Solar photo-thermal power generation device and power generation method

Abstract

The invention discloses a solar photo-thermal power generation device, and relates to the field of photo-thermal power generation, and the solar photo-thermal power generation device comprises a light-emitting diode, a vacuum layer and a photovoltaic cell layer which are sequentially arranged from top to bottom. The photovoltaic cell layer is connected with a variable load; and the light emitting diode is electrically connected with the photovoltaic cell layer. The solar photo-thermal power generation device composed of the light emitting diode, the vacuum layer and the photovoltaic cell layer enhances the overall photoelectric conversion efficiency, and meanwhile narrow-spectrum electroluminescence near band gap energy of the light emitting diode replaces wide-spectrum thermal radiation of a pure thermal radiation emitter. The device is highly matched with a photovoltaic cell with the same band gap in a spectral response range, and effective absorption of photons and conversion of the photons into electric energy can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal power generation, and in particular to a solar photothermal power generation device and a power generation method. Background Art

[0002] Solar power generation technology is mainly divided into two major fields: photovoltaic power generation and solar thermal power generation. Although photovoltaic power generation technology is relatively mature, the bottleneck of its commercial application is becoming increasingly prominent: the conversion efficiency is limited by the 40% theoretical upper limit of the Shockley-Queisser limit, coupled with the instability of regional and sunshine conditions and energy losses such as solar thermal power, which seriously restricts the comprehensive promotion of photovoltaic power generation technology and the improvement of economic benefits. Compared with photovoltaic power generation, solar thermal power generation technology provides a highly potential supplementary solution for the energy field with its high conversion efficiency, economy and good thermal stability. This technology collects solar radiation energy efficiently and heats the working fluid to drive thermal cycle power generation. It not only realizes the effective utilization of the full-band solar spectrum, but also shows low sensitivity to environmental conditions and significant energy storage potential. In particular, by optimizing the design of the concentrating module, the incident light energy density and heat absorption efficiency can be significantly improved, further enhancing the performance of the solar thermal power generation system.

[0003] However, traditional solar thermal power generation systems rely on large turbine machinery, and their high investment and operation and maintenance costs, noise pollution during operation, and mechanical wear and tear have become key factors restricting their commercialization process. In recent years, the rise of static micro-heat engine technology has brought new hope to the field of solar thermal power generation. This type of solid-state device abandons the moving parts in traditional heat engines and greatly reduces maintenance requirements and operating costs by directly converting thermal energy into electrical energy, making it possible to realize miniaturized and decentralized energy systems. Among them, thermophotovoltaic devices, as an important representative of static micro-heat engines, have demonstrated unique advantages in the field of solid-state thermoelectric conversion with their simple system design and low operating costs.

[0004] However, thermophotovoltaic devices are still limited by low output performance and the mismatch between the thermal radiation emitter and the semiconductor band gap in the photovoltaic cell. To overcome these challenges, increasing the emitter temperature or reducing the vacuum gap can improve the device output performance, but it puts more stringent requirements on the high temperature resistance of the material and the manufacturing process. At the same time, the introduction of selective emitters and filters can optimize spectral matching, but it also increases the system complexity and manufacturing cost, limiting the application potential of thermophotovoltaic devices in a wider range of fields. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention is proposed.

[0006] To solve the above technical problems, in the first aspect, the present invention provides the following technical solutions: a solar thermal power generation device, which includes a light-emitting diode, a vacuum layer and a photovoltaic cell layer arranged in sequence from top to bottom; the photovoltaic cell layer is connected to a variable load; the light-emitting diode is electrically connected to the photovoltaic cell layer.

[0007] As a preferred solution of the solar thermal power generation device described in the present invention, the light emitting diode is connected to a variable voltage source, and the variable voltage source can apply a bias voltage to the light emitting diode.

[0008] As a preferred solution of the solar thermal power generation device described in the present invention, an absorption module and a focusing module are sequentially arranged on the top of the light-emitting diode, and the focusing module is used to focus sunlight to increase the temperature of the absorption module.

[0009] As a preferred solution of the solar thermal power generation device of the present invention, a heat dissipation module is also arranged at the bottom of the photovoltaic cell layer, and the heat dissipation module is used to dissipate heat from the photovoltaic cell layer.

[0010] As a preferred solution of the solar thermal power generation device described in the present invention, a heat-conducting layer is provided between the absorption module and the light-emitting diode, and between the photovoltaic cell layer and the heat dissipation module.

