Photovoltaics energy payback times, greenhouse gas emissions and external costs: 2004–early 2005 status

Abstract

Life cycle assessments and external cost estimates of photovoltaics have been often based on old data that do not reflect the extensive technological progress made over the past decade. Our assessment uses current (2004-early 2005) manufacturing data, from twelve European and US photovoltaic companies, and establishes the Energy Payback Times (EPBT), Greenhouse Gas (GHG) emissions and external environmental costs of current commercial PV technologies. Estimates of external costs are about 70% lower than those in recent high-impact publications which were derived from the old data. Copyright # 2006 John Wiley & Sons, Ltd. INTRODUCTIONI t is well understood that production of energy by burning of fossil fuels generates a number of pollutants and carbon dioxide. What is less known is that any anthropogenic means of energy production, including solar, generate pollutants when their entire life cycle is accounted for. A life cycle starts from the mining and processing of materials that comprise solar cells, modules and balance of system, and ends to their final decommissioning, disposal and/or recycling. Costs associated with the environmental, health and societal impacts that are not included in the direct cost of electricity, are called external costs of electricity production. While societal external costs are difficult to quantify, external costs associated with environmental and health protection or damage have been quantified in monetary terms. Perhaps the most well-known effort to quantify environmental and health damages due to electricity production, is the European Union's series of ExternE (External Costs of Energy) projects. The ExternE methodology starts from emissions generated at specific sources and follows their impact to receptors through atmospheric dispersion and dose-response functions. In general, this type of environmental impact assessment is well accepted, although assumptions related to Broader Perspectives the monetary valuation of estimated impacts, especially green-house related impacts, are debateable. 'The ExternE methodology has been applied in a large number of European and national studies to give advice for environmental, energy and transport policies.' 1 Photovoltaic installations in Germany were presented in the latest ExternE report to the European Commission 1 as having 30% higher health impacts than natural gas and GHG emissions of 180 g CO 2 -eq./kWh which would be 10 times higher than those for the nuclear fuel cycle (Figure 1). These results were based on 15-years old PV systems and even older data on module production technology. z Also based on outdated PV technology data a life cycle-based comparison of energy technologies in Australia 2 showed that PV emits about 100 g CO 2 /kWh during its life cycle (Figure 1). The results from these two studies were widely circulated and especially the ExternE publication with its official status is likely to have influenced policy decisions with regard to energy technology. More recent (i.e., 2000) data are included in the Ecoinvent...

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