THERMOELECTRIC GENERATOR
A thermoelectric generator includes a plurality of thermoelectric modules that generate electrical power when subjected to a temperature differential. The generator also includes a plurality of first thermal elements to which heat is supplied by a first fluid and a plurality of second thermal elements from which heat is removed by a second fluid. The first and second thermal elements are arranged in a stack of alternating first and second thermal elements having one of the plurality of thermoelectric modules between each adjacent pair of first and second thermal elements. Each thermoelectric module is in contact on its first side with one of the first thermal elements and in contact on its second side with one of the second thermal elements such that no face of any thermal element contacts more than one of the thermoelectric modules.
This application claims priority to U.S. provisional application 61/060,377, filed Jun. 10, 2008 and titled “Combined Heat and Power and Hydrogen Generation for Whole Home or Building with Ground Heat Exchanger Using Thermoelectric Seebeck Modules”, the disclosure of which is hereby incorporated herein in its entirety for all purposes.
CROSS REFERENCE TO RELATED APPLICATIONSThis application is related to U.S. patent application Ser. No. ______ (Attorney docket number 027483-000210US), titled “Integrated Energy System for Whole Home or Building”, and to U.S. patent application Ser. No. ______ (Attorney docket number 027483-000300US), titled “Automatic Configuration of Thermoelectric Generation System to Load Requirements”, both having the same inventor as the present application and filed Jun. 10, 2009. The disclosures of those two applications are hereby incorporated herein in their entirety for all purposes.
BACKGROUND OF THE INVENTIONA thermoelectric module is a device that exploits the thermoelectric effect exhibited by many materials.
The thermoelectric effect is reversible, such that when the two sides of a thermoelectric module are held at different temperatures, the module can generate electric power. For example, in
In one embodiment, a thermoelectric generator for generating electrical power from a difference in temperature includes a plurality of thermoelectric modules. Each thermoelectric module has a first side and a second side, and each thermoelectric module generates electrical power when subjected to a temperature differential between its respective first side and second side. The thermoelectric generator also includes a plurality of first thermal elements to which heat is supplied by a first fluid, and a plurality of second thermal elements from which heat is removed by a second fluid. The first and second thermal elements are arranged in a stack of alternating first and second thermal elements having one of the plurality of thermoelectric modules between each adjacent pair of first and second thermal elements. Each thermoelectric module is in contact on its first side with one of the first thermal elements and in contact on its second side with one of the second thermal elements such that no face of any thermal element contacts more than one of the thermoelectric modules. Each of the first and second thermal elements may be a block made of a thermally conductive material, and each block may further comprises a passageway through the block through which the respective fluid flows. The thermally conductive material may be aluminum. Each block may be generally rectangular, and each passageway may traverse its respective block generally diagonally. Each passageway may include a lead-in portion at each end, each lead-in portion being generally cylindrical and of a larger dimension than the midportion of the passageway. The first and second thermal elements may be mechanically interchangeable.
In some embodiments, the thermoelectric generator further comprises a clamp that holds the stack of thermoelectric modules and first and second thermal elements in compression. In some embodiments, the thermoelectric generator comprises a first fluid inlet manifold that distributes the first fluid to the first thermal elements, and a first fluid outlet manifold that collects the first fluid from the first thermal elements. In some embodiments the thermoelectric generator further comprises a second fluid inlet manifold that distributes the second fluid to the second thermal elements, and a second fluid outlet manifold that collects the second fluid from the second thermal elements. In some embodiments, the thermoelectric generator comprises a first fluid inlet manifold that distributes the first fluid to the first thermal elements, a first fluid outlet manifold that collects the first fluid from the first thermal elements, a second fluid inlet manifold that distributes the second fluid to the second thermal elements, and a second fluid outlet manifold that collects the second fluid from the second thermal elements. The first fluid inlet manifold and the second fluid outlet manifold may be positioned adjacent each other on one side of the stack of thermoelectric modules and first and second thermal elements.
In some embodiments, the thermoelectric generator further comprises one or more flexible tubes, at least one of the tubes connecting each of the manifolds with each of its respective first or second thermal elements. At least one of the flexible tubes may be press fit into its respective manifold and thermal element. The first fluid may be water. The second fluid may be water.
