End-of-life treatment of crystalline silicon photovoltaic panels. An emergy-based case study

Although photovoltaic (PV) technology has been projected as one of the most promising candidates to replace conventional fossil based power generation, claims about the potential disadvantages of the PV panels end-of-life (EoL) deserve careful attention in order to fully establish a feasibility and viability baseline and support technological and implementation policies. The current challenge concerning PV technology resides in making them efficient and competitive in comparison with traditional power generation systems, without disregarding the appraisal of EoL impacts. The emergy analysis method proved to be a reliable approach for the evaluation of the efficiency, effectiveness and environmental friendliness of technological processes under a global scale perspective and may likely be applied to the EoL PV investigation as a complement of conventional energy and economic assessments. Therefore, this method was used in this study to evaluate the sustainability of a PV panel recycling process. In addition, this paper aims to explore the implications of methodological assumptions when Emergy Accounting (EMA) tackles waste management systems, in order to address the shortcomings in this field. Results show that the PV panel treatment can generate large environmental benefits not only at the local scale of the process, but also at the larger scale of the industrial manufacture and material recovery, as well as at the even larger scale of the biosphere where resources come from and pollution is released. The comparison between the emergy invested for electricity production via PV and fossil energy sources also including EoL resource and environmental costs, highlights that PV technology is competitive under both energy and environmental points of view. This comparison reveals that the solar technologies imply remarkable emergy savings (1.45E+12 sej/kWh for fossil sources versus 3.57E+11 sej/kWh for crystalline silicon photovoltaic down to 2.31E+11 sej/kWh for cadmium telluride photovoltaic). Results clearly show that PV solar power can be considered a mature technology and can favorably compete with other renewable and non-renewable options for electricity generation. However, efficiency improvements of PV panels thermal recovery are still possible and may lead to further decrease of still too large emergy costs of the treatment process, not to talk of potential recovery alternatives such as chemical treatment for silicon cells and better upstream industrial design.