Photovoltaic photo-thermal cooperative system based on sand heat storage and heat energy utilization method thereof

Abstract

The invention provides a photovoltaic photo-thermal collaborative system based on sand heat storage and a heat energy utilization method of the photovoltaic photo-thermal collaborative system. The system comprises a semitransparent photovoltaic battery assembly, a plate type condenser, a heat collection pipeline system, a sand heat storage unit and an auxiliary structure from top to bottom. The semitransparent photovoltaic cell assembly absorbs visible light to generate electricity, ultraviolet light and infrared light penetrate through the assembly and are focused to the heat collection pipeline system through the plate type condenser, and working media are heated and then stored in the sand heat storage unit to be used at night or in the peak load period. According to the system, the comprehensive utilization rate is increased to be larger than or equal to 85% through spectrum separation, sand heat storage cost is low, the service life is long, the structure is compact, adaptability is high, day and night energy supply can be achieved, the system is suitable for various scenes such as western deserts, remote areas and agricultural greenhouses, and the problems that an existing photovoltaic photo-thermal system is low in efficiency, weak in heat storage, high in cost and insufficient in environmental adaptability are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of solar energy utilization technology, and in particular to a photovoltaic-thermal synergistic system based on sand thermal storage and its thermal energy utilization method. Background Technology

[0002] Currently, photovoltaic (PV) power generation technology is widely used in the construction of distributed and centralized power plants, with its core advantages being high modularity and fast response speed. However, its energy conversion efficiency is limited by the non-absorbable portion of the solar spectrum (such as infrared light), resulting in a large amount of energy not being effectively utilized. Furthermore, PV systems cannot continuously output power during periods of insufficient sunlight or at night, restricting their application in scenarios requiring high-continuity energy supply. Solar thermal energy utilization, on the other hand, focuses on converting solar radiation into heat energy for heating, warming, or power generation, offering advantages such as stable thermal energy and convenient energy storage. Especially when combined with thermal storage units (such as molten salts and phase change materials), it enables spatiotemporal regulation of solar energy, improving the flexibility of the energy system. However, traditional solar thermal systems face challenges such as large equipment size, high initial investment, and long conversion chains, making them difficult to promote in small and medium-sized projects.

[0003] In recent years, photovoltaic-photothermal coupling technology has attracted researchers' attention in order to improve the overall energy utilization rate of solar energy systems. This type of system, through structural integration or spectral separation, divides solar energy into a "photovoltaic path" and a "thermal path" according to wavelength, which are used for power generation and heating respectively, showing significant potential for synergistic efficiency. Currently, some integrated dual-function components have been attempted, but most suffer from problems such as low spectral matching, poor structural integration, weak or no thermal storage capacity, high system cost, and insufficient material and environmental adaptability. Especially in western my country, characterized by long hours of sunshine, high solar radiation intensity, and abundant land resources, it is very suitable for developing solar energy systems. However, these regions also face problems such as large nighttime temperature differences and discontinuous heat use, urgently requiring a composite solar energy utilization system that can efficiently utilize the full spectrum of solar energy, has thermal storage capabilities, and adapts to harsh environments. Therefore, this invention aims to provide a photovoltaic-photothermal synergistic system based on sand thermal storage and its thermal energy utilization method to solve the above-mentioned problems existing in the prior art. Summary of the Invention

[0004] The purpose of this invention is to provide a photovoltaic-thermal synergistic system based on sand thermal storage and its thermal energy utilization method, so as to efficiently utilize the full spectrum of solar energy, have thermal storage function, adapt to harsh environments, solve the problems of low spectral matching degree, poor structural integration, weak thermal storage capacity, high cost and insufficient environmental adaptability of existing photovoltaic-thermal systems, and improve the overall energy utilization rate and energy supply flexibility of solar energy systems.

[0005] According to one objective of the present invention, a photovoltaic-thermal synergistic system based on sand thermal storage is provided, comprising, from top to bottom, a semi-transparent photovoltaic cell module, a plate concentrator, a heat collection pipe system, and a sand thermal storage unit. The semi-transparent photovoltaic cell module absorbs visible light and converts it into electrical energy. Ultraviolet and infrared light pass through the semi-transparent photovoltaic cell module and are focused by the plate concentrator onto the heat collection pipe system. The heat collection pipe system heats the internal working fluid, and the working fluid transfers the heat energy to the sand thermal storage unit for storage through a thermally conductive structure. The sand thermal storage unit releases heat energy at night or during peak load periods.

