Report: solar power can reduce Swiss reliance on hydro

The Zervreila reservoir in canton Graubünden, southeastern Switzerland. Keystone / Gian Ehrenzeller

A study has estimated the extent to which new solar infrastructure, combined with existing Alpine dams, can help Switzerland avoid a winter energy shortage.

This content was published on October 28, 2022 minutes

The Neue Zürcher Zeitung (NZZ) reportedExternal link on Friday on a quantitative model by two energy experts which analyses how the interplay between solar and hydropower in Switzerland could play out in the next years.

According to the estimates, new solar panels – specifically those in the high mountains, above the fog line – would produce most of their energy between February and May; precisely the period during which the level of Alpine reservoirs is sinking.

More solar energy in winter would thus allow the reservoirs to hold more water back for emergency shortages: concretely, the recently approved plans to speed up construction of large-scale Alpine solar parks could allow the reservoirs breathing space to save up to 3 terawatt hours per year, or 19 days of Swiss energy needs.

Using the solar energy when it is produced, then taking advantage of the natural storage capacity of the reservoirs, would also reduce the need to develop storage centres to deal with the unpredictable nature of solar energy, the study said. However, the authors also noted that the practice of hydroelectric companies using all available water in order to sell surplus electricity abroad would also have to stop in order for this strategy to be effective.

Natural batteries

Alpine reservoirs are a key source – along with river power plants – of Swiss hydropower, which accounts for 57% of domestic electricity production. The reservoirs in particular are like “batteries” which can be loaded up for the winter, and then released according to the country’s needs, the NZZ writes.

The summer months are used to fill up the reservoirs, which reach capacity in October-November, before releasing energy gradually to reach their low point in April-May.

Earlier this week, Swiss mountain reservoirs were 85% full – 2.5 percentage points higher than the average for this time of year over the past two decades.

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