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: Solar tracking technology has been widely used in large power stations, photovoltaic agriculture, and green building industry. Among them, hybrid tracking can be expected to consider both photoelectric and solar trajectory tracking. However, it is still lacking in the accurate evaluation of different weather conditions, due to the excessively broad control criterion in the solar hybrid tracking using light intensity, and the vague conditions for the weather identification. In this research, a solar hybrid tracking system was designed under complex weather conditions. Moreover, a multi-threshold control criterion was proposed to divide the weather conditions. The tracking characteristics of the system were analyzed under different tracking strategies in the concentrated and non-concentrated environments, combined with the weather conditions. The control criterion was classified into irradiance fluctuation, high irradiance, low and extremely low irradiance weather. As such, the photoelectric and solar trajectory tracking automatically adjusted, or fixed the inclination angle, according to the external weather changes. Firstly, the prototype of a hybrid tracking system was developed for solar power generation. Specifically, the Raspberry Pi 4B controlled by Node-RED was used as the control core, and the signal was divided by the analog switch of CD4052. At the same time, the photoelectric tracking signal and the fixed inclination angle placement signal were outputted by Arduino, whereas, the tracking signal of the solar trajectory was outputted by STM32F407. Three-way parallel control was adopted to avoid interference with each other in the different control strategies. Secondly, a series of tracking tests were carried out to determine the foundation for the switching of the tracking system under concentrated and non-concentrated light conditions. The switching criteria were summarized for the hybrid tracking system since the tracking performance of the system varied depending on the weather and the tracking mode. The irradiance and power generation curves were also determined that the system received under various tracking strategies. A hybrid tracking scheme was developed to investigate the influence of weather on irradiance characteristics, in order to keep tracking the temperature change of battery panels. The irradiance and temperature curves demonstrated that the irradiance was the primary determinant of the variance in PV cell output, while the temperature remained constant. As a result, the hybrid tracking system can be expected to track the high irradiance for higher power production. Finally, the tracking prototype was tested to verify the impact of the criterion program on the hybrid tracking system. The test results showed that the average power generation of a no-concentrated hybrid tracking system on a sunny day was 0.03 and 0.16 W higher than that of photoelectric and solar trajectory tracking. Additionally, the average power generation of the concentrated hybrid tracking system on a sunny day was 0.81, which was 0.03 and 0.55 W higher than that of photoelectric and solar trajectory tracking. Anyway, the experiment verified the feasibility of the developed device. The new criterion can also provide a promising idea for hybrid tracking technology under complex weather. [ABSTRACT FROM AUTHOR]

The power generation efficiency of photovoltaic (PV) cells can be greatly reduced with the increase of working temperature. The PV-thermoelectric (PV-TE) technology can convert the excess heat in the PV power generation into the electric energy through the TE cells. As such, the temperature of PV cells can be reduced to realize the cascade utilization of solar energy. However, the temperature of PV-TE system can fluctuate with the change of irradiance, leading to a great influence on the solar energy utilization rate of the whole system. In this study, the phase change material (PCM) was introduced to design a PV-PCM-TE hybrid device system. The latent heat property of PCMs was utilized to improve the stability of the system under variable irradiance. The device test was carried out to evaluate the performance of PV-PCM-TE system in the Northeast Agricultural University, Xiangfang District, Harbin, China. The test date was set from October 1, 2020 to September 30, 2021, while the test time was 8 hours from 8:00 to 16:00 on the test day. The experimental results indicated that the maximum temperature of PV cells was 326.5 K during the period from 11:00 to 14:00, which was basically maintained at the phase change temperature of PCMs. Furthermore, there was only a few cooling effects on the performance of the PV cells, indicating the excellent latent heat characteristics of PCMs. Specifically, the maximum temperature difference of TE battery was 13.4 K during water cooling. By contrast, the maximum temperature difference of TE battery was 3.6 K during natural air cooling. The water cooling was effectively reduced the temperature of the cold end of the TE battery, in order to improve the temperature difference and power of the TE battery. When the direct contact, thermal conductive silicone grease 1 (2.0 W/(m·K)), and thermal conductive silicone grease 2 (5.15 W/(m·K)) were selected between the contact surfaces of the device, the maximum temperature difference of TE cells were 5.4, 11.2, and 13.4K, respectively, the average efficiencies of PV cells were 18.10%, 18.3%, and 18.38%, respectively, and the average total efficiencies of the system were 19.6%, 19.95%, and 20.18%, respectively. The best system performance was achieved in the thermal conductive silicone grease 2 with the higher thermal conductivity. Compared with the PV-TE system, the electrical efficiency and power of PV-PCM-TE system increased by 1.05% and 16.21%, respectively, during the instantaneous test period. Therefore, the optimal cooling mode was the water cooling with the cooling water flow rate of 6L/min during the whole year. The maximum performance indexes of PV-PCM-TE system was observed in summer, particularly with the strongest irradiance. The maximum electrical, thermal, and exergy efficiencies were 22.28%, 32.55%, and 27.32%, respectively. The PV-TE hybrid power generation device combined with PCMs can be expected for the excellent adaptability in the most areas and climatic conditions. At the same time, the output considerable heat and electric energy were obtained to supply the power for the environmental monitoring and lighting system of modern greenhouse, particularly for the part of the heat energy for the plant growth. [ABSTRACT FROM AUTHOR]

Electric heating drying system has been widely used for structural drying, sanitizing with heat, and space heating at present. The metal steel plate can often be the main material of the heating box and air duct of the dryer in the mechanical arrangement. Nevertheless, a large heat transfer coefficient can make it easy to lose heat, when converting the electric current to the heat in the system. The insulation material can normally be laid on the outer layer of the steel plate. However, the traditional configuration cannot recover the heat, although the heat loss can be prevented in this case. Alternatively, thermoelectric power generation has attracted extensive attention in the field of heat recovery, because it can directly convert temperature differences into electricity. In this study, an energy-saving mode was proposed to recover the heat of the dryer using a Thermoelectric Generator (TEG). A thermoelectric power generation system was designed and developed for the dryer to directly recover the heat. In addition to recovering the heat of the metal wall of the dryer, the thermoelectric cell was also used to recover the part of the heat of the hot air, resulting in a decrease in the hot air temperature. Therefore, the Fluent software was firstly used to simulate the temperature field of the dryer before and after the installation of TEG. The measured parameters were combined to evaluate the impact of TEG installation on the dryer. Secondly, the output electric energy was controlled to obtain stable electricity in the thermoelectric power generation device. The reason was that the cold end, hot end, and power generation performance of TEG fluctuated dynamically, due to the heating power. The STM32F334 was used as the controller to realize the DC-DC conversion function. The test was also carried out to verify the performance of raising and lowering the voltage of the controller. As such, the battery was charged to fully meet the requirements of the TEG for the heat recovery of the dryer. Finally, the test platform of TEG was built for the heat recovery of the dryer. A systematic evaluation was made of the hot air temperature of the dryer before and after the installation of TEG, as well as the parameter characteristics of the power generation system. The test results showed that the installation of TEG presented no outstanding impact on the dryer. The better performance of the dryer was achieved under different operating conditions of thermoelectric power generation. Specifically, the power regulator and frequency converter were utilized to control the heating power and the wind speed of the centrifuge. There was a significant variation in the output power of thermoelectric power generation, the consumption power of the water pump, and the net output power with the cooling water flow. Among them, the water pump was controlled by the DC power supply. Consequently, there was optimal water flow to maximize the net output power under the different working conditions. An optimal parameter combination was achieved, where the optimal water flow rate was 22.3 L/min, the pump power consumption was 6.4 W, the system output power was 31.8 W, the maximum net output power was 25.40 W, and the thermoelectric conversion efficiency was 3.90%, particularly when the heating power was 3.0 kW and the wind speed was 12 m/s. Anyway, the experiment verified the feasibility of the developed device. The finding can also provide a new idea for drying energy-saving technology. [ABSTRACT FROM AUTHOR]