[0006] Furthermore, the semi-transparent photovoltaic cell module adopts a stacked semi-transparent structure, including a transparent conductive electrode, an electron / hole transport layer, a semi-transparent perovskite or CIGS light-absorbing layer, an electron / hole transport layer, and a transparent electrode on the back.

[0007] Furthermore, the plate concentrator is a reflective planar concentrator with a surface coated with a high-reflectivity material, which is an aluminum alloy substrate + silver mirror reflective coating + anti-oxidation SiO2 protective layer; the plate concentrator adopts a linear Fresnel structure; the distance between the plate concentrator and the semi-transparent photovoltaic cell module is 10-30cm; the plate concentrator is equipped with single-axis or dual-axis tracking.

[0008] Furthermore, the heat collection pipeline system includes a heat absorption tube, a transparent protective tube, and a working fluid channel; the surface of the heat absorption tube is provided with a high-absorption-rate black selective coating, which is TiNOx, black chromium, or a nano-selective absorption film; the transparent protective tube is a high borosilicate glass tube and is evacuated inside; the working fluid channel is filled with high-temperature heat transfer oil, water, or molten salt.

[0009] Furthermore, the sand thermal storage unit includes a thermal storage tank, which is filled with quartz sand, alumina sand or composite sand particles, and U-shaped or coiled heat exchange pipes are embedded inside the thermal storage tank.

[0010] Furthermore, the U-shaped or coiled heat exchange pipes within the sand thermal storage unit are connected to an organic Rankine cycle system for power generation or to a heat exchanger for heating / drying / industrial hot water supply.

[0011] Furthermore, the heat storage tank is provided with an insulation layer, which is composed of ceramic fiber blanket + polyurethane foam + external protective plate.

[0012] Furthermore, it also includes a support frame, which is an aluminum alloy structure.

[0013] According to another objective of the present invention, the present invention provides a method for utilizing the thermal energy of the above-mentioned photovoltaic-thermal synergistic system based on sand thermal storage, comprising the following steps: S1. During the day, visible light is absorbed by the semi-transparent photovoltaic cell module and converted into electrical energy, which is then output to the inverter. S2, ultraviolet light and infrared light pass through the components and irradiate the plate concentrator, and are focused onto the heat collection pipe system to heat the internal working fluid; S3. The heating working fluid introduces heat energy into the sand thermal storage unit for storage through a heat-conducting structure. S4. At night or during peak load periods, the working fluid in the sand thermal storage unit circulates and releases heat energy to supply industrial heating, building heating, hot water supply, or small-scale power generation.

[0014] Furthermore, in step S3, thermal energy is transferred to the sand particles through conduction and radiation, and in step S4, the rate and direction of thermal energy release are adjusted by controlling the structure.

[0015] This invention utilizes the spectral separation of semi-transparent photovoltaic cells and plate concentrators to generate electricity with visible light and collect heat with infrared and ultraviolet light, resulting in high overall utilization far exceeding traditional pure photovoltaic or solar thermal systems. The invention features a compact structure, high integration, and small footprint, making it suitable for various spaces. The sand thermal storage system is low-cost, long-lasting, and thermally stable, using environmentally friendly and safe materials. It can provide energy day and night and perform peak-shaving output, enhancing spatial and temporal flexibility. It is highly adaptable, easy to maintain, and safe to operate, making it suitable for harsh environments. Its strong scalability and connectivity make it suitable for various commercial applications. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the heat collection pipeline system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the sand thermal storage unit according to an embodiment of the present invention; Figure 4 This is a flowchart illustrating the process of an embodiment of the present invention.

[0018] In the diagram: 1. Semi-transparent photovoltaic cell module; 2. Plate concentrator; 3. Heat collection pipeline system; 301. Heat absorption pipe; 302. Transparent protective pipe; 303. Working fluid channel; 4. Sand heat storage unit; 401. Heat storage tank; 402. High heat capacity sand; 403. Coil-type heat exchange pipeline; 404. Insulation layer; 5. Heat conduction structure. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Example 1 like Figures 1-4 As shown, a photovoltaic-thermal synergistic system based on sand thermal storage includes a semi-transparent photovoltaic cell module 1, a plate concentrator 2, a heat collection pipe system 3, and a sand thermal storage unit 4 arranged sequentially from top to bottom.

