gradient. In a body of water 402, such as an ocean, bay, sea, or lake, the temperature of the water decreases with depth. At a depth commonly referred to as the ocean thermocline, the water temperature drops significantly. The average value of the depth at which the seafloor thermocline occurs is between 30 and 50 meters and varies worldwide. The low temperature source is preferably water at a depth below the seafloor thermocline to provide a continuous source of cold water, and is preferably in electrical current to allow continuous flow of cold water so that the water does not stagnate and therefore the temperature rises throughout the energy production operation. In addition, the location of the power plant adjacent to some other surface body of relatively cooler water should allow the water to flow through the plant and then drain with minimal thermal alteration of the water.
Thus, the cryogenic source may be in direct contact with the cold junction, or alternatively may be geographically separated from the cold junction and in fluid communication with other means of transport through a pipe or medium.
The high temperature source may be provided from inside the earth's crust 404. The earth provides a continuous, inexpensive source of extremely high heat. As illustrated in fig. 5, the temperature within the earth generally rises toward the core of the earth at an average rate of about 1 degree fahrenheit per 60 feet of depth. Thus, deeper locations within the earth may be used as a high temperature source for the thermal interface of the thermoelectric generator. Locations inside the earth may be reached via a borehole or other means for creating holes 416 in the earth's surface, and water or some other type of heat transfer medium is circulated through the holes and to or near the surface to allow heat transfer to occur by employing an efficient pump or some other method.
Certain pores, commonly referred to as dry pores, may be used to reach high temperatures inside the earth's crust. Dry holes are often present by unsuccessful efforts of the oil industry to locate oil or gas. The oil industry bores wells deep into the earth for exploration of oil. The vast majority of the delocalized oil of the worldwide drilled exploration wells is denoted "dry hole". The dry hole provides relatively easy access to the subsurface and high temperature conditions. The dry hole may be located on the ground or in a body of water. Dry holes can reach depths in excess of 30,000 feet. However, one of ordinary skill in the art will appreciate that the dry bore may be of any depth and may be an active or inactive functional or non-functional oil, natural gas, and/or geothermal well.
FIG. 5 illustrates the relationship between temperature and depth in the earth's crust of an exemplary well. As shown in fig. 5, the temperature in the well or dry hole can reach extremely high temperatures. In the exemplary depiction in fig. 5, the temperature in the drywell at 6100 feet is about 209 ° f. It will be appreciated by those of ordinary skill in the art that the present invention is not limited to the utilization of dry holes and may include any hole or well in the earth's crust that can provide a heat source including drilled holes for utilization by a thermoelectric generator and depleted or unutilized oil and gas wells. Fig. 5 is exemplary for one well. In some wells, the temperature profile may vary, and the downhole hole temperature at 6100 feet may be higher than 209 ° f.
Referring again to fig. 4, the thermoelectric generation system may include a pumping station 410, a pipe system 420, a thermoelectric generator 430, and a heat transfer fluid 440. The thermoelectric generation system may be disposed in or near the body of water 402. The pump station 410 may include a pump and associated housing for the pump. The pump may be any commercially available or specially designed pump capable of flowing a fluid at a suitable volumetric rate. The pump station 410 may be located on the ground, above the surface of the water, or below the water. The pumping station 410 is connected to a pipe system 420. The pipe system 420 comprises at least one pipe 422. The tube 422 may include an inner bore or internal passage for carrying a heat transfer fluid 440 to be heated by the earth. The inner bore may be any suitable diameter that allows sufficient heat transfer fluid 440 to be pumped through the tube system. The tube 422 extends from the pump station 410 into the aperture 416 and may be substantially U-shaped such that the tube 422 rises up out of the aperture.
The tube system 420 may interface with the
Thus, the pipe system 420 may be configured in a closed loop or substantially closed loop configuration between the pump station 410 and the thermoelectric generator 430. More specifically, the heat transfer medium is pumped from the pump station 410 into a high temperature source present in the earth's subsurface (e.g., inside an existing well) and back to the surface so that the
In some embodiments, the pump station 410 provides positive pressure to the first portion of the pipe system 420 and pumps the heat transfer fluid 440 from the surface down into the bore 416, where the fluid absorbs heat from the geological formation. The heat transfer fluid 440 then flows upward through the inner bore of the tube 422 into the thermoelectric generator 430, wherein the heat transfer fluid 440 provides heat to the thermoelectric generator 430. The heat transfer fluid 440 is then recirculated through the pumping station 410 and pressurized again downward, and the cycle is repeated.
In some embodiments, the pumping station 410 provides a suction or vacuum force on the pipe system 420, thereby drawing fluid from a portion of the pipe system 420, such as from the portion of the pipe system 420 in thermal communication with the thermoelectric generator 430. The heat transfer fluid 440 is then gravity drained or drawn down into the bore as needed for circulation.
In the exemplary embodiment illustrated in fig. 6, the tube system may include an outer tube 423 and an inner tube 424 such that an annulus 425 exists between the inner tube 424 and the outer tube 423. In this exemplary embodiment, fluid 440 may be pumped into the bore via inner tube 424, and fluid 440 heated by the earth may be pumped out of bore 416 via annulus 425 to
In some embodiments, the fluid 440 to be pumped into the bore via the annulus 425 and out of the bore via the inner tube 424. It should be appreciated that depending on the ambient environment and temperature to which the pipe system 420 should interface, returning fluid pumped down through the annulus 425 may additionally insulate the heated medium pumped up through the inner pipe 424.
In another embodiment of the thermoelectric generation system illustrated in fig. 7, the aperture 416 may be located on the ground proximate the body of water. The aperture 416 may provide a source of high temperature for the thermal interface as previously described. The body of water 402 may provide a low temperature source for the cold junction. The body of water 402 may be a river, a spring, a stream, a lake, or any other cold water supply.
In another embodiment of the thermoelectric generation system illustrated in fig. 8, the low temperature source for the
The use of water as a medium for heat transfer from deep inside the earth's crust can cause corrosion of the metallic pipe system. Hot water, especially when containing oxygen, can rapidly corrode metals. To reduce corrosion, a deoxygenation mechanism such as a high vacuum may be employed to remove oxygen from the water. Alternatively, non-corrosive metals such as stainless steel may be used for the pipe system. In another embodiment, the pipe system may comprise a high temperature resistant and non-corrosive plastic pipe. An exemplary embodiment of the plastic conduit is made of
The thermoelectric generator may be protected from a low temperature source during operation to extend the life of the thermoelectric generator. The protection may be in the form of chemical protection or any other source. The cold junction may comprise a ceramic material to resist corrosion by water. The thermoelectric generator may also be sealed so that water does not engage or corrode the thermopile.
