Thermal radiation photovoltaic power generator and power generation system

Abstract

To provide a thermal radiation photovoltaic power generator that is easy to produce, and a power generation system equipped with the same.SOLUTION: A thermal radiation photovoltaic power generator 3 comprises: a perovskite emitter 20 including a perovskite semiconductor for emitting thermal radiation light; and a perovskite PV (PhotoVoltaic) cell 10 for generating an electric power by receiving the thermal radiation light emitted from the emitter 20. The emitter 20 and the PV cell 10 are placed apart from each other. The thermal radiation photovoltaic power generator 3 makes the perovskite semiconductor of the emitter 20 be in a non-equilibrium state by supplying an electric current to the emitter 20 using a portion of the power generated by the PV cell 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thermal radiation photovoltaic power generation device and a power generation system including the same. [Background technology]

[0002] For example, Patent Document 1 describes a device that generates thermophotovoltaic (TPV) power and includes a thermal radiator and a photoelectric conversion element that receives thermal radiation light emitted by the thermal radiator. This device further includes an intermediate member that is in contact with the photoelectric conversion element and transmits light of at least a part of the wavelength within the wavelength range that is photoelectrically converted by the photoelectric conversion element. The intermediate member and the thermal radiator are disposed apart from each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-143025 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, the distance between the intermediate member and the heat radiator must be very small, 1 / 3 or less of the band gap wavelength (as a specific example, it is described that this distance is 0.2 μm or less), so there is a concern that the device may not be easy to manufacture. In addition, in the device, the semiconductor layer used in the photoelectric conversion element is mainly made of GaAs (gallium arsenide), so the material and manufacturing costs are relatively high, and in this respect, there is also a concern that the device may not be easy to manufacture.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a thermal radiation photovoltaic power generation device that is easy to manufacture and a power generation system including the same. [Means for solving the problem]

[0006] In order to achieve the above object, a thermal radiation photovoltaic power generation device according to a first aspect of the present invention comprises: A perovskite-type emitter that includes a perovskite semiconductor and emits thermal radiation light; A perovskite-type PV (PhotoVoltaic) cell that generates electricity by receiving the thermal radiation emitted from the emitter, the emitter and the PV cell are spaced apart from each other; A current is supplied to the emitter based on a portion of the power generated by the PV cell, causing the perovskite semiconductor to enter a non-equilibrium state.

[0007] The spacing may be 1 mm or greater.

[0008] The thermal radiation photovoltaic power generation device is The solar cell further includes a pair of reflectors facing each other with the emitter and the PV cell interposed therebetween, The pair of reflecting portions may have mirror surfaces on their opposing surfaces.

[0009] In order to achieve the above object, a power generation system according to a second aspect of the present invention comprises: The thermal radiation photovoltaic power generation device; a heat source for providing heat to the emitter; The power generating device further includes a power supply unit that converts the power generated by the thermal radiation photovoltaic power generating device into power that can be used at a power supply destination and supplies the power to the power supply destination. Effect of the Invention

[0010] According to the present invention, it is possible to provide a thermal radiation photovoltaic power generation device that is easy to manufacture and a power generation system including the same. [Brief description of the drawings]

[0011] [Figure 1] 1 is a configuration diagram of a power generation system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a configuration example of a PV cell and an emitter according to the embodiment. [Diagram 3] A diagram showing the perovskite structure. [Figure 4] 5A and 5B are diagrams showing analysis results by a simulation according to an embodiment, in which FIG. 5A shows the dependency of power generation density on layer thickness, and FIG. 5B shows the dependency of energy efficiency on layer thickness. [Diagram 5] 5A and 5B are diagrams showing analysis results by a simulation according to an embodiment, in which FIG. 5A shows the temperature dependency of power generation density and FIG. 5B shows the temperature dependency of energy efficiency. [Figure 6] FIG. 13 is a graph showing the gap dependence of the energy spectrum of non-equilibrium radiation, which is an analysis result by a simulation according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described with reference to the drawings.

[0013] The power generation system 1 shown in Figure 1 includes a heat source 2, a thermal radiation photovoltaic power generation device 3 that generates thermophotovoltaic power based on heat from the heat source 2, and a power supply unit 4 that supplies power to a power supply destination based on the power P generated by the thermal radiation photovoltaic power generation device 3.

