Hybridization of an alpine pumped-storage hydropower plant with floating solar photovoltaics: a study from the water resource perspective

Variable renewable energy sources, like wind and solar power, are crucial for decarbonizing electricity systems, but pose challenges due to their intermittency. Hybridization (i.e., joint operation) with reservoir-based hydropower, which is a programmable resource, can address this issue. However, an open question is still how hybridization of existing hydropower plants could affect the water resources management. We propose a modelling framework for an existing pumped-storage hydropower plant located in the Swiss pre-alpine region, complemented by a fictional floating solar photovoltaic plant with a nominal capacity equal to about 50 % of the hydropower plant. The modelling framework considers reservoir management constraints and environmental flow requirements. The hourly simulations over 38 years show: (i) a 20 % increase in overall annual energy production, (ii) an improvement in the system reliability through mutual complementarity, and (iii) a potential for enhancing downstream environmental flow up to 50 % during the hot summer season, thereby enabling more streamflow for ecological purposes.