Energy power generation has been widely used in the field of renewable energy. Only a small part of the energy can be converted into electrical energy during photovoltaic power generation, most of which is lost in the form of thermal for the great wastes. A photovoltaic and thermoelectric sysplex can be expected to combine the thermopiles using waste heat on the surface of photovoltaic cells, in order to improve the output power of power generation. However, there is uneven heat absorption of thermopiles in the process of heating. The local shadow shading on the photovoltaic cells can cause the unstable output characteristics of temperature difference, leading to the less output power of the combined power generation system. The micro heatpipe can be equipped as the heat conduction element in the temperature control device for the even heating of the thermoelectric system in the photo-thermal combined power generation module. In this study, the simulation model and test platform were built to evaluate the performance of the micro heat-pipe element, in terms of the heat transfer and output power. A chaotic quantum behavior particle swarm optimization with the linear decreasing type, and the incremental conductance of variable step-size were used as the control strategies of photovoltaic and thermoelectric systems, respectively. Ten photovoltaic cells were connected in series in MATLAB software, in order to clarify the influence of different shading areas on the output power. The different light intensities were also set to simulate the shading of shadows. The temperature was selected as the evaluation index of the heat transfer during the light-heat conversion in the whole system. The photovoltaic cell with the power of 25 W and the thermopiles with the model of sp1848-27145 were adopted as the power generation elements of the coupling system for the test platform. The number of temperature difference plates was set as 90, according to the size of a 25 W photovoltaic cell. Every 10 plates was connected in series as a group, and then the nine groups of plates were connected in parallel. The output power of photovoltaic and thermoelectric cells was calculated to evaluate their output voltage and current. The photo-thermal sysplex was measured without/with the temperature control device when the areas of shadow shielded photovoltaic panel were 10%, 30%, and 50%. The results were achieved as follows. The micro heatpipe efficiently absorbed the heat from the photovoltaic surface for the reduced temperature of the photovoltaic cell during the power generation, due to the uneven temperature of photovoltaic cells in the shadow area. The simulation indicated that there was the smallest loss of output photovoltaic power when the area of shielding photovoltaic was 10%. The photo-thermal coupling system with a temperature control device greatly enhanced the heat absorption capacity than before. The temperature control devices were optimized to simulate the local shadow by artificial shielding at the hot and cold ends. An optimal combination was achieved, where the heat flow rate at the hot port was 0.0124 m/s when the area of photovoltaic shielding was 10%, the average output power of thermoelectric increased by 1.92% when the water velocity at the cold end was 0.0135 m/s. The average temperature difference with/without the shaded areas of the photovoltaic cell was about 274.15 K. Consequently, an approximately balanced temperature of the photovoltaic cell was realized, where the average output power of photovoltaic increased by 18.79% than before. [ABSTRACT FROM AUTHOR]

Surface heat transfer has posed a great impact on the energy conservation in the non-concentrated photovoltaic-thermoelectric coupling systems. However, the one-dimensional heat transfer models were commonly used at present, particularly without considering the effects of natural convection and natural radiation heat transfer on the surface of the system. It is very necessary to introduce the contribution of the surface heat transfer in a photovoltaic cell, especially in the photovoltaic thermoelectric system with the a low surface energy flux density. In this study, a multi-physics model was established to consider the thermal radiation and convection on the surface of a non-concentrating photovoltaic-thermoelectric coupling system using an ANSYS simulation software. Three photovoltaic thermoelectric coupling systems were selected, including the non-focusing mode c-Si, CIGS, and GaAs. A systematic investigation was made on the influence of surface heat convection and thermal radiation heat transfer on the system energy during operation under different irradiance. Three photovoltaic cells with different cooling modes were selected to verify the model using the simulation and measurement data in the experiment. The result showed that the ambient temperature and the temperature of the photovoltaic cell were greatly contributed to the effect of surface convection and radiation heat transfer on the heat flux in the non-concentrated photovoltaic thermoelectric coupling system. Specifically, the convection and radiation on the surface of the system were had dissipated the heat, when the temperature of the photovoltaic cell was higher than the ambient temperature. By contrast, the surrounding environment raised the photovoltaic cell temperature through the convection and radiation below the ambient temperature. The closer the temperature of the photovoltaic cell was to the ambient temperature, the smaller the effect of convection and radiation heat transfer on the surface of the system was. In three photovoltaic cells, the heat flux of the photovoltaic backplane was reduced by up to 22.60% under different cooling modes, when considering the convection and radiation heat transfer on the surface of the system. There was the greatest impact of surface convection and radiation heat transfer on the accuracy of the system under the natural air-cooling heat dissipation mode, where the heat flux of the photovoltaic backplane was reduced by at least 9.21%. Furthermore, the surface convection and radiation heat transfer usually led to an increase of the heat flux of the photovoltaic backplane, increasing by 7.17% at most. Correspondingly, the water cooling presented the highest efficiency of power generation, followed by the forced air-cooling, and the natural air-cooling was the lowest. The CIGS photovoltaic thermoelectric coupling system in the water cooling mode presented the highest power generation efficiency of 21.09%. The temperature coefficient of a GaAs cell was the lowest, whereas, the power generation efficiency was the least due to the irradiance. By contrast, the GaAs photovoltaic-thermoelectric coupling system was had reduced the efficiency by up to 0.12% in the irradiance range of 600-1 400 W/m². The test experiment demonstrated that the maximum absolute error of the improved model was -0.299 5%, and the maximum relative error was -3.032 0%. Anyway, the new model was much more suitable for the characteristic analysis of the photovoltaic thermoelectric coupling system in a non-concentration mode. [ABSTRACT FROM AUTHOR]

