Ptimization Analysis And Experimental Research Of Stationary Solar Concentrator

With the increase of building energy consumption, solar energy as an inexhaustible clean energy, combined it with the building, is one of the effective measures of building saving energy. The need besides of electricity and hot water, also includes building heating, refrigeration, dehumidification, which require higher quality heat source, especially in winter.The concentrating PV/T technology can to some extent solve this problem. However, it should be highlighted that the solar concentrator integrated with building has its significant features, including the following:(1) It should be combined with building facade or roof, namely fixed installation, without a tracking system or seasonally adjusted, which can further reduce the system operation, maintenance costs.(2) The stationary solar concentrator should have a larger half acceptance angle, while the half acceptance angle is inversely proportional with geometrical concentration ratio. Therefore, the half acceptance angle needs to match the geometrical concentration ratio as large as possible, so that the concentrating application has more advantages, such as more electricity output or higher temperature heat source.(3) The solar concentrator should have a more uniform flux distribution, in order to ensure the more output characteristics of photovoltaic cells.This paper focusing on building energy demand significantly, put forward to a novel lens-walled CPC, and made series of theoretical design and experimental research. The main works are as follows:(1) Based on the study of the mirror CPC and solid CPC, combining refraction and reflection, a novel concept of lens-walled CPC was proposed. The optical efficiency at different incidence angle and the larger half acceptance angle of the Lens-walled CPC of2.5X and4X were simulated respectively with the method of ray tracing. In addition, the flux distribution at different incidence angle was also indicated.(2) The material with low cost, good optical performance, stable and durable properties is selected as the lens material to make the lens walled CPC. Indoor and outdoor tests were all inducted to measure the optical performance of lens-walled CPC comparison with the mirror CPC and solid CPC. Moreover, the lens-walled CPC for E-W and N-S alignment were also tested in the whole day.(3) The structure of a lens-walled CPC with air gap was introduced. At the same time, series of geometrical parameters were optimized to attain a higher optical efficiency. A yearly prediction on energy absorbing in different months with different solar radiation was simulated. The dynamic model of optical efficiency with different azimuth angle and altitude angle was established in order to provide theoretical basis for the experiment.(4) The technology with solar cell laminating on the square tube directly was used to develop the lens-walled CPC-PV/T, and a stationary lens-walled CPC-PV/T system was designed and constructed, which can be integrated with building directly. The experiment was conducted in Hefei to study the instantaneous electricity/thermal performance and the whole day performance of lens-walled CPC-PV/T. It paid more attention to discuss and analyze the optical efficiency, electrical efficiency and thermal efficiency in different time on the whole day through the comparison experiment with the non-concentrating PV/T system to verify the the rationality of the design and optimization for the lens-walled CPC-PV/T.The paper has the following innovative features;(1) Combining the refraction and reflection, a novel lens-walled CPC was proposed. It has a larger half acceptance angle than mirror CPC with the same geometrical concentration ratio, so it has more colleting-time and can improve the cost performance.(2) The total internal reflection was inducted in optimizing the structure of lens-walled CPC to increase the optical efficiency. And the lens-walled CPC has more uniform flux distribution than mirror CPC, which was beneficial to the PV output.(3) The lens-walled CPC can operate as a static solar concentrator without tracking system or season adjusted with a higher geometrical concentration ratio than mirror CPC.(4) PV was laminated on the square tube directly, which avoided the traditional process on welding process with cooling pipe, so the system has more reliability.(5) The lens-walled CPC can be integrated with building facade and roof, avoiding fixing difficulty, complex tracking system or a larger initial investment against general solar concentrator. At the same time, the lens-walled CPC-PV/T can effectively improve the heat resource temperature, and not only provide the electricity power and living hot water, but also provide the higher temperature heat resource for the civil construction heating in winter and heat driven cooling in summer, which will extend the potential application prospect of solar energy in building and is also a valuable exploration on building integrated with concentrating photovoltaic/thermal (BICPV/T) systems application.