Photovoltaic photo-thermal system coupled with biomass phase change heat storage and working method of photovoltaic photo-thermal system

Abstract

The invention belongs to the technical field of new energy utilization, and discloses a photovoltaic photo-thermal system coupled with biomass phase change heat storage and a working method of the photovoltaic photo-thermal system. In the photovoltaic photo-thermal system, a photovoltaic power generation module comprises a photovoltaic assembly, an inverter and a combiner box. The photo-thermal heat collection module comprises a paraboloid condensation heat collector, a circulation pipeline and a heat exchange cavity. In the biomass phase change heat storage module, a porous carbon paraffin composite phase change material is adopted as a biomass phase change heat storage material; and the regulation and control module is used for obtaining an energy distribution strategy by adopting an energy coupling algorithm, executing the energy distribution strategy based on PLC control to carry out closed-loop feedback regulation and control, and realizing dynamic matching of energy supply and demand. According to the technical scheme disclosed by the invention, by optimizing a photovoltaic photo-thermal coupling mode and a biomass phase change heat storage material formula, the solar comprehensive utilization efficiency and the heat storage stability are improved, and the actual application requirements can be met.

Description

Technical Field

[0001] This invention belongs to the field of new energy utilization technology, and specifically relates to a photovoltaic-thermal system coupled with biomass phase change thermal storage and its working method. Background Technology

[0002] Solar energy, as a renewable energy source, has advantages such as being clean and having abundant reserves, but its intermittency and volatility limit its large-scale application.

[0003] Photovoltaic-thermal integration (PV-T) technology can simultaneously realize the photovoltaic and photothermal conversion of solar energy, improving the efficiency of solar energy utilization. However, existing PV-T systems lack efficient energy storage units, making it difficult to solve the technical problem of the mismatch between energy supply and demand in time and space.

[0004] Currently, phase change thermal energy storage technology is a key means to solve the problem of renewable energy consumption. Among them, biomass-based phase change thermal energy storage materials have attracted attention due to their advantages such as wide availability, low cost, and environmental friendliness. However, existing traditional biomass phase change thermal energy storage materials have problems such as low thermal conductivity, easy leakage during phase change, and poor cycle stability. Moreover, the coupling method between existing photovoltaic and photothermal systems and biomass phase change thermal energy storage materials is relatively simple, resulting in low energy conversion and distribution efficiency, which cannot meet the needs of practical applications. In summary, developing an efficient and stable coupling scheme between photovoltaic and photothermal systems and biomass phase change thermal energy storage materials has become an urgent technical problem to be solved in the current renewable energy field. Summary of the Invention

[0005] The purpose of this invention is to provide a photovoltaic-thermal system coupled with biomass phase change thermal storage and its operating method, thereby solving one or more of the aforementioned technical problems. The technical solution disclosed in this invention improves the overall efficiency of solar energy utilization and the stability of thermal storage by optimizing the photovoltaic-thermal coupling method and the biomass phase change thermal storage material formulation, thus meeting practical application requirements.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this invention provides a photovoltaic-thermal system coupled with biomass phase change thermal storage, comprising: a photovoltaic power generation module, a solar thermal collector module, a biomass phase change thermal storage module, and a control module; wherein, The photovoltaic power generation module includes: photovoltaic modules, inverters, and combiner boxes; wherein, the photovoltaic modules are used to convert solar energy into direct current, the combiner boxes are used to collect the direct current from multiple photovoltaic modules, and the inverters are used to convert the combined direct current from the combiner boxes into alternating current. The solar thermal collector module includes: a parabolic concentrator, a circulation pipeline, and a heat exchange chamber; wherein, the focal point of the parabolic concentrator is in contact with the back of the photovoltaic module, and the circulation pipeline is used to transport a heat-conducting medium; the heat-conducting medium is used to absorb heat on the back of the photovoltaic module and is transported to the heat exchange chamber through the circulation pipeline for heat release; The biomass phase change thermal storage module is used to absorb and store the heat released by the heat-conducting medium in the heat exchange cavity through the biomass phase change thermal storage material, and is also used to release the stored heat through the biomass phase change thermal storage material to supply energy to the user side; wherein, the biomass phase change thermal storage material is a porous carbon paraffin composite phase change material. The control module is used to obtain an energy allocation strategy using an energy coupling algorithm, and to perform closed-loop feedback control based on PLC control to achieve dynamic matching of energy supply and demand. The energy coupling algorithm uses a fuzzy PID algorithm, with irradiance intensity, user heat load and biomass phase change thermal storage material temperature as inputs, and heat transfer medium flow rate and photovoltaic power allocation ratio as outputs to obtain the energy allocation strategy.