[0014] (heat source 2) The heat source 2 is not limited as long as the thermal radiation photovoltaic power generation device 3 can perform thermophotovoltaic power generation, but may be, for example, a rolling line for rolling metal materials. Rolling lines include hot sheet rolling, thick plate rolling, and cold rolling lines for manufacturing steel plates, rolling lines for steel shaped steel, rolling lines for steel bars and wire rods, and rolling lines for aluminum and copper. Of these, the rolling line that consumes a large amount of energy is the hot rolling line. This is because in the hot rolling line, the metal material to be processed is heated to a high temperature to soften it, and then a large deformation is applied. In particular, the hot sheet rolling line and hot thick plate rolling line are large factories and consume a large amount of energy. However, the recovery and reuse of thermal energy released from the metal material that becomes hot in the hot rolling line has not yet been sufficient. Therefore, for example, if a hot rolling line is used as the heat source 2 in the power generation system 1, the energy utilization efficiency can be improved.

[0015] (Power supply section 4) The power supply unit 4 converts the power P generated by the thermal radiation photovoltaic power generation device 3 as described below into power that can be used at the power supply destination and supplies the power to the power supply destination. The power supply unit 4 is composed of a well-known PCS (Power Conditioning System), PV (PhotoVoltaic) inverter, etc. The power supply destinations include general households, businesses, public infrastructure, etc., and the type is not limited. The supply of power to the power supply destinations also includes storing the power in a storage battery installed at any location.

[0016] (Thermal radiation photovoltaic device 3) The thermal radiation photovoltaic power generation device 3 includes a perovskite-type PV (PhotoVoltaic) cell 10, a perovskite-type emitter 20 that emits thermal radiation light by heat from a heat source 2, and a pair of reflectors 30, 40. The thermal radiation light emitted from the emitter 20 includes electromagnetic waves other than visible light and infrared rays. The emitter 20 is located on the side of the heat source 2 (i.e., the high temperature side), while the PV cell 10 is located on the opposite side of the heat source 2 (i.e., the low temperature side).

[0017] The perovskite-type PV cell 10 is a photovoltaic type photoelectric conversion element that uses the perovskite layer 14 shown in FIG. 2, and generates electricity by receiving thermal radiation emitted from the emitter 20.

[0018] 2, the PV cell 10 includes a transparent substrate 11, an electrode 12, an electron transport layer 13, a perovskite layer 14, a hole transport layer 15, an electrode 16, and an AR (anti-reflection) layer 17. The AR layer 17 is formed on the surface of the transparent substrate 11 facing the emitter 20 (the upper surface in FIG. 2). The electrode 12, the electron transport layer 13, the perovskite layer 14, the hole transport layer 15, and the electrode 16 are laminated in this order below the transparent substrate 11 in FIG. 2.

[0019] The electrode 12 is a layer that receives electrons from the perovskite layer 14. The electrode 12 is preferably a transparent electrode, and is composed of, for example, a transparent conductive film such as ITO (Indium Tin Oxide) formed on one surface of the transparent substrate 11. The electron transport layer 13 transports electrons from the perovskite layer 14 to the electrode 12. For example, the electron transport layer 13 is composed of a material such as ZnO (zinc oxide), SnO 2 It is composed of electron transport materials such as tin dioxide.

[0020] The perovskite layer 14 absorbs light and transfers excited electrons and holes to perform photoelectric conversion. Perovskite has the general formula ABX 3 Perovskite is a general term for materials having a perovskite structure represented by the formula: As shown in FIG. 3, the perovskite structure has a cubic unit cell, and in the cubic crystal, A is located at each vertex, B is located at the body center, and X is located at the center of each face. The perovskite layer 14 is made of any perovskite, and for example, CsPbI, which is a type of inorganic perovskite, can be used. 3 , methylammonium lead halide (CH 3 NH 3 )PbX 3 (X=Cl, Br, I), etc.

[0021] The hole transport layer 15 transports positively charged holes from the perovskite layer 14 to the electrode 16. For example, the hole transport layer 15 is made of a hole transport material such as Spiro-OMeTAD (Spiro-MeOTAD). The electrode 16 is a layer that receives holes from the perovskite layer 14. The electrode 16 is made of, for example, a conductive metal oxide, a conductive polymer, or the like. The AR layer 17 is formed in a single layer or multiple layers by a well-known AR coating. The AR layer 17 suppresses reflection of thermal radiation light emitted from the emitter 20 and incident on the PV cell 10.

[0022] The PV cell 10 generates electricity by guiding electrons and holes from the perovskite layer 14, where charge separation has occurred upon exposure to thermal radiation, to a pair of electrodes 12, 16 (collecting electrodes), and using the electromotive force generated between the two electrodes. Note that the positions of the electron transport layer 13 and the hole transport layer 15 may be reversed.