The thermoelectric generator may comprise an off-the-shelf thermopile. The thermoelectric generator may also employ specially designed thermopiles, such as quantum well thermoelectric generators, which will substantially increase power generation.
The thermoelectric generator may also employ nanowires to increase the efficiency of the system. Nanowires increase the density of energy states. The nanowires may be arranged in a substantially parallel array to deliver the generated power. The thermoelectric generator may also include quantum dots to increase the efficiency of the system and reduce the thermal conductivity of the system.
In another embodiment of the thermoelectric generation system, the high temperature source for the thermal junction may be from a mud pit. Mud from a mud pit is used as drilling fluid for oil well drilling. The mud extends to the bottom of the hole in which the borehole is being drilled for oil exploration. The mud is heated by the borehole and from the high temperatures inside the earth's surface. The hot junction of the thermoelectric generator may interface with the mud pit to reach the high temperature of the mud. The high temperature of the mud can be used to increase the temperature variation across the thermopile and to increase electricity generation.
Thermoelectric generation systems may have several advantages over conventional systems for power generation. For example, thermoelectric generation systems have minimal pollution problems due in part to their operation as closed loop systems and rely on the introduction of minimal, if any, non-natural materials. The thermoelectric generation system should have minimal waste and minimal atmospheric emissions. The thermoelectric generation system is also completely renewable. The thermoelectric generation system may also be scaled down to a level that can power a local area. Thermoelectric generation systems may be inexpensive to construct and operate compared to conventional power systems and may also utilize non-productive wells rather than having to cap the non-productive wells or having to drill new holes.
Fig. 9A and 9B illustrate another exemplary embodiment of a pipe system 900 having an outer pipe 910 and an inner pipe 920 concentrically arranged as described above with reference to fig. 6. As illustrated by fig. 9A, the inner tube 920 includes a plurality of tabs 930 affixed to the outer surface of the tube, and these tabs may run along at least a portion of the tube length and extend radially outward. In one example, the tabs 930 may extend substantially the entire length of the tube. However, in another example, the tabs 930 may be affixed to the inner tube 920 along the length at or near the remote portion of the tube system 900. The tabs 930 may facilitate geothermal transfer from the earth to the medium circulating therethrough and further facilitate heat dissipation within the medium. Thus, in an embodiment, a tube system 900 including tabs only at a remote portion of the tube system 900 provides an increased heat transfer mechanism at or near the deepest portion of the tube system where geothermal energy is the most. Alternatively, in another exemplary embodiment illustrated by fig. 9B, a plurality of tabs 930 may be affixed to the outer tube 910 and extend to face radially toward the inner tube 920. It should be further appreciated that the tabs 930 may be affixed to and extend between the outer tube 910 and the inner tube 910. The tabs 930 may be constructed of a material having a high thermal conductivity as is known.
The tabs as described may also be used in embodiments having a tube system that does not include an internal tube or an external tube, such as a substantially U-shaped tube system as described with reference to fig. 4. In these embodiments, the tabs may be affixed to the inner surface of the tube and extend radially inward, further improving the geothermal transfer from the earth to the fluid pumped therethrough.
Fluid 440 is pressurized via a pump by the pump station 410. A pump is used to circulate the fluid 440 through the tubes 422, the
As the fluid 440 inside the tube 422 descends from the pump station 410 toward the bottom of the bore 416, it is heated by the earth. Fluid 440 may be heated to a temperature near the soil in aperture 416. In an exemplary embodiment, the fluid 440 may be heated to more than 200 degrees Fahrenheit. After the fluid 440 reaches the lowest point of the tube 422, the heated fluid is then raised out of the aperture 416 and into the input of the
The heated fluid in the tube 422 may be a high temperature source and thermally coupled to the
The fluid 440 may comprise any fluid capable of being heated by the earth and capable of holding a substantial portion of the heat for delivery to the thermal junction of the thermoelectric generator. In the exemplary embodiment, the fluid is water, however, other fluids may be employed to reduce corrosion and to allow the heater well to exceed the boiling point of water.
The thermoelectric generator 430 may be located in the body of water 402 and in communication with the pipe system 420. The body of water 402 serves as a low temperature source for the
In an exemplary embodiment, the high temperature source may be between 100 and 600 degrees fahrenheit and the low temperature source may be between about 32 and 130 degrees fahrenheit. It will be appreciated by those of ordinary skill in the art that the high temperature source and the low temperature source are not limited to these temperature ranges but may be any suitable temperature range. In an exemplary embodiment, the temperature gradient (Δ T) between the hot and cold junctions may be between 470 and 68 degrees. One of ordinary skill in the art will appreciate that the temperature gradient is not limited to this range but may be any temperature gradient.
Thermoelectric generator 430 creates a voltage potential across
In another embodiment, the high temperature source may be utilized in conjunction with a steam powered generator. The fluid may be pumped into the earth's crust via a pipe system. The fluid may then be heated by the crust and pumped to the surface. Utilizing a high temperature source to heat the fluid can minimize the power required to operate a steam powered generator that preheats water to the steam appliance. Thus, if the fluid can reach higher temperatures due to heating inside the earth's crust, the cost of heating the fluid to its boiling point at hydrocarbon powered or other types of electrical equipment should be significantly reduced. For example, if the fluid is water, the high temperature source may heat the water to at or near its boiling point. The water may then be converted to steam for use by the steam power generator. If the fluid is a fluid, such as oil, having a boiling point greater than the boiling point of water, the fluid may be heated above 212 degrees fahrenheit so that it may transfer heat to steam to be converted to steam via a heat exchanger without the need for any or minimal fossil fuel or other energy source to water in the power generator. The steam powered generator may be utilized in conjunction with the thermoelectric generation system or entirely independently thereof.
In some embodiments, the present invention may include alternative power generation means, rather than a thermoelectric generator as described above. For example, alternative power generating components may include stirling engines, rankine engines, maynan energy cycle engines, flash power plants, dry steam power plants, binary power plants, flash/binary combined cycles, and the like. By way of illustration, the stirling engine is described as an illustrative embodiment; it should be appreciated that the power generation system may include other power generation components, such as rankine engines, maytans energy cycle engines, flash power plants, dry steam power plants, binary power plants, flash/binary combined cycles, and the like.
