Test method for regulating and controlling solar spectrum frequency division through nanometer magnetofluid

Abstract

The invention discloses a nano-magnetofluid regulated solar spectrum frequency division test method, which is characterized in that a solar simulator is adopted to irradiate a frequency divider at fixed intensity, and the frequency division frequency division test is performed under the condition that a nano-magnetofluid working medium in the frequency divider is regulated to be different in concentration. A heat energy value exported by the frequency divider and an electric energy value generated by the solar panel behind the frequency divider within a specific irradiation time are tested, and the corresponding nanometer magnetofluid working medium concentration when the photoelectric photo-thermal comprehensive performance efficiency is the maximum value is calculated as the optimal nanometer magnetofluid working medium concentration; the irradiation intensity of the solar simulator is adjusted to repeat the test, and the optimal nanometer magnetofluid working medium concentration under different solar intensities is obtained. According to the invention, how to better absorb and utilize the solar spectrum by regulating and controlling the concentration of the nano magnetic fluid under different illumination conditions can be better researched, so that solar energy absorption, conversion and utilization can be more efficiently realized after the nano magnetic fluid is applied to a frequency division type and thermal decoupling type photovoltaic thermal system.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic thermal frequency division test, and in particular to a nano-magnetic fluid control solar spectrum frequency division test method. Background Art

[0002] Energy and environmental issues are becoming increasingly severe. As one of the main renewable energy sources, solar energy has the advantages of huge reserves, wide distribution, clean and pollution-free, and plays an important role in energy conservation and consumption reduction. Solar photovoltaic power generation technology is widely used in life and industry. Solar photovoltaic cells are wavelength-dependent, and their spectral response is related to the bandgap width of the material itself. Therefore, only photons with energy greater than the bandgap width of photovoltaic semiconductor materials in the full spectrum of solar radiation can stimulate the photovoltaic effect, while the energy of most of the remaining photons will be converted into heat energy, which will increase the operating temperature of the battery and greatly reduce the open circuit voltage, resulting in a decrease in power generation efficiency and energy loss. According to research statistics, for silicon solar cells currently commonly used, every 1°C increase in temperature will cause the photoelectric conversion efficiency of the battery to decrease by 0.45%. At the same time, photovoltaic cells will also age and shorten their service life due to long-term operation under high temperature conditions.

[0003] Traditional solar photovoltaic thermal systems usually remove the heat generated by solar panels by setting a water layer on the back of the solar panels and connecting them to a water circulation system. This not only improves the photoelectric conversion efficiency of the cells but also obtains thermal energy; however, photovoltaic thermal systems with this structure can only passively absorb the heat generated by solar panels, and the comprehensive utilization efficiency of solar energy still needs to be further improved.

[0004] In order to fundamentally solve the problem of photovoltaic cells absorbing heat and raising the temperature to reduce power generation efficiency, and obtain high-quality thermal energy at the same time, people have further designed a photovoltaic thermal system with frequency division type thermal decoupling. This system sets a frequency divider in front of the solar panel, and uses the solar spectrum frequency division technology to directly incident the band with high spectral response of the photovoltaic cell, namely the "frequency division window", on the battery for photoelectric conversion, and the solar spectrum of the remaining bands is directly absorbed by the frequency divider to obtain heat. In this way, the photovoltaic unit and the photothermal unit are arranged independently and work in parallel, realizing the temperature decoupling of photovoltaic utilization and photothermal utilization. On the one hand, it avoids the absorption of the photovoltaic unusable solar radiation band by the photovoltaic module, resulting in excessive temperature and reduced power generation efficiency. On the other hand, it also removes the limitation of the collection temperature by the working temperature of the photovoltaic cell, thereby obtaining higher temperature thermal energy and expanding the application scope of solar energy.

[0005] In the frequency-dividing thermal decoupling photovoltaic thermal system, there is a technology that uses nano-magnetic fluid to achieve frequency division. Nano-magnetic fluid is composed of magnetic particles and base fluid, and has good selective spectral absorption characteristics. As a new type of working fluid, it has both the magnetic properties of solid magnetic materials and the fluidity of fluids and has good response to external magnetic fields. In this way, it is convenient to use external magnetic fields to adjust the properties of fluid working fluids. In particular, when nano-magnetic fluids use magnetic carbon nanotubes, they can form directional heat transfer channels under the action of magnetic fields, which can better adjust their heat transfer performance. Therefore, it is possible to change the morphology, concentration and base fluid parameters of magnetic nanoparticles to make them have adjustable spectral selective absorption characteristics, photothermal conversion characteristics, and thermomagnetic convection effects; it is possible to better use magnetic fields to achieve fluid flow and heat transfer control and regulation, and improve the performance of photovoltaic thermal systems. In the frequency-dividing thermal decoupling photovoltaic thermal system, how to regulate the nano-magnetic fluid working fluid to better achieve photovoltaic thermal frequency division and improve the utilization of solar energy has become a problem to be studied.