[0023] The perovskite emitter 20 receives heat from the heat source 2 and emits thermal radiation light. As illustrated in FIG. 2, the emitter 20 includes a transparent substrate 21, an electrode 22, an electron transport layer 23, a perovskite layer 24, a hole transport layer 25, an electrode 26, and an AR layer 27. The AR layer 27 is formed on the surface of the transparent substrate 21 facing the PV cell 10 (the lower surface in FIG. 2). The AR layer 27 suppresses reflection of thermal radiation light emitted from the perovskite layer 24 and transmitted through the transparent substrate 21 toward the PV cell 10, as described below. The electrode 22, the electron transport layer 23, the perovskite layer 24, the hole transport layer 25, and the electrode 26 are stacked in this order above the transparent substrate 21 in FIG. 2. As described above, each configuration of the illustrated emitter 20 is similar to that of the PV cell 10, and therefore functions different from those of the PV cell 10 will be described. The positions of the electron transport layer 23 and the hole transport layer 25 may be reversed.

[0024] A current is supplied to the electrodes 22, 26 based on a portion of the power generated by the PV cell 10, and a voltage is applied to the electron transport layer 23, the perovskite layer 24, and the hole transport layer 25 located between the electrodes 22 and 26. This puts the perovskite layer 24 (perovskite semiconductor) into a non-equilibrium state.

[0025] When a current is supplied from the PV cell 10 to the emitter 20, the recombination of electrons and holes occurs in the perovskite semiconductor, resulting in band edge emission. By placing the semiconductor in a non-equilibrium state in this way, the probability of emitting thermal radiation light can be significantly increased. In this paper, this series of light emission processes is referred to as "non-equilibrium radiation."

[0026] A pair of reflectors 30, 40 shown in FIG. 1 face each other with the emitter 20 and the PV cell 10 in between. The reflector 30 is disposed below the PV cell 10, and the reflector 40 is disposed above the emitter 20. For example, the reflector 30 is fixed to the lower surface of the PV cell 10, and the reflector 40 is fixed to the upper surface of the emitter 20. The reflectors 30, 40 are made of well-known mirrors such as mirrors formed by evaporating aluminum on a flat substrate, and have mirror surfaces 31, 41 on their opposing surfaces. That is, the mirror surface 31 faces the reflector 40, and the mirror surface 41 faces the reflector 30. Here, the thermal radiation light emitted from the emitter 20 is directed in various directions, and the PV cell 10 cannot convert all of the thermal radiation light it receives into electric power. By providing a pair of reflectors 30, 40 in this way, the thermal radiation light can be made to travel back and forth between the emitter 20 and the PV cell 10, and the thermal radiation light can be efficiently converted into electric power. This mechanism is called photon recycling.

[0027] As described above, the thermal radiation photovoltaic power generation device 3 generates power by utilizing non-equilibrium radiation, and therefore the inventors of the present application call this power generation method TPX (Thermal Photonics) power generation in contrast to TPV power generation, which does not utilize non-equilibrium radiation. The thermal radiation photovoltaic power generation device 3 that generates TPX power generation differs from conventional TPV power generation devices in that it employs an emitter 20 that generates non-equilibrium radiation, and uses a portion of the power generated by the PV cell 10 as a current source to drive the emitter 20. Here, as shown in FIG. 1, the power generated by the PV cell 10 is defined as P ABS (P ABS =I ABS V ABS ), the power to drive the emitter 20 is P EMT (P EMT =I EMT V EMT ), the net power P obtained by the power generation of the thermal radiation photovoltaic power generation device 3 is P = P ABS -P EMT The energy efficiency η of the thermal radiation photovoltaic power generation device 3 is expressed by the following formula: η=P / (EP EMTIn other words, unlike conventional TPV power generation, when considering the net power generated by the thermal radiation photovoltaic power generation device 3 that generates TPX power, it is necessary to subtract the driving power of the emitter 20 from the power generated by the PV cell 10.

[0028] Conventional TPV power generation devices require an ultra-high temperature heat source (2000°C class) that emits visible light, and have the problem of being restricted by the black body limit in the far field where the PV cell is far from the emitter. The black body limit is the theoretical limit of the thermal radiation power that can be extracted from a substance at a certain temperature into external free space. On the other hand, the thermal radiation photovoltaic power generation device 3 that generates TPX power can use a low-temperature heat source compared to conventional TPV power generation devices, and is capable of generating power in the far field. Below, we will explain examples that provide evidence for these effects.

