Modelling of silver modules incorporating a lambertian rear reflector

Abstract

Modules incorporating cells which are bifacial and narrow can make use of rear reflectors to capture most of the incident sunlight while covering only a fraction of the module area with cells. Sliver® cells, invented and developed at the ANU, meet these criteria. In this paper we analyse the performance limits of such modules for the case where a diffuse (lambertian) reflector is used. The analysis is carried out for various cell thicknesses, cell spacings and reflectivities of the lambertian reflector. The results show that excellent performance can be realised despite the simplicity of the structure. A module with a 50% coverage with 70µm thick cells can capture up to 84% of the light entering the module. Importantly, the performance of this kind of module is insensitive to module orientation. The results of the analytical model are compared with ray tracing studies and measurements and are shown to be in good agreement. It is concluded that significant module cost reductions can be achieved for only modest reductions in performance by covering half or less of the module surface with cells.