Study On Design Of Novel Fresnel Concentrator In Concentrated Photovoltaic

With the continuous increase of the photoelectric conversion efficiency ofconcentration photovoltaic cells under the conditions of high concentration, theconcentrated photovoltaic power generation technology as the third-generationphotovoltaic technology, its power generation costs reduce gradually, thus the role ofthe concentrated photovoltaic power generation technology in the field of solarphotovoltaic power use becomes more and more prominent. As the most criticalcomponents in the concentrated photovoltaic system in addition to photovoltaic cell,the performance of optical concentrator directly determines the level of powergeneration efficiency of photovoltaic cell and thus determines the electricity cost ofthe entire photovoltaic system. The flat-plate Fresnel concentrator is widely used inthe commercial large-scale concentrated photovoltaic power plant because of its thinthickness, high light transmittance, light weight, low cost, simple processing andmany other advantages. However, the traditional flat-plate Fresnel concentrator ismainly designed basing on the imaging principles of design, the concentration effectis not very good and there are many problems such as serious dispersion, large aspectratio, poor uniformity of focus spot and so on. Therefore, this paper in support of theNational863projects (2006AA05010102), carried out theoretical studies on the novelFresnel concentrator design and provided a series of effective optical solutions. Thespecific contents include the following work:1. The optimization design method of high-efficiency Fresnel concentrator was researched, which had given full consideration to the impact of the solarspectrum, the multi-junction cell response and outdooor temperature changesin the concentrator design stage. By introducing truncation efficiency ofphotovoltaic cell and finding the design main wavelength of each Fresnelconcentrator's sawtooch to optimize its surface profile, which makesphotovoltaic cell obtain the maximum of solar radiation energy. Based onthis optimization method, a new Fresnel concentrator which maximized thetransfer efficiency of the solar radiation energy was designed, whose solarenergy transfer efficiency was increased by nearly10%than the traditionalFresnel concentrator.2. The decrease of Fresnel concentrator system aspect ratio was researched.Two new Fresnel concentrator design methods, dual-reflector type and thelight guide plate type, were proposed. Their system aspect ratios can even bedesigned to below0.1and reduced to about one tenth of the traditionalFresnel concentrated photovoltaic system, which makes the whole systemmore compact, smaller and more conductive to meet the future developmenttrend of miniaturization, lightweight and integration with solar cell forconcentrated photovoltaic system.3. The improvement of irradiance uniformity on focus spot was researched. Animproved design method for the existing TIR-R Fresnel concentrator wasproposed. The energy transfer efficiency of the concentrated system isimproved effectively through the introduction of the critical point and theaddition of a total reflective prism at the bottom of secondary lens. At thesame time, several sawteech of the primary Fresnel lens can correspond to asame ring of the secondary lens, which efficiently simplified the complexityof designing and manufacturing, and thus reduced the processing costs.