Applied Sciences (Sep 2016)
A Novel Concentrator Photovoltaic (CPV) System with the Improvement of Irradiance Uniformity and the Capturing of Diffuse Solar Radiation
Abstract
This paper proposes a novel concentrator photovoltaic (CPV) system with improved irradiation uniformity and system efficiency. CPV technology is very promising its for highly efficient solar energy conversion. A conventional CPV system usually uses only one optical component, such as a refractive Fresnel lens or a reflective parabolic dish, to collect and concentrate solar radiation on the solar cell surface. Such a system creates strongly non-uniform irradiation distribution on the solar cell, which tends to cause hot spots, current mismatch, and degrades the overall efficiency of the system. Additionally, a high-concentration CPV system is unable to collect diffuse solar radiation. In this paper, we propose a novel CPV system with improved irradiation uniformity and collection of diffuse solar radiation. The proposed system uses a Fresnel lens as a primary optical element (POE) to concentrate and focus the sunlight and a plano-concave lens as a secondary optical element (SOE) to uniformly distribute the sunlight over the surface of multi-junction (MJ) solar cells. By using the SOE, the irradiance uniformity is significantly improved in the system. Additionally, the proposed system also captures diffuse solar radiation by using an additional low-cost solar cell surrounding MJ cells. In our system, incident direct solar radiation is captured by MJ solar cells, whereas incident diffuse solar radiation is captured by the low-cost solar cell. Simulation models were developed using a commercial optical simulation tool (LightTools™). The irradiance uniformity and efficiency of the proposed CPV system were analyzed, evaluated, and compared with those of conventional CPV systems. The analyzed and simulated results show that the CPV system significantly improves the irradiance uniformity as well as the system efficiency compared to the conventional CPV systems. Numerically, for our simulation models, the designed CPV with the SOE and low-cost cell provided an optical power ratio increase of about 17.12% compared to the conventional CPV without the low-cost cell, and about 10.26% compared to the conventional CPV without using both the SOE and additional low-cost cell.
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