In another embodiment, a method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature comprises providing a plurality of thermoelectric modules, each thermoelectric module having a first side and a second side, and each thermoelectric module generating electrical power when subjected to a temperature differential between its respective first side and second side. The method further comprises providing a plurality of first thermal elements configured to receive heat from a first fluid, and providing a plurality of second thermal elements configured to be cooled by a second fluid. The first and second thermal elements are arranged in a stack of alternating first and second thermal elements having one of the thermoelectric modules between each adjacent pair of first and second thermal elements. Each thermoelectric module is in contact on its first side with one of the first thermal elements and is in contact on its second side with one of the second thermal elements such that no face of any thermal element contacts more than one of the thermoelectric modules. In some embodiments, the method further comprises providing a first fluid inlet manifold configured to receive the first fluid and distribute it to the plurality of first thermal elements. The method may further comprise providing a second fluid inlet manifold configured to receive the second fluid and distribute it to the plurality of second thermal elements. The method may further comprise providing a first fluid outlet manifold configured to receive the first fluid from the plurality of first thermal elements and carry the first fluid away from the thermoelectric generator. The method may further comprise providing a second fluid outlet manifold configured to receive the second fluid from the plurality of second thermal elements and carry the second fluid away from the thermoelectric generator. The method may further comprise connecting each thermal element to a fluid inlet manifold and to a fluid outlet manifold. The method may further comprise clamping the stack of first thermal elements, second thermal elements, and thermoelectric modules, so that that stack is held in compression.
Thermoelectric module 100 is but one example of a thermoelectric device usable by embodiments of the invention. Module 100 is made up of a number of thermoelectric elements 104, each of which is a length of conductive or semiconductive material with favorable thermoelectric properties. For example, the elements may be pieces of n-type and p-type semiconductor material, labeled “N” and “P” in
Preferably, thermoelectric modules used in embodiments of the invention are optimized for power generation. Research has shown that the total power available is maximized when the length “L” of the thermoelectric elements is quite short—for example about 0.5 millimeters. However, the conversion efficiency of a thermoelectric module (the fraction of available thermal energy actually converted to electrical energy) increases with increasing length L. For example, a thermoelectric element with a length of 5.0 millimeters may be several times more efficient than one with a length of 0.5 millimeters. The optimum length for a particular application (providing the minimum cost per expected unit of electrical energy) will be a function of the cost of the thermoelectric modules and associated hardware, the cost of the thermal energy supplied to the thermoelectric generator, and the expected life of the thermoelectric generator. A more complete discussion of the factors involved in optimizing the performance of a thermoelectric module may be found in D. M. Rowe and Gao Min, Evaluation of thermoelectric modules for power generation, Journal of Power Sources 73 (1998) 193-198.
For maximum power output, it is advantageous to supply heat to the hot side of each thermoelectric module as efficiently as possible, and to remove heat from the cold side as efficiently as possible.
The assembly shown in
If the outputs of more than one thermoelectric module are to be combined, it is preferable that the complexity of fluid and electrical connections be minimized, and that each thermoelectric module makes good thermal contact with a heat source and a heat sink. Achieving good thermal contact for all thermoelectric modules may be complicated by the variability of dimensions inherent in any manufacturing process. For example, not all thermoelectric modules may be of the same height.
One approach to this problem is described in co-pending U.S. patent application Ser. No. 10/823,353, filed Apr. 13, 2004 and titled “Same Plane Multiple Thermoelectric Mounting System”, the disclosure of which application is hereby incorporated herein in its entirety for all purposes. That application describes an arrangement in which at least some of the thermal elements are configurable to accommodate tolerance variations in the system components, enabling the efficient coupling of multiple thermoelectric modules.
Example thermoelectric generator 400 includes a plurality of thermoelectric modules 401. Each thermoelectric module 401 generates electrical power when subjected to a temperature differential between its two sides. Thermoelectric generator 400 also includes a plurality of first thermal elements 402 to which heat is supplied by a first fluid 403, and a plurality of second thermal elements 404, from which heat is removed by a second fluid 405. The first and second thermal elements 402 and 404 are arranged in a stack of alternating first and second thermal elements, with a thermoelectric module 401 sandwiched between each adjacent pair of a first thermal element 402 and second thermal element 404. While only four thermoelectric modules 401 are shown in Figure, with three first thermal elements 402 and two second thermal elements 404, one of skill in the art will recognize that more or fewer thermoelectric modules may be used.