[0023] Specifically, the semi-transparent photovoltaic module 1 adopts a stacked semi-transparent structure, including a transparent conductive electrode, an electron / hole transport layer, a semi-transparent perovskite or CIGS light-absorbing layer, an electron / hole transport layer, and a back transparent electrode. The transparent conductive electrode is FTO or ITO glass, and the back transparent electrode is a thin silver / ITO composite layer with a thickness controlled to <15nm. The perovskite component in the semi-transparent perovskite or CIGS light-absorbing layer uses a mixed halogen material with a wide bandgap of 1.65-1.8eV. The encapsulation material of the semi-transparent photovoltaic module uses double-sided glass and UV-stabilized encapsulating adhesive. The photoelectric conversion efficiency of the semi-transparent photovoltaic module is ≥10%, the average light transmittance (400-2500nm) is >30%, and the infrared transmittance (>800nm) is >50%.

[0024] The panel concentrator 2 is a reflective planar concentrator designed as a fixed flat plate or freeform surface. Its surface is coated with a high-reflectivity material, consisting of an aluminum alloy substrate, a silver mirror reflective coating, and an anti-oxidation SiO2 protective layer. The panel concentrator adopts a linear Fresnel structure, with a focusing angle controlled within ±10° and a concentration ratio of 10-20 times. The distance between the panel concentrator 2 and the semi-transparent photovoltaic module 1 is 10-30cm, and the installation tilt angle is consistent with the local latitude. It is used in conjunction with a single-axis or dual-axis solar tracking device. The unit mirror width of the panel concentrator 2 is 80-150mm, with 5-10 mirrors per module. Each mirror is independently fixed, and the angle of incidence is pre-designed to be ±5-15°.

[0025] The heat collection pipe system 3 includes a heat-absorbing tube 301, a transparent protective tube 302, and a working fluid channel 303. The heat-absorbing tube 301 is the inner layer, and its surface is coated with a high-absorptivity black selective coating, which may be TiNOx, black chromium, or a nano-selective absorption film. The transparent protective tube 302 is the outer layer, made of high borosilicate glass, and its interior is evacuated to form an insulation cavity. The working fluid channel 303 is filled with a heat transfer fluid, which may be high-temperature heat transfer oil, water, or molten salt. The heat collection pipe system 3 has a pipe diameter of 20-40 mm, a thermal efficiency >70%, and a working fluid operating temperature of 80°C-300°C. The high-absorptivity black selective coating on the surface of the heat-absorbing tube of the heat collection pipe system 3 has an absorptivity >95% and an emissivity <10%.

[0026] The sand thermal storage unit 4 includes a thermal storage tank 401 and a control structure. The outer shell of the thermal storage tank 401 is made of stainless steel or high-temperature resistant carbon steel, and the interior is filled with dried and screened high-heat-capacity sand 402. The high-heat-capacity sand is quartz sand, alumina sand or composite sand particles. U-shaped or coiled heat exchange pipes 403 are also embedded inside. The insulation layer 404 of the thermal storage tank 401 is a ceramic fiber blanket + polyurethane foam + external protective plate.

[0027] In this embodiment, the heat storage temperature range of the sand thermal storage unit 4 is 200°C-600°C, the heat capacity is 1.1-1.3 kJ / kg·K, the heat loss rate is less than 5% / 12h under good insulation conditions, and the lifespan of the thermal storage unit is greater than 10 years. The heat energy of the heat collection pipeline system 3 is transported to the U-shaped or coiled heat exchange pipelines inside the sand thermal storage unit 4 through the heat conduction structure 5, forming a circulation pipeline. The heat conduction structure 5 includes high-temperature corrosion-resistant metal pipes or ceramic pipes.