[0007] A further improvement of the technical solution of the present invention is that, in the photovoltaic power generation module, the photovoltaic module adopts a double-glass double-sided heterojunction photovoltaic cell, and the surface is coated with an anti-reflection coating.

[0008] A further improvement of the technical solution of the present invention is that, in the photovoltaic power generation module, the inverter adopts a high-frequency isolated inverter.

[0009] A further improvement of the technical solution of the present invention is that, in the solar thermal collector module, the circulation pipeline is equipped with an electromagnetic flow valve, which is used to control the flow rate of the heat-conducting medium in the circulation pipeline under the control of the control module; wherein, when the back temperature of the photovoltaic module is greater than or equal to a first preset threshold, the control module controls the electromagnetic flow valve to increase the flow rate of the heat-conducting medium; when the temperature of the biomass phase change thermal storage material is greater than or equal to a second preset threshold, the control module controls the electromagnetic flow valve to decrease the flow rate of the heat-conducting medium.

[0010] A further improvement of the technical solution of the present invention is that the flow rate of the heat-conducting medium is adjustable within a range of 0.5m / s to 2m / s.

[0011] A further improvement of the technical solution of the present invention is that the heat-conducting medium is graphene-modified heat-conducting oil.

[0012] A further improvement to the technical solution of this invention lies in that the specific preparation process of the porous carbon-paraffin composite phase change material includes: Sugarcane bagasse is dried, carbonized, pulverized and sieved to obtain powdered carbonized biomass material; KOH is added as a modifier after carbonization during the drying, carbonization, pulverization and sieving process of sugarcane bagasse. Excess paraffin wax is ultrasonically mixed with powdered carbonized biomass material until homogeneous. Then, the molten paraffin wax phase change core material is vacuum impregnated into the porous carbonized biomass material to obtain a composite phase change material. Excess paraffin phase change core material is removed from the composite phase change material to obtain a porous carbon paraffin composite phase change material.

[0013] A further improvement to the technical solution of the present invention is that the biomass phase change thermal storage module includes: a thermal storage tank and a biomass phase change thermal storage material; wherein, The biomass phase change thermal storage material is encapsulated and disposed within the thermal storage tank through an encapsulation structure. The heat storage tank is equipped with a heat absorption pipeline, which is used to absorb the heat released by the heat conduction medium in the heat exchange chamber through the built-in circulating heat exchange medium, and store the heat in the biomass phase change heat storage material. The heat storage tank is also equipped with a heat release pipeline, which is used to absorb the heat released by the biomass phase change heat storage material through the built-in circulating heat exchange medium and deliver the heat to the user side.

[0014] A further improvement of the technical solution of the present invention is that the photovoltaic power distribution ratio includes: grid connection ratio, self-use drive ratio and energy storage reserve ratio.

