Life Cycle Assessment of Crystalline Photovoltaics in the Swiss ecoinvent Database

This paper describes the life cycle assessment (LCA) for photovoltaic (PV) power plants in the new ecoinvent database. Twelve different, grid-connected photovoltaic systems were studied for the situation in Switzerland in the year 2000. They are man-ufactured as panels or laminates, from monocrystalline or polycrystalline silicon, installed on facades, slanted or flat roofs, and have 3 kWp capacity. The process data include quartz reduction, silicon purification, wafer, panel and laminate production, mounting structure, 30 years operation and dismantling. In contrast to existing LCA studies, country-specific electricity mixes have been considered in the life cycle inven-tory (LCI) in order to reflect the present market situation. The new approach for the allocation procedure in the inventory of silicon purification, as a critical issue of for-mer studies, is discussed in detail. The LCI for photovoltaic electricity shows that each production stage is important for certain elementary flows. A life cycle impact assessment (LCIA) shows that there are important environmental impacts not directly related to the energy use (e.g., process emissions of NOx from wafer etching). The assumption for the used supply energy mixes is important for the overall LCIA results of different production stages. The presented life cycle inventories for photovoltaic power plants are representative for newly constructed plants and for the average photovoltaic mix in Switzerland in the year 2000. A scenario for a future technology (until 2010) helps to assess the relative influence of technology improvements for some processes. The very detailed ecoinvent database forms a good basis for similar studies in other European countries or for other types of solar cells. Copyright # 2005 John Wiley & Sons, Ltd. key words: allocation; ecoinvent; electricity mixes; life cycle assessment; LCA; multi-output process; photovoltaic; Switzerland