[0028] The U-shaped or coiled heat exchange pipe 403 of the sand thermal storage unit 4 is connected to the Rankine cycle system for power generation or to the heat exchanger for heating / drying / industrial hot water supply. The sand thermal storage unit 4 is equipped with a control structure, which includes a temperature stratification sensor array for automatically controlling valves to regulate the inlet and outlet heat flow. It also includes an electric heating auxiliary unit for maintaining the thermal storage temperature during periods of low sunlight.

[0029] It also includes a support frame for supporting the system structure. The support frame adopts an aluminum alloy frame structure to support the entire system. The outer shell material of the support frame is 304 / 316 stainless steel, with a temperature resistance greater than 600°C, and the protection level of the heat collection area reaches IP65.

[0030] This invention also provides a method for utilizing thermal energy in a photovoltaic-thermal synergistic system based on sand thermal storage, comprising the following steps: S1. During the day, when sunlight shines, visible light is absorbed by the semi-transparent photovoltaic cell module and converted into electrical energy, which is then output to the inverter device through series and parallel connection. S2, ultraviolet and infrared light shine through the semi-transparent photovoltaic cell module and onto the plate concentrator. The plate concentrator focuses the light onto the heat collection pipe system, which absorbs heat energy and raises the temperature of the internal working fluid. S3. The heated working fluid transfers its heat energy into the sand thermal storage unit for storage through a heat-conducting structure. S4. At night or during peak load periods, the working fluid in the sand thermal storage unit is recirculated, releasing heat energy for industrial heating, building heating, hot water supply, or small-scale power generation.

[0031] Example 2 like Figures 1-4 As shown, the structure of this embodiment is basically the same as that of Embodiment 1. The photovoltaic-thermal synergistic system based on sand thermal energy storage in this embodiment consists of the following parts from top to bottom: Top layer: Semi-transparent photovoltaic cell module; Middle layer: Plate-type concentrator structure; Lower layer: Heat collection piping system; Auxiliary structures: support frame and thermal storage unit.

[0032] Among them, the semi-transparent photovoltaic cell module 1 adopts a stacked semi-transparent structure, which mainly includes a transparent conductive electrode (such as FTO or ITO glass), an electron / hole transport layer, a semi-transparent perovskite or CIGS light-absorbing layer, an electron / hole transport layer, and a back transparent electrode (such as a thin silver / ITO composite layer).

[0033] For the perovskite component, it is recommended to use a wide-bandgap (~1.65-1.8 eV) mixed halogen material, with the back electrode thickness controlled to <15 nm, to improve the transmittance of light in the sub-visible band (especially 800~2500 nm). The encapsulation material should be double-sided glass + UV-stabilized encapsulant. The photoelectric conversion efficiency (PCE) of the semi-transparent photovoltaic module should be ≥10%; the average light transmittance (400-2500 nm) >30%; and the infrared transmittance (>800 nm) >50%.

[0034] Among them, the plate concentrator 2 is a reflective planar concentrator structure, which can be designed as a fixed flat plate or a free-form surface. The surface is coated with a high-reflectivity material, such as an aluminum alloy substrate + silver mirror reflective coating + anti-oxidation SiO2 protective layer. The plate concentrator adopts a linear Fresnel structure, with the focusing angle controlled within ±10°; the concentration ratio is 10–20 times, ensuring consistent focal length of the collector tubes; the distance between the concentrator and the photovoltaic module is 10–30 cm, optimized according to the light divergence angle and concentration requirements. The installation tilt angle is consistent with the local latitude, and it can be used with single-axis / dual-axis tracking. Single-axis or dual-axis solar tracking devices can improve the utilization rate of incident light by 10–25%, and are recommended for large-scale systems.

[0035] The heat collection piping system 3 includes a heat-absorbing tube, a transparent protective tube, and a working fluid channel. The heat-absorbing tube (inner layer) has a high-absorption-rate black selective coating (such as TiNOx). The transparent protective tube (outer layer) is made of high borosilicate glass and is evacuated to form an insulation cavity. The working fluid channel is filled with a heat transfer medium, such as high-temperature heat transfer oil, water, or molten salt.

[0036] The heat collection pipe system has a pipe diameter of 20-40 mm and a pipe length depending on the module design; the thermal efficiency (heat conversion after receiving infrared light) is >70%; the working temperature of the working fluid is 80°C-300°C (selected according to the application scenario).