[0015] In a second aspect, the present invention provides a method for operating the photovoltaic-thermal system coupled with biomass phase change thermal storage as described in the first aspect of the present invention, comprising: Solar energy is received through photovoltaic modules; the front of the photovoltaic modules converts light energy into electrical energy, which is then output through an inverter and a combiner box; the back of the photovoltaic modules absorbs solar thermal energy through a parabolic concentrator and transfers it to a heat-conducting medium. The heat transfer medium flows in the circulation pipeline and transfers heat to the biomass phase change thermal storage material through the heat exchange chamber. When the temperature of the biomass phase change thermal storage material reaches the phase change temperature, the biomass phase change thermal storage material undergoes a phase change and stores latent heat. When there is a heat demand on the user side, the biomass phase change thermal storage material releases heat and transfers it to the heat-using equipment. The control module employs an energy coupling algorithm to obtain an energy allocation strategy. Based on PLC control, the energy allocation strategy is executed to perform closed-loop feedback control, thereby achieving dynamic matching of energy supply and demand. The energy coupling algorithm uses a fuzzy PID algorithm, with irradiance intensity, user heat load, and biomass phase change thermal storage material temperature as inputs, and heat transfer medium flow rate and photovoltaic power allocation ratio as outputs to obtain the energy allocation strategy.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a photovoltaic-thermal system coupled with biomass phase change thermal storage. The system integrates a photovoltaic power generation module, a solar thermal collector module, a biomass phase change thermal storage module, and a control module. It utilizes a porous carbon-paraffin composite phase change material. Through modification and optimization of the biomass phase change thermal storage material, the cost of the material is reduced, achieving efficient capture, conversion, and storage of photovoltaic-thermal energy. Furthermore, the focal point of the parabolic concentrator is attached to the back of the photovoltaic module, allowing for the recovery of waste heat from the photovoltaic cells. Additionally, a novel staged energy coupling strategy, combined with a control algorithm, addresses issues such as energy supply-demand mismatch and poor stability of the thermal storage material during photovoltaic-thermal utilization, thereby improving the overall efficiency of solar energy utilization and the stability of thermal storage.

[0017] The technical solution of this invention is applicable to multiple scenarios such as industrial waste heat recovery and building heating, and has significant economic and environmental benefits, which can meet the needs of practical applications.

[0018] In a further improved technical solution of the present invention, a double-glass, double-sided heterojunction photovoltaic cell is used, and the surface is coated with an anti-reflection film, which can simultaneously absorb direct light from the front and reflected light from the back, thereby increasing the photoelectric conversion efficiency to over 24%.

[0019] In a further improved technical solution of the present invention, the inverter adopts a high-frequency isolated inverter, which can reduce power conversion losses.

[0020] In a further improved technical solution of the present invention, graphene-modified heat transfer oil is used as a heat transfer medium, and its thermal conductivity is increased by 30% to 50% compared with traditional heat transfer oil; in addition, an electromagnetic flow valve is provided in the circulation pipeline to precisely adjust the flow rate of the medium.

[0021] In a further improved technical solution of the present invention, the core of the biomass phase change thermal storage module is a sugarcane bagasse carbon-based skeleton composite paraffin phase change core material. The porous structure of the sugarcane bagasse carbon-based skeleton can effectively adsorb the phase change core material and prevent leakage. After multiple phase change cycles, a shape-stable composite phase change material is obtained. In addition, the control module can dynamically adjust the energy distribution strategy according to real-time irradiance intensity, user heat load and other data to achieve the coordinated supply of photovoltaic power and solar thermal energy.

[0022] This invention also discloses a working method for a photovoltaic-thermal system coupled with biomass phase change thermal storage, including four steps: photovoltaic-thermal energy capture, heat transfer and storage, energy release and distribution, and dynamic regulation and optimization. Through phased energy coupling and regulation, the efficient capture, conversion and storage of solar energy are achieved. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the framework of a photovoltaic-thermal system coupled with biomass phase change thermal storage in an embodiment of the present invention. The explanations of the reference numerals in the figure are as follows: 1. Photovoltaic power generation module; 2. Solar thermal collector module; 3. Biomass phase change thermal storage module; 4. Control module. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention; obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Based on the technical solutions disclosed in the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

[0027] Please see Figure 1 The present invention provides a photovoltaic-thermal system coupled with biomass phase change thermal storage, comprising: A photovoltaic power generation module 1 includes: a photovoltaic module, an inverter, and a combiner box; wherein, the photovoltaic module serves as a power generation unit, used to convert solar energy into direct current (DC); the combiner box is used to collect DC power from multiple photovoltaic modules; the inverter is used to convert the DC power collected by the combiner box into grid-connected or usable alternating current (AC); illustratively, the photovoltaic power generation module 1 is used to convert solar energy into electrical energy, and the photovoltaic module, inverter, and combiner box together complete the conversion from solar energy to usable electrical energy. In a preferred embodiment of the present invention, the photovoltaic module uses a double-glass bifacial heterojunction photovoltaic cell with an anti-reflection coating on its surface. Additionally, the inverter can be a high-frequency isolated inverter to reduce power conversion losses.