[0006] Patent CN202110665393.8 applied for by the applicant once disclosed a test method for cold storage working fluid in a cold storage tank, but this method can only be used to obtain the concentration ratio of magnetic nanoparticles with better heat transfer efficiency, and the corresponding control magnetic field size.

[0007] CN201711283408.4 has disclosed a device for testing the full spectrum frequency division output of solar energy regulated by nano-magnetic fluid, the device includes a Helmholtz coil and a photovoltaic integrated device, the photovoltaic integrated device includes a flow control valve, a data acquisition device, a photovoltaic device, a cold water circulation system, a throttle valve, a second water pump, a heat exchanger, a nanofluid insulation water tank and a first water pump; the photovoltaic device in the photovoltaic integrated device is placed in the center of the Helmholtz coil, located in the magnetic field generated by the Helmholtz coil vertically and horizontally in the vertical direction. The invention uses the Helmholtz coil as a magnetic field generator, applies a magnetic field vertical or horizontal to the direction of the magnetic field while irradiating light, and judges the degree of frequency division absorption of light by the magnetic nanofluid under the action of the magnetic field by observing the numerical display of voltage, current and temperature in Agilent. However, the test device mainly studies the influence of the magnetic field on the absorption degree of light after the magnetic field changes when the magnetic field directly acts on the frequency divider.

[0008] Therefore, for those skilled in the art, how to design a technology that can study different lighting conditions and how to better absorb and utilize the solar energy spectrum by regulating the concentration of nanomagnetic fluid has become a problem to be solved. Summary of the invention

[0009] In view of the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to provide a nanomagnetic fluid regulation solar spectrum frequency division test method that can better study how to better absorb and utilize the solar energy spectrum under different lighting conditions by regulating the concentration of nanomagnetic fluid, so that after it is used in a frequency division type thermally decoupled photovoltaic thermal system, it can achieve more efficient solar energy utilization according to the lighting conditions.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions: A test method for regulating the frequency division of solar spectrum with nanomagnetic fluid, which uses nanomagnetic fluid working fluid to realize the frequency division control of photovoltaic thermal system, is characterized in that a solar simulator is used to irradiate the divider with a fixed intensity, the nanomagnetic fluid working fluid in the divider is adjusted to different concentrations, the thermal energy value derived by the divider within a specific irradiation time and the electric energy value generated by the solar panel behind the divider are tested, and the nanomagnetic fluid working fluid concentration corresponding to the maximum value of the comprehensive photoelectric and thermal performance efficiency is calculated as the optimal nanomagnetic fluid working fluid concentration; the irradiation intensity of the solar simulator is adjusted to repeat the test, so as to obtain the optimal nanomagnetic fluid working fluid concentration under different solar intensities.

[0011] In this way, this method can experimentally obtain the optimal nano-magnetic fluid concentration of the frequency-divided thermal decoupled photovoltaic thermal system under different solar intensities, so that the absorption and utilization efficiency of solar energy can be maximized by using it for system control. Therefore, the test results obtained by this method are suitable for application in realizing system control when the frequency-divided thermal decoupled photovoltaic thermal system is working and there are no specific requirements for photovoltaic and light-heat conversion.

[0012] Furthermore, when adjusting the concentration of the nano-magnetic fluid working medium, an electromagnet adsorption device is connected in the circulation pipeline of the nano-magnetic fluid working medium, and a layer of magnetic nanoparticles is adsorbed on the outer surface of the electromagnet adsorption device for standby use. When the concentration of the nano-magnetic fluid working medium needs to be increased, the magnetic attraction of the electromagnet adsorption device is controlled to be reduced and some of the magnetic nanoparticles are released into the circulation pipeline. When the concentration of the nano-magnetic fluid working medium needs to be reduced, the magnetic attraction of the electromagnet adsorption device is controlled to be increased and some of the magnetic nanoparticles are absorbed to attach to the outer surface.