Other than the first thermal elements on the ends of the stack, each first thermal element 402 is then in contact with two of thermoelectric modules 401, one at each of two opposing faces of the respective first thermal element 402. Similarly, each second thermal element 404 is in contact with two of thermoelectric modules 401, one at each of two opposing faces of the respective second thermal element 404. However, no face of any thermal element is in contact with more than one thermoelectric module 401. In this way, efficient use of the thermal elements 402, 404 is made, but manufacturing variances in the components are tolerated. Height variations in the thermoelectric modules 401 do not compromise the system performance, because each face of the thermal elements 402, 404 need only conform flatly to one side of one thermoelectric module 401. The thermoelectric modules 401 and thermal elements 402, 404 are free to conform in various translational and rotational degrees of freedom during assembly to accomplish the conformance.
Thermal elements 402, 404 may be made from a thermally conductive material, such as a metal. Aluminum is a preferred material, due to its high thermal conductivity and resistance to corrosion. Example thermal elements will be described in more detail below.
First fluid 403 is distributed to the first thermal elements 402 by a first fluid inlet manifold 406. First fluid 403 may be, for example, water that has been heated for the purpose of generating electric power from thermoelectric generator 400, waste hot water from a industrial process, or from some other source. First fluid 403 may be another kind of fluid, for example a natural or synthetic oil, or any other kind of suitable fluid. For the purposes of this disclosure, the term “fluid” is intended to be interpreted broadly, and encompasses liquids such as water, oil, or other liquids, and encompasses gasses such as air, steam, and other gasses. First fluid 403 preferably passes through a passageway in each of first thermal elements 402, exemplified by passageway 407. After passing through first thermal elements 402, first fluid 403 is collected by a first fluid outlet manifold 408 to be carried away from thermoelectric generator 400. Fluid 403 may be returned to a heating system, or simply exhausted from the system.
Similarly, second fluid 405 is distributed to second thermal elements 404 by a second fluid inlet manifold 409. Second fluid 405 is at a different temperature than first fluid 403, and may be of the same kind as first fluid 403, or may be a different kind of fluid. For example, both first and second fluids 403 and 405 may be water, or one may be water while the other is a kind of oil. Any suitable combination is possible. Preferably, second fluid 405 passes through passageways in second thermal elements 404, exemplified by passageway 410. After passing through second thermal elements 404, second fluid 405 is collected by a second fluid outlet manifold 411, to be carried away. Second fluid 405 may be recycled, or exhausted from the system.
The net result is that each of thermoelectric modules 401 is exposed to a temperature differential, by virtue of being between one of first thermal elements 402 and one of second thermal elements 404. Thermal energy flowing through each thermoelectric module 401 is converted to electrical energy, and a voltage is developed across each set of electrical leads 412. In some embodiments, leads 412 may be interconnected such that thermoelectric generator 400 produces a single voltage on a single set of leads. For example, thermoelectric modules 401 may be connected in series, so that thermoelectric generator 400 produces a voltage that is the sum of the voltages produced by the individual thermoelectric modules 401.
While a particular arrangement of components has been described above, one of skill in the art will recognize that variations are possible within the scope of the claims. For example, thermoelectric generator 400 has been described has having “hot” first thermal elements 402 and “cold” second thermal elements 404. This relationship may be reversed, so that the end thermal elements are “cold”. Similarly, thermoelectric generator 400 is shown having first fluid 403 and second fluid 405 flowing counter to each other through the thermal elements 402, 404. That is, as shown in
In one arrangement, the fluids pass through their respective thermal elements generally diagonally. As is shown in
The generally diagonal traverse of element 402 by passageway 407 enables identical mechanical parts to be used for first thermal elements 402 and second thermal elements 404. In other words, the first and second thermal elements 402, 404 are mechanically interchangeable. First thermal elements 402 and second thermal elements 404 are simply flipped with respect to each other, so that their respective passageways cross. When thermoelectric modules 401 are positioned as shown in
Many other arrangements are possible. For example, the passageways through the thermal elements may be orthogonal to the sides of the thermal elements.
In other embodiments, the various connections between the components may be made in any number of ways. One method of connecting flexible tubes 501 to thermal elements 402, 404 was illustrated in
Similar kinds of connections may be used to connect flexible tubes 501 to the fluid inlet and outlet manifolds, such as manifolds 406, 408, 409, and 411. That is, tubes 501 may be pressed, threaded, or otherwise inserted into openings in the manifolds, may be fitted over tubes protruding from the manifolds, with or without clamps, or may be connected in any other suitable way. Combinations of connection types may be used. For example, the connections to the thermal elements may be of one type, while the connections to the manifolds may be of another type. Connection types may also be mixed within the connections to the thermal elements, within the connections to the manifolds, or both.