[0028] The solar thermal collector module 2 includes a parabolic concentrator, a circulation pipeline, and a heat exchange chamber. The focal point of the parabolic concentrator is attached to the back of the photovoltaic module. The circulation pipeline transports a heat-conducting medium. The heat-conducting medium absorbs heat on the back of the photovoltaic module and is then transported through the circulation pipeline to the heat exchange chamber for heat release. The circulation pipeline is equipped with an electromagnetic flow valve to precisely regulate the flow rate of the heat-conducting medium. Explained, by attaching the focal point of the parabolic concentrator to the back of the photovoltaic module, the solar thermal collector module 2 and the photovoltaic power generation module 1 are coupled. The heat-conducting medium used is graphene-modified heat-conducting oil. In this module, the parabolic concentrator focuses solar energy onto the back of the photovoltaic module, transferring heat to the graphene-modified heat-conducting oil. The circulation pipeline transports the heated graphene-modified heat-conducting oil to the heat exchange chamber, which facilitates heat exchange and the coordinated collection and transmission of solar thermal energy. The focal point of the parabolic concentrator is attached to the back of the photovoltaic module, which can recover the waste heat of the photovoltaic cell.

[0029] A biomass phase change thermal storage module 3 is used to absorb and store the heat released by the heat-conducting medium in the heat exchange cavity through a biomass phase change thermal storage material, and also to release the stored heat through the biomass phase change thermal storage material to supply energy to the user side; wherein, the biomass phase change thermal storage material is a porous carbon-paraffin composite phase change material; in a specific exemplary technical solution, the biomass phase change thermal storage module 3 includes: a thermal storage tank and a biomass phase change thermal storage material, the biomass phase change thermal storage material being encapsulated in the thermal storage tank by an encapsulation structure; the thermal storage tank is provided with a heat absorption pipeline, the heat absorption pipeline being used to absorb the heat released by the graphene-modified heat-conducting oil in the heat exchange cavity through a circulating medium therein, and store it in the biomass phase change thermal storage material; the thermal storage tank is also provided with a heat release pipeline, the heat release pipeline being used to absorb the heat released by the biomass phase change thermal storage material through a circulating medium therein and deliver it to the user.

[0030] The control module 4 is used to obtain an energy allocation strategy using an energy coupling algorithm. Based on a PLC (Programmable Logic Controller), the energy allocation strategy is executed through closed-loop feedback control to achieve dynamic matching of energy supply and demand. The energy coupling algorithm employs a fuzzy PID (Fuzzy Proportional Integral Derivative) algorithm, using irradiance intensity, user heat load, and biomass phase change thermal storage material temperature as inputs, and heat transfer medium flow rate and photovoltaic power allocation ratio as outputs to obtain the energy allocation strategy. In a specific exemplary technical solution, the control module 4 is electrically connected to the photovoltaic power generation module 1, the solar thermal collector module 2, and the biomass phase change thermal storage module 3, and includes a sensor group and a controller. The sensor group includes temperature, pressure, and irradiance sensors, etc., and the controller has a built-in PLC control system and energy coupling algorithm.

[0031] In a specific exemplary technical solution of the present invention, the circulation pipeline of the solar thermal collector module is equipped with an electromagnetic flow valve, which is electrically connected to the controller of the control module. The flow rate of the heat transfer medium can be adjusted according to the temperature on the back of the photovoltaic module, and the flow rate adjustment range is 0.5~2m / s.