The accurate identification of blueberry fruit maturity is very important for modern automatic picking and early yield estimation. To realize the accurate and rapid identification of blueberry fruit in the natural environment, by improving the structure of YOLOv4-Tiny network, a target detection network with attention module (I-YOLOv4-Tiny) was proposed. The detection network used CSPDarknet53-Tiny network model as the backbone network, and the convolution block attention module (CBAM) was added to the feature pyramid network (FPN) model. Feature compression, weight generation and reweighting were carried out on the feature channel dimension and feature space dimension of the target detection network, The two dimensions of channel attention and spatial attention selectively integrated the deep and shallow features. High order features guided low-order features for channel attention acquisition, and low-order features reversed guide high-order features for spatial attention screening, which could improve the feature extraction ability of network structure without significantly increasing the amount of calculation and parameters, and realized the real-time detection performance of network structure, the correlation of features between different channels was learned by weight allocation of features of each channel, and the transmission of deep information of network structure was strengthened, to reduce the interference of complex background on target recognition. Moreover, the detection network has fewer network layers and low memory consumption, to significantly improve the accuracy and speed of blueberry fruit detection. The performance evaluation and comparative test results of the research recognition method showed that the Mean Average Precision (mAP) of the trained I-YOLOv4-Tiny target detection network under the verification set was 97.30%, which could effectively use the color images in the natural environment to identify blueberry fruits and detect fruit maturity. The average accuracy and F1 score of I-YOLOv4-Tiny detection network were 97.30% and 96.79% respectively, which were 2.58 percentage points and 2.13 percentage points higher than that of YOLOv4-Tiny target detection network respectively. In terms of the memory occupied by the network structure, I-YOLOv4-Tiny was 1.05 M larger than that of YOLOv4-Tiny, and the detection time was 5.723 ms, which was only 0.078 ms more than that of YOLOv4-Tiny target detection network, which did not affect the real-time detection, However, many indicators have been improved significantly. Compared with I-YOLOv4-Tiny, YOLOv4-Tiny, YOLOv4, SSD-MobileNet and Faster R-CNN target detection networks in different scenes, the average accuracy of I-YOLOv4-Tiny target detection network was the highest, reaching 96.24%, 1.51 percentage points higher than YOLOv4-Tiny, 4.84 percentage points higher than Faster R-CNN, 1.54 percentage points higher than YOLOv4 and 10.74 percentage points higher than SSD-MobileNet. In terms of network structure size, this study was less than one tenth of the size of YOLOv4 network structure, only 24.20 M. In terms of the detection of three blueberries with different maturity, the I-YOLOv4-Tiny target detection network performed best, which could provide accurate positioning guidance for picking robots and early yield estimation. In this study, the target detection network I-YOLOv4-Tiny suffered more interference in the process of blueberry fruit recognition, but the average accuracy of three types blueberry fruits with different maturity was higher than 95%, of which the average accuracy of mature blueberry fruits was the highest. Due to the similar color of immature fruits and background color, the detection accuracy of immature blueberry fruits was relatively poor. It could be seen that the overall performance of the target detection network in this study was the best, which could meet the needs of recognition accuracy and speed at the same time. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging system can widely be expected to acquire a set of sample images within certain spectral bands in each pixel at the same time. In this study, a rapid detection was proposed for the myoglobin content in pork samples using spectral images and deep learning. The pork was placed under the cold storage conditions at 4°C, where a total of 250 pork samples were settled at different times (0, 24, 48, 72, 96 and 120 h). A hyperspectral imager was used to collect the pork hyperspectral images (400 to 1 000 nm). ENVI5.3 software was also selected to determine the region of interest (ROI) in the hyperspectral images, thereby to extract the full-band average spectrum and principal component image of ROI. Subsequently, a savitzky-golay (SG) filter was used to denoise the spectral information for the curve smoothness and spectral resolution. A convolutional auto encoder (CAE) was utilized to extract spectral depth features. A prediction model was finally established for the content of deoxymyolglobin (DeoMb), oxymyoglobin (OxyMb) and metmyoglobin (MetMb) in the pork samples. The results showed that the determination coefficients of test datasets were 0.923 8, 0.920 3, and 0.909 2, and the root mean square errors (RMSE) were 0.033 4, 0.619 7, and 0.809 1, respectively. Furthermore, the image information of adjacent wavelengths was highly correlated against the image extraction and storage. Principal Component Analysis (PCA) was utilized to reduce the dimension of hyperspectral images for better storage and processing. As such, the images under all bands were linearly combined to form a principal component image in the ENVI5.3 software. The first three principal component images represented 90.62% of the original hyperspectral image, where the contribution rate of the first principal component was 88.50%, indicating the most information. Therefore, the first principal component image was selected for the subsequent image extraction. The first principal component image was unified to the size of 16×16 pixels, and then converted into a 768-dimensional column vector for the extraction of image depth features using a convolutional encoder. DeoM, OxyMb, and MetMb content prediction models were established using image depth features, in which the determination coefficients of test datasets were 0.772 1, 0.828 7, and 0.825 4, while the RMSE of prediction were 0.105 8, 1.302 7, and 1.566 7. The spectral and image features were fused at the data level, and then the fusion data was input into the CAE to extract the deep fusion features. The DeoMb, OxyMb and MetMb content prediction models were also established using the fusion depth features. The determination coefficients of test datasets were 0.964 5, 0.973 2, and 0.958 5, while the RMSE of prediction were 0.015 8, 0.226 6, and 0.381 6. Obviously, the determination coefficients of test dataset were improved, while the RMSE were reduced, compared with the individual image and spectrum information. Partial least square regression (PLSR) and support vector machine regression (SVR) prediction models were also established to further verify the relationship between the graph-spectrum fusion feature and pork myoglobin. It was found that the determination coefficients of the test dataset were greater than 0.85. Consequently, the convolutional autoencoder can be expected to extract the deep fusion features of image and spectral information. Moreover, the fusion features can better reflect the internal and external information of pork. The CNN regression model using the fusion features can also be used to improve the prediction accuracy. This finding can provide a new better way to detect the myoglobin content in pork using hyperspectral imaging. [ABSTRACT FROM AUTHOR]

An effective supply mode, solar power is gradually gaining much attention for the environmental friendliness and convenience. Among them, a photovoltaic/thermal co-generation technology is usually utilized to improve the power generation efficiency of photovoltaic cells, as the operating temperature rises. As such, the redundant heat generated by the photovoltaic cells was reused as the heat source for the temperature difference of power generation system to realize secondary power generation. Moreover, the Maximum Power Point Tracking (MPPT) control is also required to achieve the optimal potential of co-generation system. In this study, a new MPPT control of photovoltaic/temperature difference was proposed further to combine the constant voltage and hyperbolic tangent type adaptive variable step size, in response to the oscillation and misjudgment caused by the fixed step size of traditional conductance increment. Two advantages were included here: First, the control was the fast tracking to the area near the nonlinear region of the maximum power point using 0.78 times of the system open circuit voltage, suitable for the great changing environmental conditions. Second, the step size was adjusted adaptively and quickly, according to the change of external environmental conditions, when the MPPT was tracking to the nonlinear region near the maximum power points. For instance, the light intensity was used to reduce the system oscillation, indicating the monotonic increase and fast variation in the hyperbolic tangent function. Furthermore, a simulation model was established to evaluate the performance of adaptive variable step conductance increment in the MPPT control of a combined photovoltaic/thermal power generation system using the Matlab/Simulink software. Specifically, Jinao JAMG-6-60-250/SI photovoltaic module was set as the photovoltaic cell model, and Xinghe F40550 was the thermoelectric chip model. Simulation results show that the step changes were consistent under the drastic variation in the light intensity, while the response speed was obviously improved with the rapid adjustment for tracking the maximum power point. At the same time, the step size was kept at 0, after the output power of system was stabilized. There were only small fluctuation and error in the steady-state output power, indicating that the MPPT control performed well. Correspondingly, a MPPT hardware experiment was conducted to further verify the feasibility at Northeast Agricultural University in Harbin in October 2020. Two periods A (8:00-9:00) and B (12:00-13:00) were selected, when the illumination and temperature were gradually enhanced to remain unchanged. The hardware experimental results show that the system was quickly tracked and stabilized at the maximum power point within 15ms, where the steady-state error was less than 0.3%, indicating more robust to external environmental disturbances and higher energy utilization. Consequently, an excellent balance was achieved in the system response speed and steady-state accuracy. The finding can provide a promising potential to the implementation on hardware, such as digital signal processors in practice. [ABSTRACT FROM AUTHOR]

