Multi-stage thermophotovoltaic generators arrangement

Abstract

A multi-stage thermophotovoltaic generators arrangement (1000) comprising two or more thermophotovoltaic generators (201, 202, 203, 204). Each thermophotovoltaic generator (201, 202, 203, 204) comprises a combustion unit (110), configured to receive a fuel (F) flow and an oxidant (OX) flow and to perform a combustion process so to generate hot exhaust gases (HE), and a generation unit (120), fluidly coupled to the combustion unit (110) and configured to receive the hot exhaust gases from the combustion unit (110) and to discharge cold exhaust gases (CE). The generation unit (120) comprises two emitter layers (231, 232, 331, 332), spaced apart between each other and defining a flow path in which the hot exhaust gases (HE) flow, and two thermophotovoltaic cells layers (241, 242, 341, 342), each thermophotovoltaic cells layers (241, 242, 341, 342) respectively facing one of the two emitter layers (231, 232, 331, 332) and spaced apart from it. The two emitter layers (231, 232, 331, 332) are configured to receive heat energy from the hot exhaust gases (HE) and to transform heat energy into radiant energy emitted by the two emitter layers (231, 232, 331, 332) and the two thermophotovoltaic cells layers (241, 242, 341, 342) are configured to convert the radiant energy incident on the thermophotovoltaic cells layers (241, 242, 341, 342) into electrical energy. The two or more thermophotovoltaic generators (201, 202, 203, 204) are arranged in series and fluidly coupled, so that the cold exhaust gases (CE) discharged by the upstream thermophotovoltaic generator (201, 202, 203) are received by the downstream thermophotovoltaic generator (202, 203, 204) as oxidant (OX) flow.

Description

TITLEMulti-stage thermophotovoltaic generators arrangementDESCRIPTIONTECHNICAL FIELD

[0001] The subject-matter disclosed herein relates to an innovative multistage thermophotovoltaic generators arrangement.BACKGROUND ART

[0002] In the last decade thermophotovoltaic (TPV) systems have gained an increasing attention due to the fact that they have a high fuel utilization factor, low produced noise levels (due to the absence of moving parts) and great fuel flexibility.

[0003] A thermophotovoltaic (TPV) system is a system to convert thermal radiations from a heat source into electricity. Typically, a TPV system comprises at least: a generator to provide heat energy (for example from a fuel combustion process), a radiator to translate the heat energy into an emission spectrum (thermal radiation) and a TPV cell to convert the photon radiation into electrical energy.

[0004] In general, TPV generators have a cylindrical shape in which combustion is used to heat a cylindrical tube which emits infrared radiant energy, the tube being surrounding by an array of low bandgap photovoltaic (PV) cells to convert radiant energy into electrical energy.

[0005] From US6489553B1 there is known a cylindrical TPV generator with a hermetic seal that allows the AntiReflection coated Refractory Metal (AR / RM) IR emitter of the TPV generator to operate in a non-oxidizing inert gas atmosphere.

[0006] From US2023025491 Al there is known a combustion system configured to combust preheated air with fuel at various combustion zones spaced apart from one another along a length of the combustion system. The combustion system generates heat of combustion absorbed via heat modules (which can be TPV units) thermally coupled to the combustion zones.

[0007] However, it is desired to have a TPV generator system which has an increased efficiency and a scaled up electrical power whit respect to the known. Advantageously, it is desired to have a TPV generator system which has a higher homogeneity in the heating process of the emitter and therefore a uniformity of the emitting spectra of the emitter.SUMMARY

[0008] According to an aspect, the subject-matter disclosed herein relates to a multi-stage thermophotovoltaic generators arrangement comprising two or more thermophotovoltaic generators. Each thermophotovoltaic comprises: a combustion unit configured to receive a fuel flow and an oxidant flow and to perform a combustion process so to generate hot exhaust gases, and a generation unit fluidly coupled to the combustion unit and configured to receive the hot exhaust gases from the combustion unit and to discharge cold exhaust gases, the generation unit comprising:- two emitter layers spaced apart between each other and defining a flow path in which the hot exhaust gases flow, the emitter layers being configured to receive heat energy from the hot gases and to transform heat energy into radiant energy, the radiant energy being emitted by the emitter layers;- two thermophotovoltaic cells layers, each layer of thermophotovoltaic cells being respectively facing one of the two emitter layers and spaced apart from it, the twothermophotovoltai c cells layers being configured to convert the radiant energy incident on the thermophotovoltaic cells layers into electrical energy.The two or more thermophotovoltaic generators are arranged in series, so that the cold exhaust gases discharged by the upstream thermophotovoltaic generator are received by the downstream thermophotovoltaic generator as oxidant flow.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 shows a schematic diagram of an embodiment of an innovative multistage thermophotovoltaic generators arrangement,Fig. 2 shows a first example of a generation unit according to the present disclosure,Fig. 3 shows a second example of a generation unit according to the present disclosure, andFig. 4 shows a schematic diagram of a section of the generation unit of Fig. 2 or Fig. 3 with the energy flows highlighted.DETAILED DESCRIPTION OF EMBODIMENTS

