Fire Behaviour and Performance of Photovoltaic Module Backsheets

Given that photovoltaic (PV) power plant can cause and/or contribute to fires in buildings, the fire risk resulting from a PV power plant installation on a building roof or façade should be assessed in order to meet building fire-safety requirements. In fact, PV plant installed on a roof or a façade could fail and cause a fire and/or promote or facilitate its spread. Accident analyses have shown that PV systems are often installed without due consideration of fire propagation and fire spread caused by the presence of modules, cables and electrical boards on the roof. This paper shows a proposal for a method to evaluate the reaction-to-fire characteristics of a PV module and provides experimental results that compare the behaviours and performances of four kinds of PV module backsheet. Some of the commonest type of backsheet materials available on the market have been selected in order to evaluate and compare the reaction-to-fire performances of these products: Backsheet no.1 has three layers (PET/PET/Primer), Backsheet no.2 is composed of four layers (PET/Aluminium/PET/Primer), Backsheet no.3 is a Fluoro-Coating/PET/EVA three-layer sheet and Backsheet no. 4 comprises an outside coating, a PET layer and an inside Coating. Test results show that the choice of a single layer for Backsheet no.4 represents the best solution among the ones tested. Even though Backsheet no.2 shows the same reaction-to-fire rating as that of Backsheet no.4, the PV module production process could be critical as regards the electrical behaviour of the module itself, since aluminium foil is a material that conducts electricity. Moreover, since the fire-performance assessment of PV panels in Europe is left at a national level, the approach reported in this paper could represent a useful reference to be used as a baseline for developing a European standard or, better still, an International standard.