[0011] As a preferred solution of the solar thermal power generation device of the present invention, the heat dissipation module dissipates heat by forced convection or natural convection.

[0012] In a second aspect, the present invention provides a method for generating electricity by a solar thermal power generation device, which is applied to the above-mentioned solar thermal power generation device, and the method includes heating and raising the temperature of a light-emitting diode by concentrating sunlight; the light-emitting diode emits photons to a photovoltaic cell layer by thermal radiation; the photovoltaic cell layer receives the photons and generates current.

[0013] As a preferred solution of the power generation method of the solar thermal power generation device described in the present invention, the method of concentrating sunlight includes sequentially arranging an absorption module and a focusing module on the top of the light emitting diode.

[0014] As a preferred scheme of the power generation method of the solar thermal power generation device described in the present invention, wherein: the light emitting diode is connected to a variable voltage source, the photovoltaic cell layer is connected to a variable load, and the photovoltaic cell layer is at maximum power generation efficiency by adjusting the variable voltage source and the variable load.

[0015] As a preferred solution of the power generation method of the solar thermal power generation device described in the present invention, the light emitting diode is electrically connected to the photovoltaic cell layer, and part of the electric power generated by the photovoltaic cell layer is used to drive the light emitting diode.

[0016] The beneficial effects of the present invention are as follows: the solar thermal power generation device composed of a light-emitting diode, a vacuum layer and a photovoltaic cell layer enhances the overall photoelectric conversion efficiency, and at the same time, the narrow-spectrum electroluminescence near the band gap energy of the light-emitting diode replaces the wide-spectrum thermal radiation of the pure thermal radiation emitter, and is highly matched with the photovoltaic cell with the same band gap within the spectral response range, so that effective absorption of photons can be achieved and converted into electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a structural cross-sectional view of a solar thermal power generation device.

[0019] Figure 2 Figure 2 is a graph showing the relationship between different voltages and device efficiency.

[0020] Figure 3 The graph is a graph showing the relationship between the concentration, the thermal photon converter efficiency and the overall efficiency of the device.

[0021] Figure 4 The graph is a graph showing the relationship between the thickness of the light emitting diode or photovoltaic cell layer and the efficiency of the thermal photon converter and the overall efficiency of the device.

[0022] Figure 5 This is a curve diagram showing the relationship between concentration and thermal photon thermoelectric conversion efficiency. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0026] Example 1

[0027] Reference Figure 1 to Figure 5 , which is the first embodiment of the present invention, provides a solar thermal power generation device, which includes a light-emitting diode 100, a vacuum layer 200 and a photovoltaic cell layer 300 arranged in sequence from top to bottom.

[0028] Specifically, an absorption module 600 and a focusing module 700 are sequentially arranged on the top of the light emitting diode 100. The focusing module 700 is a Fresnel concentrator, that is, a Fresnel lens. The absorption module 600 is a solar absorber. The light emitting diode 100 uses a gallium arsenide light emitting diode, which has a very high external quantum efficiency and has significant advantages in cost control.

[0029] The photovoltaic cell layer 300 is made of indium phosphide photovoltaic cells, which are electrically connected to the light emitting diode 100 , so that part of the power of the photovoltaic cell layer 300 can be transmitted to the light emitting diode 100 and drive it.

[0030] The light-emitting diode 100 and the photovoltaic cell layer 300 are in the same vacuum chamber with a certain gap between them, which is the vacuum layer 200. The vacuum layer 200 separates the light-emitting diode 100 and the photovoltaic cell layer 300, so that the light-emitting diode 100 can only emit photons to the photovoltaic cell layer 300 in the form of thermal radiation but cannot heat the photovoltaic cell layer 300 in the form of thermal conduction.

[0031] A heat dissipation module 800 is also provided at the bottom of the photovoltaic cell layer 300 to dissipate heat from the photovoltaic cell layer 300 to prevent the high temperature from damaging the photovoltaic cell layer 300 or affecting the power generation efficiency. The heat dissipation module 800 can effectively transfer the waste heat that is not converted into electrical energy to the outside by forced convection (additional cooling fluid) or natural convection to achieve energy balance.