[0037] The heat output method of the heat collection pipeline system 3 is as follows: hot water or hot oil is output through the heat exchanger, which can be connected to the Organic Rankine Cycle (ORC) system for power generation.

[0038] In this embodiment, the matching structure design of the plate concentrator and the heat collection tube... The plate concentrator 2 adopts a linear Fresnel plate concentrator structure, and the mirror material is anodized aluminum substrate + silver-plated reflective layer + SiO2 protective film. It uses Fresnel structure + multi-mirror design to achieve large-area light collection and small focal point concentration. The system geometric parameters are strictly matched with the focal point size of the heat collection tube to improve infrared utilization efficiency. The semi-transparent photovoltaic module has uniform transmitted light distribution, which is suitable for linear concentrating structure design.

[0039] The collector tubes are arranged in a fixed, straight-line configuration, with multiple tubes arranged parallel below the concentrator module, the spacing determined by the concentrator's focal length. A single-focal-line or multi-focal-line arrangement can be used. Single-focal-line arrangement: All mirrors focus on the center of a single collector tube, increasing heat power density. Multi-focal-line arrangement: Different mirror groups focus on adjacent collector tubes, suitable for large-area arrangements to reduce heat load. The collector tubes are made of a high-absorptivity / low-emissivity composite material, resistant to high temperatures and aging. Medium- and low-temperature heat energy (150-250°C) is transferred via heat transfer oil, resulting in low heat loss, suitable for industrial heating or ORC power generation. A vacuum-sealed glass protective layer forms an insulating cavity, effectively reducing convective heat loss.

[0040] The supporting structure uses an aluminum alloy frame to support the entire system, providing wind resistance and easy installation. Heat-conducting grooves and insulation layers can be installed at the bottom of the thermal modules to reduce heat loss.

[0041] The heat-conducting structure 5 includes a high-temperature corrosion-resistant metal pipe or ceramic pipe, which transports heat energy to the sand thermal storage unit. The heat storage medium of the sand thermal storage unit 4 is natural quartz sand, alumina sand, or composite sand; it is equipped with an external insulation layer, an insulation tank, and a temperature control system; it can be used for heat release: heating / power generation / drying, etc.

[0042] The sand thermal storage unit 4 includes a thermal storage tank 401. The outer shell of the thermal storage tank 401 is made of stainless steel (304 / 316) or high-temperature resistant carbon steel. The interior of the thermal storage tank 401 includes a filling area and a pipe structure. The filling area is uniformly filled with dried and screened high heat capacity sand (such as quartz sand). The pipe structure is embedded with U-shaped or coiled heat exchange pipes 403 for heat transfer of the working fluid. The exterior of the thermal storage tank 401 is provided with an insulation layer 404, which adopts a structure of ceramic fiber blanket + polyurethane foam + external protective plate.

[0043] The working principle and method of the system in this embodiment 1. Photovoltaic power generation path: The incident sunlight first reaches the upper semi-transparent photovoltaic module, where the visible light portion is absorbed and converted into electrical energy, which is then output to the inverter device through series and parallel connections. The ultraviolet and infrared bands continue to propagate downwards through the module.

[0044] 2. Photothermal conversion pathway: The transmitted UV and IR light shines on the middle plate concentrator, which focuses the light onto the heat collection tube below. The heat collection tube absorbs heat energy, the working fluid heats up, and the heat energy is output to the heat storage device or heat load equipment.

[0045] 3. Coordinated energy output: Electrical energy can be used for grid-connected power generation or electrical equipment, while thermal energy can be used for heating, hot water supply, or steam power generation.

[0046] In this embodiment, the plate concentrator efficiently focuses the ultraviolet and infrared light transmitted from above onto the surface of the heat collection tube, improving heat collection efficiency. The size, angle, and focal length of the concentrator must precisely correspond to the diameter and position of the heat collection tube to ensure that the light is concentrated without deviation or excessive scattering. This ensures uniform heating of the heat collection tube and avoids localized overheating that could lead to material aging or a decrease in heat transfer efficiency.