Stirling engines are very different thermal engines from typical internal combustion engines and can be more efficient than gasoline or diesel engines. Today, however, stirling engine use is generally limited to specialized applications, such as in the sea floor or as an auxiliary power generator for yachts, where quiet operation is important. The stirling engine utilizes the stirling cycle, which, unlike the cycle used for internal combustion engines, operates according to the principle of the carnot cycle. Exemplary stirling engines may include an alpha or beta type stirling engine utilizing a single displacer piston or a gamma type stirling engine utilizing an at least dual piston configuration. The gases utilized within the stirling engine do not escape the engine. There is no exhaust valve that exhausts high pressure gases, such as in a gasoline or diesel engine, and no combustion occurs. Due to this, the stirling engine is extremely quiet.
An exemplary embodiment of a stirling engine may include a cylindrical hot chamber with a piston, a cylindrical cold chamber with a piston, a gas, and a connecting tube. A high temperature source may be applied or thermally coupled to the thermal chamber to increase the temperature of the gas inside the thermal chamber. Heat from the high temperature source may be transferred to the gas via conduction, convection, radiation, or any other means. A cryogenic source may be applied or thermally coupled to the cold chamber to reduce the temperature of the gas inside the cold chamber. Heat extracted from the gas by the cold temperature source may be via conduction, convection, radiation, or any other means.
As known to those of ordinary skill in the art, stirling engines are operated by pressurizing and depressurizing gas by applying a high temperature source to a hot chamber and a low temperature source to a cold chamber. The efficiency and power generated by the stirling engine may also be increased by utilizing an increased high temperature source and a decreased low temperature source to create a substantial temperature gradient across the hot and cold chambers. The temperature gradient across the hot and cold chambers should increase the pressure distribution across the engine which causes the piston to move more actively. Thus, the greater the temperature difference between the hot and cold heat exchangers, the more efficient the operation of the stirling engine. The piston may be connected to the shaft such that movement of the piston rotates the shaft. An electrical generator may be attached to the shaft to convert mechanical energy of the rotating shaft into electrical power.
FIG. 10 illustrates an exemplary embodiment of a system employing a Stirling engine. In much the same manner as described with reference to fig. 4-9 and the embodiments employing thermoelectric generators, the stirling engine generation system may include a
The
The heated medium inside the tubes provides a high temperature source for thermal interface with the thermal heat exchanger of the
The cold heat exchanger or cold chamber (also referred to herein as a "cold junction" or "cold heat exchanger") of the stirling engine generator may be in thermal communication with a low temperature source, such as a body of water, as further described above with reference to fig. 4-8. In an exemplary embodiment of the stirling engine generator, the cold chamber of the generator is in thermal communication with the body of water at a point below the thermopile of the body of water such that the cold chamber can reach the low temperature water below the thermopile or cold water from the thermopile can be pumped to the surface to provide a low temperature heat sink.
In an exemplary embodiment, the high temperature source may be between 100 and 600 degrees fahrenheit and the low temperature source may be about 32 and 130 degrees fahrenheit. However, it should be understood that the high temperature source and the low temperature source are not limited to these temperature ranges but may be any suitable temperature ranges. In exemplary embodiments, the temperature gradient (Δ T) between the hot and cold junctions may be between about 470 degrees and about 68 degrees. Further, however, it should be understood that the temperature gradient is not limited to this range but may be any temperature gradient. Thus, utilizing the thermal energy available from the interior of the earth's crust to increase the temperature at the heat exchanger of the stirling engine generator and utilizing the cooling of the water to cool the temperature of the cold heat exchanger creates a more powered heat sink for dissipating heat from the engine, maximizing the temperature gradient and producing a large amount of electricity. The power may be generated as direct current. The direct current can be converted to alternating current. Three-phase currents may also be generated. The electrical power generated by the stirling engine generator may be transmitted to any destination via a power line. In an exemplary embodiment, existing power transmission facilities and power transmission pipelines may provide power to any electrical current or newly generated grid.
As previously stated, other power generation means that add advantage in the case of larger temperature differences may be coordinated with the thermal energy transferred from the earth's crust by the systems and methods described herein. In one example, the rankine engine can be used in many of the same ways as a thermoelectric generator or stirling engine, with the heat transfer medium being circulated from the pumping station to the bottom of the well or bore, then through the rankine engine and back, while also taking full advantage of the low temperature source, such as a body of water.
Fig. 11 illustrates another exemplary embodiment including a power generation means 1110 that may include a turbine 1112 and a
It should further be appreciated that the
The
In an exemplary embodiment utilizing a samoll energy cycle device as the power generating means 1110, the heat transfer medium may be one that is liquid at normal room temperature but has a boiling point lower than that of water to allow it to vaporize at lower temperatures. In the samoll energy cycle, the low boiling point medium is delivered directly down into the
The use of a low flash point fluid such as isobutane or cyclopentane in the turbine may result in better turbine performance compared to the use of water or steam. Low flash point fluids can be utilized at lower pressures and lower flow rates (compared to water or steam), which causes less wear on the blades and metallic parts of the turbine and other equipment. The use of a low flash point fluid allows for higher flow rates, which allows for the use of larger diameter turbines. This should also reduce the velocity of the working fluid and may cause less wear and damage to the turbine components. Furthermore, low flash point fluids are less likely to contain entrained liquids, bushings and other components that can be impinged on the turbine blades and damage the turbine.
In another exemplary embodiment, the power-generating
In still other embodiments, a dry steam power plant or a flash cycle power plant may be used as the power generating means 1110. In a dry cycle power plant embodiment, steam is delivered from inside the well (and in one embodiment an open circuit configuration that delivers steam present inside the earth's crust) to the turbine 1112 for power generation. In a flash steam power plant, heated water is delivered from within the well (which may include a closed loop configuration or an open loop configuration as described above with reference to fig. 4-10) to an additional flash tank (not shown) for use in generating steam prior to delivery to the turbine 1112. Similarly, a binary power plant or a combined flash/binary combined cycle plant may employ a secondary working fluid in thermal communication with the
It should be appreciated that where the exemplary embodiments are described using the term "pump station," the "pump station" need not include the actual pump or pumping capacity as is known. Thus, a "pump station" as utilized herein may simply refer to a mechanism that is operable to: the heat transfer medium is delivered to one or both of the high temperature source and the low temperature source via a pipe system and returned to the power generating components, such as a thermoelectric generator, an exemplary heat engine, an exemplary turbine generator, and the like. For example, while any pump means as known may be considered in some exemplary embodiments, other exemplary embodiments may be gravity fed, siphon based, displacement based, and the like.