While several example manifolds have been described, it is to be understood that these are examples, and other arrangements using different combinations of features and fabrication techniques may be envisioned within the scope of the claims.
A thermoelectric generator in the configuration of generator 1200 may be especially suitable for systems that do not recirculate the heated or cold fluids. Generator 1200 may produce more electrical energy from a single pass of fluids 403, 405 through it as compared with a generator without series-connected thermal elements, although the efficiency of generator 1200 may be slightly reduced. Whether to use series-connected thermal elements or not may be an economic decision based on many factors, such as the cost of thermoelectric modules 401, whether fluid is recycled for reheating after passing through the thermoelectric generator, and other factors. One of skill in the art will recognize that any practical number of series-connected columns of thermal elements may be used, and the columns may contain any practical number of thermoelectric elements 401, from as few as one and ranging upward. The thermoelectric modules 401 may be electrically connected in any suitable configuration, including in series, in parallel, or in a combination of serial and parallel connections.
While a thermoelectric generator such as those shown in
Fluids are provided to and received from the bank manifolds via large manifolds 1302, 1303, 1304, 1305. Large manifolds 1302-1305 may be made, for example, of 2-inch (50.8 mm) square tubing with round hose connection tubes formed, welded, or brazed on the ends. The lower ends are crimped, capped, welded shut, or otherwise sealed.
In the example of
The banks of
A thermoelectric generator such as thermoelectric generator 500, 1200, or 1300 may be especially suited for use when low-cost sources of hot and cold fluids are available. For example,
In system 1400, a solar collector 1401 concentrates incoming energy from the sun 1404 onto a tube 1403 that carries a fluid such as water or an oil. Solar collector 1401 may be driven by a motor 1402 or other actuator to follow the sun during the day, for optimum energy collection. One of skill in the art will recognize that other kinds of solar collectors may be used besides the concentrating trough type collector 1401. The fluid in tube 1403 heats a reservoir 1405. Preferably, reservoir 1405 is filled with water, which has good thermal storage characteristics and is inexpensive, although other media could be used. The fluid from reservoir 1406 may be circulated directly through tube 1403, or may be heated indirectly, such as by a heat exchanger that extracts heat from the fluid in tube 1403 and imparts it to the fluid in reservoir 1405. Preferably, the fluid in reservoir 1405 is circulated through thermoelectric generator 500, providing the “hot” side of a temperature differential from which thermoelectric generator 500 generates electric power.
While thermoelectric generator 500 is depicted in
In system 1400, the cold side of the temperature differential is provided by a fluid, preferably water, that is cooled using an earth-coupled piping loop 1406. Such a loop takes advantage of the fact that at sufficient depths, the underground soil temperature stays relatively constant throughout the year. For example, in some parts of the United States, the underground temperature may be about 54-57° F. (12-14° C.). A sufficiently long earth-coupled loop will exhaust to the earth the heat gathered by the cold fluid during electricity generation in thermoelectric generator 500, cooling the fluid so that it can once again provide the cold side of the temperature differential exploited by thermoelectric generator 500. Both the hot and cold fluids and the fluid in tube 1403 may be circulated by pumps not shown in
Electric power is thus generated and is available at leads 1407 of thermoelectric generator 500. Multiple thermoelectric modules within thermoelectric generator 500 may be connected in series, parallel, or in a combination of series and parallel connections to provide power having appropriate voltage, current, or other characteristics. One or more components of the system may be configurable to adjust the amount or character of the available power. For example, a matrix switch may be provided that configures the electrical interconnections of the thermoelectric modules or banks of such modules included in thermoelectric generator 500. Such configurable components, including a matrix switch, are described in co-pending U.S. patent application Ser. No. ______ titled “Automatic Configuration of Thermoelectric Generation System to Load Requirements”, previously incorporated by reference herein.
The invention has now been described in detail for the purposes of clarity and understanding. However, it will be appreciated that certain changes and modifications may be practiced within the scope of the appended claims.