When photovoltaic power generation is in sufficient light, heat generated by solar radiation will hinder photoelectric conversion effect. Excessive temperature will also shorten the working life of the photovoltaic cell itself. The photovoltaic-thermoelectric hybrid power generation technology is to add thermoelectric cell to the photovoltaic cell backplane, using the heat that affects the conversion efficiency and working life of photovoltaic cell as heat source for thermoelectric power generation. Through thermoelectric cell converting waste heat of photovoltaic cell into electrical energy. In actual application of photovoltaic-thermoelectric system uses a combination of multiple thermoelectric cells and photovoltaic cells. Multiple thermoelectric cell wires need to be wired，thermoelectric cells also have dimensional errors. Therefore, the area of photovoltaic cell is usually larger than that of thermoelectric cell. Part of photovoltaic cell backplane conducts natural convection and natural radiation heat exchange with the outside world. The thermal coupling characteristics of photovoltaic-thermoelectric interface are more complicated, and the law of influence on the efficiency of hybrid power generation system needs to be explored. These research use finite element software to simulate interface thermal field distribution of photovoltaic-thermoelectric hybrid power generation system, verification by experiment, in the case of 4 types of thermoelectric cell and photovoltaic cell area ratios investigating the influence law of hybrid power generation system temperature and hybrid power generation efficiency. The results show that the area ratio of thermoelectric cell to photovoltaic cell affects the temperature of hybrid power generation system, and system cooling effect of the photovoltaic cell in the hybrid power generation system increases when the area ratio of thermoelectric cell to photovoltaic cell increases. Respectively, under the standard conditions system with area ratios of 0.25, 0.50, 0.75 and 1.00 reduces the temperature of photovoltaic cell by 11.02%, 13.34%, 13.80% and 23.12%. Increasing area ratio of thermoelectric cell to photovoltaic cell can improve the efficiency of hybrid power generation system. Reducing contact thermal resistance can improve efficiency of hybrid power generation system on the same area ratio. As interface contact thermal resistance increases, efficiency of the hybrid power generation system decreases. Under condition of low irradiance, efficiency of photovoltaic-thermoelectric hybrid power generation system with different area ratios tends to be close. Through finite element simulation analysis and test verification, using high thermal conductivity interface materials, the hybrid power generation system with area ratio of 1.00 has the highest power generation efficiency. Therefore, in the practical application of photovoltaic-thermoelectric hybrid power generation, on the premise of ensuring the quality of the thermoelectric cell wiring, increasing the area ratio of thermoelectric cell and photovoltaic cell as much as possible. As the area ratio of thermoelectric cell to photovoltaic cell increases, contact thermal resistance influence on hybrid power generation system increases. For improve the efficiency of hybrid power generation system, the system interface contact thermal resistance requires the use of high thermal conductivity interface materials to reduce contact thermal resistance. The experiment uses cell widely used in the market to study the influence law of hybrid power generation system temperature and hybrid power generation efficiency, providing a reference for the combined use of photovoltaic cell and thermoelectric cell. [ABSTRACT FROM AUTHOR]

Greenhouses in remote areas have difficulty to access power. This paper aims to resolve this problem with a new system that can supply electricity to low-power devices such as energy-saving lamps, temperature and humidity monitoring system, digital equipment and other electrical equipment in greenhouses in remote areas. Current power supply to greenhouses uses distributed energy sources from wind and solar, which are not portable and susceptible to environmental changes. Under certain circumstances, power supplied from these systems is insufficient or even fails. As such, there is an increase in developing portable power generation systems. For example, in China, portable multi-purpose photovoltaic power generation system had been developed for agricultural production using remote-control system (programmable logic controller, PLC) to monitor pumping stations. There was also portable multi-power source power generation system to compliment wind power, solar energy and hand-cranked energy generation. Devices to generate power using the difference in temperature between human body and ambient environment exist, which are powerful enough to power LED lights. Another portable device is to generate thermal energy by burning combustibles in the field. All these portable devices have their pros and cons and the purpose of this paper is to present a new portable thermoelectric power generation system. The size of the system was 20 cm × 20 cm × 5 cm weighted 2580 grams, and its energy sources was from combusting biomass. A flat heat pipe was used for thermal conduction. We simulated performance of the system using the ANSYS, and set an experimental platform to test it. The experimental data showed that the highest temperature at the hot end of the system was 270.1 ℃, the maximum power output was 10.7 W, and the electrical efficiency was 5.73%. The results also revealed that the system had advantages of high hot-end temperature and high thermoelectric efficiency. It can generate electricity under extreme conditions in remote areas. Numerical and experimental analysis of various inputs and outputs indicated that the system is portable, the hot end temperature is high, and the thermoelectric efficiency is high. It provides a baseline for study of portable power generation system. [ABSTRACT FROM AUTHOR]

Thermoelectric power generation technology is a hotspot of scientific research on energy utilization in today's society because of its advantages of no noise, no pollutant emission, small volume, light weight, etc. However, its output power is too low, and the heat transfer effect is still a big problem. In this paper, the micro-heat pipe was applied to the solar temperature difference power generation under low temperature, and the system design of the thermoelectric power generation was optimized, and the problem of low light-heat output power and low-temperature output power was improved, and the dual-axis tracking and black by PLC were adopted. The chrome-plated gold film increased the solar heat absorption capacity by 5.32%. At the same time, the liquid metal was used to fill the silicon grease during the heat transfer and heat dissipation process, so that the micro heat pipe array could reduce the heat loss during the heat transfer process of the solar temperature difference power generation, so that the light heat was averaged. The output power could be increased by 2.21%. During the thermoelectric conversion process, the MPPT of the variable length conductance increment method improved the instability of the power output and the accuracy was not high. The overall photoelectric output power could reach 28.32 W. Compared with the previous one, the photoelectric output power increased by 5.19%. Through the tracking optimization of the solar temperature difference power generation system and the improvement of the heat transfer structure, the application of photovoltaic panels in agriculture was improved. We have proposed a collector-type thermoelectric micro-heat pipe array at low temperature. The complexity of control, and the use of liquid metal-filled silicone grease and insulation frame reduced heat loss, increased output power, and increased the area of the collector according to the characteristics of solar radiation dispersion. The use of PLC dual-axis tracking not only increased the solar heat absorption rate, but also increased the surface temperature. In the solar temperature difference power generation, the application of the micro heat pipe array could effectively utilize the solar radiation dispersion in the low-temperature power generation technology. Low flow density characteristics, this module had the characteristics of collectors, such as easy to integrate with buildings, simple tracking mode, and also had strong frost resistance and stable operation, which could improve the overall output power. Solar temperature difference power generation using micro-heat pipe arrays explored power optimization from two aspects of photothermal and thermal power, and improved the power generation power per unit area, which provided a reference for large-scale application of temperature difference power generation technology at low temperature. The micro heat pipe was a component that used internal working liquid to conduct heat transfer. During operation, the working liquid inside the micro heat pipe was evaporated into a gaseous state by the heat transferred from the hot end, and the middle pipe transferred the gaseous working liquid to a temperature difference. At the cold end, the liquid obtained after cooling was transported to the hot end by the capillary having a capillary action and evaporated again. [ABSTRACT FROM AUTHOR]