[0029] (Example) The inventors of the present application analyzed the characteristics of a thermal radiation photoelectric conversion element by performing a fluctuating electromagnetic simulation using theoretical calculations on a computer. Here, the energy spectrum E of non-equilibrium radiation is λ follows the generalized Planck law, which is expressed as follows:

[0030]

number

[0031] In the formula, c 0 is the speed of light, ξ is the energy transfer coefficient, β is the wave vector, ω is the angular frequency, μ is the chemical potential, k B is the Boltzmann constant, and T is temperature. The following symbols represent the reduced Planck constants:

[0032]

number

[0033] The generalized Planck's law expresses the probability distribution of photons using the Bose-Einstein distribution function, and thus non-equilibrium light emission and thermal radiation can be expressed by the same equation. The inventors of the present application adopted a fluctuating electromagnetic simulation to solve this equation. This numerical analysis method can directly express the absorption and emission of photons inside a substance. The generalized Planck's law is described in detail in "Wurfel et al., Applied Physics A, 1995". In addition, this numerical analysis method (specifically, a calculation method that takes into account a fluctuating current source inside a substance and can directly analyze non-equilibrium radiation between objects) is described in detail in "Chen et al., Computer Physics Communications, 2018".

[0034] The calculation conditions are as shown in the table below. In the table, Emitter is a configuration corresponding to the emitter 20 on the high temperature side, and Absorber is a configuration corresponding to the PV cell 10 on the low temperature side. 1 is the temperature of the emitter (the temperature of the high-temperature heat source), T 2 is the temperature of the absorber (room temperature). EMT is the thickness of the emitter, t ABS is the thickness of the absorber. EMT is the chemical potential of the emitter, μ ABSis the chemical potential of the absorber. Since this is a theoretical calculation, these indicate the thickness and chemical potential of each perovskite layer. In addition, the optical properties of the perovskite film of each of the emitter and absorber were taken from the properties described in RK Singh et al., Journal of the Taiwan Institute of Chemical Engineers, 2018. The mirror in the table corresponds to the reflecting parts 30 and 40. The gap d between the emitter and absorber was set to vacuum. Although not shown in the table, the band gap energy of the perovskite layer was set to 1.67 eV.

[0035] [Table 1]

[0036] 4 to 6 show the analysis results from the simulation.

[0037] (layer thickness dependence) Figure 4(a) and (b) show the T 1 =450[K], T 2 = 300[K]. Figure 4(a) shows the relationship between the power generation density and the thickness of the perovskite layer (layer thickness, film thickness in the figure). Figure 4(b) shows the relationship between the Carnot efficiency ratio of the energy efficiency of TPX power generation and the layer thickness. The maximum power generation density in Figure 4(a) is 2.03[W / cm 2 In Fig. 4(b), the Carnot efficiency ratio (η / η Carnot ) was approximately 80% over the layer thickness range of 90 nm to 2000 nm, with a maximum value of 87%. Figure 4(b) shows that the Carnot efficiency ratio of energy efficiency was sufficient even in the thin layer region with a layer thickness of less than 500 nm, and even at a layer thickness of 90 nm.

[0038] (temperature dependence) Figure 5(a) and (b) show the layer thickness of 90 nm (t EMT =t ABS Fig. 5(a) shows the power generation density and the emitter temperature T 1 Fig. 5(b) shows the relationship between the Carnot efficiency ratio of the energy efficiency of TPX power generation and temperature T 1 The maximum power generation density in Fig. 5(a) is 2.5 [W / cm 2 In Fig. 5(b), the Carnot efficiency ratio (η / η Carnot ) was 80% or more over the temperature range of 350K to 600K, with a maximum value of 87%. These results show that high power density and efficiency can be maintained even with thin-film emitters and absorbers. It is also suggested that the power density may increase with an increase in the temperature of the thin-film.

[0039] (Gap Dependence) In the above simulations, in order to investigate the layer thickness dependence and temperature dependence, the gap d was set to 10 μm as shown in [Table 1] to simplify the calculations. Although not shown in [Table 1], Figure 6 shows the energy spectrum E of non-equilibrium radiation when the gap d between the emitter and absorber is set to 1 μm, 10 μm, and 1 mm. λ As can be seen from Fig. 6, the energy spectrum of non-equilibrium radiation related to TPX power generation is uniform regardless of the gap d, and it is assumed that the results will be similar in principle even if the gap d is 1 mm or more.

[0040] Based on the above explanation, various effects that can be achieved by the thermal radiation photovoltaic power generation device 3 that generates TPX power will be summarized.