[0013] In this way, the concentration of the nano-magnetic fluid working medium can be adjusted online without exporting the nano-magnetic fluid working medium into the circulation pipeline, which has the advantages of being convenient, fast, efficient and reliable. The magnetic nanoparticles used in the nano-magnetic fluid working medium are magnetic carbon nanotubes, which have better heat transfer and controllability.

[0014] Furthermore, the method is implemented by using a nanomagnetic fluid regulating solar spectrum frequency division test system, which includes a solar simulator, a frequency divider using nanomagnetic fluid as a frequency division fluid is arranged opposite to the irradiation direction of the solar simulator, and a photovoltaic panel is arranged behind the frequency divider. The inlet and outlet of the frequency divider are connected to a hot water storage tank through pipelines to form a circulation pipeline, and a heat flow circulation maintaining device and a frequency division fluid concentration control module are arranged on the circulation pipeline. The output end of the photovoltaic panel is connected to a power analyzer, and a water tank temperature sensor is arranged in the hot water storage tank. The power analyzer, the water tank temperature sensor and the solar simulator are respectively connected to a control computer.

[0015] In this way, a control computer is used to control the solar simulator to continuously irradiate the frequency divider at a specific intensity, and the concentration of the nanomagnetic fluid is controlled and adjusted by the frequency division liquid concentration control module to maintain different sizes. After irradiation for the same time, the power analyzer is used to detect the amount of electric energy obtained by the photovoltaic panel, and the water tank temperature sensor is used to detect the temperature change of the hot water storage tank and calculate the amount of heat energy absorbed and converted. The comprehensive performance efficiency of photoelectric and thermal energy can be calculated by using the numerical values ​​of the two and then compared to obtain the concentration of the nanomagnetic fluid that can obtain the maximum solar spectrum conversion efficiency under a specific light intensity. And it can be fed back for control and use in the frequency division type thermal decoupling photovoltaic thermal system with the same application structure. Among them, the solar simulator, power analyzer and other devices are mature existing equipment, and the specific structure and usage are not introduced in detail here.

[0016] Furthermore, the portion of the circulation pipeline located in the hot water storage tank is in a coil shape, and a cold water inlet is provided at the upper end of the hot water storage tank, and a hot water outlet is provided at the lower end.

[0017] In this way, after a test is completed, the water in the hot water storage tank can be replaced through the cold water inlet and hot water outlet to quickly restore it to the same initial temperature for a second test, ensuring the reliability of each test result for comparison. At the same time, such a hot water storage tank is consistent with the structure of the frequency-divided thermal decoupled photovoltaic thermal system targeted by the test method, making the test results more suitable for practical use.

[0018] Furthermore, a frequency divider temperature sensor is provided in the frequency divider and is connected to a control computer.

[0019] In this way, the temperature of the frequency divider can be detected during each test to better ensure the reliability of the heat conversion detection. That is, during the test, if the temperature of the frequency divider rises too much in this test, the increased heat energy in the frequency divider can be added when calculating the heat energy of the heat conversion, so as to better ensure the reliability of the test results.

[0020] Furthermore, a photovoltaic panel temperature sensor is provided on the photovoltaic panel and is connected to a control computer.

[0021] In this way, the temperature rise of the photovoltaic panels can be detected and monitored, providing more test data and facilitating auxiliary judgment of the test conclusions.

[0022] As an option, the heat flow circulation maintaining device is a water pump, which is suitable for photovoltaic thermal system tests using a water pump as power.

[0023] As another option, the heat flow circulation maintaining device is a magnetic field generating device, and at least a portion of the section of the circulation pipeline from the outlet of the divider to the hot water storage tank is located in the magnetic field of the magnetic field generating device, and the flow direction of this section of the pipeline is consistent with the magnetic field direction.

[0024] This is suitable for photovoltaic thermal system tests using a magnetic field generating device as a heat flow cycle maintaining device. Because prior art research has found that under the synergistic effect of the magnetic field and the temperature field, the nanomagnetic fluid has the characteristics of self-driven heat collection circuit flow and heat transfer, and can flow spontaneously from the high temperature end to the low temperature end under the action of the magnetic field. At the same time, after using magnetic carbon nanotubes as nanoparticles, it is more possible to complete the sequential connection arrangement between the carbon nanotubes along the length direction under the action of the magnetic field, and directly generate a directional heat transfer channel in the frequency division liquid, which is connected between the high temperature end and the low temperature end. Therefore, although the flow speed of the frequency division liquid itself under the action of the magnetic field may be slower than that of the water pump, the generated heat transfer channel can directly complete the high-speed transfer of heat, so that the heat absorbed by the frequency divider can be quickly transferred from the frequency divider to the hot water storage tank, so that its overall heat transfer efficiency is not lower than that of the water pump. It can also avoid the damage of the water pump operation itself to the magnetic fluid working medium and the instability of the system.