[0032] In a specific exemplary technical solution of the present invention, the inner wall of the heat storage tank is provided with a heat insulation layer, which is a composite structure of aerogel felt and vacuum insulation board with a thermal conductivity ≤0.02W / (m·K); the outside of the tank is provided with a heat release pipeline, which is connected to the user-side heating / heat consumption equipment.

[0033] In a specific exemplary technical solution of the present invention, the preparation of biomass phase change thermal storage material includes the following steps: S1, a porous carbon-based framework is prepared by drying, carbonizing, and pulverizing sugarcane bagasse. The carbonization temperature is 750℃ and the holding time is 2h. KOH is added as a modifier after carbonization. S2, the molten phase change core material is vacuum impregnated into the carbon-based skeleton at an impregnation pressure of -0.1 MPa for 1 hour; S3. Place the composite phase change material in an oven at 80°C to remove excess paraffin until there are no traces of excess paraffin overflow on the filter paper. Then, the porous carbon / paraffin composite phase change material made from modified sugarcane bagasse is obtained.

[0034] In a specific exemplary technical solution, the preparation steps of biomass phase change thermal storage material are as follows: Step 1: Take sugarcane bagasse, dry and crush it to a particle size of 200 mesh, place it in a tube furnace, heat it to 750℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and hold it for 2 hours to prepare a porous carbon-based framework.

[0035] Step 2: Mix KOH and carbonized sugarcane bagasse evenly at a mass ratio of 1:4, place the mixture in a ceramic sample boat, and then place it in a tube furnace. In a tube furnace under a nitrogen atmosphere, incubate at 2°C / min. 1 The temperature was increased to 800℃ at a rate of [missing information], held for 2 hours, and then increased to 5℃·min [missing information]. 1 After being cooled to room temperature at a certain rate, a mixture of KOH and carbon material was obtained; then it was placed in a Buchner funnel and washed with deionized water until pH=7, and then dried in a forced-air drying oven to finally obtain the modified carbonized biomass carrier material.

[0036] Step 3: The pre-prepared carbonized biomass carrier material is crushed and sieved to obtain powdered carbonized biomass material. Then, it is placed in a beaker with an excess of paraffin (e.g., carbonized biomass mass: paraffin = 1:20), and then vibrated in an ultrasonic oscillator at 70℃ for 30 minutes to mix the carbonized biomass material and paraffin evenly. After that, the composite material is vacuum-insulated in a vacuum drying oven at 80℃ and -0.1MPa for 1 hour. After the temperature of the vacuum drying oven drops to room temperature, the composite material is taken out and placed on filter paper. It is then placed in a forced-air drying oven at 80℃ to remove excess paraffin from the composite material. The filter paper is changed continuously until there are no traces of paraffin overflow on the filter paper, thus obtaining a porous carbon / paraffin composite phase change material made from modified sugarcane bagasse, with a core material loading of 73.59%.

[0037] The performance testing process of this invention embodiment is as follows: The porous carbon / paraffin composite phase change material was placed on filter paper and subjected to a leak test in an 80°C electric forced-air drying oven until no excess paraffin overflowed from the filter paper. The weight of the sample was then measured using an analytical balance, and the corresponding adsorption rate was calculated.

[0038] The sample was crushed into powder and spread evenly on the stage of a scanning electron microscope (SEM). The microstructure of the sample was analyzed using SEM. The sample was characterized using a multifunctional X-ray diffraction (XRD) instrument and a Fourier transform-infrared spectroscopy (FT-IR) instrument to determine and analyze the internal molecular structure and functional group types. The latent heat of phase transition and phase transition temperature of the sample were determined using differential scanning calorimetry (DSC). Thermogravimetric analysis (TG) and Brunauer emmett teller (BET) were used to determine the thermal conductivity of the sample before and after modification, as well as the number and distribution of pores in the material.

