| Concentrating photovoltaic (CPV) technology has been showing a fast growing trend in recent years. However, one challenge that CPV technology faces is how to cool down the CPV solar cells effectively and then the system efficiency can be improved. Aiming at eliminating the shortages of conventional CPV cooling approaches, a direct liquid-immersion cooling method was proposed for linear CPV systems. The thesis consists of five parts. The effects of liquid-immersion cooling on the characteristics of silicon CPV cells for linear CPV systems were investigated.(1) The spectral transmittance of de-ionised (DI) water, isopropyl alcohol (IPA), ethyl acetate, and dimethyl silicon oil was measured through spectrophotometer. The real spectral transmittance was achieved based on the developed photometry correction method. The calculated Jnp of solar cell indicated that there were insignificant changes in power output of silicon solar cells when operated in the candidate liquids, but the four candidate liquids were not suitable as immersion cooling liquids for CPV systems with multijunction solar cells.(2) The electrical characteristics of silicon CPV cells were examined under 10-30X concentration, which were in both the absence and presence of the immersion liquids. The results showed that the improvements of the electrical performance of cells were observed as the liquid film presence and the biggest percentage change was 15.2%, arising from the optical effect and electrical effect caused by liquid film. With the increase in liquid thickness, the extent of the improvement of the efficiencies of the cells operated in liquids decreased. Because more light was absorbed by the liquid when cells operated in thicker liquids. Furthermore, more power output from the cells operated in liquids was achieved under higher concentration ratio. However, the electrical performance of the silicon CPV cells degraded after a long time immersion in DI water, but the stable electrical characteristics of the silicon CPV cells immersed in the other three organic liquids for a long time were achieved.(3) The possible factors that caused the degradation in electrical performance of silicon CPV cells operated in DI water were investigated separately by running the bare cells test, lead based-soldered tabbed cells test as well as the epoxy tabbed cells test in parallel. Within immersion period, the electrical characteristics of bare cells had only a minor change. The presence of lead and tin black oxides on the lead based-soldered tabbed cells and red deposition on the epoxy tabbed cells confirmed the occurrence of galvanic corrosion on the tabbed cells with copper tabs. However, further experimental results indicated that the bare cells themselves were not damaged after long-time DI water immersion.(4) Conformal coating technology was proposed to apply for the silicon CPV cells to eliminate the degradation when operated in DI water for a long time. The reliability of the selected silicone coatings and the silicone coated silicon CPV cells was assessed through designed accelerated aging tests. The tests results showed that the performance changes in both of them were less than the total degradation allowed for them under these tests. In addition, the increase in electrical performance of the silicon CPV cells was detected in the presence of silicone coatings. Moreover, the temperature of the coated cell in DI water can be still maintained lower than that of conventionally encapsulated cell.(5) A novel linear receiver incorporating direct liquid-immersion cooling was developed for linear CPV system. The prototype of this kind of receiver was fabricated with silicon CPV cells. The thermal performance of the silicon CPV solar module in the designed receiver was simulated with Fluent software. The results established that low and uniform cell temperature can be achieved.
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