Geothermal production systems encounter obstacles to efficient or cost-effective power generation. For example, about 40% of all geothermal wells drilled are non-productive, meaning that they do not or cannot withstand low cost systems for several reasons including, but not limited to: insufficient heat sources, insufficient thermal conductivity, insufficient earth pressure to carry hot brine to the surface, and others. Furthermore, brine as a heat carrier in geothermal layers can have a number of environmental and operational problems. In a conventional geothermal process, hot brine is pumped out of the surface from a production well, heat is extracted above the surface, and brine is pumped back into the surface. Typical systems remove about 15-20% of the heat from the brine and reintroduce the brine into the geothermal layer in the injection well at a significant distance, e.g., 1-2 kilometers or more, from the production well. Because heat has been removed from the brine, the saturation conditions of the brine change and precipitation (fouling) of the brine components may occur on the tubes, pumps and heat exchange surfaces. The brine precipitation may clog the piping, reduce heat transfer capacity, increase pumping power requirements, and cause pipe bursts. To prevent the brine from settling, a large amount of water must be added back into the brine. Water requirements can be as high as 1,000 acres-feet of water per MW of power produced. Thus, a 50MW geothermal plant can utilize 163 billion gallons of fresh water per year.
In addition, the brine may contain caustic and toxic components including heavy metals such as cadmium, arsenic, selenium and hydrogen sulfide (H) for example2S) toxic gases like these. Moving the brine to the surface can result in undesirable exposure and release of these components to the environment. Furthermore, brine is highly corrosive, and steps must be taken to protect the piping exposed to brine from corrosion.
Embodiments of the present invention overcome and/or minimize conventional geothermal power production problems. The embodiments described herein minimize the amount of piping and equipment that is used to treat or come into contact with the brine. The embodiments described herein do not pump brine to the surface, but exchange heat in the ground, in the geothermal layers. This eliminates the need for large amounts of make-up or fresh water. The components of the hazardous brine remain inside the geothermal layer rather than moving to the surface. Additional systems described below may use existing, utilized, or used oil and gas wells that may not have sufficient earth pressure to move brine to the surface.
The present invention relates to geothermal power systems using in-ground heat exchangers having a primary heat transfer fluid therein, on-ground heat exchangers in which the primary heat transfer fluid provides its heat to a secondary heat transfer fluid, and a generation section using the secondary heat transfer fluid as a working fluid. The system can advantageously utilize an organic rankine cycle in which an organic liquid (secondary heat exchange fluid) having a relatively low boiling point, such as isobutylene, isopentane, cyclopentane, etc., should undergo a phase change from liquid to gas in a heat exchanger and then the gas passes through a turbine and is recondensed and recycled.
FIG. 12A depicts an exemplary embodiment of a system for extracting heat from a geothermal component. The generation system 1200 includes a primary heat exchanger portion 1205, a secondary heat exchanger portion 1207, and a generation portion 1208.
The primary heat exchanger portion 1205 includes a hole or well 1240 drilled into the geothermal layer 1245 and the primary heat exchanger 1220. Well 1240 may be a new borehole well. Geothermal layer 1245 can have a source of geothermal energy and a heat carrier such as brine inside the geothermal layer. In some embodiments, well 1240 may be a dry well, a spent oil or gas well, or an unutilized well. The primary heat exchanger 1220 has a supply portion 1222 and a return portion 1224 that are inserted into the well 1240 and in or disposed inside the geothermal layer 1245 and communicate with the secondary heat exchanger portion 1207. Portions of the supply portion 1222 and the return portion 1224 extend out of the well 1240 to connect to other components of the system 1200.
In some embodiments, the temperature in the well may increase with increasing depth. In some wells, temperatures up to 3000 feet may drop, i.e., become cooler. In some embodiments, the temperature may increase below 300 feet so that useful heat transfer from the geothermal layer 1245 may occur. In some embodiments, the geothermal member may have an increasing temperature from 3000 feet to 12,000 feet or more. Downhole hole temperatures of 600 ° f or greater may facilitate operation of the system 1200. The heat exchange fluid temperature exiting the return portion 1224 may advantageously be about 600 ° f. The primary heat exchanger 1220 may extend along the full depth of the well or nearly the full depth of the well, and heat transfer may occur all along the depth of the well. In some embodiments, the heat exchanger may extend only through portions of the well having high in-ground temperatures sufficient for efficient heat transfer.
The primary heat exchanger 1220 will be described in more detail below. The pump 1210 is in fluid communication with the supply portion 1222 and the return portion 1224 and provides a motive force for circulating the primary heat transfer fluid through the supply portion 1222 and the return portion 1224. In some embodiments, pump 1210 may generate a positive pressure to cause the primary heat transfer fluid to descend in well 1240 inside geothermal layer 1245. In some embodiments, pump 1210 may provide negative pressure to draw the primary heat transfer fluid upward out of the well via return 1224. This may be advantageous because the static head of fluid in the supply portion 1222 may assist in moving the primary heat transfer fluid away from the well 1240.
The pump 1210 may be a centrifugal pump, a positive displacement pump, a source of pressurized air or inert gas, or any other type of pump. The pump 1210 may be electrically, mechanically, or fluid driven. One skilled in the art will appreciate that the pump 1210 may be any component capable of providing a motive force to circulate a primary heat transfer fluid into and out of the well 1240.
In some embodiments, the primary heat transfer fluid may be a fluid having a high heat capacity, such as water. In some embodiments, the primary heat transfer fluid may be a high temperature gas/liquid phase fluid or an organic heat transfer fluid. Can advantageously utilizeOf the ultra-high temperature heat transfer fluid. In some embodiments, the primary heat transfer fluid may be a mixture of Therminol and a nanopowder (such as nanopowder magnesium). By using means such as
Heat flow occurs in the primary heat exchanger 1220 when the primary heat transfer fluid is pumped down into the well 1240 or otherwise moved via motive force into the well 1240. Heat from geothermal layer 1245 is carried to supply portion 1222 by a heat carrier or brine. Heat from the heat carrier or brine is transferred through the walls of the supply portion 1222 and into the primary heat transfer fluid. The heat transfer fluid absorbs heat and moves via motive force, such as a pump, to the secondary heat exchanger portion 1207, where the primary heat transfer fluid releases its heat to the secondary heat transfer fluid. The cooler primary heat transfer fluid is recirculated down the well to repeat the cycle.
