FIELD OF INVENTION

The present invention relates to the optimization of thermoelectric power generation by considering the arrangement of Thermoelectric Generator (TEG) to recover the maximum energy from boiler flue gas ducting system. More particularly, this invention relates to an apparatus for thermoelectric power generation by optimization of hot plate area per unit area of TEG under natural and forced convective heat transfer modes and different operating temperatures using extended heat transfer surface on cold side of the TEG system.
BACKGROUND OF THE INVENTION
The prime energy demands are met by combustion of fossil fuel in which 40% of the primary energy is being thrown to the ambient as waste heat. Firing fossil fuels result in emissions into the atmosphere and a heat loss of 5 to 6% through dry flue gas. Energy security and emission reduction are the major concerns of today’s world. The waste heat leaving the flue gas at air heater outlet of thermal power plants at 135 °C to 150 °C which can be recovered using thermoelectricity. It has been known for a long that this waste heat can be converted into useful energy. Several techniques are being used to improve the performance of the plant by minimizing the waste heat thrown into the atmosphere. One of the novel technique, under development is recovery of waste heat using Thermo electric generators. Thermoelectric generator is a static solid-state device that convert temperature difference between hot and cold side of the TEG module to electrical power due to Seebeck effect. The success of the process mainly depends on temperature difference between hot and cold side of the TEG module. Hence, a suitable heat transfer mechanism is to be identified for increasing this temperature difference across TEG. Hence, it is required to optimize the performance of heat exchangers present at the TEG system, which greatly influence the electrical power generation as well as the occupancy rate or size of thermoelectric generators and the working conditions to make it an economically viable option of heat recovery.
US 2013/0152561 A1: A thermoelectric generator apparatus may include a high temperature member having an exhaust pipe, a ring-shaped first heat transfer plate surrounding the exhaust pipe, and a plurality of first heat exchange pins radially extending outwards from the first heat transfer plate in a predetermined degree, a low temperature member having an internal casing surrounding the exhaust pipe, an external casing surrounding the internal casing with a predetermined gap, a ring-shaped second heat transfer plate contacting with an internal wall of the internal casing, and a plurality of second heat exchange pins radially extending inwards from the second heat transfer plate in a predetermined angle, and a plurality of thermoelectric modules being in contact with the first heat exchange pins and the second heat exchange pins so as to generate electricity using a thermoelectric phenomenon caused by a temperature gap between the first heat exchange pins and the second heat exchange pins. This patent describes about heat exchanger for automobile exhaust pipe but this invention is discussed the arrangement of TEG on the boiler flue gas ducting system.
US 2013/0025644 A1: Apparatuses, methods, and systems are disclosed to use thermoelectric generating (TEG) devices to generate electricity from heat generated by a power cable. An apparatus includes multiple thermoelectric generating (TEG) devices. Each of the TEG devices has a first surface configured to be positioned in thermal communication with an outer surface of the power cable and a second surface configured to be positioned proximate to an ambient environment around the power cable. The apparatus also includes a set of terminals electrically coupled to the TEG devices. When a temperature differential exists between the first surface and the second surface, the TEG devices convert heat into electricity presented at the set of terminals. A waste heat recovery from power feeders in power distribution systems was used for TEG application but this invention is related to optimize the arrangement of distance between two successive TEGs.
The present invention relates to a heat transfer mechanism for increasing this temperature difference across TEG.
The information disclosed in this background of the disclosure section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
OBJECTS OF THE INVENTION
The principal object of the present invention is to optimize the hot plate area per unit area of TEG and to maximize the performance and make it an economically viable option for waste heat recovery.
Another objective of the present invention is to present TEG system considering arrangement of TEG (distance between two successive TEG) and area of the duct.
Yet another objective of the present invention is to carry out thermal performance evaluation of commercially available Bismuth Telluride TEG system under natural and forced convective heat transfer modes using extended heat transfer surface on cold side of TEG.
These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
One or more drawbacks of conventional coal beneficiation process, and additional advantages are provided through the process as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.