In order to improve the conversion efficiency of low-temperature utilization in solar energy resources, the micro heat pipe was used in solar thermal power generation to make a solar thermal power generation component, and the factors influencing the light-heat conversion efficiency and the thermoelectric efficiency of the component were analyzed in this article. At present, in the utilization of solar energy resources, this article mainly focused on the characteristics of strong dispersion of solar radiation and low energy density. The micro-thermal-tube-based solar thermal power generation device proposed in this article is a solar energy medium-low temperature utilization device. Solar low-temperature power generation technology can effectively compensate for the shortage of solar high-temperature thermal power generation. Medium-low temperature power generation technology can effectively utilize the characteristics of strong solar radiation dispersion and low energy flow density. And solar low temperature power generation technology can effectively avoid the limitations of high temperature power generation, such as the use of large areas of high temperature areas, high focus ratio, complexity of tracking method and control methods, high operating costs of installation and maintenance, technical difficulties and so on. The solar thermal power generation using the micro heat pipe array fully utilizes the strong dispersion characteristics of the solar radiation, expands the contact area, increases the heat absorption efficiency, and adopts heat preservation treatment to realize heat storage, radiation reduction, and convection with the environment. This module does not only have the characteristics of flat panel solar collectors, such as easy integration with buildings and simple tracking methods, but also has strong frost resistance and stable operation. This article conducted experimental research and simulation analysis on the factors influencing solar thermal differential power generation efficiency of micro heat pipe arrays and discussed the effects of factors such as solar radiation, ambient temperature, thermoelectric unit logarithm, and series-parallel connection mode on the efficiency of the components and made a major difference in temperature difference power generation technology. Scale application provided reference. When the temperature difference was 30 ℃, different logarithm thermoelectric units had almost no effect on conversion efficiency; the greater the temperature difference was, the greater the effect of thermoelectric logarithm on conversion efficiency would be. 127 pairs of thermoelectric units, when the temperature difference was 270 ℃, increased to 6.53%, the conversion efficiency was 4.12% higher than 1 pair of thermoelectric units. The same number of temperature difference power generation chips adopt different series-parallel connection mode, which also has a great influence on power generation efficiency; the load resistance is lower than 2 Ω, and the output power of four parallel circuits is the largest; when the load resistance is 1 Ω, the output power of four parallel circuits can reach 0.39 W; When the load resistance is between 2 and 15 Ω, the output power of the two series and the parallel is the largest; when the load resistance is 5 Ω, the latter one reaches 0.52 W; the load resistance is greater than 15 Ω, and the output power of the four components is the largest when connected in series. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve the conversion efficiency of low-temperature utilization in solar energy resources, the micro heat pipe was used in solar thermal power generation to make a solar thermal power generation component, and the factors influencing the light-heat conversion efficiency and the thermoelectric efficiency of the component were analyzed in this article. At present, in the utilization of solar energy resources, this article mainly focused on the characteristics of strong dispersion of solar radiation and low energy density. The micro-thermal-tube-based solar thermal power generation device proposed in this article is a solar energy medium-low temperature utilization device. Solar low-temperature power generation technology can effectively compensate for the shortage of solar high-temperature thermal power generation. Medium-low temperature power generation technology can effectively utilize the characteristics of strong solar radiation dispersion and low energy flow density. And solar low temperature power generation technology can effectively avoid the limitations of high temperature power generation, such as the use of large areas of high temperature areas, high focus ratio, complexity of tracking method and control methods, high operating costs of installation and maintenance, technical difficulties and so on. The solar thermal power generation using the micro heat pipe array fully utilizes the strong dispersion characteristics of the solar radiation, expands the contact area, increases the heat absorption efficiency, and adopts heat preservation treatment to realize heat storage, radiation reduction, and convection with the environment. This module does not only have the characteristics of flat panel solar collectors, such as easy integration with buildings and simple tracking methods, but also has strong frost resistance and stable operation. This article conducted experimental research and simulation analysis on the factors influencing solar thermal differential power generation efficiency of micro heat pipe arrays and discussed the effects of factors such as solar radiation, ambient temperature, thermoelectric unit logarithm, and series-parallel connection mode on the efficiency of the components and made a major difference in temperature difference power generation technology. Scale application provided reference. When the temperature difference was 30 ℃, different logarithm thermoelectric units had almost no effect on conversion efficiency; the greater the temperature difference was, the greater the effect of thermoelectric logarithm on conversion efficiency would be. 127 pairs of thermoelectric units, when the temperature difference was 270 ℃, increased to 6.53%, the conversion efficiency was 4.12% higher than 1 pair of thermoelectric units. The same number of temperature difference power generation chips adopt different series-parallel connection mode, which also has a great influence on power generation efficiency; the load resistance is lower than 2 Ω, and the output power of four parallel circuits is the largest; when the load resistance is 1 Ω, the output power of four parallel circuits can reach 0.39 W; When the load resistance is between 2 and 15 Ω, the output power of the two series and the parallel is the largest; when the load resistance is 5 Ω, the latter one reaches 0.52 W; the load resistance is greater than 15 Ω, and the output power of the four components is the largest when connected in series. [ABSTRACT FROM AUTHOR]

In order to improve the conversion efficiency of low-temperature utilization in solar energy resources, the micro heat pipe was used in solar thermal power generation to make a solar thermal power generation component, and the factors influencing the light-heat conversion efficiency and the thermoelectric efficiency of the component were analyzed in this article. At present, in the utilization of solar energy resources, this article mainly focused on the characteristics of strong dispersion of solar radiation and low energy density. The micro-thermal-tube-based solar thermal power generation device proposed in this article is a solar energy medium-low temperature utilization device. Solar low-temperature power generation technology can effectively compensate for the shortage of solar high-temperature thermal power generation. Medium-low temperature power generation technology can effectively utilize the characteristics of strong solar radiation dispersion and low energy flow density. And solar low temperature power generation technology can effectively avoid the limitations of high temperature power generation, such as the use of large areas of high temperature areas, high focus ratio, complexity of tracking method and control methods, high operating costs of installation and maintenance, technical difficulties and so on. The solar thermal power generation using the micro heat pipe array fully utilizes the strong dispersion characteristics of the solar radiation, expands the contact area, increases the heat absorption efficiency, and adopts heat preservation treatment to realize heat storage, radiation reduction, and convection with the environment. This module does not only have the characteristics of flat panel solar collectors, such as easy integration with buildings and simple tracking methods, but also has strong frost resistance and stable operation. This article conducted experimental research and simulation analysis on the factors influencing solar thermal differential power generation efficiency of micro heat pipe arrays and discussed the effects of factors such as solar radiation, ambient temperature, thermoelectric unit logarithm, and series-parallel connection mode on the efficiency of the components and made a major difference in temperature difference power generation technology. Scale application provided reference. When the temperature difference was 30 °C, different logarithm thermoelectric units had almost no effect on conversion efficiency; the greater the temperature difference was, the greater the effect of thermoelectric logarithm on conversion efficiency would be. 127 pairs of thermoelectric units, when the temperature difference was 270 °C, increased to 6.53%, the conversion efficiency was 4.12% higher than 1 pair of thermoelectric units. The same number of temperature difference power generation chips adopt different series-parallel connection mode, which also has a great influence on power generation efficiency; the load resistance is lower than 2 Ω, and the output power of four parallel circuits is the largest; when the load resistance is 1 Ω, the output power of four parallel circuits can reach 0.39 W; When the load resistance is between 2 and 15 Ω, the output power of the two series and the parallel is the largest; when the load resistance is 5 Ω, the latter one reaches 0.52 W; the load resistance is greater than 15 Ω, and the output power of the four components is the largest when connected in series. [ABSTRACT FROM AUTHOR]

