BAPV array: Thermal modeling and cooling effect of exhaust fan

Abstract

Thermal modeling and mitigation methods of thermal effects for building-applied photovoltaic (BAPV) systems have become important for the industry in order to predict energy production and lower the cost per kilowatt-hour (kWh). The operating temperature of BAPV modules can reach as high as 90°C in desert climatic conditions such as Phoenix, Arizona. These high operating temperatures will have a significant impact on the power generation and a dramatic impact on the lifetime of PV modules. The traditional method of minimizing the operating temperature of BAPV modules has been to include a suitable air gap for ventilation between the rooftop and the modules. The previous work at Arizona State University (ASU) was aimed at identifying the effects of various air gaps on the temperature of individual BAPV modules. The goal in this work was to develop a thermal model for a small residential BAPV array consisting of 12 closely packed identical polycrystalline silicon modules at a single air gap of 2.5 inches from the rooftop of 23° tilt with ceramic tiles. The thermal model coefficients for the array are empirically derived from a simulated field test setup at ASU and are presented in this paper. Additionally, this project investigates the effects of cooling the array with a small 40-watt exhaust fan. The fan had only a small effect on power output or efficiency for this 2.5-inch air gap array, but provided slightly lower temperatures (higher lifetime) and better temperature uniformity (higher power output) across the array.