Socio-economic analysis of a nano-enabled technology : nano-tio2 coatings solar panel efficiency
Résumé
While alleged properties of nanotechnologies are generally known, their development may be undermined because of scientific uncertainty surrounding their potential health and environmental impacts; Hence the ongoing efforts from international organizations (OECD, European Commission, CEN) to promote their socio-economic analyses. But, to our knowledge, very few studies have performed case-studies of full comparison of potential social costs and alleged benefits (but see [1]). Our work consists in such a socio-economic analysis in the specific case of a nano-TiO2-based coating that can be sprayed onto solar panel surfaces. Relying on photocatalytic properties of TiO2, the coating is expected to prevent the decreasing in efficiency of solar panels due to their organic fouling [2]. This study, whose perimeter is the whole 2013 French photovoltaic park, is based on the comparison of two alternative scenarios: a benchmark scenario corresponding to the actual status quo, namely the absence of any cleaning operation on the solar panel; and a scenario corresponding to the progressive treatment, over 5 years, of the solar panels. Because different products relying on the same technology may have different characteristics and performances two different marketed products were studied in the second scenario. From a methodological point of view, our study relies (1) on the identification of the major potential impacts expected from the development of such a technology, (2) on their quantification, and (3) on their monetization. Adressing the above questions, issues and related uncertainties did take the authors to consider a wide set of scientific and technical fields of expertise. The study is thus based on interviews of experts from different disciplines, namely metrology, toxicology and ecotoxicology. The main benefit is obviously linked to the preservation of solar panel yields which allow the owners to sell electricity whereas they could have not in the benchmark scenario. Simultaneously, preserving solar panel yields prevents the emission of greenhouse gases that would have been emitted if the electricity has had to be produced by the French energy mix. Concerning the costs – beyond the costs of implementation themselves – the potential impacts on health and environment were studied. This first required a full characterization of the aerosols sprayed on the panels and potentially released in the environment or inhalated by workers in charge of the panels’ coating. No relevant ecotoxicological impact has eventually been found. Concerning health issues, chronic bronchitis and lung tumors have been identified as potential adverse effects. This issue being highly uncertain, we voluntarily developed a worst-case scenario in terms of exposure coupled with state-of-the-art toxicological results [3, 4]. Our study concludes to a positive benefit - cost index even with the most conservative assumptions corresponding to a precautionary approach.