Meta-study of potential for photovoltaic installations in Switzerland

Numerous studies have been conducted to evaluate the potential of photovoltaic systems in Switzerland, considering roofs, facades, infrastructure, or free land installations. These studies differ by the datasets used, their methods, the assumptions on the system performance, and the installation details, but more importantly, by the various reduction factors introduced to obtain a realistic estimate of the photovoltaic potential. The present study reviews the critical elements of these studies, especially for roofs and facades, and their influences on the potential value. The system integration and grid aspects are not taken into account. It is observed that the system performance alone, given mainly by the considered module efficiency, does not permit to unify the results. The details of the methods, especially in the case of the analysis based on machine-learning techniques and flat reductions to account for unsuitable or forbidden roofs or facades, are the main reasons for the discrepancies in the results. A potential of 50-60 TWh/a from roofs and 20 TWh/a from facades can be estimated from the most recent studies, while a minimum potential of more than 20 TWh/a from other surfaces (infrastructure, lakes, alpine and agrivoltaics) could be exploited. A conservative potential of 70 TWh/a is sufficient for the realisation of the Swiss Energy transition.