CN111765652A - A tower photovoltaic photothermal combined power generation device - Google Patents

Abstract

The invention discloses a tower type photovoltaic and photothermal combined power generation device which comprises a heliostat, a heat collection tower, a heat collector, a heat storage tank, a steam generator, a steam turbine and a power generator. The heliostats are provided with a plurality of heliostats and are arranged on the ground in a circumferential annular mode around the heat collecting tower, infrared rays in sunlight can be reflected to the heat collector, and steam is generated to be supplied to the steam turbine to do work to drive the generator to generate electricity. The heliostat comprises an infrared reflecting layer, a thin film solar cell and a bracket which are sequentially arranged from a light-facing surface. The thin film solar cell sequentially comprises a transparent glass layer, a conductive glass layer, an electron transport layer, an active layer, a hole transport layer and a back electrode layer along a light incidence direction. The heat collector is composed of a spiral heat collecting pipe and a vertical heat collecting pipe which are spirally wound on the top of the heat collecting tower, and selective infrared absorption coatings are coated on the outer surfaces of the spiral heat collecting pipe and the vertical heat collecting pipe; the solar heliostat cleaning system has the advantages of high comprehensive energy utilization rate, convenience in heliostat cleaning, high photo-thermal focusing ratio, compact equipment structure and the like.

Description

A tower photovoltaic photothermal combined power generation device

technical field

The invention relates to the field of solar energy utilization, in particular to a tower-type photovoltaic photothermal combined power generation device that utilizes solar energy to simultaneously perform photothermal power generation and photovoltaic power generation.

Background technique

Energy is the fundamental guarantee for human development and survival. With economic development and population growth, energy consumption is increasing day by day, and fossil energy is facing depletion. To solve the problem of human energy utilization in the future, it is necessary to vigorously develop new energy and clean energy, and it is an inevitable trend to replace old energy with new energy. Solar energy occupies an important place in the future energy structure with its unique "infinity" of reserves, universality of existence, and cleanness of development and utilization. The total amount of solar radiation received by China’s land every year is equivalent to 2.4×10 ⁴⁰⁰ million tons of standard coal, which is equivalent to about 600 times of China’s average annual energy consumption, that is, as long as 1/600 of the solar energy is utilized, it can solve China’s problems. energy supply problems. The development of solar energy is a "hundred-year plan and a thousand-year plan". Solar thermal power generation, photovoltaic power generation, etc. are all optional ways to utilize solar energy.

Solar thermal power generation is the use of trough, dish, tower and other reflective concentrating heat-concentrating devices to gather the heat of solar energy to heat air, heat transfer oil, molten salt and other working media, and then pass the Rankine cycle or Stirling cycle prime mover. Output power to drive the generator to generate electricity, but in CSP, part of the energy in the visible light and ultraviolet frequency bands is converted into heat, and this part of the energy can be directly converted into electricity through photovoltaic power generation. The conversion efficiency into electricity is about 50%, which is much higher than 25% of CSP.

Photovoltaic power generation is a technology that directly converts light energy into electrical energy by using the photovoltaic effect of the semiconductor interface. Sunlight illuminates the semiconductor p-n junction to form a new hole-electron pair. Under the action of the built-in electric field of the p-n junction, the holes flow from the n region to the p region, and the electrons flow from the p region to the n region. current. In terms of materials, solar cells can be roughly divided into the following categories:

(1) The first generation of silicon-based solar cells mainly refers to solar cells based on monocrystalline silicon, polycrystalline silicon and their composites with amorphous silicon. At present, the laboratory efficiency can reach more than 25%. According to the Schottky limit prediction, The ideal maximum efficiency is about 32%.

(2) The second generation of multi-compound thin film solar cells, mainly including GaAs, InP, CIGS, CdTe solar cells, etc. These cells have high photoelectric conversion efficiency and device performance. Stable, the thickness of the light absorbing layer of the battery is thin, which can greatly reduce the consumption of raw materials.