In order to improve the conversion efficiency of low-temperature utilization in solar energy resources, the micro heat pipe was used in solar thermal power generation to make a solar thermal power generation component, and the factors influencing the light-heat conversion efficiency and the thermoelectric efficiency of the component were analyzed in this article. At present, in the utilization of solar energy resources, this article mainly focused on the characteristics of strong dispersion of solar radiation and low energy density. The micro-thermal-tube-based solar thermal power generation device proposed in this article is a solar energy medium-low temperature utilization device. Solar low-temperature power generation technology can effectively compensate for the shortage of solar high-temperature thermal power generation. Medium-low temperature power generation technology can effectively utilize the characteristics of strong solar radiation dispersion and low energy flow density. And solar low temperature power generation technology can effectively avoid the limitations of high temperature power generation, such as the use of large areas of high temperature areas, high focus ratio, complexity of tracking method and control methods, high operating costs of installation and maintenance, technical difficulties and so on. The solar thermal power generation using the micro heat pipe array fully utilizes the strong dispersion characteristics of the solar radiation, expands the contact area, increases the heat absorption efficiency, and adopts heat preservation treatment to realize heat storage, radiation reduction, and convection with the environment. This module does not only have the characteristics of flat panel solar collectors, such as easy integration with buildings and simple tracking methods, but also has strong frost resistance and stable operation. This article conducted experimental research and simulation analysis on the factors influencing solar thermal differential power generation efficiency of micro heat pipe arrays and discussed the effects of factors such as solar radiation, ambient temperature, thermoelectric unit logarithm, and series-parallel connection mode on the efficiency of the components and made a major difference in temperature difference power generation technology. Scale application provided reference. When the temperature difference was 30 °C, different logarithm thermoelectric units had almost no effect on conversion efficiency; the greater the temperature difference was, the greater the effect of thermoelectric logarithm on conversion efficiency would be. 127 pairs of thermoelectric units, when the temperature difference was 270 °C, increased to 6.53%, the conversion efficiency was 4.12% higher than 1 pair of thermoelectric units. The same number of temperature difference power generation chips adopt different series-parallel connection mode, which also has a great influence on power generation efficiency; the load resistance is lower than 2 Ω, and the output power of four parallel circuits is the largest; when the load resistance is 1 Ω, the output power of four parallel circuits can reach 0.39 W; When the load resistance is between 2 and 15 Ω, the output power of the two series and the parallel is the largest; when the load resistance is 5 Ω, the latter one reaches 0.52 W; the load resistance is greater than 15 Ω, and the output power of the four components is the largest when connected in series. [ABSTRACT FROM AUTHOR]

In order to improve the conversion efficiency of low-temperature utilization in solar energy resources, the micro heat pipe was used in solar thermal power generation to make a solar thermal power generation component, and the factors influencing the light-heat conversion efficiency and the thermoelectric efficiency of the component were analyzed in this article. At present, in the utilization of solar energy resources, this article mainly focused on the characteristics of strong dispersion of solar radiation and low energy density. The micro-thermal-tube-based solar thermal power generation device proposed in this article is a solar energy medium-low temperature utilization device. Solar low-temperature power generation technology can effectively compensate for the shortage of solar high-temperature thermal power generation. Medium-low temperature power generation technology can effectively utilize the characteristics of strong solar radiation dispersion and low energy flow density. And solar low temperature power generation technology can effectively avoid the limitations of high temperature power generation, such as the use of large areas of high temperature areas, high focus ratio, complexity of tracking method and control methods, high operating costs of installation and maintenance, technical difficulties and so on. The solar thermal power generation using the micro heat pipe array fully utilizes the strong dispersion characteristics of the solar radiation, expands the contact area, increases the heat absorption efficiency, and adopts heat preservation treatment to realize heat storage, radiation reduction, and convection with the environment. This module does not only have the characteristics of flat panel solar collectors, such as easy integration with buildings and simple tracking methods, but also has strong frost resistance and stable operation. This article conducted experimental research and simulation analysis on the factors influencing solar thermal differential power generation efficiency of micro heat pipe arrays and discussed the effects of factors such as solar radiation, ambient temperature, thermoelectric unit logarithm, and series-parallel connection mode on the efficiency of the components and made a major difference in temperature difference power generation technology. Scale application provided reference. When the temperature difference was 30 ℃, different logarithm thermoelectric units had almost no effect on conversion efficiency; the greater the temperature difference was, the greater the effect of thermoelectric logarithm on conversion efficiency would be. 127 pairs of thermoelectric units, when the temperature difference was 270 ℃, increased to 6.53%, the conversion efficiency was 4.12% higher than 1 pair of thermoelectric units. The same number of temperature difference power generation chips adopt different series-parallel connection mode, which also has a great influence on power generation efficiency; the load resistance is lower than 2 Ω, and the output power of four parallel circuits is the largest; when the load resistance is 1 Ω, the output power of four parallel circuits can reach 0.39 W; When the load resistance is between 2 and 15 Ω, the output power of the two series and the parallel is the largest; when the load resistance is 5 Ω, the latter one reaches 0.52 W; the load resistance is greater than 15 Ω, and the output power of the four components is the largest when connected in series. [ABSTRACT FROM AUTHOR]

