| As one kind of the new and renewable energy, solar energy is clean and universal. As a consequence, solar energy application technologies attract tremendous attention in the last decades. Among these technologies, photovoltaic technology and solar thermal technology are the most popular and studied sufficiently. Particularly, solar cell utilization is cut down by adopting concenctrator photovoltaic (CPV) technology, which uses optics to focus sunlight onto a small receiving solar cell. In this way, the intensity of sunlight on solar cell is multiplied by the concentration ratio. On the other hand, PV/T technology has been investigated for years. The idea of PV/T technology is to integrate solar cells and solar thermal collectors and therefore the overall efficiency would be enhanced because both electricity and heat can be produced at the same time.Among the CPV modules/systems, those with point-focus Fresnel lens recently have attracted more attention because of the advantages lie in Fresnel concentrator such as small volume, light-weight, mass production with low cost as well as effectively increasing the energy density. Most of all, uniform illumination on solar cell could be obtained by optimizing the Fresnel concentrator, even the concentration ratio is over 1000× suns. Studies on CPV systems with point-focus Fresnel are plentiful at home and abroad. In sharp contrast, those systems which can generate electricity and heat simultaneously are rarely reported. Another point to state is that most of the theoretical and experimental investigations on PV/T technology are aiming at non-concentrating systems. The researches on concentrator photovoltaic/thermal (CPV/T) modules/systems, especially on high concentrator photovoltaic/thermal (HCPV/T) systems are fragment.To solve these challenges and problems, this research originally proposed a novel HCPV/T module based on point-focus Fresnel lens. The module is equipped with high-efficiency InGaP/GaAs/Ge triple-junction solar cells and its geometry concentration ratio is as high as 1090× suns. An outdoor experimental setup was built with these HCPV/T modules and the outdoor experiments were conducted. On the basis of experimental data, the electrical and thermal performance of the module are evaluated. A classic method for estimating cell operating temperature is also developed based on the experimental data, which is difficult to be obtained in a Fresnel CPV system. Besides, numerical methods are employed to establish the electrical and thermal models of the module. The models are developed to simulate, predict and evaluate module’s performance, aiming to serve as a classic case of HCPV/T fields. By the virtue of the validated models, influences of different parameters on module performance are analyzed in detail. On this basis, two HCPV/T systems with roll-tilt tracking stands and another two HCPV/T systems with radar tracking supports were built. Their performance are evaluated according to experimental measurements under sorts of conditions. To summarize, the main contents and achievements of this research are as follows:A concentrator with point-focus Fresnel lens and secondary optical prism structure is adopted in the HCPV/T module. The illumination on solar cell is simulated by TracePro under STC condition. The results show that relatively flat Normal distribution sunlight appears on the cell, which means satisfactory concentrating illumination is obtained with this kind of concentrator. A kind of heat exchanger with axis-grooved tube is designed for the CPV/T receiver. By employing it, extra heat energy can be collected by the module without increasing its cost.Based on outdoor experiments, the electrical and thermal performances of the module are investigated by energetic and exergetic analysis. The results show that the HCPV/T module can obtain an instantaneous electrical efficiency of 28% and a highest instantaneous thermal efficiency of 55%, which means its overall energetic efficiency can exceed 80%. From the second law point of view, a highest exergetic efficiency of 33.9% can be achieved. This indicates that it is feasible and effective to integrate Fresnel CPV modules and the solar thermal collector from the viewpoint of either scientific research or engineering application.Both electrical and thermal models of the module are also developed by numerical methods in this research. The electrical model is based on the Shockley diode equation, and its primary function is to simulate module’s IV characteristic and PV characteristic. The thermal model is grounded on a two-dimensional steady-state heat transfer model, which is developed by analyzing the energy distribution and flux on the CPV/T receiver. Both experimental and simulated results present that the electrical efficiency of the module is mainly determined by solar irradiation rather than cell temperature. It increases when irradiance increases, while it enters a plateau when direct irradiance is above 600W/m2. The thermal efficiency increases with the increment of irradiance, ambient temperature and water mass flow rate. On the contrary, increasing water temperature and wind speed will lower the thermal efficiency.Last but not the least, two kinds of HCPV/T systems were built, one is installed on roll-tilt tracking stands and the other is mounted on radar tracking supports. The outdoor experiments under sorts of conditions were conducted. According to the results, the electrical effiencies of these two system are approximate. Over 24% of solar energy could be transformed by each of the systems. However, their thermal performance are extremely distinguished, with an intercept value of 56% and 37%, respectively. This is mainly because the roll-tilt system has longer pipelines than the radar system, which leads to larger heat loss to the environment. Thus, the thermal efficiency of the radar system is notably higher than the roll-tilt system’s. Whereas, the roll-tilt system shows more advantages when considering the convenience of installation, cleaning and maintenance of the systems. |
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