(3) The third generation of new solar cells, mainly including perovskite solar cells PSC, dye-sensitized solar cells, organic solar cells, quantum dot solar cells, etc. In the past 10 years, the emerging hybrid perovskite solar cell PSC has rapidly attracted worldwide attention. As of August 2019, the highest efficiency of this type of thin-film cell has increased from 3.8% in 2009 to 25.2%. This perovskite film can be coated on the surface of objects of any shape to form photovoltaic cells, but such cells only absorb energy in the ultraviolet and visible light regions, and absorb less energy in the infrared region. The energy in the infrared region is more suitable for producing thermal energy and using thermal energy to generate electricity. The practical efficiency of using steam generated by thermal energy to drive steam turbine power generation has reached 50%. If the sun is regarded as a black body of 5800K, and the ambient temperature of the earth is regarded as 300K, then a boiler is set up between the sun and the ground, and the maximum efficiency of power generation according to the Carnot cycle can reach 85%. It can be seen that both pure photovoltaic power generation and solar thermal power generation are far below this ideal phase rate.

SUMMARY OF THE INVENTION

The invention aims to provide a tower-type photovoltaic photothermal combined power generation device, which fully considers the spectral characteristics of solar energy utilization, combines photovoltaic power generation operating in the ultraviolet region and visible light region and photothermal power generation in the infrared region, and utilizes solar energy as much as possible. Provides outputs such as heat and electricity.

The present invention is achieved through the following technical solutions:

A tower-type photovoltaic photothermal combined power generation device includes a heliostat, a heat collecting tower, a heat collector, a heat storage tank, a steam generator, a steam turbine and a generator, and the heliostat can convert infrared rays in sunlight to The heat collector reflects, the heat collector is connected with the steam generator and the steam turbine in sequence, and the generated steam is used for the steam turbine to do work to drive the generator to generate electricity; The infrared reflection layer and the thin film solar cell, and the bracket, the thin film solar cell is sequentially composed of a transparent glass layer, a conductive glass layer, an electron transport layer, an active layer, a hole transport layer and a back electrode layer along the light incident direction; The heat collector is composed of a spiral heat collecting tube and a vertical heat collecting tube wound on the top of the heat collecting tower in a spiral manner, and the outer surfaces of the spiral heat collecting tube and the vertical heat collecting tube are both coated with a selective infrared absorption coating; A number of mirrors are provided and arranged in a circular ring around the heat collecting tower on the ground.

In the above technical solution, the infrared reflection layer is a composite coating comprising silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), and tantalum pentoxide (Ta ₂ O ₅ ). The multi-layer dielectric film, the active layer is a perovskite material with an ABX ₃ structure.

In the above technical solution, the shape of the heliostat is a trapezoid, and the lower base angle α of the trapezoid is 80-89°.

In the above technical solution, the device further comprises a bracket, the bracket is mounted on the upper part of the bracket, and a heliostat rotation adjustment mechanism is arranged in the bracket.

In the above technical solution, the angle β between the generatrix of the spirally wound helix and the horizontal direction of the spiral heat collector is 10-30°, the spiral heat collector and the vertical heat collector are arranged in bundles, and the spiral heat collector is arranged in the vertical direction. On the upper part of the heat collecting tube, the spiral heat collecting tube and the vertical heat collecting tube are connected through the header.

In the above technical solution, the selective infrared absorption coating on the outer surface of the spiral heat collecting tube and the vertical heat collecting tube is a nitrided aluminum coating.

In the above technical solution, the heat-conducting oil or molten salt is used as the heat-exchanging working medium for the heat collector, and the heat-conducting oil or molten salt flows through the vertical heat collecting tube, the header and the spiral heat collecting tube in sequence from bottom to top.

The present invention has the following advantages and outstanding effects: (1) the solar energy can be used to produce electric energy and thermal energy at the same time, and heat can be stored for power generation; (2) the comprehensive utilization rate of energy is improved, the power generation efficiency can be increased to more than 30%, and the comprehensive energy utilization efficiency is more than 70% ; ④ Planar structure reflective concentrating thin-film solar cell components are easy to manufacture, install and clean; ⑤ High light-to-heat focusing ratio and compact device structure.

