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Life cycle assessment of photovoltaic technologies

Solar energy systems (Photovoltaic technologies) are proved to be safe, sustainable and environmental-friendly source of energy in comparison to the conventional energy sources. With the emerging of new manufacturing technologies, the environmental performance of PV technologies is expected to be further improved in the near future (Peng, Lu, and Yang, 2013; Cucchiella & D’Adamo, 2012; Evans, Strezov, & Evans, 2009; Tsoutsos, Frantzeskaki, & Gekas, 2005). PV technologies have shown significant progress lately in terms of annual production capacity and life cycle environmental performances, which necessitates the assessment of environmental impacts of such technologies. The different PV technologies show slight variations in the emissions when compared the emissions from conventional energy technologies that replaced by the latest PV technologies (Vasilis M. Fthenakis, Kim, & Alsema, 2008). With the up scaling of thin film module production for meeting future energy needs, there is a growing need for conducting the life cycle assessment of such technologies to analyze the future environmental impacts resulting from such technologies (Raugei, Bargigli, & Ulgiati, 2007). The manufacturing processes of solar cell involve the emissions of several toxic, flammable and explosive chemicals. Lately, in the field of photovoltaic research, there has been a continual rise in research and development efforts focused on reducing mass during cell manufacture. Such efforts have resulted in reducing the thickness of solar cells and thus the next generation solar cells are becoming thinner and eventually risks of exposure are reduced nevertheless, all chemicals must be carefully handled to ensure minimal human and environmental contact. The large scale deployment of such renewable energy technologies could result in potential negative environmental implications. These potential problems can pose serious challenges in promulgating such technologies to a broad segment of consumers (Evans, Strezov, & Evans, 2009; Tsoutsos, Frantzeskaki, & Gekas, 2005; Vasilis M Fthenakis, 2003). There are studies which have shown that the PV environmental impacts come mainly from the production of the cells; operation and maintenance requirements and associated impacts are relatively small. However, in a more recent study by Collier, Wu, and Apul (2014), they conducted the life cycle assessment for CZTZ and Zn3P2 PV technologies for the first time. In this study, the cradle to gate environmental impacts from CZTS and Zn3P2 are assessed and compared with those from current commercial PV technologies such as CdTe and CIGS. The four impacts including Primary energy demand (PED), Global warming Potential (GWP), freshwater use and eco-toxicity were primarily studied. It has been claimed by the authors (Collier et al, 2014) that for all four impacts studied, CdTe and Zn3P2 performed better than CIGS and CZTS. In general, the contribution of raw (absorber) material extraction and processing to the total impacts was low compared with impacts coming from electricity consumption during manufacturing. Therefore, to reduce environmental impact, future PV technology development should focus more on the process improvement (Collier et al, 2014).The future research should also focus on the water-energy nexus as it is crucial to understand the water impacts of potential PV technologies in order to better manage our water resources.

References
 * 1) Collier, J., Wu, S., & Apul, D. (2014). Life cycle environmental impacts from CZTS (copper zinc tin sulfide) and Zn 3 P 2 (zinc phosphide) thin film PV (photovoltaic) cells. Energy, 74, 314-321.
 * 2) Cucchiella, F., & D'Adamo, I. (2012). Estimation of the energetic and environmental impacts of a roof-mounted building-integrated photovoltaic systems. Renewable and sustainable energy reviews, 16(7), 5245-5259.
 * 3) Evans, A., Strezov, V., & Evans, T. J. (2009). Assessment of sustainability indicators for renewable energy technologies. Renewable and sustainable energy reviews, 13(5), 1082-1088.
 * 4) Fthenakis, V. M. (2003). Overview of potential hazards (pp. 2): Elsevier, New York.
 * 5) Fthenakis, V. M., Kim, H. C., & Alsema, E. (2008). Emissions from Photovoltaic Life Cycles. Environmental science & technology, 42(6), 2168-2174. doi: 10.1021/es071763q
 * 6) Peng, J., Lu, L., & Yang, H. (2013). Review on life cycle assessment of energy payback and greenhouse gas emission of solar photovoltaic systems. Renewable and sustainable energy reviews, 19, 255-274.
 * 7) Raugei, M., Bargigli, S., & Ulgiati, S. (2007). Life cycle assessment and energy pay-back time of advanced photovoltaic modules: CdTe and CIS compared to poly-Si. Energy, 32(8), 1310-1318.
 * 8) Tsoutsos, T., Frantzeskaki, N., & Gekas, V. (2005). Environmental impacts from the solar energy technologies. Energy Policy, 33(3), 289-296.