[0025] Furthermore, the magnetic field generating device is an electromagnet device.

[0026] In this way, the electromagnetic intensity can be controlled as needed to control the heat transfer rate and test the photovoltaic thermal conversion efficiency under different electromagnetic intensities.

[0027] As a preferred embodiment, the frequency division liquid concentration control module includes a frequency division liquid concentration adjustment branch, two ends of the frequency division liquid concentration adjustment branch are connected in parallel on the circulation pipeline using three-way control valves, a regulation container is connected in the frequency division liquid concentration adjustment branch, an electromagnet adsorption device is arranged in the regulation container, a layer of magnetic nanoparticles is pre-adsorbed around the electromagnet adsorption device, and the three-way control valve and the electromagnet adsorption device are respectively connected to the control computer.

[0028] In this way, when the concentration of the frequency division liquid needs to be adjusted, the three-way control valve is switched to control the adjustment container to enter the circulation pipeline. At this time, the control center can control the increase of the electromagnetic strength of the electromagnet adsorption device, so that the magnetic nanoparticles in the frequency division liquid flowing through are adsorbed, thereby reducing the concentration of the magnetic nanoparticles in the frequency division liquid. It is also possible to control the reduction of the electromagnetic strength of the electromagnet adsorption device so that some of the adsorbed magnetic nanoparticles are released, thereby increasing the concentration of the magnetic nanoparticles in the frequency division liquid. In this way, the online adjustment of the concentration of the frequency division liquid is realized without stopping for replacement, which better meets the requirements of the test process.

[0029] Furthermore, a speed-up pump is arranged in series in the frequency-dividing liquid concentration regulating branch.

[0030] In this way, the flow rate can be increased by speeding up the pump, the time required for concentration adjustment can be shortened, waiting can be avoided, and the test efficiency can be better improved.

[0031] Furthermore, a plurality of magnetic ribbons are fixedly connected to the periphery of the electromagnet adsorption device and are made of a rubber material containing magnetic material powder.

[0032] In this way, the magnetic ribbon can form an extension effect of the electromagnetic field of the electromagnet adsorption device, produce a great adsorption effect on the magnetic nanoparticles, and can adsorb a sufficient number of magnetic nanoparticles around the electromagnet adsorption device to facilitate the effect of adjusting the concentration of the frequency-dividing liquid.

[0033] Furthermore, an ultrasonic oscillator is also arranged in the adjustment container.

[0034] In this way, when adjusting to increase the concentration of the frequency division liquid, while reducing the magnetic field size of the electromagnet adsorption device, the ultrasonic oscillator can be turned on to allow the magnetic nanoparticles that are not adsorbed to be better released into the circulating frequency division liquid, thereby improving the adjustment effect and efficiency.

[0035] Furthermore, a magnetic fluid concentration measuring instrument is also arranged in the circulation pipeline.

[0036] In this way, measurement feedback control can be performed when adjusting the concentration of the frequency division fluid to ensure the stability and reliability of the adjustment result. During implementation, the magnetic fluid concentration measuring instrument is a mature existing device, and the specific structure is not described in detail here.

[0037] As another option, the frequency division liquid concentration control module includes a frequency division liquid concentration regulating branch, and the two ends of the frequency division liquid concentration regulating branch are arranged in parallel on the circulation pipeline using three-way control valves. A regulating container is connected in the frequency division liquid concentration regulating branch, and an adding chamber and a recovery chamber are arranged in the regulating container. The recovery chamber is connected to the liquid inlet end of the frequency division liquid concentration regulating branch and a recovery pump is arranged at this end. The adding chamber is connected to the liquid outlet end of the frequency division liquid concentration regulating branch and an adding pump is arranged at this end.

[0038] In this way, the frequency division liquid that needs to be replaced and adjusted to the required concentration is added to the adding chamber of the adjusting container in advance, and the recovery chamber remains empty. When the concentration of the frequency division liquid needs to be adjusted, the three-way control valve is switched to control the adjusting container to connect it to the circulation pipeline, and the recovery chamber and the recovery pump are used to recover the previous concentration of the frequency division liquid. Then, the adding chamber and the adding pump are used to add new frequency division liquid. This structure is simpler and the cost is lower, but the adjustment is more inconvenient and stepless adjustment cannot be achieved.