Description of drawings

FIG. 1 is a schematic diagram of a tower-type photovoltaic photothermal combined power generation device involved in the present invention.

FIG. 2 is a schematic diagram of the structure of the heliostat film layer involved in the present invention.

FIG. 3 is a schematic diagram of the shape of the heliostat involved in the present invention.

FIG. 4 is a schematic diagram of the arrangement of the spiral heat collecting tubes and the vertical heat collecting tubes on the heat collecting tower according to the present invention.

FIG. 5 is a schematic diagram of the arrangement of the heliostats involved in the present invention around the heat collecting tower.

In the figure: 1-heliostat; 2-collecting tower; 41-collector; 42-spiral collector; 43-vertical collector; 44-header; 45-heat storage tank; 3-steam generator; 4-steam turbine; 5-DC/AC conversion unit; 6-power grid; 7-heat user; 8-generator; 11-infrared reflection layer; 12-transparent glass layer; 13-conductive glass layer; 14-electron transmission layer; 15-active layer; 16-hole transport layer; 17-back electrode layer; 18-thin film solar cell; 19-support; 20-support.

Detailed ways

The specific implementation manner and working process of the present invention will be further described below with reference to the accompanying drawings and examples.

Orientation terms such as upper, lower, left, right, front and rear in this application document are established based on the positional relationship shown in the accompanying drawings. If the drawings are different, the corresponding positional relationship may also change accordingly, so this should not be construed as a limitation on the protection scope.

99.9% of the energy in the solar electromagnetic radiation is concentrated in the infrared, visible and ultraviolet regions. Solar radiation is mainly concentrated in the visible light part (400-760nm), and the wavelengths of infrared rays (>760nm) longer than visible light and ultraviolet rays (<400nm) are less. In the total radiant energy, the wavelength between 150 and 4000nm accounts for more than 99%, and it is mainly distributed in the visible light region and the red and ultraviolet regions. The visible light region accounts for about 50% of the total solar radiation energy, and the infrared region accounts for about 43%. The ultraviolet region accounts for about 7% of the total. The wavelength range of solar radiation received on the ground is about 295 to 2500 nm. Solar radiation with wavelengths less than 295nm and greater than 2500nm cannot reach the ground due to the strong absorption of ozone, water vapor and other atmospheric molecules in the earth's atmosphere.

In terms of photovoltaic power generation, solar photovoltaic cells mainly absorb visible light, and can also absorb light in a part of the infrared band, generally the absorption band is 300nm to 1100nm. In terms of photothermal utilization, radiant energy in ultraviolet, visible and infrared regions can be converted into heat energy.

The present invention provides a tower-type photovoltaic photothermal combined power generation device, as shown in FIG. 1, comprising a heliostat 1, a bracket 20, a heat collecting tower 2, a heat collector 41, a heat storage tank 45, a steam generator 3, Steam turbine 4 , DC/AC conversion unit 5 and generator 8 . Both the generator 8 and the DC/AC conversion unit 5 are connected to the grid 6 .

The heliostat 1 can reflect infrared rays in sunlight to the heat collector 41 , and the heliostat 1 includes an infrared reflection layer 11 , a thin film solar cell 18 , and a bracket 19 arranged in sequence from the light-facing surface. The infrared reflection layer 11 is a multilayer dielectric film comprising silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), and tantalum pentoxide (Ta ₂ O ₅ ) combined and coated, It has the advantages of adjustable cut-off frequency, selective reflectivity and high transmittance. The infrared reflectance of the infrared reflection layer is close to 1 for wavelengths above 750nm, and the transmittance for radiation with wavelengths less than 750nm is close to 1, so that visible light and ultraviolet radiation of solar radiation pass through the infrared reflection layer to reach the active layer and use photovoltaic effect to generate electricity.

