A comparative life-cycle assessment of photovoltaic electricity generation in Singapore by multicrystalline silicon technologies

This paper presents a comparative life-cycle assessment of photovoltaic (PV) electricity generation in Singapore by various p-type multicrystalline silicon (multi-Si) PV technologies. We consider the entire value chain of PV from the mining of silica sand to the PV system installation. Energy payback time (EPBT) and greenhouse gas (GHG) emissions are used as indicators for evaluating the environmental impacts of PV electricity generation. Three roof-integrated PV systems using different p-type multi-Si PV technologies (cell or module) are investigated: (1) Al-BSF (aluminum back surface field) solar cells with the conventional module structure (i.e. glass/encapsulant/cell/encapsulant/backsheet); (2) PERC (passivated emitter and rear cell) devices with the conventional module structure; and (3) PERC solar cells with the frameless double-glass module structure (i.e. glass/encapsulant/cell/encapsulant/glass). The EPBTs for (1) to (3) are 1.11, 1.08 and 1.01 years, respectively, while their GHG emissions are 30.2, 29.2 and 20.9 g CO2-eq/kWh, respectively. Our study shows that shifting from the conventional Al-BSF cell technology to the state-of-the-art PERC cell technology will reduce the EPBT and GHG emissions for PV electricity generation. It also illustrates that mitigating light-induced degradation is critical for the PERC technology to maintain its environmental advantages over the conventional Al-BSF technology. Finally, our study also demonstrates that long-term PV module reliability has great impacts on the environmental performance of PV technologies. The environmental benefits (in terms of EPBT and GHG emissions) of PV electricity generation can be significantly enhanced by using frameless double-glass PV module design.