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Photovoltaic (PV) technologies have shown remarkable progress recently in terms of annual production capacity and life cycle environmental performances, which necessitate timely updates of environmental indicators. Based on PV production data of [2004][2005][2006], this study presents the life-cycle greenhouse gas emissions, criteria pollutant emissions, and heavy metal emissions from four types of major commercial PV systems: multicrystalline silicon, monocrystalline silicon, ribbon silicon, and thin-film cadmium telluride. Life-cycle emissions were determined by employing average electricity mixtures in Europe and the United States during the materials and module production for each PV system. Among the current vintage of PV technologies, thin-film cadmium telluride (CdTe) PV emits the least amount of harmful air emissions as it requires the least amount of energy during the module production. However, the differences in the emissions between different PV technologies are very small in comparison to the emissions from conventional energy technologies that PV could displace. As a part of prospective analysis, the effect of PV breeder was investigated. Overall, all PV technologies generate far less life-cycle air emissions per GWh than conventional fossil-fuelbased electricity generation technologies. At least 89% of air emissions associated with electricity generation could be prevented if electricity from photovoltaics displaces electricity from the grid.

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Water use by the electric power industry is attracting renewed interest as periods and zones of arid weather are increasingly encountered, and various regional energy-production scenarios are evaluated. However, there is a scarcity of data on upstream water factors and discrepancies of data from different sources. We reviewed previous studies of water use in electricity generation and used full-life cycle accounting to evaluate water demand factors, both withdrawal and consumption, for conventional-and renewable-electrical power plants. Our investigation showed that moving to technologies like photovoltaics and wind offers the best option for conserving our water supply. We also emphasize the importance of employing a transparent, balanced approach in accounting life-cycle water usages.