[0039] In summary, the present invention can better study how to better absorb and utilize the solar energy spectrum by regulating the concentration of nanomagnetic fluid under different lighting conditions, so that after it is used in a frequency-divided thermally decoupled photovoltaic thermal system, it can more efficiently realize solar energy absorption, conversion and utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of a magnetic fluid frequency division control photovoltaic thermal system used in the implementation of the present invention.

[0041] Figure 2 It is a schematic diagram of another frequency division liquid concentration control module used in the implementation of the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with specific implementation modes.

[0043] Specific implementation method: A nanomagnetic fluid control solar spectrum frequency division test method, using nanomagnetic fluid working fluid to achieve frequency division control of photovoltaic thermal system, its characteristics are: using a solar simulator to irradiate the divider with a fixed intensity, adjusting the nanomagnetic fluid working fluid in the divider to different concentrations, testing the thermal energy value derived by the divider within a specific irradiation time and the electrical energy value generated by the solar panel behind the divider, calculating the nanomagnetic fluid working fluid concentration corresponding to the maximum value of the comprehensive photoelectric and thermal performance efficiency as the optimal nanomagnetic fluid working fluid concentration; adjusting the irradiation intensity of the solar simulator to repeat the test, that is, obtaining the optimal nanomagnetic fluid working fluid concentration under different solar intensities.

[0044] In this way, this method can experimentally obtain the optimal nano-magnetic fluid concentration of the frequency-divided thermal decoupled photovoltaic thermal system under different solar intensities, so that the absorption and utilization efficiency of solar energy can be maximized by using it for system control. Therefore, the test results obtained by this method are suitable for application in realizing system control when the frequency-divided thermal decoupled photovoltaic thermal system is working and there are no specific requirements for photovoltaic and light-heat conversion.

[0045] Specifically, the method is implemented by using a nano-magnetic fluid regulating solar spectrum frequency division test system, the nano-magnetic fluid regulating solar spectrum frequency division test system, see Figure 1 , including a solar simulator 1, a frequency divider 2 using nano-magnetic fluid as a frequency dividing liquid is arranged opposite to the solar simulator 1 in the irradiation direction, a photovoltaic panel 3 is arranged behind the frequency divider 2, the inlet and outlet of the frequency divider are connected to a hot water storage tank 4 through pipelines to form a circulation pipeline 5, and a heat flow circulation maintaining device and a frequency dividing liquid concentration control module are arranged on the circulation pipeline 5, the output end of the photovoltaic panel 3 is connected to a power analyzer 9, and a water tank temperature sensor 10 is arranged in the hot water storage tank, and the power analyzer 9, the water tank temperature sensor 10 and the solar simulator 1 are respectively connected to a control computer 11.

[0046] In this way, a control computer is used to control the solar simulator to continuously irradiate the frequency divider at a specific intensity, and the concentration of the nanomagnetic fluid is controlled and adjusted by the frequency division liquid concentration control module to maintain different sizes. After irradiation for the same time, the power analyzer is used to detect the size of the electric energy obtained by the photovoltaic panel, and the water tank temperature sensor is used to detect the temperature change of the hot water storage tank and calculate the size of the thermal energy absorbed and converted. The comprehensive performance efficiency of the photoelectric and thermal energy is calculated by using the two numerical values ​​and then compared, and the concentration of the nanomagnetic fluid that can obtain the maximum solar spectrum conversion efficiency under a specific light intensity can be obtained. And it can be fed back for control and use in the frequency division type thermal decoupling photovoltaic thermal system with the same application structure. Among them, the solar simulator (which can be realized by a xenon lamp), the power analyzer and other devices are mature existing equipment, and the specific structure and usage are not introduced in detail here.

[0047] The portion of the circulation pipe 5 located in the hot water storage tank 4 is in a coil shape. The hot water storage tank 4 is provided with a cold water inlet 6 at the upper end and a hot water outlet 7 at the lower end.

[0048] In this way, after a test is completed, the water in the hot water storage tank can be replaced through the cold water inlet and hot water outlet to quickly restore it to the same initial temperature for a second test, ensuring the reliability of each test result for comparison. At the same time, such a hot water storage tank is consistent with the structure of the frequency-divided thermal decoupled photovoltaic thermal system targeted by the test method, making the test results more suitable for practical use.