[0047] The working principle of the system in this embodiment 1. Daytime solar radiation system: Visible light → photovoltaic modules → power generation Infrared / ultraviolet → Concentration → Heat collection tube → Working fluid heating → Heat transfer to sand storage chamber; 2. Heat energy is transferred to the sand thermal storage unit: The high-temperature working fluid flows through the heat exchange pipes inside the heat storage chamber, and the heat energy is transferred to the sand particles through heat conduction and radiation. The sand particles absorb heat, increase in temperature, and stably store the heat energy.

[0048] 3. At night or during peak load periods: The working fluid inside the thermal storage unit is recirculated, and the heat energy is released to supply industrial heating, building heating, hot water supply or small-scale power generation.

[0049] Example 3 like Figures 1-4 As shown in the figure, the photovoltaic-thermal synergistic system based on sand thermal storage in this embodiment is applied to industrial heating scenarios in western desert regions.

[0050] The system, from top to bottom, includes a semi-transparent photovoltaic cell module 1, a plate concentrator 2, a heat collection pipe system 3, and a sand heat storage unit 4. It also includes auxiliary structures, including a support frame, a heat-conducting structure 5, and a control system.

[0051] Specifically, the semi-transparent photovoltaic cell module 1 adopts a stacked semi-transparent structure. The transparent conductive electrode is FTO glass. The perovskite component in the semi-transparent perovskite light-absorbing layer is a mixed halogen material with a wide bandgap of 1.7eV. The back transparent electrode is a thin silver / ITO composite layer with a thickness of 12nm. The encapsulation material uses double-sided glass + UV-stabilized encapsulating adhesive.

[0052] The plate concentrator 2 is a reflective planar concentrator designed as a fixed flat plate with a surface coated with a high-reflectivity material. The high-reflectivity material consists of an aluminum alloy substrate, a silver mirror reflective coating, and an anti-oxidation SiO2 protective layer. It adopts a linear Fresnel structure, with the focusing angle controlled within ±10° and a concentration ratio of 15 times. The distance between it and the semi-transparent photovoltaic cell module is 20cm, and the installation tilt angle is consistent with the local latitude, in conjunction with dual-axis tracking.

[0053] The heat collection pipe system 3 has a pipe diameter of 32mm. The surface of the heat absorption pipe is coated with a TiNOx high-absorption rate black selective coating. The transparent protective pipe is made of high borosilicate glass and is evacuated inside. The working fluid channel is filled with high-temperature heat transfer oil and the working fluid operating temperature is 250°C.

[0054] The outer shell of the sand storage unit 4 is made of 304 stainless steel, and the interior is filled with quartz sand and embedded with U-shaped heat exchange pipes; the insulation layer is ceramic fiber blanket + polyurethane foam + external protective plate; the heat outlet end is connected to a heat exchanger for industrial heating.

[0055] The supporting frame adopts an aluminum alloy frame structure; the heat-conducting structure is a high-temperature corrosion-resistant metal pipe; and the control system controls the operation of the entire system.

[0056] The thermal energy utilization method of this system is as follows: S1. During the day, when sunlight shines, visible light is absorbed by the semi-transparent photovoltaic cell module and converted into electrical energy, which is then output to the inverter device through series and parallel connection to provide power for industrial equipment. S2, ultraviolet and infrared light shine through the semi-transparent photovoltaic cell module and onto the plate concentrator. The plate concentrator focuses the light onto the heat collection pipe system, which absorbs heat energy and raises the temperature of the internal high-temperature heat transfer oil. S3. The heated high-temperature heat transfer oil transfers heat energy into the sand heat storage unit through a high-temperature corrosion-resistant metal pipe for storage. S4. At night or during peak industrial heating periods, the high-temperature heat transfer oil in the sand thermal storage unit is recirculated, releasing heat energy to provide heat energy for industrial production through the heat exchanger.

[0057] Example 4 like Figures 1-4 As shown, the photovoltaic-thermal synergistic system based on sand thermal storage in this embodiment is applied to a comprehensive energy supply scenario in remote areas, providing residents with electricity and heating.

[0058] The transparent conductive electrode of the semi-transparent photovoltaic cell module 1 is ITO glass, the semi-transparent CIGS light-absorbing layer is a thin silver / ITO composite layer with a thickness of 10nm, and the encapsulation material is double-sided glass + UV-stabilized encapsulating adhesive.