With the development of the global economy and the improvement of people’s living standards, the demand for traditional energy is increasing, which has led to serious energy shortage, and increasingly serious environmental pollution. More and more attention has been paid to thermoelectric power generation technology which takes the industrial and automobile waste heat as heat source. In order to plant out-of-season plants and southern plants, the northern greenhouses generally use heating pipeline for heating. Cathodic protection, as the main protective measure for buried pipelines, plays an important role in pipeline protection. In order to alleviate the corrosion rate of heating pipelines, the method of joint use of external anti-corrosion insulation layer and cathodic protection is generally adopted during the deployment of metal pipelines. This is also the most economical and reasonable anti-corrosion measure. Cathodic protection protects the metal from being corroded by the environmental media (such as soil), protect pipeline or equipment by corrosion with auxiliary anode or sacrificial anode materials, thereby achieving the purpose of prolonging the service life of the protected pipeline and improving its safety and economy. However, the cost for conventional external-current cathodic protection method is high with large footprint, and the protection life of the sacrificial anode method is too short. Therefore, in order to provide reliable external-current cathodic protection for greenhouse heating pipelines, this article uses the waste heat from the surface of the underground heating pipelines, through direct conversion of thermal energy into electrical energy by a thermoelectric power plant, to provide the cathodic protection of the external current mode for the buried heating pipeline. The technology has the advantages of green, environmental protection, simple structure, safety and reliability. This article focuses on the research of thermoelectric power generation systems, introduces the basic theory of thermoelectric power generation and derives the relationship of characteristic parameters of the thermobattery. Based on the output characteristics of the thermobattery, this article designs a self-powered system based on BQ25504 chip. The system collects the thermoelectric energy and continuously supplies it in the maximum power point tracking mode during operation. The thermoelectric conversion energy is collected by the BQ25504 chip produced by TI, and then supplied by the step-down regulator chip LM317 to cathodically protect the buried heating pipeline. The design uses the temperature of the pipeline as a heat source, and it has the advantages of almost no land occupation, long-term use, flexible protection and energy saving. Through field tests, the temperature difference between the cold and the hot ends of the device was found to be 33.2°C, which proved that the greenhouse heating pipeline was a heat source worthy of utilization. Finally, through the natural corrosion test, it was found that when the horizontal distance of the anode bed was 1.69m and the protective potential provided by the device was -1100 mV, the degree of protection to the pipeline could reach 92.79%. This study provides a more feasible solution for the protection of greenhouse heating pipelines, and at the same time, the short-distance pipeline protection technology of external current mode is also explored.. [ABSTRACT FROM AUTHOR]

The power supply of the sensors driving circuit inside the solar greenhouse was restricted by the wired power supply, it is necessary to modularize and simplify the installation of the sensor and the design of the power supply. The wireless transmission and microwave transmission technologies were used as the power supply for the sensor drive circuit in the greenhouse in this paper. Based on the built-in photovoltaic microwave wireless power transmission system, the influence of various environmental factors on the transmission efficiency during the transmission process from the transmitting end to the receiving end was explored. The electromagnetic radiation of the transmitting antenna was simulated by using Ansoft HFSS software, and the radiation range of the transmitting antenna was obtained. On basis of energy conservation law and microwave theory, the relationship between received power and radiation efficiency, receiving distance and antenna size under the conditions of ideal environment and illumination intensity was analyzed by using MATLAB software. Taking the electromagnetic wave environment in the greenhouse at different distances and different time periods in one day of December in Harbin’s winter as the test object, the influence of the electromagnetic wave environment on the receiving power of photovoltaic microwave wireless power transmission system was tested and analyzed. The method of improving the transmission efficiency of solar greenhouse wireless transmission system was further explored. The structure of microstrip antenna array was given and the design concept of RC varactor diode automatic phase modulation circuit was proposed, and the reason why the RC varactor automatic phase modulator was used to make the phase of each array element in phase was deduced theoretically. Based on this theory and research, the microstrip antenna array was simulated and analyzed subsequently. Aiming at the design problem of microwave emission source, a design scheme of microwave power source with low power loss was proposed. The theoretical circuit diagram was given and simulated. The effect that microstrip antenna array can improve and enhance wireless transmission efficiency in solar greenhouse had been verified by further experiments. The test results showed that the system can effectively supply power for the sensor equipment within 8 m when the transmitting power was 500 W by microwave wireless transmission method and it can get 19.28 dB antenna gain of the maximum radiation direction of the microstrip antenna with 6×7 structure. Compared with the horn antenna, the gain of the microstrip antenna array is improved, that is, the orientation of the microstrip antenna array is better. The transmission efficiency can be improved by using the microstrip antenna array method, and the average receiving power can be increased by 1.58 W in the range of 0 ~8 m. [ABSTRACT FROM AUTHOR]

In the 21st century, the intensive use of fossil fuels has inevitably brought extreme damage to our living environment. The air pollution of many cities is grave, and the global greenhouse effect is increasing unknowingly. All those problems have had a tremendous impact on human production and life, which also make it is urgent to solve energy problems. Solar energy is one of the most promising, the most realistic, the most renewable and cleanest energy sources that can be exploited on a large scale in the world today. With the increasing environmental pollution and the increasing scarcity of energy, the development and use of solar energy have become an urgent task for human development. But, the efficiency is low, and there is a waste of heat energy. Therefore, in order to solve the problems about large-scale energy consumption of conventional energy resources in modern greenhouses, lower solar energy utilization efficiency and waste of waste-heat energy. This research bases on the photoelectric conversion and the photothermal conversion to design a concentration solar PV/TE compound power generation system. Photovoltaic cells use the photovoltaic effect principle to generate electricity. The parabolic concentrator converges solar to the surface of photovoltaic cells and enhances solar radiation intensity. The thermoelectric cells are attached to the back panel of photovoltaic cells, and the thermoelectric cells are used to simultaneously convert the excess heat generated by photovoltaic cells to electricity energy. A triangular heat pipe is treated as heat transfer element, and a certain amount of water is used to effectively transfer the remaining heat. The following objectives have been accomplished: some of the heat generated during the operation of photovoltaic cells was used to increase the temperature of hot side on thermoelectric cells; the other heat was transferred to heat storage by the convection of water in heat pipe and reused in heat storage tank. In order to test the electrical performance and thermal performance of this compound system, the corresponding electrical/thermal mathematical model was established in this paper, and the energy conversion of the system was analyzed to obtain the effect on the system about different solar radiation intensities and different flow quantities. At the same time, the system's test platform was set up, and annual tests were conducted according to the four seasons of spring, summer, autumn and winter. Tests were conducted from 09:00 to 15:00 which the intensity of solar radiation was the strongest on the test day. The results show that the electrical efficiency and thermal efficiency of concentration solar PV/TE compound power generation system are greater than those of a single power generation method, so that the gradient utilization of energy could be realized by the system. During the test, the electrical efficiency of this compound system could reach 20.18%, the thermal efficiency could reach 37.31%, and the energy efficiency could reach 32.5%. It can be seen that the concentration solar PV/TE compound power generation system has better power property than a without concentration solar PV-TE hybrid power generation system. Moreover, the power obtained by operating this system can supply power for environmental monitoring and lighting systems of the greenhouse. Especially in winter, the heat energy obtained can provide heat for the growth of crops in the greenhouse. [ABSTRACT FROM AUTHOR]

