Investigation of temperature effects in efficiency improvement of non-uniformly cooled photovoltaic cells

Abstract

This study investigates the performance of photovoltaic (PV) modules with respect to temperature and proposes pipe layouts enabling efficient cooling. The operating temperatures of the PV cells are not equal since the fluid flowing through the cooling pipes has a temperature difference between the inlet and the outlet of the pipes. The warm atmosphere affects the current density/voltage J/V characteristics of the PV modules. Therefore, the PV cells under cooling tend to operate at a relatively lower temperature resulting in an enhancement in their efficiencies. This paper calculates the J/V characteristics of each PV cell depending on its operating temperature. Then the overall J/V characteristics of the PV module are recorded. The module is cooled by a fluid flowing through pipes underneath the PV module backside. The fluid serves as both heat sink and solar heat collector. In contrast to the existing models, where a PV module and its PV cells are assumed to be having the same operating temperature, our model tries to address the non-uniform distribution of the operating temperatures of the PV cells. The main idea of this paper is to consider the effect of the cooling process on the performance of each PV cell independently in order to more accurately calculate the effect of temperature on the PV parameters of the module. Different designs of cooling pipes are also introduced in this work to find the effect of pipe geometries on the performance of the PV modules. The geometry can improve the PV cell parameters and consequently the performance of the PV module. In all designs, the flow rate of the fluids must be kept the same in order emphasize the effect of geometry only. The best design is the one which keeps the operating temperature of the PV cells as minimum as possible resulting in a maximum energy yield of the PV cells.