[0032] Preferably, the positive and negative electrodes of the light emitting diode 100 are respectively connected to the positive and negative electrodes of the variable voltage source 400, and the positive and negative electrodes of the photovoltaic cell layer 300 are respectively connected to the positive and negative electrodes of the variable load 500. The variable voltage source 400 can apply a bias voltage to the light emitting diode 100. By adjusting the variable voltage source 400 or the variable load 500, the photoelectric conversion efficiency of the device can be maximized.

[0033] It should be noted that the light emitting diode 100 , the variable voltage source 400 , the photovoltaic cell layer 300 and the variable load 500 may be collectively referred to as a thermal photon converter.

[0034] The working principle of this device is as follows: the focusing module 700 gathers sunlight to the absorption module 600, and increases the temperature of the absorption module 600. The heat energy is conducted from the absorption module 600 to the light-emitting diode 100, causing it to heat up to a thermal equilibrium state at the same temperature as the absorption module 600. The light-emitting diode 100 is heated to a certain temperature, emits photons through thermal radiation and is absorbed by the photovoltaic cell layer 300, and electron transitions generate electron-hole pairs to form a photocurrent. A portion of the power generated by the photovoltaic cell layer is transmitted to the light-emitting diode 100 through an external circuit and drives the driver to work. As a result, under the dual effects of forward bias and increased temperature, the radiation power of the light-emitting diode 100 can be increased by multiple orders of magnitude. It should be noted that the electric power generated by the photovoltaic cell layer 300 is greater than the electric power consumed by the variable voltage source 400, and the device generates net electric power.

[0035] In order to better illustrate the beneficial effects of the present invention, the following is verified by experiments. First of all, it should be noted that the performance evaluation of this power generation device as an energy conversion device is mainly based on two indicators: output power density P and energy conversion efficiency η. The calculation of the performance parameters of this device follows the law of conservation of energy and Newton's law of heat transfer. And in order to simplify the formula expression and maintain consistency, all components involved, including the contact surfaces of the absorption module 600, the light-emitting diode 100, the photovoltaic cell layer 300 and the heat dissipation module 800, have been defaulted to unit area and omitted in the formula expression. This means that in subsequent formulas and calculations, parameters related to area have been preset to unit area, thereby eliminating explicit references to area parameters.

[0036] First, the incident power of solar radiation per unit area is Q sol The light is collected by the focusing module 700 and then collected by the absorption module 600, which can be expressed as:

[0037]

[0038] Among them, C is the concentration, I sol is the direct normal solar spectrum irradiance, the wavelength λ varies in the range of 0.28 to 4 μm, and the absorption module 600 and the light emitting diode 100 are at an average temperature of T abs Thermal equilibrium state. Considering Newton's law of heat transfer, there is the following energy balance relationship:

[0039] Q in =αQ sol -Q rad -Q conv

[0040] Wherein, α is the absorption rate of the absorption module 600, Q in Q is the heat flux from the module into the LED 100 through heat conduction. rad Q is the heat radiation loss between the absorption module 600 and the environment. conv It is the convective heat loss between the surface of the absorption module 600 and the environment.

[0041] While receiving sunlight, the absorption module 600 will inevitably dissipate heat to the environment in the form of radiation due to its high temperature operating conditions. This energy release process follows the Stefan-Boltzmann law:

[0042]

[0043] Where, σ = 5.67 × 10 -8 Wm -2 K -4 is the Stefan-Boltzmann constant, ε=0.1 is the effective thermal emissivity of the absorption module 600, T abs is the average temperature of the absorption module 600, T E is the average temperature of the environment.

[0044] Convective heat loss Q caused by the temperature gradient between the surface of the absorption module 600 and the environment conv Satisfies Newton's cooling formula:

[0045] Q conv =h(T abs -T E )

[0046] Where h = 5Wm -2 K -1 is the natural convection heat transfer coefficient. The light-to-heat conversion efficiency of the concentrating module 700 can be determined as:

[0047]

[0048] The high temperature conducted by the absorption module 600 drives the light emitting diode 100 to radiate photons to the photovoltaic cell layer 300. The current density caused by the radiation carriers between the light emitting diode 100 and the photovoltaic cell layer 300 can be expressed as:

[0049] I PV =q[F PV -R PV ]

[0050] I LED =q[F LED -R LED ]

[0051] Where q is the electron charge, R LED and RPV are the non-radiative recombination rates of the light emitting diode 100 and the photovoltaic cell layer 300, respectively. LED and F PV is the photon flux of the light emitting diode 100 and the photovoltaic cell layer 300, both satisfying:

[0052]

[0053] in, is a modified Bose-Einstein distribution, the subscript "j" represents the light emitting diode 100 or the photovoltaic cell layer 300, h is the Planck constant, K B is the Boltzmann constant, E is the photon energy, and E g,LED and E g,PV The band gap energy of the light emitting diode 100 or the photovoltaic cell layer 300 can be expressed as:

[0054]

[0055] Where E g,j (0) is the band gap energy at 0K, α (not different from the absorption rate) and β are fitting constants related to material properties. Considering the non-radiative losses of Auger and Shockley-Read-Hall (SRH) processes, the non-radiative recombination rate can be expressed as:

[0056]

[0057] Wherein, t is the material thickness of the light emitting diode 100 or the photovoltaic cell layer 300, C n and C P are the Auger recombination coefficients of holes and electrons, τ is the carrier lifetime, n, p and n i are the electron, hole and intrinsic carrier concentrations respectively, and we have:

[0058]

[0059] p=nn d

[0060] Among them, n d is the electron doping concentration, is the intrinsic carrier concentration, N C and N V are the corresponding effective state densities in the valence band and conduction band, respectively. At this point, the thermal photon (TPC) thermoelectric conversion efficiency of the power generation module can be determined:

[0061]

[0062] Where, the electrical power density P of the thermal photon converter is TPC =P PV -PLED =I PV V PV -I LED V LED In a stable state, the following energy conservation equation exists between the light emitting diode 100 and the photovoltaic cell layer 300:

[0063] Q in =Q rad,net -P LED

[0064] Q rad,net =Q loss +P PV

[0065] Among them, Q loss =K*(T PV -T E ) represents the heat convection loss between the photovoltaic cell and the radiator, K = 500Wm -2 K -1 Forced heat transfer coefficient, is the net photon radiation energy flux between the light-emitting diode and the photovoltaic cell, and:

[0066]

[0067] Under the conditions of given concentration, solar radiation intensity (taking AM1.5D as an example) and material properties, the temperature of the light-emitting diode 100 and the photovoltaic cell layer 300 can be dynamically determined according to the first law of thermodynamics and the law of conservation of charge, and the output power and efficiency of the device are also determined accordingly. The overall energy conversion efficiency of the concentrated solar thermal photon power generation device is:

[0068]

[0069] Among them, η con =85% is the solar concentration efficiency of the Fresnel lens.

[0070] When the concentration of the concentrator module 700 is constant, the voltage of the light emitting diode 100 or the photovoltaic cell layer 300 can be adjusted by the adjustable load 500 or the variable voltage source 400 to maximize the efficiency of the device.

[0071] After numerical calculation, Figure 2 The overall efficiency η of the device is given under the condition of concentration of 20 Solar and voltage (V LED 、V PV ). It is easy to see from the figure that there is an optimal voltage that makes the efficiency of the device reach the maximum value.

[0072] exist Figure 2On this basis, by changing the concentration C, the relationship between the concentration and the maximum efficiency of the power generation device can be obtained. Figure 3 The dependence of the maximum conversion efficiency on the concentration C is given. As can be seen from the figure, the maximum efficiency (η TPC , η Solar ) first increase and then decrease with the increase of concentration C.

[0073] exist Figure 2 On this basis, by changing the thickness t of the semiconductor material, the relationship between thickness and the maximum efficiency of the power generation device can be obtained. Figure 4 The dependence of the maximum conversion efficiency on the thickness t is given. As can be seen from the figure, the maximum efficiency (η TPC , η Solar ) decreases monotonically with the increase of thickness.

[0074] exist Figure 3 On the basis of the above, the relationship between the overall conversion efficiency and the corresponding optimal power density of the CSP device and the thermophotovoltaic system and different concentrations C is compared. As can be seen from the figure, in terms of output performance in the low concentration (low temperature) range, the CSP device has a more obvious advantage than the photovoltaic system.

[0075] Figures 1 to 5 The specific implementation method of the device and the calculation method of the key performance indicators have been given in detail. A large heat flux density is achieved by using the focusing module 700 and the absorption module 600 to complete the conversion of solar energy into thermal energy. Using a thermal photon converter, a lower-cost light-emitting diode is selected to replace the traditional thermal emitter, so as to achieve precise matching of the spectrum and complete the efficient conversion of thermal energy into electrical energy. The structure of the present invention is simple, and each module operates independently, which effectively reduces the risk of failure. The device is adaptable to low-concentration conditions and is suitable for remote areas or off-grid areas with unstable lighting conditions. In addition, while reducing costs and system complexity, a higher overall photoelectric conversion efficiency is achieved.