This invention is carried out for a hot side temperature of 100°C and 150°C using square pitch array arrangement with different hot plate area per unit area of TEG in the range of 1.42 to 240.25 area of hot plate occupied by TEG for optimizing maximum TEG electrical power output for TEG arrays. When the economy of power generated for the investment is of importance, power generated per TEG will be the best parameter. Peak power density over hot plate is found to be an appropriate measure for optimizing the occupancy ratio for TEGs over hot plate when maximum total power is of importance. The peak power density increases with increase in hot plate temperature and heat transfer coefficient. Optimized hot plate area per unit area of TEG is independent of the cold side heat transfer coefficient and depends mainly on the cold side hot plate temperature. The maximum peak power density is used to evaluate the performance of TEG at different arrangements. Power density reaches peak at a hot plate area per unit area of TEG and then drops drastically. The particular hot plate area per unit area of TEG where the power density peaks could be taken as optimized hot plate area per unit area of TEG. The hot plate area per unit area of TEG of square pitch arrangement is 9.61 for the heat transfer coefficient of 5 W/m2C as a natural convection and operating temperatures of 100ºC and 150ºC. However, the hot plate area per unit area of TEG of square pitch arrangements are 1.67 and 2.4 for operating temperature of 100ºC and 150ºC, respectively for the heat transfer coefficient of 25 W/m2C as a forced convection.
It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
Fig. 1 shows the elevation view of typical thermal power plant (prior art).
Fig. 2 shows the plan view of typical thermal power plant (prior art).
Fig. 3 shows the front view of arrangement for TEG system in duct.
Fig. 4 shows the side view of arrangement for TEG system in duct.
Fig. 5 shows the power density with respect to hot plate area per
unit area of TEG.
The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure
described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.
It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
From Fig. 1 and Fig. 2, it can be observed that the potential areas for TEG to extract waste heat from flue gas. Hot flue gases after producing steam from boiler (1) passes through air heater (2). Hereafter, the flue gas (9) passes through duct (3) from air heater outlet to ESP inlet. The flue gas after passing through another duct from ESP outlet to Induced Draft (ID) fan inlet (5) and then ID fan outlet to chimney inlet duct (7) and finally exhausted through chimney (8). The ID fan (6) is used for remove the exhaust gases from boiler (1) and ESP (4) is used to clean particulate matter from the flue gas. The areas for potential waste heat recovery includes ESP inlet duct (3), ESP surface (4) ID fan inlet duct (5) and chimney inlet duct (7).
It is required to optimize the performance of heat exchangers present at the TEG system, which greatly influence the electrical power generation as well as the occupancy rate or size of thermoelectric generators and the working conditions to make it an economically viable option of heat recovery. Therefore, the duct is the prime area of interest and the arrangement of the TEG in the same is shown in Fig. 3 and Fig. 4.
The transverse pitch arrangement (14) and longitudinal pitch arrangement (12) of TEG (11) are square pitch arrangement of the duct (10) in which the TEG cold side is in contact with finned surface (13). The TEG (11) is sandwiched between the duct and extended surface and it is coupled by using bolts and nuts (15). These arrangements are simply called as hot plate area per unit area of TEG. Then the hot plate area per unit area of TEG may be defined as the inverse of hot plate area per unit area of TEG which could be calculated as given below.
hot plate area per unit area of TEG=(W × L)/(W_TEG × L_TEG × N)
where W is the width of the hot plate (mm), L is the length of the hot plate (mm), WTEG is the width of the single TEG (mm), LTEG is the length of the single TEG (mm), N is the number of TEG.
A different hot plate area per unit area of TEG is considered from 1.42 to 240.25 for square pitch arrangement at two different temperatures of 100°C and 150°C and two different heat transfer coefficients of 5 W/m2C and 25 W/m2C. Here, the commercial TEGs are used at dimensions of 40 X 40 X 4 mm thickness. As discussed, power density over hot plate is found to be an appropriate measure for optimizing the occupancy ratio for TEGs over hot plate when maximum total power is of importance.
The power density increases with increase in heat transfer coefficient and hot plate temperature as shown in Fig. 5. The power density of TEG of square pitch arrangement (11) at heat transfer coefficient at a 25 W/m2C forced convection at 150ºC (18). The power density of TEG (11) at heat transfer coefficient at a 25 W/m2C forced convection at 100ºC (19). Also, the power density of TEG (11) at heat transfer coefficient at a 25 W/m2C natural convection at 150ºC (20) and 100ºC (21). From these figures, the maximum peak power density is used to evaluate the performance of TEG at different arrangements and different operating parameters. Power density reaches peak at a hot plate area per unit area of TEG and then drops drastically. The particular hot plate area per unit area of TEG where the power density peaks could be taken as optimized hot plate area per unit area of TEG. The peak power density and the particular hot plate area per unit area of TEG where the power density peaks depend on hot plate temperature and heat transfer coefficient as seen in Table 1:

Table 1 Performance of Square pitch arrangements TEG system
Hot plate temperature (°C) Heat transfer coefficient (W/m2C) Peak power density (W/m2) Optimised hot plate area per unit area of TEG
100 5 (Natural convection) 19.86 9.61
100 25 (Forced convection) 101.94 1.67
150 5 (Natural convection) 49.53 9.61
150 25 (Forced convection) 257.45 2.40

As per Table 1, optimized hot plate area per unit area of TEG is independent of the heat transfer coefficient and depends mainly on hot plate temperature. The peak power density depends on both heat transfer coefficient and the hot plate temperature.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) 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 inventions 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” and/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 recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, 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” will be understood to include the possibilities of “A” or “B” or “A and B.”
It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

WE CLAIM:

1. An apparatus for thermoelectric power generation comprising;
plurality of thermoelectric generating (TEG) devices (11), wherein each of the TEG devices has a TEG hot surface configured to be positioned in thermal communication with boiler flue gas duct and TEG cold surface is exposed to ambient;
All TEGs are arranged in traverse pitch (14) and longitudinal pitch (12) arrangement on the boiler flue gas duct;
Characterized in that the transverse pitch arrangement (14) and longitudinal pitch arrangement (12) of TEG (11) are square pitch arrangement of a duct (10) in which the TEG cold side is in contact with a finned surface (13);
the plurality of TEG devices (11) are sandwiched between the duct (10) and extended surface and it is coupled by using bolts and nuts (15).
2. The apparatus of claim 1, further comprising one or more extended surfaces that extended away from the cold surface of the TEG system and exposed to ambient.

3. The apparatus of claim 1, further comprising the bolts and nuts are used to couple the extended surface with boiler flue gas duct.

4. The apparatus as claimed in claim 1, wherein the plurality of TEG devices (11) are configured all four side of the boiler flue gas ducting system.

5. The apparatus as claimed in claim 1, wherein the flue gas passes through one or more zone; the flue gas flow from air heater outlet to ESP inlet duct;
the flue gas flow from ESP outlet to Induced Draft (ID) fan inlet (5); and
the flue gas flow from ID fan outlet to chimney inlet duct (7).

6. The apparatus as claimed in claim 1, wherein the hot plate area per unit area of TEG is independent of the cold side heat transfer coefficient.

7. The apparatus as claimed in claim 1, wherein the hot plate area per unit area of TEG depends mainly on the cold side hot plate temperature and the peak power density depends on both heat transfer coefficient and the hot plate temperature.

8. The apparatus as claimed in claim 1, wherein the hot plate area per unit area of TEG of square pitch arrangement is 9.61 for the heat transfer coefficient of 5 W/m2C as a natural convection and operating temperature of 100ºC and 150ºC.

9. The apparatus as claimed in claim 1, wherein the hot plate area per unit area of TEG of square pitch arrangement is 1.67 for the heat transfer coefficient of 25 W/m2C as a forced convection and operating temperature of 100ºC.

10. The apparatus as claimed in claim 1, wherein the hot plate area per unit area of TEG of square pitch arrangement is 2.40 for the heat transfer coefficient of 25 W/m2C as a forced convection and operating temperature of 150ºC.

11. The apparatus as claimed in claim 1, wherein the hot plate area per unit area of TEG of square pitch arrangement is 9.61 for the heat transfer coefficient of 5 W/m2C as a natural convection and operating temperature of 100ºC and 150ºC.

12. The apparatus as claimed in claim 1, wherein the peak power densities of TEG of square pitch arrangement are 19.86 W/m2 and 49.53 W/m2 for the operating temperature of 100 ºC and 150 ºC respectively at a heat transfer coefficient of 5 W/m2C as a natural convection.

13. The apparatus as claimed in claim 1, wherein the peak power densities of TEG of square pitch arrangement are 101.94 W/m2 and 257.45 W/m2 for the operating temperature of 100 ºC and 150 ºC respectively at a heat transfer coefficient of 25 W/m2C as a forced convection.