The primary heat transfer fluid returned to the well has been heated beyond ambient because it does not give off all of its heat to the secondary heat transfer fluid. In a typical geothermal operation, only about 15-25% of the heat (from the brine or steam) is extracted from the heat source, and the remainder of the brine or steam is reinjected away from the extraction point and thus not used further in the process. However, the current application is designed to allow this residual heat (between 75-85% of the original heat) to be reinjected back into the same well from which it was extracted. The primary fluid may be reheated to a desired temperature in this manner with less heat input from the geothermal layer to the desired temperature for desired thermal operation of the system. This results in less waste heat in the system 1200 and improves operating efficiency.
It should be appreciated, however, that the total surface area of the primary heat exchanger 1220 may be increased by increasing the tube diameter as much as possible. In some embodiments, such as (for example) when utilizing existing wells, the diameter of the existing well 1240 may only accommodate heat exchangers having a diameter smaller than the diameter of the existing casing. However, by employing an expanded reamer, the diameter of the open-hole portion of the well, i.e., the portion of the well that does not have a casing, may be increased (beyond the diameter of the existing casing), and an expandable casing or support collar as described elsewhere herein may be inserted into the open-hole portion of the well, thus providing a larger diameter primary heat exchanger 1220.
The secondary heat exchanger portion 1207 includes a secondary heat exchanger 1215, a hot fluid line 1232, and a cold fluid line 1234. In some embodiments, the secondary heat exchanger 1215 may be a shell and tube type heat exchanger. In some embodiments, the supply portion 1222 and the return portion 1224 are in fluid communication with tube portions of the secondary heat exchanger 1215. Hot fluid line 1232 and cold fluid line 1234 are in fluid communication with a shell portion of secondary heat exchanger 1215. The primary heat transfer fluid flows through the tube portions of the secondary heat exchanger 1215 and provides its heat to the secondary heat transfer fluid in the secondary heat exchanger 1215, which flows on the shell side of the secondary heat exchanger 1215. The heat passed through the primary heat transfer fluid vaporizes the secondary heat transfer fluid, and the vaporized secondary heat transfer fluid flows into generator portion 1208.
The secondary heat transfer fluid is circulated through hot fluid line 1232 and cold fluid line 1234 via feed pump 1237. The feed pump 1237 may be any type of pump capable of delivering motive force to circulate the secondary heat transfer fluid into the secondary heat exchanger 1215, and may be similar to the pumps described elsewhere herein.
In some embodiments, the primary and secondary heat transfer fluids do not mix and are isolated from each other in the secondary heat exchanger 1215.
The secondary heat transfer fluid may be a fluid that vaporizes at the temperature achieved inside the secondary heat exchanger 1215. In some embodiments, the secondary heat transfer fluid may be water. In some embodiments, the secondary heat transfer fluid may advantageously be an organic compound having a flash point lower than that of water. In some embodiments, the secondary heat transfer fluid may advantageously be isobutane or cyclopentane.
The generator portion 1208 includes a turbine 1230, a generator 1232, and a condenser 1235. The vaporized secondary heat transfer fluid impinges against blades of turbine 1230, which rotates a turbine shaft mechanically connected to generator 1232. As the turbine 1230 rotates, the generator 1232 generates electrical power. The turbine 1230 may advantageously be part of an organic rankine cycle.
The condenser 1235 operates to condense a secondary heat transfer fluid with the coolant supplied by the cooler 1238. The cooler 1238 may comprise one or more water or air cooling towers as known in the art. In some embodiments, the cooler 1238 may be a large radiator, such as a body of water, and the coolant may be pumped via a pump (not shown) or naturally circulated through the condenser 1235, similar to the radiators described elsewhere herein. The condensed secondary heat transfer fluid is circulated via feed pump 1237 to secondary heat exchanger 1215 where it is again heated and vaporized.
Heat exchangers 1215 and 1235 are described herein as shell and tube type heat exchangers. However, as guided by the present disclosure, it should be understood by those skilled in the art that any type of heat exchanger may be utilized. Additionally, those skilled in the art will appreciate that the fluid flowing in the shell and tube side of the heat exchanger may be varied without departing from the scope of the present invention.
In some embodiments, the generation system 1200 may not include the secondary heat exchanger 1215. In this case, the primary heat transfer fluid is heated in the well 1240, circulated to the turbine 1230 as a working fluid for the turbine 1230, and then condensed in the condenser 1235 to return to the well 1240.
Fig. 12B depicts a close-up cross-sectional view of a portion of the primary heat exchanger 1220 inside the well 1240. The well 1240 may be a hole formed inside the geothermal layer and may be similar to the holes described elsewhere herein. Inside the geothermal layer 1245, a liquid such as brine may be present. The brine is heated inside the geothermal layer 1245 by geological effects. The heated brine flows inside geothermal layer 1245 and inside well 1240 and supplies heat to heat exchanger 1220. It will be appreciated that in hot/dry downhole hole conditions, such as conditions where brine is not present, heat may be transferred through the thermal conductivity of the surrounding rock and a high temperature and high thermal conductivity material may be inserted between the exterior of the heat exchanger and the wall of the dry well to enhance thermal conductivity in hot/dry downhole conditions. In this case, the highly thermally conductive material may be a heat carrier to transfer heat from the hot rock to the primary heat exchanger 1220.
The primary heat exchanger 1220 includes a supply portion 1222 and a return portion 1224. The supply portion 1222 is bounded by an outer casing 1264 in contact with the geothermal layer 1245 and bounded by a return portion 1224. The outer housing 1264 comprises a plurality of casing units or sections connected to one another end-to-end using casing joints or casing couplers 1227. The casing body 1264 may in this way be as long as necessary to reach the depth of the geothermal layer 1245. The sleeve coupler 1227 connects one portion of the sleeve to another portion that forms the outer boundary of the primary heat exchanger 1220.
The outer casing 1264 may be casing in a depleted or unutilized oil or gas well. In some embodiments, the outer housing 1264 may be provided or positioned inside a borehole that has no casing. In the case where a pre-existing casing is present in the well, the primary heat exchanger 1220 may be formed by inserting the return portion 1224 inside the casing and sealing to prevent leakage of brine inside or leakage of primary heat transfer fluid outside. The return portion 1224 or the supply portion 1222 may be supported inside the casing as described herein.