[0049] The frequency divider 2 is provided with a frequency divider temperature sensor 12 connected to the control computer 11 .

[0050] In this way, the temperature of the frequency divider can be detected during each test to better ensure the reliability of the heat conversion detection. That is, during the test, if the temperature of the frequency divider rises too much in this test, the increased heat energy in the frequency divider can be added when calculating the heat energy of the heat conversion, so as to better ensure the reliability of the test results.

[0051] The photovoltaic panel 3 is provided with a photovoltaic panel temperature sensor 13 which is connected to the control computer 11 .

[0052] In this way, the temperature rise of the photovoltaic panels can be detected and monitored, providing more test data and facilitating auxiliary judgment of the test conclusions.

[0053] In this embodiment, the heat flow circulation maintaining device is a magnetic field generating device 14, and at least a portion of the section of the circulation pipeline 5 from the outlet of the divider to the hot water storage tank is located in the magnetic field of the magnetic field generating device, and the flow direction of this section of the pipeline is consistent with the magnetic field direction.

[0054] This is suitable for photovoltaic thermal system tests using a magnetic field generating device as a heat flow cycle maintaining device. Because prior art research has found that under the synergistic effect of the magnetic field and the temperature field, the nanomagnetic fluid has the characteristics of self-driven heat collection circuit flow and heat transfer, and can flow spontaneously from the high temperature end to the low temperature end under the action of the magnetic field. At the same time, after using magnetic carbon nanotubes as nanoparticles, it is more possible to complete the sequential connection arrangement between the carbon nanotubes along the length direction under the action of the magnetic field, and directly generate a directional heat transfer channel in the frequency division liquid, which is connected between the high temperature end and the low temperature end. Therefore, although the flow speed of the frequency division liquid itself under the action of the magnetic field may be slower than that of the water pump, the generated heat transfer channel can directly complete the high-speed transfer of heat, so that the heat absorbed by the frequency divider can be quickly transferred from the frequency divider to the hot water storage tank, so that its overall heat transfer efficiency is not lower than that of the water pump. It can also avoid the damage of the water pump operation itself to the magnetic fluid working medium and the instability of the system.

[0055] Wherein, the magnetic field generating device 14 is an electromagnet device.

[0056] In this way, the electromagnetic intensity can be controlled as needed to control the heat transfer rate and test the photovoltaic thermal conversion efficiency under different electromagnetic intensities.

[0057] As another feasible option, the heat flow circulation maintaining device may also be a water pump, which is suitable for photovoltaic thermal system tests using a water pump as power.

[0058] In this embodiment, the frequency division liquid concentration control module includes a frequency division liquid concentration adjustment branch 15, and the two ends of the frequency division liquid concentration adjustment branch 15 are connected in parallel on the circulation pipeline 5 using three-way control valves 16. A regulation container 21 is connected in the frequency division liquid concentration adjustment branch 15, and an electromagnet adsorption device 17 is arranged in the regulation container 21. A layer of magnetic nanoparticles is pre-adsorbed around the electromagnet adsorption device, and the three-way control valve 16 and the electromagnet adsorption device 17 are respectively connected to the control computer.

[0059] In this way, when the concentration of the frequency division liquid needs to be adjusted, the three-way control valve is switched to control the adjustment container to enter the circulation pipeline. At this time, the control center can control the increase of the electromagnetic strength of the electromagnet adsorption device, so that the magnetic nanoparticles in the frequency division liquid flowing through are adsorbed, thereby reducing the concentration of the magnetic nanoparticles in the frequency division liquid. It is also possible to control the reduction of the electromagnetic strength of the electromagnet adsorption device so that some of the adsorbed magnetic nanoparticles are released, thereby increasing the concentration of the magnetic nanoparticles in the frequency division liquid. In this way, the online adjustment of the concentration of the frequency division liquid is realized without stopping for replacement, which better meets the requirements of the test process.

[0060] Furthermore, a speed-up pump 19 is provided in series in the frequency-dividing liquid concentration regulating branch 15 .

[0061] In this way, the flow rate can be increased by speeding up the pump, the time required for concentration adjustment can be shortened, waiting can be avoided, and the test efficiency can be better improved.

[0062] Furthermore, a plurality of magnetic ribbons 20 are fixedly connected to the periphery of the electromagnet adsorption device 17 and are made of a rubber material containing magnetic material powder.

