Reduction of environmental impacts in crystalline silicon photovoltaic technology - an analysis of driving forces and opportunities

Over the past 10-15 years the environmental impacts of photovoltaic modules based on crystalline silicon have decreased substantially. Improved process technology has led to more efficient material use and lower energy consumption. This has for example led to a reduction of the energy payback time by 50% over the past 15 years. Also waste emissions have decreased significantly. In this paper we will investigate what the major driving forces for this improvement have been, whether it was to reduce material cost, to improve cell efficiency or other factors. To what extent has sustainability or eco-efficiency been a driving force in the technology improvement? After this historical perspective we will look into future prospects with respect to new c-Si cell concepts and future module production technology. Could another 50% reduction of energy payback be reached? We will investigate how, in terms of greenhouse gas emission and other environmental impacts, c-Si technology compares with thin film photovoltaics and with other sustainable energy options, like wind, biomass, nuclear and carbon sequestration. On which aspects can c-Si photovoltaics face the competition and on which aspects would improvements be necessary or helpful. Thirdly we will investigate which of the expected improvements in c-Si technology, driven by cost reduction objectives, will help to reduce environmental impacts further and which could even be counter-effective. Finally we will look at the question whether it is necessary to make environmental improvement a separate objective in R&D and in process optimization, and in what way this may be achieved.