As mentioned above, brine is highly corrosive and prone to deposit scale on the outer housing 1264 of the supply portion 1222. Scale material such as iron silicate or barium sulfate may deposit or accumulate on the well-side surface of the outer shell 1264. Calcium carbonate may not scale on the outer shell 1264 because the heat transfer process in the well 1249 is isobaric. Scale build up on the outer shell 1264 reduces the thermal conductivity of the outer shell 1264, which reduces the amount of heat transfer from the brine to the primary heat transfer fluid.
To prevent or minimize corrosion and scale build-up and to extend the useful service life of the primary heat exchanger, the material of the outer shell 1264 may be carefully selected. For example, the outer housing may be formed out of stainless steel that is then clad with a corrosion resistant material, such as nickel alloy 625. Nickel alloy 625 resists corrosion and scaling, and maintains the high thermal conductivity of outer shell 1264. The corrosion resistant material may also be an effective scale inhibitor because the corrosion resistant material resists the formation of nucleation sites required for scale to begin to form.
Further, the outer surface 1242 of the outer housing 1264 that is in contact with the saline during operation may be coated with a very smooth, non-metallic material. With a coating of a non-metallic material such as carbon or boron. This non-metallic material may be coated via Chemical Vapor Deposition (CVD) or Vapor Deposition Alloying (VDA). The non-metallic material prevents the formation of ionic bonding sites and thus prevents scale formation.
A Diamond Like Carbon (DLC) coating may be advantageously applied to the outer surface 1242 of the outer shell 1264. DLC to have a large number of sp3A kind of amorphous carbon material hybridized with carbon atom. A form of DLC, such as tetrahedral amorphous carbon (ta-C), may be advantageously utilized. A 2mm thick ta-C coating can greatly increase the abrasion, fouling, and other fouling resistance of stainless steel (or lower or higher grades of steel). Other forms of DLC can also be advantageously utilized, such as forms with hydrogen, graphitic carbon, or metals can be used to reduce costs and to impart other desirable characteristics. In some embodiments, it may be advantageous to apply carbon nitride, boron nitride, or other carbon or boron containing materials to the outer surface 1242 of the outer shell 1264 to prevent or minimize fouling and corrosion. The boron nitride coating (applied via CVD or VDA or similar methods) may improve the operable life of the primary heat exchanger 1220 by a factor of ten.
In some embodiments, the outer housing 1264 may be formed from or coated with a highly thermally conductive ceramic that is resistant to scaling and corrosion by salt water.
The return portion 1224 includes a return tube 1254 concentrically disposed inside an outer housing 1264 of the supply portion 1222. The flow rate through the return portion 1254 should be higher than the flow rate in the supply portion 1222 because the return tube 1254 has a smaller diameter than the outer housing 1264. As the primary heat transfer fluid moves upward in the return tube 1254, the higher flow rate in the return tube 1254 may limit heat loss to the cooler portion of the primary heat transfer fluid in the supply portion 1222 via the wall of the return tube.
In addition, to minimize heat transfer between the supply portion 1222 and the return portion via the return tube 1254, a thermal insulation layer 1225 may be added to the surface of the return tube 1254. The insulation layer may prevent, reduce, and/or minimize undesirable heat transfer between the supply portion 1222 and the return portion 1224. An insulation layer 1225 may be disposed on the inner surface, the outer surface, or both the inner and outer surfaces of the return tube 1254. In some embodiments, the thermal barrier layer may comprise a heat resistant polymer such as, for example, Polybenzimidazole (PBI) or other similar materials having high heat resistance and low thermal conductivity.
In some embodiments, the return tube 1254 may be a vacuum isolation conduit. The vacuum insulated conduit is a double walled conduit having an evacuated space between two walls. The evacuated space isolates the primary heat transfer fluid in the return tube 1254 from the primary heat transfer fluid in the supply portion 1222. In some embodiments, the return tube may be a vacuum insulated conduit and additionally have an insulation coating thereon.
The return tube 1254 is concentrically supported in place within the outer housing 1264 by one or more centralizers 1228. The centralizer is an angled stent centralizer 1228 extending from the inner surface 1253 of the outer housing 1264 at or near the sleeve coupler 1227 and connected with the outer surface of the return tube 1254, angled downwardly from the inner surface 1253 of the outer housing 1264 towards the outer surface of the return tube 1254. Although fig. 12B depicts only a centralizer 1228 on one side of the primary heat exchanger 1224, it may extend around the circumference of the return tube 1254 as will be described with respect to fig. 12D. A centralizer 1228 is used to support and keep the return tube 1254 centered inside the outer housing 1264. The centralizer 1228 has a narrow profile to minimize hydrodynamic resistance to primary heat transfer fluid flow.
A return tube 1254 is formed having one or more holes 1223 therein. One or more orifices 1223 provide a fluid path between supply portion 1222 and return portion 1224. In some embodiments, the return tube 1254 is capped on the lower surface 1255 and a hole is formed circumferentially near the bottom surface 1255 of the return tube 1254. In some embodiments, lower surface 1255 of return tube 1254 is uncapped and the heated primary heat transfer fluid flows upward into the bottom of return tube 1254. In some embodiments, return tube 1254 includes a hole 1223 and is uncapped on lower surface 1255.
The orifices 1223 may advantageously provide an improvement in power requirements to circulate the first heat transfer fluid through the primary heat exchanger 1220 by reducing the pressure on the bottom portion of the shell due to the pumping action.
The primary heat transfer fluid flows through primary heat exchanger 1220 in the directions indicated by arrows 1222a and 1222 b. To illustrate, cold or relatively cold primary heat transfer fluid flows from the secondary heat exchanger 1215 downwardly into the well 1240 in the supply portion 1222, around the centralizer 1228, and at or near the bottom surface 1255 of the primary heat exchanger 1220, as shown by arrow 1222 a. As the primary heat transfer fluid flows down into the supply portion 1222, it picks up heat from the geothermal layer 1245 via the outer casing 1264 which is thermally connected with brine. Heat from the geothermal layer conducts through the outer casing 1264 and conducts and/or convects into the primary heat transfer fluid.
