| Countries like Germany. Spain, the United States and Japan have launched large-scale "PV roof plan" to promote the photovoltaic (PV) power generation technology. To ease the power shortage in its western areas, China has also developed the western solar power projects. But solar panels are deployed in complex environment and ages easily, which can lead to fire hazards. As PV becoming more and more popular and spreading from sparsely populated areas to densely populated areas and evolving from the photovoltaic power station to BIPV, fires of PV will become a direct threat to the safety of life.Previous studies on the safety of photovoltaic panels mainly explored the causes to start a fire and few of them focused on PV panels’ damage once they were on fire. In this paper, by analyzing real-life PV fire cases and surveying about PV fire reference literature, we classify PV fire causes into two categories:(1) arc malfunction and (2) spontaneous combustion. PV fire has its specialty, mainly reflected in two aspects:electric shock on firefighters and its "occupation" of the roof and other rescue channels. Safety testing of PV modules generally follows three standards:IEC 61215:2005,IEC 61730-2:2004. UL 1703:2004. We have compared the three standards in the experimental sections, with regards to aspects including:temperature test, hot spot endurance test, lire test and reverse current overload test. We choose the most popular PV material, polycrystalline silicon solar cells in our experiments. We conduct experiments on the cone calorimeter platform under five kinds of radiation intensity, namely,28 kW/m2,30 kW/m2,35 kW/m2,40 kW/m2 and 45 kW/m2. We have calculated key parameters such as time to light (TTI), critical radiant flux (CHR), heat release rate (HRR), mass loss rate (MLR), and so on. PV panels’ heat hazard and smoke toxicity are then evaluated and analyzed base on Petrella evaluation system.According to the theoretical analysis, photovoltaic modules are thermal thick. Experimental results also verified this conclusion. Petrella analysis system shows that the flashover risk of photovoltaic modules is low when the external radiation heat fluxes are less than 30 kW/m2. While, the flashover risk of photovoltaic modules is moderate when the external radiation heat fluxes are between 35 and 45 kW/m2. In addition, the total heat release of photovoltaic modules is between 38-57 kW/m2, which makes them at the moderate degree of risk in Petrella evaluation system. In fact, photovoltaic modules widely used in power stations are 5 to 10 times as thick as the experimental ones. Moreover, flame temperature of roof fires can reach 800-900℃. or even 900-1000℃ when fires spread to the whole house. That is, flame heat fluxes in real fires are much larger than the experiment ones. Thus, the total heat release of photovoltaic modules in power station will be far higher than the experimental values. Experimental results show that the toxic gases generated by solar panels can be ignored.In addition, EVA, the main combustible material in the photovoltaic modules, has also been studied and analyzed.according to the experimental results, the thermal risk and toxic gases released by EVA when it is burning are both evaluated. |
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