[0076] Example 2

[0077] This is the second embodiment of the present invention, which is based on the previous embodiment. This embodiment provides a power generation method of a solar thermal power generation device, which is based on the solar thermal power generation device in embodiment 1, and includes:

[0078] S1: The light emitting diode 100 is heated by concentrating sunlight.

[0079] Specifically, the concentrating module 700 concentrates sunlight to the absorption module 600, raising the temperature of the absorption module 600. The heat energy is conducted from the absorption module 600 to the light emitting diode 100, raising its temperature to a thermal equilibrium state with the same temperature as the absorption module 600.

[0080] S2: The light emitting diode 100 emits photons to the photovoltaic cell layer 300 by means of thermal radiation.

[0081] Specifically, the light emitting diode 100 is heated to a certain temperature, emits photons through thermal radiation and is absorbed by the photovoltaic cell layer 300 .

[0082] S3: The photovoltaic cell layer 300 receives photons and generates current.

[0083] The electron transition generates electron-hole pairs, forming photocurrent. A part of the power generated by the photovoltaic cell layer is transmitted to the light emitting diode 100 through an external circuit and drives the driver to work.

[0084] It should be noted that the radiation power of the light emitting diode 100 can be increased by several orders of magnitude under the dual effects of forward bias and increased temperature. It should be noted that the power generated by the photovoltaic cell layer 300 is greater than the power consumed by the variable voltage source 400, and the device generates net power.

[0085] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A solar thermal power generation device, characterized in that: It comprises a light emitting diode (100), a vacuum layer (200) and a photovoltaic cell layer (300) which are arranged in sequence from top to bottom; The photovoltaic cell layer (300) is connected to a variable load (500); The light emitting diode (100) is electrically connected to the photovoltaic cell layer (300).

2. The solar thermal power generation device according to claim 1, characterized in that: The light emitting diode (100) is connected to a variable voltage source (400), and the variable voltage source (400) is capable of applying a bias voltage to the light emitting diode (100).

3. The solar thermal power generation device according to claim 1 or 2, characterized in that: An absorption module (600) and a light-concentrating module (700) are sequentially arranged on the top of the light-emitting diode (100); the light-concentrating module (700) is used to concentrate sunlight to increase the temperature of the absorption module (600).

4. The solar thermal power generation device according to claim 3, characterized in that: A heat dissipation module (800) is also provided at the bottom of the photovoltaic cell layer (300), and the heat dissipation module (800) is used to dissipate heat from the photovoltaic cell layer (300).

5. The solar thermal power generation device according to claim 4, characterized in that: A heat-conducting layer (900) is provided between the absorption module (600) and the light-emitting diode (100), and between the photovoltaic cell layer (300) and the heat-dissipating module (800).

6. The solar thermal power generation device according to claim 5, characterized in that: The heat dissipation module (800) dissipates heat by forced convection or natural convection.

7. A method for generating electricity using a solar thermal power generation device, characterized in that: Applied to the solar thermal power generation device according to any one of claims 2 to 6, the method comprises: The light emitting diode (100) is heated by concentrating sunlight; The light emitting diode (100) emits photons to the photovoltaic cell layer (300) by means of thermal radiation; The photovoltaic cell layer (300) receives the photons and generates electric current.

8. The solar thermal power generation device according to claim 7, characterized in that: The method for concentrating sunlight comprises sequentially arranging an absorption module (600) and a concentrating module (700) on the top of the light-emitting diode (100).

9. The solar thermal power generation device according to claim 8, characterized in that: The light emitting diode (100) is connected to a variable voltage source (400), and the photovoltaic cell layer (300) is connected to a variable load (500). By adjusting the variable voltage source (400) and the variable load (500), the photovoltaic cell layer (300) is at a maximum power generation efficiency.

10. The solar thermal power generation device according to claim 9, characterized in that: The light-emitting diode (100) is electrically connected to the photovoltaic cell layer (300), and part of the electric power generated by the photovoltaic cell layer (300) is used to drive the light-emitting diode (100).

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