The hot or relatively hot primary heat transfer fluid flows through the holes 1223 and into the return tube 1254. The insulation on the return tube minimizes heat transfer between the hot primary heat transfer fluid in the return tube 1254 and the cooler primary heat transfer fluid flowing downward in the supply portion 1222. The hot primary heat transfer fluid then flows up in the return tube 1254 and into the secondary heat exchanger 1215, or in some embodiments into the turbine 1230.
An outer shell 1264 of the primary heat exchanger 1220 is supported in place inside the well 1240. The outer housing 1264 generally has a diameter less than the diameter of the well 1240 such that a gap exists between the outer housing 1264 and the inner wall 1263 of the well 1240.
In some utilized wells or dry oil and gas wells, portland cement or high silica cement has been used to support casing inside the well 1240. In some embodiments described herein, the sleeve may form an outer shell 1264 of the primary heat exchanger 1220. Portland cement and other similar structural materials used in wells have very low thermal conductivity. Specifically, Portland cement has a thermal conductivity of about 0.2W/m.K. It has been found that the use of a carrier material having a low thermal conductivity greatly inhibits heat transfer in the well 1240. The structural material supporting the primary heat exchanger 1220 having such low thermal conductivity should greatly inhibit heat transfer from the geothermal layer 1245 and the brine to the primary heat exchanger 1220. When utilizing an existing well, such as a dry oil or natural gas well, a portion of the existing well has been cased and cemented with low conductivity cement until the casing is the well inside the geothermal layer so that the geothermal brine cannot flow backwards and into the shallower freshwater aquifer. Below a particular depth, in some embodiments, the bottom 2/3 depth of the well, the well where there is a bore or non-sealed casing at very high temperatures inside geothermal layer 1245 and where a heat exchanger may be inserted and where the heat transfer operations described herein may be performed. In one example, in a 12,000ft. deep well, the subsurface temperature is cooler than the return primary heat transfer fluid temperature (355 ° f) for the first three thousand feet, so the non-conductive cement prevents heat loss from the upper formation during its initial return cycle, and the only portion that is unutilized is the depth between 3,000 and 4,000ft. (where the well is open to the geothermal layer).
It has been found that a preferred thermal conductivity value for the structural material used to support the primary heat exchanger 1220 inside the well 1240 is about 15W/m-K. Thermal conductivities below 15W/m-K may not provide sufficient heat flux for efficient use or for maximum use of geothermal energy, and thermal conductivity values greater than 15W/m-K further increase heat flux but to the point of reducing the cost of returning for providing a material with a higher thermal conductivity. Cement or structural materials having high thermal conductivity may be advantageously used to support the casing or outer housing 1264 inside the well 1240. In some embodiments, as will be described in more detail below, the primary heat exchanger 1220 may be suspended or supported inside the well 1240 without the use of cement, concrete, or grout.
To achieve better or higher thermal conductivity of the support material, concrete or cement paste with thermally enhanced material may be utilized. For example, cement or cement slurries can be thermally enhanced by the addition of metal powders such as aluminum, copper, magnetite, and the like. The addition of these materials with high thermal conductivity values to cement or cement slurries increases the thermal conductivity of the resulting concrete. The cement or cement slurry should have a neutral or near neutral pH to avoid reaction with the added metal powder. Alkaline or acidic cement slurries can react with added metal materials and this can cause gas generation, corrosion and weakening of the cement or cement slurry.
In some embodiments, such as depicted in fig. 12B, the outer casing 1264 is supported in place by utilizing thermally enhanced cement 1260. A thermally enhanced cement 1260 may be disposed between the outer casing 1264 and the inner wall 1263 of the well 1240. Thermally enhanced cement 1260 improves heat transfer between geothermal layer 1245 and primary heat exchanger 1220 and supports outer casing 1264 in place inside well 1240.
Fig. 12C depicts an embodiment of a primary heat exchanger 1220 inside the well 1240 with a plurality of lateral support collars 1261 supporting the outer casing 1264 in place. A lateral support collar 1261 extends from an inner wall 1263 of the well 1240 and contacts the outer housing 1264. The lateral support collars 1261 may be spaced around the circumference of the outer housing 1264 and along the length of the outer housing 1264 and may extend at an angle downwardly from the outer housing 1264 towards the inner surface 1263 of the well 1240. Accordingly, a gap 1246 remains between the inner wall 1263 of the well 1240 and the outer housing 1264 with the lateral support collar 1261. Brine in the geothermal layer may flow around and through the gap 1246, and the brine may directly contact the outer casing 1264 of the primary heat exchanger 1220. This arrangement increases heat transfer from the geothermal layer to the primary heat exchanger 1220. It should be understood that in some wells 1240, there may be fresh groundwater or other heat transfer medium other than brine in contact with the outer casing 1264.
Extending the lateral support collars 1261 radially outward and downward from the outer casing 1264 also provides support or limits the movement of the primary heat exchanger down into the well 1240 or in the negative y-axis direction, but allows upward movement, away from the well 1240 or in the positive y-axis direction. The lateral support collar 1261 may be attached to the outer surface 1242 of the outer housing 1264 at a moveable junction or hinge. Prior to inserting the heat exchanger 1220 into the well, the first end of the lateral support collar may be secured to the outer housing of the heat exchanger via a biased and hinged, pivotable, or movable but non-removable interface. The other end of the lateral support collar may be folded down against the outer surface 1242 of the outer housing 1264 and may be held in place by a temporary connection or degradable material. When the heat exchanger 1220 is inserted into the well 1240, the lateral support collar is flush or nearly flush with the outer surface 1242 of the outer casing 1264, and the heat exchanger 1220 may extend into the well 1240 without interference from the lateral support collar 1261. When the heat exchanger is in place in the well 1240, the temporary connections or degradable material may be degraded. When the temporary connection is degraded, the biasing force in the junction at the first end of lateral support collar 1261 causes lateral support collar 1261 to extend to the position shown in fig. 12C and impinge the inner surface of well 1240, supporting heat exchanger 1220 inside well 1240.
In some embodiments, the temporary connection or degradable material is configured to degrade due to caustic conditions in the well 1240 or thermal degradation due to high temperatures down the well 1240, or both. Another degradation mechanism may also be utilized.
This arrangement allows the primary heat exchanger 1220 to be easily removed upward out of the well 1240 when necessary, but prevents the primary heat exchanger 1220 from moving further downward into the well 1240. In some embodiments, the primary heat exchanger 1220 may advantageously be suspended in the well 1240 from the ground or water surface.
