Can new renewable energies replace nuclear power plants?

In principle, yes. New renewable energy sources in Switzerland have sufficient potential to replace our nuclear power plants. But only if we develop seasonal storage for electricity from renewable sources and replace direct electric heating and water heating with solutions based on renewable heat production.

The five reactors of the four Swiss nuclear power plants produce an average of 24 TWh of electricity per year (2018). Striking coincidence: the combined potential of new renewable energies for the production of green electricity is estimated at 24 TWh! Thus, if we look at the annual overall balance alone, electricity from new renewable energy sources could almost entirely replace the output of our nuclear power plants.

In reality, the situation is a little more complicated… Nuclear production is very constant over the year (so-called “ribbon” electricity), while the potential for green electricity production fluctuates over the day and is much greater in summer than in winter, due to the combined contribution of photovoltaics and run-of-river hydropower, which is about 2.5 times higher in summer than in winter [→ Q11]. While daily storage, particularly via pumped storage, can smooth the curves of daily renewable electricity production, the seasonal difference is more complex to resolve.

One option could be to export our surplus green electricity in the summer and, in the winter, import wind power (for example). Our overall renewable balance would thus be even over the year. This is the solution recommended in the 100% renewable scenario [→ Q87]. But if we want to replace our nuclear power plants exclusively with renewable electricity produced in Switzerland, then we would have to be able to transfer the surplus electricity from the summer to the winter season. In other words, we would have to be able to store around 5 TWh of electricity for a period of six months. This is a major challenge, for which we do not yet have a mature technological solution [→ Q74].

But why should we limit ourselves to replacing only nuclear electricity with renewable electricity? In cases where nuclear electricity is currently used to produce heat, substitution by heat from renewable sources is already possible. Today, about 5 TWh of electricity is consumed in water heaters and direct electric heaters (resistance heating), 2/3 of which is consumed in the period from October to April. The as yet untapped potential of wood biomass (5 TWh) [→ Q54] and environmental heat via heat pumps (7 TWh) [→ Q59] could largely replace this winter electricity consumption.

Arithmetically speaking, it would therefore be possible to replace nuclear power plants with new renewable energy sources. However, this accounting exercise should not obscure two facts:

Firstly, getting out of nuclear power is not the only challenge facing Switzerland. Renewable energies must serve a broader purpose than simply replacing nuclear power. In particular, they must contribute to the decarbonisation of our energy mix, which means gradually replacing our consumption of fossil fuels.

Secondly, the replacement of nuclear power plants by new renewable energies will only be possible in practice if there is sufficient social acceptance for these forms of energy, if the necessary manpower is found, if adequate market rules are proposed to allow these energies to compete, and if citizens participate in the energy shift by adopting these forms of energy [→ Q98].