Design and investigation of a novel lens-walled compound parabolic concentrator with air gap

Stationary solar concentrators can be integrated with building façade and roof, which can reduce the area of solar cells and attain higher temperature heat resource, especially in winter for building application. In this paper, a stationary lens-walled compound parabolic concentrator (CPC) with air gap was designed and investigated to meet the application requirements. The lens-walled CPC with air gap differs from the original lens-walled CPC in that it has an air gap between the lens structure and the reflector that maximizes total internal reflection and improves optical efficiency by reducing the optical losses of the specular reflection. The simulation and experiment verified the function of the new structure, and the results indicated that the lens-walled CPC with air gap increases optical efficiency by more than 10% compared with the original lens-walled CPC. In addition, the flux distribution of the lens-walled CPC with air gap is more uniform than that of the common mirror CPC. Thus, the lens-walled CPC with air gap not only has a larger half acceptance angle and a more uniform flux distribution than the common mirror CPC but also operates at a higher optical efficiency than the original lens-walled CPC. Thus, the lens-walled CPC with air gap provides a realistic and valid solution to Building Integrated with Concentrating Photovoltaic (BICPV) as a stationary concentrator and has good prospects for several applications.