In order to solve the problem of inefficiency of photovoltaic conversion caused by temperature rise when photovoltaic cell panel generates the electricity after receiving solar radiation, the present paper discussed about a method that the thermoelectric power generation technology could cool down the photovoltaic cell panel, this method was a kind of active cooling mode. However, when the temperature difference between the hot side and cold side of thermoelectric generator was close to each other, the thermoelectric conversion efficiency was too low, which had a negative effect on the device. To solve the above problem, the thermal switch was adopted to control the equipment, the switch would close when the temperature of the photovoltaic cell panel reached the predetermined value, and the heat passed down. On the contrary, the switch was in the off state. Through the control of the thermal switch, the thermoelectric generator could work stably and efficiently in the working range. Meanwhile, it could also improve the adaptive capacity to environment of the device. At the same time, the flat heat pipe had been chosen as the heat transfer unit, using water convection to cool down the system. After cooling the photovoltaic cell panel, not only its temperature would decrease, but also the service life could be extended. On the other hand, the cold side temperature of the thermoelectric generator could also decrease. Firstly, the present paper analyzed the effect caused by different intensity of optical radiation, different panel temperatures and different cold side temperatures in the system. Secondly, the whole experimental platform of system had been established. Last but not the least, the hybrid power generation system had been examined so as to test the property of hybrid power generation equipment which was based on PV/TE (photovoltaic/thermoelectricity) of thermal switch. The result revealed that the efficiency of hybrid power generation equipment was higher than a single electricity generating method included the photovoltaic power generation mode and the thermoelectric power generation mode. At the same time, the gradient utilization of energy could be realized by the equipment. In view of the experimental equipment had been built, the performance of the PV/TE hybrid power generation device based on thermal switch was investigated in two different ways, including the instant property and full-day performance test. The instant property of the PV/TE hybrid power generation device based on thermal switch was tested during 08:00-16:00 on August 27, 2017. The results showed that the efficiency of power generation could reach the peak point of 19.45% and the output of power generation could reach the peak point of 32.15 W. The full-day performance of the PV/TE hybrid power generation device based on thermal switch was tested from August 22 to 27, 2017. The results showed that the average power generating efficiency of the PV/TE hybrid power generation device based on thermal switch could reach 17.72% and its highest point could reach 18.37%. The test place was located in Northeast Agricultural University, Harbin. Finally, the test results showed the electricity acquired could basically meet the power supply needs of testing system of agricultural greenhouse and remote sensor. [ABSTRACT FROM AUTHOR]

When using the principle of collecting light to produce thermoelectric power, some lights can not arrive condenser plate due to the fact that light travels in straight line and some are blocked by the battery plate, so the bottom of the battery plate produces shadow area, resulting in the overall output power decreasing. In order to improve the overall output power, based on the example of the parabolic condenser plate, this paper proposed the planar type and parabolic type design to make up the shadow area. Based on the construction model, the parameters of shadow area were acquired, and thus the optimal compensation size and setting angle of planar and parabolic reflector were obtained. After that, the compensation design of planar and parabolic reflector was made. The best solution of planar compensation was as follows. The size of 2 planar reflectors was √2 times the width of shadow region, the left planar reflector’s setting angle was 135°, and the right planar reflector’s setting angle was 45°. If there was a deviation angle, the setting angle for the left and right reflector would change to 135° minus the deviation angle and 45° minus the deviation angle accordingly, and at the same time, the left planar reflector must be increased to a certain height. Also, the related parameters of parabolic compensation were obtained, such as arc length, placement angle and aperture size. In the case of planar compensation, the simulation was carried out with Tracepro. By setting different size and setting angle in Tracepro, the correctness of the theoretical compensation method was proved. And under the same conditions, the effects of the 2 kinds of compensation methods were compared. The results showed that the planar reflector’s compensation illumination range was about 1 W/m2, and the parabolic reflector’s illumination range was about 2 W/m2, so the performance of parabolic reflector was better than that of planar reflector. By compensation, the shadow area at the bottom of the cell panel was well eliminated. In order to verify the simulation results, experiments were carried out at Northeast Agricultural University on October 21, 2015. Measurement parameters included ambient temperature, surface temperature of heat collector, temperature of cold end, and the output voltage and current. The measure period was from 09:00 to 14:00. The energy of hot end of the thermoelectric module came from the parabolic condenser plate, and the cold end used the natural wind cooling. It should be pointed out that the outside influence factors were ignored. Compared with no compensation, the temperature of thermoelectric generator (TEG) under planar compensation and parabolic compensation had a significant increase in the hot end, and the parabolic compensation and planar compensation ranged from 315.14 to 357.46 K and from 312.6 to 453.4075 K respectively, while the temperature of the cold end was almost constant and ranged from 285.12 to 290.47 K. The output power of no compensation, planar compensation and parabolic compensation ranged from 20.05 to 28.94 W, from 20.36 to 29.78 W and from 21.04 to 30.35 W respectively. The originality of this paper was the research on the effect of the compensation of shadow area at the bottom of solar thermoelectric power generation sheet on overall output power. In conclusion, the work above shows that the overall output power is improved by effective compensation, more precisely, parabolic compensation is better than planar compensation. [ABSTRACT FROM AUTHOR]

Due to environmental and energy security concerns, many researches are being conducted in harvesting the energy of the sun. Thermoelectric is one material which generates a voltage in the presence of a temperature gradient. When these materials are sandwiched between a solar absorber and a heat sink to establish a temperature difference and generate power, they are called solar thermoelectric generators (STEGs), converting solar power to electric power. In this paper, we conducted performance analysis and testing of a concentration solar thermoelectric generation device based on thermoelectric generator (TEG). The device included an electrical generating unit with 10 serially connected thermoelectric modules using a traditional semiconductor material, Bi2Te3. The semiconductor was illuminated by concentrated solar radiation on hot side and cooled by running water through flat heat pipe on the cold side with the condensation of the heat pipe in water tank and the evaporation of the heat pipe connected with the cold side of TEG. A sun-tracking parabolic trough concentrators was used to concentrate solar radiation. Its orientation towards the sun was achieved with a stepper motor. In order to express the performance of concentration solar thermoelectric power generation system accurately, a comprehensive energy transfer model was established, the simulation results showed that when the ambient temperature were constants, the increases of solar irradiance making the solar-thermal conversion efficiency dropped from 58.86% to 54.94%, but thermoelectric conversion efficiency was enhanced from 1.17% to 6.15%. Under the influence of processing technology and materials, even if the same type of thermoelectric modules under the same temperature difference, open circuit voltage and internal resistance were different. When in series with 10 modules, the temperature at the hot side of thermoelectric modules were different spatially due to uniformed heat flow. fl At the same time, due to effect of peltier the temperature of the modules changed along with the different of output power, these factors would lead to different output characteristic of each thermoelectric module. When multiple modules were in series together, it can't make each module working at maximum power output state, resulting in the overall electric energy production reduced. In this research, we used centralized-distributed-hybrid MPPT (Maximum Power Point Tracking) control scheme to overcome the maximum power points mismatching among different thermoelectric generator modules and maximized the energy efficiency of the device. The results of tests showed that the output power of TEG with MPPT was achieved fast, accurately and steadily, and in 30 minutes working time the average power added 3.2 W. In addition, we determined the influence of water flow quantity and optimal load for the performance. The results showed that when flow quantity was less than 8 L/min, temperature of heat pipe condensation and TEG cold side were drop rapidly. But when the flow quantity was greater than 8 L/min, the temperature change was flat out. Output power was rising along with the increase of temperature difference. The maximum power was 30.2 W. The optimal match load was near resistance when temperature difference was low. The optimal load increases gradually along with the increase of temperature difference. The optimal load resistance was 38 Ω with temperature difference of 150 K. Whole day tests for the device have done during the 08:00-16:00 on June 16, 2015, from which the output power smoothly changing and it was between 22.8-30.1 W. With eight-hour test, the average power was 27.8 W, and the electric quantity was 222.4 W·h. The thermoelectric conversion efficiency was up to 5.4% and the maximum efficiency of the device was 4.1%. These test results were consistent with theoretical model analysis. The concentration solar thermoelectric generation device is solid-state device, it has no moving parts, which increases reliability and reduces maintenance. It has many applications such as rural electrification in developing countries and power supply for remote sensors. [ABSTRACT FROM AUTHOR]