| Summary: | 碩士 === 國立東華大學 === 光電工程學系 === 101 === In this paper, we use two innovative methods to measure actual concentration ratio (CRA) and global optical efficiency (OEg) of Fresnel lenses with ultraviolet light aging. The first method is using III-V triple-junction solar cell to receive the focus sunlight power. The second method is using ND filter to reduce the focus sunlight energy that can be measured with handheld solar power meter. The CRA and OEg can be simply calculated, and the concentrated light intensity can be obtained. The advantage of first method is that it has a wide absorption spectrum, but the conversion efficiency (η) is variable when the incident sunlight intensity is changed. The second method can measure the OEg simply, but the disadvantage is that the measuring absorption spectrum is narrow and the concentrated spot is difficult to align on the photodiode. For UV aging, the OEg values of 2×4 SOG, PMMA and 2×2 PMMA Fresnel lens are declined 1%, 7% and 0.41% respectively when the UV exposure dose is about 50 KWh/m2. Under the same UV exposure condition, the values of transmission spectrum in the range of 400nm to 1100nm for bulk samples of SOG and PMMA are declined about 1% and 0.85% respectively, and the yellow index value of PMMA bulk is greater than that of SOG. The result shows that the ultraviolet durability for the SOG Fresnel lens is better than that for the PMMA Fresnel lens.
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