[0010] According to an aspect, the subject-matter disclosed herein relates to an innovative arrangement of multi-stage thermophotovoltaic generators which is more compact and has a higher efficiency with respect to knownthermophotovoltai c generators.

[0011] The innovative arrangement disclosed herein provides a in series system arrangement of combustors and post combustors to generate hot exhaust gases being interspersed with generation units comprising two emitting layers facing each other and defining a space in which the hot exhaust gases flow and two thermophotovoltaic layers, each of which faces an emitting layer so to produce electrical power. This innovative arrangement guarantees the maximum homogeneity in the heating process of the emitter and an increase in the efficiency of the system (which is directly correlated to the emissivity of the emitter).

[0012] Reference now will be made in detail to embodiments of the disclosure, examples of which are illustrated in the drawings. The examples and drawing figures are provided by way of explanation of the disclosure and should not be construed as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may be not repeated in all the figures.

[0013] Referring now to the drawings, Fig. 1 is a schematic diagram of an embodiment of an innovative multi-stage thermophotovoltaic generators arrangement 1000, referred in the following as “arrangement 1000”. The arrangement 1000 comprises two or more thermophotovoltaic generators (please note that in Fig. 1 are shown four thermophotovoltaic generators 201, 202, 203 and 204) arranged in series and fluidly coupled. In particular, a first thermophotovoltaic generator 201 is fluidly coupled to a second thermophotovoltaic generator 202 arranged downstream the firstthermophotovoltai c generator 201, the second thermophotovoltaic generator 202 is then fluidly coupled to a third thermophotovoltaic generator 203 arranged downstream the second thermophotovoltaic generator 202, the third thermophotovoltaic generator 203 is then fluidly coupled to a fourth thermophotovoltaic generator 204 arranged downstream the third thermophotovoltaic generator 203.

[0014] Each thermophotovoltaic generator 201, 202, 203 and 204 comprises a combustion unit 110 and a generation unit 120.

[0015] The combustion unit 110 is configured to receive a fuel flow F and an oxidant flow OX and to perform a combustion process so to generate hot exhaust gases HE. Advantageously, the combustion unit 110 of each thermophotovoltaic generator 201, 202, 203 and 204 comprises a combustion chamber in which the combustion process is performed.

[0016] The generation unit 120 of each thermophotovoltaic generator 201, 202, 203 and 204 is fluidly coupled to the respective combustion unit 110 and is configured to receive the hot exhaust gases HE from the combustion unit 110 and to discharge cold exhaust gases CE. It is to be noted that the cold exhaust gases CE are indicated as “cold” with respect to the hot exhaust gases HE generated by the combustion unit 110 and received by the generation unit as inputs.

[0017] With non limiting reference to Fig. 4, the generation unit 120 comprises two emitter layers 231, 232, 331 and 332 spaced apart between each other and defining a flow path in which the hot exhaust gases HE flow. The two emitter layers 231, 232, 331 and 332 are configured to receive heat energy from the hot exhaust gases HE and to transform heat energy into radiant energy, the radiant energy being then emitted by the two emitter layers 231, 232, 331 and 332.

[0018] In particular, the combustion chamber of each combustion unit 110 is fluidly coupled to the flow path defined by the two emitter layers 231, 232, 331 and 332 of the generation unit so to supply hot exhaust gases HE in the flow path.

[0019] The generation unit 120 further comprises two thermophotovoltaic cells layers 241, 242, 341 and 342, each thermophotovoltaic cells layers 241, 242, 341 and 342 being respectively facing one of the two emitter layers 231, 232, 331 and 332 and spaced apart from it. The two thermophotovoltaic cells layers 241, 242, 341 and 342 are configured to convert the radiant energy incident on the thermophotovoltaic cells layers 241, 242, 341 and 342 into electrical energy.