[0063] In this way, the magnetic ribbon can form an extension effect of the electromagnetic field of the electromagnet adsorption device, produce a great adsorption effect on the magnetic nanoparticles, and can adsorb a sufficient number of magnetic nanoparticles around the electromagnet adsorption device to facilitate the effect of adjusting the concentration of the frequency-dividing liquid.

[0064] Furthermore, an ultrasonic oscillator 22 is also disposed in the adjustment container 21 .

[0065] In this way, when adjusting to increase the concentration of the frequency division liquid, while reducing the magnetic field size of the electromagnet adsorption device, the ultrasonic oscillator can be turned on to allow the magnetic nanoparticles that are not adsorbed to be better released into the circulating frequency division liquid, thereby improving the adjustment effect and efficiency.

[0066] Furthermore, a magnetic fluid concentration measuring instrument 23 is also provided in the circulation pipeline 5 .

[0067] In this way, measurement feedback control can be performed when adjusting the concentration of the frequency division fluid to ensure the stability and reliability of the adjustment result. During implementation, the magnetic fluid concentration measuring instrument is a mature existing device, and the specific structure is not described in detail here.

[0068] In view of the contents disclosed so far, the present invention also discloses an online stepless adjustment method for the concentration of frequency dividing liquid applied to photovoltaic thermal systems. When adjusting the concentration of nanomagnetic fluid working fluid, this method connects an electromagnet adsorption device in the circulation pipeline of the nanomagnetic fluid working fluid, adsorbs a layer of magnetic nanoparticles on the outer surface of the electromagnet adsorption device for standby use, and when it is necessary to increase the concentration of the nanomagnetic fluid working fluid, controls the magnetic attraction of the electromagnet adsorption device to be reduced and releases some of the magnetic nanoparticles into the circulation pipeline; when it is necessary to reduce the concentration of the nanomagnetic fluid working fluid, controls the magnetic attraction of the electromagnet adsorption device to be increased and absorbs some of the magnetic nanoparticles to attach to the outer surface.

[0069] In this way, the effect of online adjustment of the concentration of the nano-magnetic fluid working medium can be achieved without exporting the nano-magnetic fluid working medium into the circulation pipeline, which has the advantages of being convenient, fast, efficient and reliable. Furthermore, the online stepless adjustment method of the frequency division liquid concentration can also be implemented by the above-mentioned frequency division liquid concentration control module and has corresponding advantages and effects.

[0070] As an alternative, see Figure 2 The frequency division liquid concentration control module includes a frequency division liquid concentration regulating branch 15, and two ends of the frequency division liquid concentration regulating branch 15 are connected in parallel on the circulation pipeline 5 using three-way control valves 16. A regulating container 30 is connected in the frequency division liquid concentration regulating branch, and an adding chamber 31 and a recovery chamber 32 are arranged in the regulating container 30. The recovery chamber 32 is connected to the liquid inlet end of the frequency division liquid concentration regulating branch 15 and a recovery pump 33 is arranged at this end. The adding chamber 31 is connected to the liquid outlet end of the frequency division liquid concentration regulating branch 15 and an adding pump 34 is arranged at this end.

[0071] In this way, the frequency division liquid that needs to be replaced and adjusted to the required concentration is added to the adding chamber of the adjusting container in advance, and the recovery chamber remains empty. When the concentration of the frequency division liquid needs to be adjusted, the three-way control valve is switched to control the adjusting container to connect it to the circulation pipeline, and the recovery chamber and the recovery pump are used to recover the previous concentration of the frequency division liquid. Then, the adding chamber and the adding pump are used to add new frequency division liquid. This structure is simpler and the cost is lower, but the adjustment is more inconvenient and stepless adjustment cannot be achieved.

Claims

1. A nano-magnetic fluid solar spectrum frequency division test method, using nano-magnetic fluid working fluid to achieve frequency division control of photovoltaic thermal system, characterized in that: A solar simulator is used to irradiate the divider with a fixed intensity. The nanomagnetic fluid working fluid in the divider is adjusted to different concentrations. The thermal energy value exported by the divider and the electrical energy value generated by the solar panel behind the divider within a specific irradiation time are tested. The nanomagnetic fluid working fluid concentration corresponding to the maximum value of the comprehensive photoelectric and thermal performance efficiency is calculated as the optimal nanomagnetic fluid working fluid concentration. The irradiation intensity of the solar simulator is adjusted to repeat the test to obtain the optimal nanomagnetic fluid working fluid concentration under different solar intensities.