[0039] In this invention, high-temperature carbonization is used to treat biomass materials, giving them a distinct porous structure. KOH is then used as a modifier to further modify the carbonized biomass, increasing its porous structure and providing more space and conditions for the adhesion of phase change materials. Single-factor experiments determined the optimal experimental conditions: a carbonization temperature of 750℃ and a modification mass ratio of 1:4. The phase change material and carrier material are composited using a melt impregnation method. A series of characterization tests demonstrate that melt impregnation effectively mixes the two materials, resulting in a composite phase change material. Infrared and X-ray diffraction tests confirm that the melt impregnation process is a simple physical composite process without any chemical reactions or the formation of new functional groups or substances. Thermogravimetric and DSC tests demonstrate that the prepared composite phase change material possesses certain thermal durability and latent heat of phase change.

[0040] In a specific exemplary technical solution of this invention, the working method of photovoltaic-thermal coupled biomass phase change thermal storage includes the following steps: Step 1, Photovoltaic solar thermal energy capture: The photovoltaic module receives solar energy, and its front side converts light energy into electrical energy, which is then output to the grid or energy storage battery through the inverter and combiner box. Its back side absorbs solar thermal energy through the parabolic concentrator and transfers it to the heat transfer medium. Step 2, Heat Transfer and Storage: The heat transfer medium flows in the circulation pipeline and transfers heat to the biomass phase change thermal storage material through the heat exchange chamber; when the temperature of the biomass phase change thermal storage material reaches the phase change temperature, the biomass phase change thermal storage material undergoes a phase change and stores latent heat. The control module monitors the temperature and pressure of the thermal storage tank in real time through sensors. When the temperature exceeds the set threshold, the flow rate of the heat transfer medium is adjusted to reduce the heat input. Step 3, Energy Release and Distribution: When there is a heat demand on the user side, the valve of the heat release pipeline is opened to absorb the heat released by the biomass phase change thermal storage material and transfer it to the heat-using equipment; at the same time, the electrical energy generated by the photovoltaic power generation module can assist in driving the circulating pump, temperature control equipment, etc., to achieve the coordinated supply of electric and thermal energy. Step 4, Dynamic Control and Optimization: Based on real-time irradiance intensity and user energy demand data, the photovoltaic power output ratio and the solar thermal storage / release rate are dynamically adjusted through an energy coupling algorithm. When solar irradiance is insufficient, the heat release mode of the biomass phase change thermal storage material is activated to supplement the energy supply. The energy coupling algorithm of this invention uses irradiance intensity, user heat load, and thermal storage material temperature as inputs, and heat transfer medium flow rate and photovoltaic power distribution ratio as outputs to achieve dynamic matching of energy supply and demand.

[0041] In a specific exemplary technical solution, the assembly and testing process of the photovoltaic-thermal coupled biomass phase change thermal storage device is as follows: The photovoltaic power generation module uses a double-glass bifacial heterojunction photovoltaic module (size 166mm×166mm, power 300W) and is equipped with a 5kW high-frequency isolated inverter (conversion efficiency ≥98.5%). The solar thermal collector module uses a parabolic concentrator (focal length 0.8m, concentration ratio 10:1), with graphene-modified heat transfer oil as the heat transfer medium, graphene addition of 3% (by mass percentage), and thermal conductivity of 0.68W / (m·K). The biomass phase change thermal storage module has a 500L storage tank and contains the biomass phase change thermal storage material prepared in the above embodiments. The control module is equipped with a PT100 temperature sensor (accuracy ±0.1℃), a pressure sensor (accuracy ±0.01MPa), an irradiance sensor (accuracy ±5W / m²), and a Siemens S7-1200 PLC controller.

[0042] In outdoor performance testing, the device was placed in Tsinghua Garden, Haidian District, Beijing (39.99°N, 116.31°E) and tested under conditions of irradiance of 800 W / m² and ambient temperature of 25°C; among which, Photovoltaic performance: The front-side photoelectric conversion efficiency of the module is 24.2%, the back-side photoelectric conversion efficiency is 12.5%, and the overall photoelectric efficiency is 20.1%; the inverter output power quality meets the GB / T19939-2005 standard, with total harmonic distortion ≤2%; Photothermal performance: The parabolic concentrator has a photothermal conversion efficiency of 55.3%, and the temperature difference between the inlet and outlet of the heat transfer medium can reach 32℃. The temperature on the back of the photovoltaic module is reduced from 78℃ to 52℃, which effectively alleviates the thermal degradation problem of photovoltaic cells. Thermal storage performance: The thermal storage efficiency of the biomass phase change thermal storage module is 92.1%, the thermal storage rate is 8.5kW / h, and the heat loss rate of the tank is ≤0.8% / d under full thermal storage conditions.