[0020] With non-limiting reference to Figs. 2 and 3, are shown respectively a first embodiment of a generation unit 220 and a second embodiment of a generation unit 320.

[0021] Fig. 2 show a generation unit in the form of a hollow cylinder; in particular, the two emitter layers 231 and 232 of the generation unit 220 are in the form of lateral surfaces of coaxial cylinders. Advantageously, the combustion chamber (not shown in the figure) has an annular shape.

[0022] With non-limiting reference to Fig. 2, the two thermophotovoltaic cells layers 241 and 242 of the generation unit 220 are also in the form of lateral surfaces of coaxial cylinders. In particular, a first thermophotovoltaic cells layer 241 is arranged outside a first emitter layer 231 and a second thermophotovoltaic cells layer 242 is arranger inside a second emitter layer 232.

[0023] Fig. 3 shows a generation unit 320 in the form of hollow rectangular parallelepiped; in particular, the two emitter layers 331 and 332 of the generation unit 320 are in the form of parallel flat surfaces. Advantageously,the combustion chamber (not shown in the figure) has a linear shape.

[0024] With non-limiting reference to Fig. 3, the two thermophotovoltaic cells layers 341 and 342 of the generation unit 320 are also in the form of parallel flat surfaces. In particular, a first thermophotovoltaic cells layer 341 is arranged outside a first emitter layer 331 and a second thermophotovoltaic cells layer 342 is arranger outside a second emitter layer 332.

[0025] As it will be better described in the following, with non-limiting reference to Fig. 1, the fuel flows F-l, F-2, F-3 and F-4 and the oxidant flows OX-1, OX-2, OX-3 and OX-4 respectively received by each combustion unit 110-1, 110-2, 110-3 and 110-4 may be different flows in terms of composition and / or mass flow. Advantageously, the fuel flows F-l, F-2, F-3 and F-4 have the same composition and different mass flows (in particular, the fuel flow F- 1 received by the first combustion unit 110-1 has a higher mass flow). Advantageously, the oxidant flows OX-1, OX-2, OX-3 and OX-4 have different compositions and different mass flows. Consequently, the hot exhaust gases flows HE-1, HE-2, HE-3 and HE-4 may be different flows in terms of composition and / or mass flow.

[0026] In particular, the combustion unit 110-1 of the first thermophotovoltaic generator 201 (i.e. the upstream thermophotovoltaic generator) may be considered a combustor of the arrangement 1000 and the combustion units 110-2, 110-3 and 110-4 of the downstream thermophotovoltaic generators 202, 203 and 204 may be considered postcombustor stages of the arrangement 1000.

[0027] It is to be noted that the combustion unit 110-1 of the first thermophotovoltaic generator 201 (i.e. the combustor of the arrangement 1000) is configured to reach an operative temperature of the thermophotovoltaic generators, in particular to generate hot exhaust gases HE-1 at the operative temperature (for example an operative temperature of about 900 K) while thecombustion units 110-2, 110-3 and 110-4 of the downstream thermophotovoltai c generators 202, 203 and 204 (i.e. the post-combustors of the arrangement 1000) are configured to maintain the operative temperature of the thermophotovoltaic generators, in particular to generate hot exhaust gases HE-2, HE-3 and HE-4 substantially at the same operative temperature of the hot exhaust gases HE-1 generated by the combustion unit 110-1.

[0028] Advantageously, the combustion unit 110-1 receives an oxidant flow OX-1 of ambient air comprising about 21% of oxygen O2. Advantageously, the oxidant flow OX-1 is pre-heated before being received by the combustion unit 110-1; for example, the oxidant flow OX-1 is at 800 K.

[0029] According to a possibility, the fuel flows F-l, F-2, F-3 and F-4 comprise or consist of methane CEU or LNG or hydrogen EE; for example, the fuel flows -1, F-2, F-3 and F-4 are supplied at the respective combustion unit 110-1, 110-2, 110-3 and 110-4 at a temperature of around 300 K.

[0030] It is to be noted that the percentage of oxygen of the oxidant flow may vary depending on the fuel used to perform the combustion process.

[0031] Advantageously, the combustion chamber of the combustion unit 110- 1 is provided with a plurality of swirlers configured to ensure an optimal mixing and homogeneity during an initial burning phase of the combustion process. In particular, the combustion chamber of the combustion unit 110-1 is configured to perform the combustion process to generate hot exhaust gases HE at the operating temperature, for example at 1900 K.