Claims
1 A thermoelectric generator for generating electrical power from a difference in temperature, the thermoelectric generator comprising:
- a plurality of thermoelectric modules, each thermoelectric module having a first side and a second side, and each thermoelectric module generating electrical power when subjected to a temperature differential between its respective first side and second side;
- a plurality of first thermal elements to which heat is supplied by a first fluid;
- a plurality of second thermal elements from which heat is removed by a second fluid;
- wherein the first and second thermal elements are arranged in a stack of alternating first and second thermal elements having one of the plurality of thermoelectric modules between each adjacent pair of first and second thermal elements, each thermoelectric module in contact on its first side with one of the first thermal elements and in contact on its second side with one of the second thermal elements such that no face of any thermal element contacts more than one of the thermoelectric modules.
2. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, wherein each of the first and second thermal elements is a block made of a thermally conductive material, each block further comprising a passageway through the block through which the respective fluid flows.
3. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 2, wherein the thermally conductive material is aluminum.
4. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 2, wherein each block is generally rectangular, and wherein each passageway traverses its respective block generally diagonally.
5. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 2, wherein each passageway comprises a lead-in portion at each end of the passageway, each lead-in portion being generally cylindrical and of a larger dimension than the midportion of the passageway.
6. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, wherein the first and second thermal elements are mechanically interchangeable.
7. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, further comprising a clamp that holds the stack of thermoelectric modules and first and second thermal elements in compression.
8. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, further comprising:
- a first fluid inlet manifold that distributes the first fluid to the first thermal elements; and
- a first fluid outlet manifold that collects the first fluid from the first thermal elements.
9. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, further comprising:
- a second fluid inlet manifold that distributes the second fluid to the second thermal elements; and
- a second fluid outlet manifold that collects the second fluid from the second thermal elements.
10. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, further comprising:
- a first fluid inlet manifold that distributes the first fluid to the first thermal elements;
- a first fluid outlet manifold that collects the first fluid from the first thermal elements;
- a second fluid inlet manifold that distributes the second fluid to the second thermal elements; and
- a second fluid outlet manifold that collects the second fluid from the second thermal elements.
11. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 10, wherein the first fluid inlet manifold and the second fluid outlet manifold are positioned adjacent each other on one side of the stack of thermoelectric modules and first and second thermal elements.
12. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 10, further comprising one or more flexible tubes, at least one of the tubes connecting each of the manifolds with each of its respective first or second thermal elements.
13. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 12, wherein at least one of the flexible tubes is press fit into its respective manifold and thermal element.
14. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, wherein the first fluid is water.
15. The thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 1, wherein the second fluid is water.
16. A method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature, the method comprising:
- providing a plurality of thermoelectric modules, each thermoelectric module having a first side and a second side, and each thermoelectric module generating electrical power when subjected to a temperature differential between its respective first side and second side;
- providing a plurality of first thermal elements configured to receive heat from a first fluid;
- providing a plurality of second thermal elements configured to be cooled by a second fluid;
- arranging the first and second thermal elements in a stack of alternating first and second thermal elements having one of the thermoelectric modules between each adjacent pair of first and second thermal elements, each thermoelectric module in contact on its first side with one of the first thermal elements and in contact on its second side with one of the second thermal elements such that no face of any thermal element contacts more than one of the thermoelectric modules.
17. The method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 16, the method further comprising:
- providing a first fluid inlet manifold configured to receive the first fluid and distribute it to the plurality of first thermal elements.
18. The method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 16, the method further comprising:
- providing a second fluid inlet manifold configured to receive the second fluid and distribute it to the plurality of second thermal elements.
19. The method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 16, the method further comprising:
- providing a first fluid outlet manifold configured to receive the first fluid from the plurality of first thermal elements and carry the first fluid away from the thermoelectric generator.
20. The method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 16, the method further comprising:
- providing a second fluid outlet manifold configured to receive the second fluid from the plurality of second thermal elements and carry the second fluid away from the thermoelectric generator.
21. The method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 16, the method further comprising:
- connecting each thermal element to a fluid inlet manifold and to a fluid outlet manifold.
22. The method of fabricating a thermoelectric generator for generating electrical power from a difference in temperature as recited in claim 16, the method further comprising:
- clamping the stack of first thermal elements, second thermal elements, and thermoelectric modules, so that that stack is held in compression.
Type: Application
Filed: Jun 10, 2009
Publication Date: Dec 10, 2009
Inventor: Phillip C. Watts (Longmont, CO)
Application Number: 12/481,741
International Classification: H01L 35/02 (20060101); H01L 35/34 (20060101);