Fig. 12C also depicts a centralizer 1228 as a horizontal support connected to the return tube 1254 at junction 1229 and not connected to the outer housing 1264. This arrangement centers the return tube 1254 inside the housing 1264 and makes it possible to remove the return tube 1254 from the housing 1264 (or casing) or well 1240 for maintenance, replacement, inspection and the like. When the return tube 1254 is removed from the casing, the centralizer 1228 is removed with the return tube 1254. This arrangement also allows the return tube 1254 to be inserted into the housing 1264 without having to navigate an array of structures connected with the housing 1264.
In some embodiments, the centralizer 1228 can be arranged horizontally and connected to the return tube 1254 and the housing 1264.
Although the angled centralizer 1228 arrangement of fig. 12B is shown in the embodiment with thermally enhanced concrete 1260 and the horizontal centralizer 1228 arrangement of fig. 12C is shown in the embodiment with support collar 1261, it is expressly contemplated that the horizontal centralizer 1228 could be used for a heat exchanger supported by the thermally enhanced concrete 1260 and the angled centralizer could be used for a heat exchanger supported by the support collar 1261.
Fig. 12D is a top view of the primary heat exchanger 1220 illustrating the arrangement of the centralizer 1228. As shown, the centralizer extends radially outward from the return tube 1254 and toward the outer housing 1264, and is disposed circumferentially around the return tube 1254. A space exists between the centralizers 1228 to allow flow of the primary heat transfer fluid. The view of the centralizer 1228 shown in fig. 12D can be applied to an angled or horizontal centralizer 1228. Fig. 12D depicts that the centralizer 1228 should be narrow to minimize hydraulic resistance to the first heat transfer fluid flow.
The systems and methods for generating electrical power may also be adapted for heating and cooling facilities, equipment, and the like. In heating and cooling applications, the system need not include a turbine or generator, but may utilize a heat exchanger and control system to provide temperature control of buildings, rooms, equipment, and the like. Additionally, utilizing absorption or adsorption chillers may advantageously provide cooling for facilities and equipment utilizing geothermal energy sources described herein or may be used to condense atmospheric water vapor.
The generation system and related details of the primary heat exchanger described with respect to fig. 12 may be advantageously used with embodiments having a thermoelectric generator, a stirling engine, a maytansine cycle, an organic rankine cycle, a conventional rankine cycle, or any other cycle or method described herein.
In some embodiments, for example, where the well has insufficient geothermal pressure or heat carrier movement inside the geothermal layer is less than desired, steps may be taken to ensure that there is sufficient heat carrier flow inside the geothermal layer and well. For example, hydraulic fracturing may be performed in the area near the well to increase the overall volume exposure of the heat carrier to the geothermal layers, and by creating a circulation path around, above, and over the primary heat exchanger. In some embodiments, the hydraulic breach may be performed using, for example, sand having an average particle size of about 80 mesh or 177 microns included in the breach water. Guided by the present disclosure, those skilled in the art will understand how other sand diameters may be used with the embodiments described herein. In some embodiments, the sand may be coated with or mixed with a scale-inhibiting chemical. A scale inhibiting chemical may be inserted into the hydraulic breach to prevent scale formation on the outer shell of the primary heat exchanger. These chemicals may include acrylic polymers, maleic polymers, and phosphonates. In some embodiments, the scale-inhibiting chemical may be selected for its desired solubility, thermal stability, and dose efficiency characteristics.
Construction of the well may be accomplished by inserting a plurality of support collars as described herein into a drilled well in a geothermal member. The casing units or casing sections may be assembled on the surface and subsequently inserted into the well and supported in place by the support collar. In some embodiments, the casing sections are inserted separately into the well and supported by the support collars. When the sleeve section is complete, the return tube can be inserted coaxially into the sleeve, and appropriate inlet and outlet ports and connections can be made. In some embodiments, the heat exchanger may be inserted into the well as a complete unit and may be supported by a support collar. When the heat exchanger has fouled or is unable to provide effective heat transfer, the unit may be removed from the well and replaced with a new heat exchanger, or the removed heat exchanger may be cleaned/repaired and reinserted into the well.
It should be apparent that the foregoing relates only to exemplary embodiments of the present invention and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined herein.
The above description discloses several methods and materials of the present invention. The present invention is susceptible to modifications in method and material, as well as variations in manufacturing method and equipment. Such modifications will become apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments disclosed herein, but that the invention cover all modifications and alternatives falling within the true scope and spirit of the invention.
The foregoing description details certain embodiments of the systems, devices, and methods disclosed herein. It should be appreciated, however, that no matter how detailed the foregoing appears in text, the systems, devices, and methods may be practiced in many ways. As also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being redefined herein to be restricted to including any specific characteristics of the features or aspects of the technology with which that terminology is associated.
It will be apparent to those skilled in the art that various modifications and changes may be made without departing from the scope of the described technology. Such modifications and variations are intended to fall within the scope of the embodiments. It will also be appreciated by those of skill in the art that portions included in one embodiment may be interchanged with other embodiments; one or more portions from the depicted embodiments may be included in any combination with other depicted embodiments. For example, any of the various components described herein and/or depicted in the drawings may be combined with, interchanged with, or excluded from the other embodiments.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. Various singular/plural permutations may be expressly set forth herein for clarity.
It will be understood by those within the art that, in general, terms used herein are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations.
In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two specimens," without other modifiers, typically means at least two specimens, or two or more specimens). Moreover, in those instances where a conventional analog of "at least one of A, B and C, etc." is utilized, in general such an interpretation is intended in the sense one having ordinary skill in the art would understand it (e.g., "a system having at least one of A, B and C" would include, but not be limited to, systems having a alone, B alone, C alone, a and B in combination, a and C in combination, B and C in combination, and/or A, B and C in combination, etc.). In those instances where at least one of A, B or C, etc. "is utilized, in general, such an interpretation is intended in the sense one of ordinary skill in the art would understand to be conventional (e.g.," a system having at least one of A, B or C "would include, but not be limited to, systems having a alone, B alone, C alone, a and B in combination, a and C in combination, B and C in combination, and/or A, B and C in combination, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "a or B" should be understood to include the possibility of "a" or "B" or "a and B".
As used herein, the term "comprising" is synonymous with "including", "containing" or "characterized by", and is inclusive or open-ended and does not exclude additional unrecited elements or method steps.
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