[0032] As already mentioned, the downstream thermophotovoltaic generators 202, 203 and 204 are fluidly coupled to the upstream thermophotovoltaic generators 201, 202 and 203, so that the cold exhaust gases CE discharged by the upstream thermophotovoltaic generator 201, 202 and 203 are received by the downstream thermophotovoltaic generator 202, 203 and 204 as oxidant OXflow.

[0033] It is to be noted that the oxidant OX flow received by the downstream thermophotovoltai c generators 202, 203 and 204 has a content of oxygen O2 less than the oxidant flow OX-1 received by the combustion unit 110-1.

[0034] With non-limiting reference to Fig. 1, the generation unit 120-1 of the first thermophotovoltaic generator 201 is fluidly coupled to the combustion unit 110-2 of the second thermophotovoltaic generator 202; the generation unit 120-2 of the second thermophotovoltaic generator 202 is fluidly coupled to the combustion unit 110-3 of the third thermophotovoltaic generator 203; the generation unit 120-3 of the third thermophotovoltaic generator 203 is fluidly coupled to the combustion unit 110-4 of the fourth thermophotovoltaic generator 204.

[0035] In particular, the combustion chamber of the downstream thermophotovoltaic generator 202, 203 and 204 is fluidly coupled both to the flow path of the upstream thermophotovoltaic generator 201, 202 and 203 and to the flow path of the downstream thermophotovoltaic generator 202, 203 and 204 so to receive the cold exhaust gases CE discharged by the upstream thermophotovoltaic generator 201, 202 and 203 and to generate hot exhaust gases HE to be supplied in the flow path of the downstream thermophotovoltaic generator 202, 203 and 204.

[0036] Advantageously, with non-limiting reference to Fig. 1, the arrangement 1000 further comprises a heat exchanger 300 fluidly coupled to the last downstream thermophotovoltaic generator 204 and configured to remove heat from the cold exhaust gases CE discharged by the last downstream thermophotovoltaic generator 204, in particular to exploit the residual heat of the cold exhaust gases CE, for example to heat an external fluid flow.

[0037] Even more advantageously, the heat exchanger 300 is further fluidlycoupled to the first upstream thermophotovoltai c generator 201, so that the heat exchanger 300 is further configured to provide the heat removed from the cold exhaust gases CE to the oxidant OX flow received by the first upstream thermophotovoltai c generator 201.

[0038] According to a preferred embodiment, the arrangement 1000, in particular the generation unit 120, further comprises a cooling system (not shown in the figures) coupled to the thermophotovoltaic cells layers 241, 242,341 and 342 and configured to remove heat from the thermophotovoltaic cells layers 241, 242, 341 and 342. In particular, the cooling system may be coils in which flows a cooling medium, for example water.

[0039] In particular, the cooling system (which advantageously is in the form of coils exchanging heat by conduction and / or convection) is coupled at least to one opposite side of the thermophotovoltaic cells layers 241, 242, 341 and342 which is not facing any of the emitter layers 231, 232, 331 and 332.

Claims

CLAIMS1. A multi-stage thermophotovoltaic generators arrangement (1000) comprising two or more thermophotovoltaic generators (201, 202, 203, 204), each thermophotovoltaic generator (201, 202, 203, 204) comprising: a combustion unit (110), configured to receive a fuel (F) flow and an oxidant (OX) flow and to perform a combustion process so to generate hot exhaust gases (HE); a generation unit (120) fluidly coupled to the combustion unit (110) and configured to receive the hot exhaust gases from the combustion unit (110) and to discharge cold exhaust gases (CE), the generation unit (120) comprising:- two emitter layers (231, 232, 331, 332) spaced apart between each other and defining a flow path in which the hot exhaust gases (HE) flow, the two emitter layers (231, 232, 331, 332) being configured to receive heat energy from the hot exhaust gases (HE) and to transform heat energy into radiant energy, the radiant energy being emitted by the two emitter layers (231, 232, 331, 332);- two thermophotovoltaic cells layers (241, 242, 341, 342), each thermophotovoltaic cells layers (241, 242, 341, 342) being respectively facing one of the two emitter layers (231, 232, 331, 332) and spaced apart from it, the two thermophotovoltaic cells layers (241, 242, 341, 342) being configured to convert the radiant energy incident on the thermophotovoltaic cells layers (241, 242, 341, 342) into electrical energy; wherein the two or more thermophotovoltaic generators (201, 202, 203, 204) are arranged in series and fluidly coupled, so that the cold exhaust gases (CE) discharged by the upstream thermophotovoltaic generator(201, 202, 203) are received by the downstream thermophotovoltai c generator (202, 203, 204) as oxidant (OX) flow.

2. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 1, wherein the combustion unit (110) of each thermophotovoltaic generator (201, 202, 203, 204) comprises a combustion chamber in which the combustion process is performed, the combustion chamber being fluidly coupled to the flow path defined by the two emitter layers (231, 232, 331, 332) of the generation unit (120) so to supply hot exhaust gases (HE) in the flow path.

3. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 2, wherein the combustion chamber of the downstream thermophotovoltaic generator (202, 203, 204) is fluidly coupled both to the flow path of the upstream thermophotovoltaic generator (201, 202, 203) and to the flow path of the downstream thermophotovoltaic generator (202, 203, 204) so to receive the cold exhaust gases (CE) discharged by the upstream thermophotovoltaic generator (201, 202, 203) and to generate hot exhaust gases (HE) to be supplied in the flow path of the downstream thermophotovoltaic generator (202, 203, 204).

4. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 1, wherein the combustion unit (110-1) of the upstream thermophotovoltaic generator (201) is a combustor configured to perform the combustion process so to reach the operative temperature of the thermophotovoltaic generator and to generate hot exhaust gases (HE-1) at the operative temperature.

5. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 4, wherein the combustion unit (110-2, 110-3, 110-4) of the downstream thermophotovoltaic generator (202, 203, 204) is a postcombustor configured to perform the combustion process so to maintain the operative temperature of the thermophotovoltaic generator and to generate hot exhaust gases (HE-2, HE-3, HE-4) substantially at thesame operative temperature of the hot exhaust gases (HE-1) generated by the combustion unit (110-1).

6. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 1, wherein the generation unit (220) is in the form of a hollow cylinder.

7. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 6, wherein the two emitter layers (231, 232) of the generation unit (220) are in the form of lateral surfaces of coaxial cylinders.

8. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 6, wherein the two thermophotovoltaic cells layers (241, 242) of the generation unit (220) are in the form of lateral surfaces of coaxial cylinders, a first thermophotovoltaic cells layer (241) being arranged outside a first emitter layer (231) and a second thermophotovoltaic cells layer (242) being arranged inside a second emitter layer (232).

9. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 2, wherein the combustion chamber has an annular shape.

10. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 1, wherein the generation unit (320) is in the form of a hollow rectangular parallelepiped.

11. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 10, wherein the two emitter layers (331, 332) of the generation unit (320) are in the form of parallel flat surfaces.

12. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 11, wherein the two thermophotovoltaic cells layers (341, 342) of the generation unit (320) are in the form of parallel flat surfaces, a first thermophotovoltaic cells layer (341) being arranged outside a first emitter layer (331) and a second thermophotovoltaic cells layer (342) being arranged outside a second emitter layer (332).

13. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 2, wherein the combustion chamber has a linear shape.

14. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 1, further comprising a heat exchanger (300), the heat exchanger (300) being fluidly coupled to the last downstream thermophotovoltaic generator (202, 203, 204) and being configured to remove heat from the cold exhaust gases (CE) discharged by the last downstream thermophotovoltaic generator (202, 203, 204).

15. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 14, wherein the heat exchanger (300) is further fluidly coupled to the first upstream thermophotovoltaic generator (201, 202, 203), wherein the heat exchanger (300) is further configured to provide the heat removed from the cold exhaust gases (CE) to the oxidant (OX) flow received by the first upstream thermophotovoltaic generator (201, 202, 203).

16. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 15, wherein the oxidant (OX) flow received by the first upstream thermophotovoltaic generator (201, 202, 203) is ambient air.

17. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 14, wherein the heat exchanger (300) is further fluidly coupled to a power generation system, wherein the heat exchanger (300) is further configured to provide the heat removed from the cold exhaust gases (CE) to the power generation system.

18. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 1, wherein the generation unit (120) further comprises a cooling system coupled to the thermophotovoltaic cells layers (241, 242, 341, 342), in particular coils in which flows a cooling medium, the cooling system being configured to remove heat from the thermophotovoltaic cells layers (241, 242, 341, 342).

19. The multi-stage thermophotovoltaic generators arrangement (1000) of claim 18, wherein the cooling system is coupled at least to one oppositeside of the thermophotovoltai c cells layers (241, 242, 341, 342) which is not facing any of the emitter layers (231, 232, 331, 332).

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