The thin film solar cell 18 is sequentially composed of a transparent glass layer 12 , a conductive glass layer 13 , an electron transport layer 14 , an active layer 15 , a hole transport layer 16 and a back electrode layer 17 along the light incident direction. The active layer 15 is a perovskite material with an ABX ₃ structure. Perovskite materials have the advantage of being easy to coat. The light transmitted through the infrared reflection layer 11 converts the light energy into electrical energy through the photovoltaic effect in the thin film solar cell 18 .

The shape of the heliostat 1 is a trapezoid, and the lower base angle α of the trapezoid is 80-89°. The streamline principle is used to facilitate the natural flow of dust from top to bottom, avoiding the edge effect that causes dust to accumulate on the edge of the mirror and become new dust accumulation. Growth points for easy cleaning and soot blowing.

The bracket 19 is installed on the upper part of the bracket 20 , and a rotation adjustment mechanism of the heliostat 1 is arranged in the bracket 20 . The heliostats are arranged in a circle around the heat collecting tower on the ground, one heat collecting tower corresponds to several heliostats, and the heliostats 1 are arranged in a circle around the heat collecting tower 2 on the ground. The heliostat 1 tracks the sunlight through the rotating adjustment mechanism and the control system. Through mirror reflection, the infrared reflection layer reflects the infrared part of the sunlight to the top of the absorption tower, and the infrared heat is coated on the surface of the collector at the top of the absorption tower. Nitrogen-aluminum selective absorption coating for collector tube absorption. Specular reflection is a point focusing method, with a focusing ratio of 300-1000, high efficiency, and can heat the working fluid to a higher temperature.

The heat energy of the infrared radiation reflected by the heliostat 1 can be collected by the heat collector 41, and the collected heat energy is used to heat the heat transfer oil or molten salt working medium in the heat collector 41, and the heat transfer oil or the molten salt working medium flows through. The heat storage tank 45 enters the steam generator 3, heats the feed water in the steam generator 3 to generate steam, and the steam is supplied to the heat user 7 and/or the steam turbine 4 to drive the generator 8 to generate electricity. The exhausted steam is supplied to heat users to realize cogeneration. The heat storage tank 45 has the function of buffering heat storage. When there is no sunlight, the heat stored in the heat storage tank 45 can be released as heat, and the feed water is continuously heated by the steam generator to generate steam, and the heat storage is used to generate electricity. The combined cascade utilization of photovoltaics further realizes the peak regulation of heat storage power generation, and the synergy and complementation of photovoltaic/photothermal power generation.

The heat collector 41 is composed of a spiral heat collecting tube 42 and a vertical heat collecting tube 43 wound on the top of the heat collecting tower 2 in a spiral manner. Use nitrided aluminum coating. . The heat collector 41 selects heat transfer oil or molten salt as the heat exchange working medium, and the heat transfer oil or molten salt flows through the vertical heat collector tube 43 , the header 44 and the spiral heat collector tube 42 in sequence from bottom to top.

The angle β between the generatrix of the helically wound helix and the horizontal direction of the spiral heat collector tube 42 is 10-30°, the spiral heat collector tube 42 and the vertical heat collector tube 43 are arranged in bundles, the spiral heat collector tube 42 is arranged on the upper part of the vertical heat collector tube 43, The heat collecting tubes 42 and the vertical heat collecting tubes 43 are connected through the header 44 .

The collector tubes on the collector tower are composed of vertical collector tubes and spiral collector tubes in series in bundles, which is convenient for absorbing thermal stress and facilitating quick start and stop. The heat transfer medium such as heat transfer oil or molten salt flows through the vertical heat collector tube and the spiral heat collector tube from bottom to top, which is convenient to increase the flow rate of the heat transfer medium in the high heat load area, improve the heat transfer capacity, and avoid the damage to the heat transfer oil or the heat transfer oil due to the high wall temperature of the heat collector tube. Molten salt heat transfer medium.