[0041] In the thermal radiation photovoltaic power generation device 3, both the PV cell 10 and the emitter 20 are of the perovskite type using a perovskite layer (perovskite film). The perovskite layer can be easily produced by a coating technique (spin coating), making it easier to manufacture than conventional PV cells. Furthermore, the PV cell 10 and the emitter 20 can be made flexible and lightweight, making it possible to install them in places where it is difficult to install conventional TPV power generation devices.

[0042] As described above, in the device described in Patent Document 1, the distance between the intermediate member and the thermal radiator must be very small, less than 1 / 3 of the band gap wavelength (as a specific example, it is described that this distance is less than 0.2 μm). Considering the influence of thermal expansion of the material, it is not easy to realize this distance. On the other hand, according to the thermal radiation photovoltaic power generation device 3, as shown in FIG. 6, the gap d between the emitter and absorber may be not only 1 μm or 10 μm, but also 1 mm or more. Therefore, in this respect, the thermal radiation photovoltaic power generation device 3 is easy to manufacture. Furthermore, in principle, the gap d can be made as large as possible in TPX power generation using non-equilibrium radiation, so it is fully possible to make the gap d several centimeters or several meters or more. However, since the conditions vary depending on the configuration of the thermal radiation photovoltaic power generation device 3, it is considered that in the future, it will be necessary to give the thermal radiation photovoltaic power generation device 3 a function of directional energy transport.

[0043] As mentioned above, the conventional TPV power generation device requires an ultra-high temperature heat source (2000°C class). On the other hand, the thermal radiation photovoltaic power generation device 3 requires only a high temperature heat source temperature T 1Good energy efficiency can be achieved at any of the following temperatures: 600K (approximately 327°C), 450K (approximately 177°C), and 350K (approximately 77°C). Therefore, it is possible to select a heat source 2 that generates low-temperature exhaust heat, such as 300°C or less, or even 200°C or less, and a low-cost, highly efficient energy recovery technology can be realized. Currently, it is said that Japan generates 700 [PJ] of exhaust heat per year, of which about 70% is low-temperature exhaust heat at 200°C or less. Thermoelectric power generation using the Seebeck effect can be considered for low-temperature exhaust heat, but since it is a contact type, it is difficult to create a temperature difference with the heat source. However, even with conventional TPV power generation devices, it is difficult to recover energy from low-temperature exhaust heat for the reasons mentioned above. On the other hand, it is considered that the thermal radiation photovoltaic power generation device 3 can recover energy from low-temperature exhaust heat at 200°C or less with high efficiency.

[0044] The present invention is not limited to the above-described embodiment and drawings. Modifications (including the deletion of components) can be made as appropriate within the scope of the present invention.

[0045] In the above description, in order to facilitate understanding of the present invention, descriptions of well-known technical matters have been omitted as appropriate.

[0046] Various embodiments and modifications of the present invention are possible without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the invention equivalent thereto are considered to be within the scope of the present invention. [Explanation of symbols]

[0047] 1. Power generation system 2…Heat source 3. Thermal radiation photovoltaic power generation device 4…Power supply section 10…PV cell 11...Transparent substrate, 12...Electrode, 13...Electron transport layer 14…Perovskite layer 15...hole transport layer, 16...electrode, 17...AR layer 20…Emitter 21...Transparent substrate, 22...Electrode, 23...Electron transport layer 24…Perovskite layer 25...hole transport layer, 26...electrode, 27...AR layer 30,40...Reflection part, 31,41...Mirror surface

Claims

1. A perovskite-type emitter that includes a perovskite semiconductor and emits thermal radiation light; A perovskite-type PV (PhotoVoltaic) cell that receives the thermal radiation emitted from the emitter and generates electricity, the emitter and the PV cell are spaced apart from one another; Supplying a current to the emitter based on a portion of the power generated by the PV cell to put the perovskite semiconductor in a non-equilibrium state; Thermal radiation photovoltaic device.

2. The interval is 1 mm or more. The thermal radiation photovoltaic power generation device according to claim 1 .

3. Further comprising a pair of reflectors facing each other across the emitter and the PV cell, The pair of reflecting portions have mirror surfaces facing each other, The thermal radiation photovoltaic power generation device according to claim 1 or 2.

4. A thermal radiation photovoltaic power generation device according to claim 1 or 2; a heat source for providing heat to the emitter; and a power supply unit that converts the power generated by the thermal radiation photovoltaic power generation device into power that can be used at a power supply destination and supplies the power to the power supply destination. Power generation system.

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