[0059] The plate concentrator 2 is designed with a free-form surface shape and a concentration ratio of 10 times. The distance between it and the semi-transparent photovoltaic cell module is 10cm, and the installation tilt angle is consistent with the local latitude, which is combined with single-axis tracking.

[0060] The diameter of the heat collection pipe system 3 is 25mm. The surface of the heat absorption pipe is coated with a black chrome high-absorption selective coating. The transparent protective pipe is made of high borosilicate glass and is evacuated inside. The working medium channel is filled with water and the working temperature of the working medium is 150°C.

[0061] The outer shell of the sand thermal storage unit 4 is made of 316 stainless steel, and the interior is filled with alumina sand and embedded with coiled heat exchange pipes; the heat outlet is connected to an organic Rankine cycle system for power generation and a heat exchanger for heating.

[0062] The other structures are similar to those in Example 3.

[0063] The thermal energy utilization method of this system is similar to that of Example 2. During the day, the system generates electricity for residents' use and stores the thermal energy in the sand thermal storage unit. At night, the system releases the thermal energy for residents' heating and to drive the organic Rankine cycle system to generate electricity.

[0064] Example 5 like Figures 1-4 As shown, the photovoltaic-thermal synergistic system based on sand thermal storage in this embodiment is applied to agricultural greenhouses to provide electricity and heating for the greenhouses, as well as heat energy for drying agricultural products.

[0065] The transparent conductive electrode of the semi-transparent photovoltaic cell module 1 is FTO glass. The perovskite component in the semi-transparent perovskite light-absorbing layer is a mixed halogen material with a wide bandgap of 1.8eV. The transparent electrode on the back is a thin silver / ITO composite layer with a thickness of 14nm. The encapsulation material uses double-sided glass + UV-stabilized encapsulating adhesive.

[0066] The plate concentrator 2 is a reflective planar concentrator designed as a fixed flat plate with a concentration ratio of 20 times. The distance between it and the semi-transparent photovoltaic cell module is 30cm, and the installation tilt angle is consistent with the local latitude, and it is equipped with single-axis tracking.

[0067] The heat collection pipe system 3 has a pipe diameter of 40mm. The surface of the heat absorption pipe is covered with a nano-selective absorption film. The transparent protective pipe is made of high borosilicate glass and is evacuated inside. The working medium channel is filled with molten salt and the working medium temperature is 300°C.

[0068] The outer shell of the sand storage tank of unit 4 is made of high-temperature resistant carbon steel, and the inside is filled with composite sand particles and embedded with coil-type heat exchange pipes; the heat outlet end is connected to a heat exchanger for greenhouse heating and agricultural product drying.

[0069] The other structures are similar to those in Example 3.

[0070] The thermal energy utilization method of this system is similar to that of Example 2. During the day, the system generates electricity to provide power for the greenhouse's lighting, ventilation and other equipment. The thermal energy is stored in the sand thermal storage unit and released at night to heat the greenhouse. At the same time, it provides thermal energy for drying agricultural products during the harvest season.

[0071] This invention significantly improves the overall utilization rate of spectral energy. By adopting a spectral separation structure of semi-transparent photovoltaic cells and plate concentrators, about 40% of the visible light energy in sunlight can be used for power generation, while the remaining about 50% of the infrared and ultraviolet parts can be used for heat collection. The overall energy utilization rate of the system can reach ≥85% (photovoltaic + photothermal), which is significantly higher than that of traditional pure photovoltaic (about 15-20%) or pure photothermal systems (40-60%).

[0072] This invention features a compact structure, high integration, and strong installation adaptability: the system adopts a vertical stacked structure design, integrating photovoltaic, concentrating, and thermal collection components, occupying a small area, and is suitable for various spaces such as building roofs, deserts, and agricultural greenhouses.

[0073] The sand thermal storage system of this invention is low in cost, long in life and high in thermal stability: compared with the traditional molten salt system, the sand thermal storage system has readily available, environmentally friendly and safe materials, can be repeatedly heated at high temperature without decomposition, and is suitable for areas with strong sunlight and large temperature difference between day and night.

[0074] This invention enables day and night energy supply and peak-shaving output: the system, through a thermal storage sand bed module in conjunction with a heat exchange and control system, can store heat during the day and release heat energy at night or on cloudy days for heating, drying or driving the ORC system to generate electricity, thereby improving the system's spatiotemporal flexibility.