About 57% of the ultraviolet and visible light energy in solar energy is used for photovoltaic power generation, the full-spectrum photovoltaic power generation efficiency is about 20%, and the power generation efficiency is about 35% calculated according to the actual absorption spectrum energy benchmark. 43% of the infrared energy is used for CSP, and the efficiency of CSP based on the actual endothermic heat is around 28%. Therefore, the comprehensive power generation efficiency is about (35%×57%+28%×43%)=32%, which is higher than the theoretical limit of pure photovoltaic power generation Schottky. If the infrared radiation energy is only used for heat utilization, the energy utilization efficiency can be close to (35%×57%+43%)=63%.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A tower type photovoltaic and photothermal combined power generation device comprises a heliostat (1), a heat collection tower (2), a heat collector (41), a heat storage tank (45), a steam generator (3), a steam turbine (4) and a power generator (8), wherein infrared rays in sunlight can be reflected to the heat collector (41) by the heliostat (1), the heat collector (41) is sequentially connected with the heat storage tank (45), the steam generator (3) and the steam turbine (4), and generated steam is used for the steam turbine (4) to work to drive the power generator (8) to generate power; the method is characterized in that: the heliostat (1) comprises an infrared reflecting layer (11), a thin film solar cell (18) and a bracket (19), wherein the infrared reflecting layer and the thin film solar cell are sequentially arranged from a light-facing surface, and the thin film solar cell (18) sequentially comprises a transparent glass layer (12), a conductive glass layer (13), an electron transport layer (14), an active layer (15), a hole transport layer (16) and a back electrode layer (17) along a light incidence direction; the heat collector (41) is composed of a spiral heat collecting pipe (42) and a vertical heat collecting pipe (43) which are spirally wound on the top of the heat collecting tower (2), and selective infrared absorption coatings are coated on the outer surfaces of the spiral heat collecting pipe (42) and the vertical heat collecting pipe (43); the heliostats (1) are circumferentially and annularly arranged on the ground around the heat collecting tower (2).

2. The tower-type photovoltaic and photothermal combined power generation device according to claim 1, wherein: the infrared reflecting layer (11) comprises silicon dioxide and dioxideThe multilayer dielectric film is coated by combining titanium, niobium pentoxide and tantalum pentoxide, and the active layer (15) is selected to have ABX₃A perovskite material of structure.

3. The tower-type photovoltaic and photothermal combined power generation device according to claim 1, wherein: the heliostat (1) is trapezoidal, and the lower bottom angle alpha of the trapezoid is 80-89 degrees.

4. The tower-type photovoltaic and photothermal combined power generation device according to claim 1, wherein: the device also comprises a support (20), the bracket (19) is installed on the upper portion of the support (20), and a heliostat (1) rotation adjusting mechanism is arranged in the support (20).

5. The tower-type photovoltaic and photothermal combined power generation device according to claim 1, wherein: the spiral heat collecting tube is characterized in that the angle beta between the generatrix of a spiral winding spiral line of the spiral heat collecting tube (42) and the horizontal direction is 10-30 degrees, the spiral heat collecting tube (42) and the vertical heat collecting tube (43) are arranged in a bundle, the spiral heat collecting tube (42) is arranged on the upper portion of the vertical heat collecting tube (43), and the spiral heat collecting tube (42) is connected with the vertical heat collecting tube (43) through a header (44).

6. The tower-type photovoltaic and photothermal combined power generation device according to claim 1, wherein: the selective infrared absorption coatings on the outer surfaces of the spiral heat collecting pipes (42) and the vertical heat collecting pipes (43) are nitrided aluminum coatings.

7. The tower-type photovoltaic and photothermal combined power generation device according to claim 1, wherein: the heat collector (41) selects heat conduction oil or fused salt as a heat exchange working medium, and the heat conduction oil or the fused salt sequentially flows through the vertical heat collecting tube (43), the header (44) and the spiral heat collecting tube (42) from bottom to top.

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