[0043] In the energy supply stability test, when the user-side heat load is 10kW, the device can stably supply energy for 8.2 hours, and the outlet water temperature fluctuation during the energy supply process is ≤2℃; when the solar irradiance drops to 200W / m², the heat release rate of the thermal storage module is automatically adjusted to 10kW, and the energy supply stability error is ≤2.5%; in the continuous 72-hour test, the device's comprehensive energy utilization efficiency reached 76.8%, which is 38.5% higher than that of the traditional PV-T system (without energy storage).

[0044] In summary, the photovoltaic-thermal coupled biomass phase change thermal storage scheme provided by the embodiments of the present invention has the following significant advancements: (1) High energy utilization efficiency: The photovoltaic photothermal coupling structure is reasonably designed. The parabolic concentrator is attached to the back of the photovoltaic module, which not only recovers the waste heat of the photovoltaic cell, but also improves the photothermal collection efficiency. The comprehensive utilization efficiency of solar energy is 20%~30% higher than that of the traditional PV-T system. The thermal conductivity of the biomass phase change thermal storage material is increased by about 490%, and the thermal storage efficiency reaches more than 92%.

[0045] (2) Excellent performance of thermal storage materials: The use of agricultural sugarcane bagasse carbon-based skeleton encapsulation technology solves the problems of easy leakage and low thermal conductivity of traditional phase change materials.

[0046] (3) Intelligent and precise control: The control module adopts a fuzzy PID algorithm to realize the dynamic allocation of photovoltaic power and solar thermal energy. It can be adjusted in real time according to user needs and environmental conditions, with a power supply stability error of ≤3%. It is suitable for multiple scenarios such as industrial waste heat recovery, building heating, and agricultural greenhouse heating. In addition, the use of sugarcane bagasse to prepare biomass phase change thermal storage materials realizes the resource utilization of waste, reduces the environmental pollution caused by sugarcane bagasse, has the economic feasibility for large-scale promotion, and has significant environmental and economic benefits.

[0047] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A photovoltaic-thermal system coupled with biomass phase change thermal storage, characterized in that, include: Photovoltaic power generation modules, solar thermal collector modules, biomass phase change thermal storage modules, and control modules; among them, The photovoltaic power generation module includes: photovoltaic modules, inverters, and combiner boxes; wherein, the photovoltaic modules are used to convert solar energy into direct current, the combiner boxes are used to collect the direct current from multiple photovoltaic modules, and the inverters are used to convert the combined direct current from the combiner boxes into alternating current. The solar thermal collector module includes: a parabolic concentrator, a circulation pipeline, and a heat exchange chamber; wherein, the focal point of the parabolic concentrator is in contact with the back of the photovoltaic module, and the circulation pipeline is used to transport a heat-conducting medium; the heat-conducting medium is used to absorb heat on the back of the photovoltaic module and is transported to the heat exchange chamber through the circulation pipeline for heat release; The biomass phase change thermal storage module is used to absorb and store the heat released by the heat-conducting medium in the heat exchange cavity through the biomass phase change thermal storage material, and is also used to release the stored heat through the biomass phase change thermal storage material to supply energy to the user side; wherein, the biomass phase change thermal storage material is a porous carbon paraffin composite phase change material. The control module is used to obtain an energy allocation strategy using an energy coupling algorithm, and to perform closed-loop feedback control based on PLC control to achieve dynamic matching of energy supply and demand. The energy coupling algorithm uses a fuzzy PID algorithm, with irradiance intensity, user heat load and biomass phase change thermal storage material temperature as inputs, and heat transfer medium flow rate and photovoltaic power allocation ratio as outputs to obtain the energy allocation strategy.