2. The nano-magnetic fluid control solar spectrum frequency division test method according to claim 1, characterized in that: When adjusting the concentration of the nano-magnetic fluid working medium, an electromagnet adsorption device is connected in the circulation pipeline of the nano-magnetic fluid working medium, and a layer of magnetic nanoparticles is adsorbed on the outer surface of the electromagnet adsorption device for standby use. When the concentration of the nano-magnetic fluid working medium needs to be increased, the magnetic attraction of the electromagnet adsorption device is controlled to be reduced and some magnetic nanoparticles are released into the circulation pipeline. When the concentration of the nano-magnetic fluid working medium needs to be reduced, the magnetic attraction of the electromagnet adsorption device is controlled to be increased and some magnetic nanoparticles are absorbed to attach to the outer surface.

3. The nano-magnetic fluid control solar spectrum frequency division test method according to claim 1, characterized in that: The method is implemented by using a nano-magnetic fluid regulating solar spectrum frequency division test system, the nano-magnetic fluid regulating solar spectrum frequency division test system comprises a solar simulator, a frequency divider using nano-magnetic fluid as a frequency division liquid is arranged opposite to the irradiation direction of the solar simulator, a photovoltaic panel is arranged behind the frequency divider, the inlet and outlet of the frequency divider are connected to a hot water storage tank through pipelines to form a circulation pipeline, a heat flow circulation maintaining device and a frequency division liquid concentration control module are arranged on the circulation pipeline, the output end of the photovoltaic panel is connected to a power analyzer, a water tank temperature sensor is arranged in the hot water storage tank, and the power analyzer, the water tank temperature sensor and the solar simulator are respectively connected to a control computer.

4. The nano-magnetic fluid control solar spectrum frequency division test method as claimed in claim 3, characterized in that: The part of the circulation pipeline located in the hot water storage tank is in a coil shape. The upper end of the hot water storage tank is provided with a cold water inlet, and the lower end is provided with a hot water outlet.

5. The nano-magnetic fluid control solar spectrum frequency division test method as claimed in claim 3, characterized in that: A frequency divider temperature sensor is arranged in the frequency divider and is connected to a control computer.

6. The nano-magnetic fluid control solar spectrum frequency division test method as claimed in claim 3, characterized in that: The photovoltaic panel is provided with a photovoltaic panel temperature sensor which is connected to a control computer.

7. The nano-magnetic fluid control solar spectrum frequency division test method as claimed in claim 3, characterized in that: The heat flow circulation maintaining device is a water pump; Alternatively, the heat flow circulation maintaining device is a magnetic field generating device, at least a portion of the section of the circulation pipeline from the outlet of the divider to the hot water storage tank is located in the magnetic field of the magnetic field generating device, and the flow direction of the section of the pipeline is consistent with the magnetic field direction; and the magnetic field generating device is an electromagnet device.

8. The nano-magnetic fluid control solar spectrum frequency division test method as claimed in claim 3, characterized in that: The frequency division liquid concentration control module comprises a frequency division liquid concentration regulating branch, two ends of the frequency division liquid concentration regulating branch are connected in parallel on a circulation pipeline by three-way control valves, a regulating container is connected in the frequency division liquid concentration regulating branch, an electromagnet adsorption device is arranged in the regulating container, a layer of magnetic nanoparticles is pre-adsorbed around the electromagnet adsorption device, and the three-way control valve and the electromagnet adsorption device are respectively connected to a control computer.

9. The nano-magnetic fluid control solar spectrum frequency division test method according to claim 8, characterized in that: A speed-up pump is arranged in series in the frequency-dividing liquid concentration regulating branch; A plurality of magnetic ribbons are fixedly connected to the periphery of the electromagnet adsorption device and are made of a rubber material containing magnetic material powder; An ultrasonic oscillator is also arranged in the regulating container.

10. The nano-magnetic fluid control solar spectrum frequency division test method according to claim 3, characterized in that: The frequency division liquid concentration control module comprises a frequency division liquid concentration regulating branch, two ends of the frequency division liquid concentration regulating branch are arranged in parallel on a circulation pipeline by using three-way control valves, a regulating container is connected in the frequency division liquid concentration regulating branch, an adding chamber and a recovery chamber are arranged in the regulating container, the recovery chamber is connected to the liquid inlet end of the frequency division liquid concentration regulating branch and a recovery pump is arranged at this end, and the adding chamber is connected to the liquid outlet end of the frequency division liquid concentration regulating branch and an adding pump is arranged at this end.

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