[0075] This invention is highly adaptable, easy to maintain, and safe to operate: the system materials are designed to be resistant to high temperatures and corrosion, and the modular structure facilitates maintenance and replacement, making it suitable for long-term operation in windy and sandy environments, high-altitude areas, and uninhabited areas.

[0076] This invention features high scalability and flexible access capabilities: the modular photovoltaic thermal unit + independent sand thermal storage chamber design can be flexibly combined, supporting the parallel access of multiple systems to large-scale energy systems, and can also be connected to microgrid / micro heating network systems, making it suitable for various commercial deployment scenarios.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic-thermal synergistic system based on sand thermal energy storage, characterized in that, The system includes, from top to bottom, a semi-transparent photovoltaic cell module, a plate concentrator, a heat collection pipe system, and a sand heat storage unit. The semi-transparent photovoltaic cell module absorbs visible light and converts it into electrical energy. Ultraviolet and infrared light pass through the semi-transparent photovoltaic cell module and are focused by the plate concentrator onto the heat collection pipe system. The heat collection pipe system heats the internal working fluid, and the working fluid transfers the heat energy to the sand heat storage unit for storage through a heat-conducting structure. The sand heat storage unit releases heat energy at night or during peak load periods.

2. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 1, characterized in that, The semi-transparent photovoltaic cell module adopts a stacked semi-transparent structure, including a transparent conductive electrode, an electron / hole transport layer, a semi-transparent perovskite or CIGS light-absorbing layer, an electron / hole transport layer, and a transparent electrode on the back.

3. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 1, characterized in that, The plate concentrator is a reflective planar concentrator with a surface coated with a high-reflectivity material, which consists of an aluminum alloy substrate, a silver mirror reflective coating, and an anti-oxidation SiO2 protective layer. The plate concentrator adopts a linear Fresnel structure. The distance between the plate concentrator and the semi-transparent photovoltaic cell module is 10-30 cm. The plate concentrator is equipped with single-axis or dual-axis tracking.

4. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 1, characterized in that, The heat collection pipeline system includes a heat absorption tube, a transparent protective tube, and a working fluid channel; the surface of the heat absorption tube is coated with a high-absorption-rate black selective coating, which is TiNOx, black chromium, or a nano-selective absorption film; the transparent protective tube is a high borosilicate glass tube and is evacuated inside; the working fluid channel is filled with high-temperature heat transfer oil, water, or molten salt.

5. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 1, characterized in that, The sand thermal storage unit includes a thermal storage tank, which is filled with quartz sand, alumina sand or composite sand particles, and U-shaped or coiled heat exchange pipes are embedded inside the thermal storage tank.

6. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 5, characterized in that, The U-shaped or coiled heat exchange pipes within the sand thermal storage unit are connected to an organic Rankine cycle system for power generation or to a heat exchanger for heating / drying / industrial hot water supply.

7. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 5, characterized in that, The heat storage tank is equipped with an insulation layer, which consists of a ceramic fiber blanket, polyurethane foam, and an external protective panel.

8. The photovoltaic-thermal synergistic system based on sand thermal energy storage according to claim 1, characterized in that, It also includes a support frame, which is an aluminum alloy structure.

9. The method for utilizing thermal energy in a photovoltaic-thermal synergistic system based on sand thermal storage according to any one of claims 1-8, characterized in that, Includes the following steps: S1. During the day, visible light is absorbed by the semi-transparent photovoltaic cell module and converted into electrical energy, which is then output to the inverter. S2, ultraviolet light and infrared light pass through the components and irradiate the plate concentrator, and are focused onto the heat collection pipe system to heat the internal working fluid; S3. The heating working fluid introduces heat energy into the sand thermal storage unit for storage through a heat-conducting structure. S4. At night or during peak load periods, the working fluid in the sand thermal storage unit circulates and releases heat energy to supply industrial heating, building heating, hot water supply, or small-scale power generation.

10. The method for utilizing thermal energy in a photovoltaic-thermal synergistic system based on sand thermal storage according to claim 9, characterized in that, In step S3, thermal energy is transferred to the sand particles through conduction and radiation. In step S4, the rate and direction of thermal energy release are adjusted by controlling the structure.

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