2. The photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, In the photovoltaic power generation module, the photovoltaic module adopts a double-glass bifacial heterojunction photovoltaic cell, and the surface is coated with an anti-reflection coating.

3. The photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, In the photovoltaic power generation module, the inverter is a high-frequency isolated inverter.

4. A photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, In the solar thermal collector module, the circulation pipeline is equipped with an electromagnetic flow valve, which is used to control the flow rate of the heat-conducting medium in the circulation pipeline under the control of the control module. Specifically, when the back surface temperature of the photovoltaic module is greater than or equal to a first preset threshold, the control module controls the electromagnetic flow valve to increase the flow rate of the heat-conducting medium; when the temperature of the biomass phase change thermal storage material is greater than or equal to a second preset threshold, the control module controls the electromagnetic flow valve to decrease the flow rate of the heat-conducting medium.

5. A photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 4, characterized in that, The flow rate of the heat-conducting medium can be adjusted within the range of 0.5 m / s to 2 m / s.

6. A photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, The heat-conducting medium is graphene-modified heat-conducting oil.

7. A photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, The specific preparation process of the porous carbon-paraffin composite phase change material includes: Sugarcane bagasse is dried, carbonized, pulverized and sieved to obtain powdered carbonized biomass material; KOH is added as a modifier after carbonization during the drying, carbonization, pulverization and sieving process of sugarcane bagasse. Excess paraffin wax is ultrasonically mixed with powdered carbonized biomass material until homogeneous. Then, the molten paraffin wax phase change core material is vacuum impregnated into the porous carbonized biomass material to obtain a composite phase change material. Excess paraffin phase change core material is removed from the composite phase change material to obtain a porous carbon paraffin composite phase change material.

8. A photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, The biomass phase change thermal storage module includes: a thermal storage tank and biomass phase change thermal storage material; wherein... The biomass phase change thermal storage material is encapsulated and disposed within the thermal storage tank through an encapsulation structure. The heat storage tank is equipped with a heat absorption pipeline, which is used to absorb the heat released by the heat conduction medium in the heat exchange chamber through the built-in circulating heat exchange medium, and store the heat in the biomass phase change heat storage material. The heat storage tank is also equipped with a heat release pipeline, which is used to absorb the heat released by the biomass phase change heat storage material through the built-in circulating heat exchange medium and deliver the heat to the user side.

9. A photovoltaic-thermal system coupled with biomass phase change thermal storage according to claim 1, characterized in that, The photovoltaic power allocation ratio includes: grid connection ratio, self-use drive ratio, and energy storage backup ratio.

10. A method for operating the photovoltaic-thermal system coupled with biomass phase change thermal storage as described in claim 1, characterized in that, include: Solar energy is received through photovoltaic modules; the front of the photovoltaic modules converts light energy into electrical energy, which is then output through an inverter and a combiner box; the back of the photovoltaic modules absorbs solar thermal energy through a parabolic concentrator and transfers it to a heat-conducting medium. The heat transfer medium flows in the circulation pipeline and transfers heat to the biomass phase change thermal storage material through the heat exchange chamber. When the temperature of the biomass phase change thermal storage material reaches the phase change temperature, the biomass phase change thermal storage material undergoes a phase change and stores latent heat. When there is a heat demand on the user side, the biomass phase change thermal storage material releases heat and transfers it to the heat-using equipment. The control module employs an energy coupling algorithm to obtain an energy allocation strategy. Based on PLC control, the energy allocation strategy is executed to perform closed-loop feedback control, thereby achieving dynamic matching of energy supply and demand. The energy coupling algorithm uses a fuzzy PID algorithm, with irradiance intensity, user heat load, and biomass phase change thermal storage material temperature as inputs, and heat transfer medium flow rate and photovoltaic power allocation ratio as outputs to obtain the energy allocation strategy.

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