Hydropower (HP) is the backbone of the Swiss electricity system providing around 60% (36 TWh/a) of the total electricity generated on a yearly average. With the planned phase-out of nuclear power plants, HP and other Renewable Energy Sources (RES) will need to fill the substantial gap in domestic electricity generation, particularly in the winter season. Because of the intermittent nature of RES generation (mainly solar photovoltaics and wind) and their typically lower production in winter, the need for storage up to the seasonal time scale increases. Such large-scale storage is offered mainly by storage HP. However, maintaining the HP infrastructure will pose significant challenges, mainly due to market and legal conditions. For the latter, partly diverging interests according to the Swiss legislation will need to be fulfilled at the same time.
On the one hand, HP is supposed to be extended in the scope of the Energy Strategy (ES) 2050 and to keep climate goals by reducing greenhouse gas emissions. On the other hand, current negative effects of mainly older HP infrastructure on aquatic ecology will need to be remediated according to the Swiss Waters Protection Act to fulfill biodiversity goals. Meeting all these goals will require to systematically refurbish the existing Swiss HP fleet, to extend it in a smart way with prioritization on large storage HP to foster electricity generation in the critical winter season and to construct new HP schemes, again with a focus on electricity generation in winter.
As to new HP facilities, the retreating glaciers open new opportunities for high-altitude storage plants that, besides generating quasi CO₂-free electricity, have also other benefits like protection from natural hazards and water supply for irrigation. Extending existing storage lakes by heightening of their dams is a complementary option to create additional storage with generally low environmental impact and possibly higher public acceptance. [...]