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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 haz- ards 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. Both the environmental legislation and economic and market conditions currently hinder investment in HP infrastructure. Regarding legal conditions, certain energy infrastructure has been declared to be of "national interest" in the Swiss Energy Act. However, wetlands of national importance are excluded from this weighing of interest, limiting hence the HP development potential at retreating glaciers that feature such protected wetlands in their forefields. Regarding market environments and general framework conditions, the major uncertainties during typical concession periods of 80 years in combination with long planning and approval procedures do not foster investments in HP. The target values of the ES 2050 in terms of annual generation by HP can be met only in an upper-bound scenario, which would require more favourable framework conditions for HP than today. Otherwise, a intermediate scenario is more realistic, according to which the annual generation is expected to increase by 0.5 TWh/a until 2050, which is well below the target of 2.6 TWh/a. A lower-bound scenario predicts a decrease by -3.0 TWh/a, mainly due to mitigation measures to fulfill the Waters Protection Act, with reductions in generation primarily from increased residual flow requirements. In terms of energy storage, an effective increase of 1.2 TWh by 2050 is forecast in the intermediate scenario including dam heightening and a few new periglacial storage HP plants. Such an increase would correspond to almost 20 % of today’s energy storage capacity of the Swiss HP reservoirs. It is expected that the increase of storage capacity of 2 TWh by 2040 envisaged in the recently revised draft version of the Electricity Supply Act cannot be implemented by HP within this rather short time frame. However, setting such targets is important. All in all, significant efforts are required to maintain the electricity generation from HP around its current level. Potential increases are very limited because a high share of the Swiss HP generation potential is already exploited. In contrast to generation, the storage capabilities of HP shall be significantly expanded because more large-scale seasonal storage is an essential prerequisite for the efficient integration of a higher share of RES into the electricity supply system.
ETH Zurich2021
