Thermal Response of Building Integrated Photovoltaic Systems: Analysis of Monitoring Data from Installations at Three Sites in Europe

Building Integrated Photovoltaic (BIPV) systems comprise any system where photovoltaic (PV) components are incorporated into the building envelope, thereby replacing traditional construction elements of roofs or facades for example, and hence ensuring their functions (water tightness, esthetics, mechanical strength etc.). A significant advantage of BIPV compared to non-integrated systems is the lack of the need to allocate neither land nor additional mounting structures and to favor local use of energy (self-consumption solutions at building or district level). As a drawback, the operating temperature of BIPV systems are usually higher compared to free standing PV systems because of limited cooling (1,2). Maintaining or reducing the operating temperature of PV elements is important during the photovoltaic energy conversion process since it influences the efficiency, the decline in performance over time and the lifetime of the PV system. In this paper, we present and analyze experimental results of the monitoring of ten BIPV systems realized within the “Performance BIPV” project (partners CSTB, CEA, CNRS, Transénergie and Cythelia) and by EURAC in three European locations. The aim of our study is to investigate and compare the operative temperature issue in different BIPV applications. Each BIPV system is instrumented to record component temperatures (at the backside of PV modules), electrical production and environmental conditions. The monitored BIPV systems dataset is compared with two ground mounted PV plants located in Bolzano, which are monitored by EURAC since 2010 (3–5). The variation of PV module temperatures rise above ambient temperature is studied as a function of the global irradiation. Based on measured data, an empirical equivalent thermal resistance between PV modules and ambient temperature is considered for various time scales based on a static model. An overview on empirical equivalent thermal resistance values for each analyzed system is provided, resulting in a range from 0.0297 to 0.0397 for most of the BIPV systems and from 0.0249 to 0.0291 for the not-integrated PV systems. As further studies, collaborative projects will be launched between some partners in order to propose solutions to improve the thermal operating conditions of BIPV systems.