What will it take to achieve a climate-neutral energy system?

Net-zero is a target that the Swiss energy system has to meet by 2050. This means that the entire energy value chain of generation, distribution, storage and use will no longer emit climate-changing greenhouse gases into the atmosphere, and will be climate-neutral overall. The replacement of fossil fuels will play a key role in this regard, and can be achieved in Switzerland through the electrification of the transport and heating sectors. “Research shows us that it is technically and economically possible for the Swiss energy system to function without fossil fuels by 2050.”

These were the words of Vanessa Wood, ETH Vice President for Knowledge Transfer and Corporate Relations, at the public symposium of “Energy Week 2021”, the annual ETH energy conference. It is an viewpoint shared by Monika Krüsi, Chair of the Board of Directors of Repower, a Swiss distribution and service company in the energy sector. The energy industry and its approaches to solutions are still highly heterogeneous, she says; pragmatic solutions and an investment-friendly market environment are essential for the future, along with collaboration, flexibility and digitalisation.

In recent weeks, ETH researchers have calculated possible energy scenarios with a view to highlighting the various development possibilities for the composition of a climate-neutral energy system in Switzerland by 2050. Five main trends have emerged, as Gabriela Hug, Professor of Electrical Energy Systems and Chair of the Energy Science Center (ESC) explained at the symposium:

• Electricity imports during the winter months are likely to be higher in the future than they are today, at least in the medium term, as Switzerland phases out nuclear energy and demand for electricity increases due to the electrification of heating systems (heat pumps) and passenger cars (e-mobility).
• If the process of electrification in mobility and heating progresses faster in the near future than is currently the case, Switzerland’s dependence on foreign electricity imports will increase further in the medium term (around 2040). From a technical and economic perspective, however, this would be feasible, although flexible gas-fired power plants (including the capture and storage of greenhouse gases) may become an option or a necessity, depending on the scenario.
• Climate change and increasing weather extremes will affect the seasonal availability of hydropower. This will have an impact on the possible or necessary expansion of the energy system – in extremely dry years, electricity production from hydropower will decrease and the electricity production peaks of run-of-river plants are likely to shift from winter to spring. This decline means that less energy will be available overall, thereby increasing the need for investment. On the other hand, the energy will tend to be available when it is needed. The greater differences between extremely wet and dry years make investment decisions more complicated.
• Cost-optimised development of the Swiss electricity system depends greatly on developments in neighbouring countries: the more France, Germany, Austria and Italy rely on renewable energy sources and create overcapacity in this area, the more cost-efficient it would be to expand flexible electricity production (e.g. gas-fired power plants, pumped storage) in Switzerland.
• If cross-border electricity trade between Switzerland and Europe were to be severely restricted in the long term (e.g. by 50 percent in the scenarios), significantly less electricity would be available for trading with other countries and Switzerland would have to increase its domestic electricity generation capacity.

The energy scenarios are not forecasts. They do not make any predictions about the future, but show what trends are possible based on certain assumptions and starting points.

Expanding the deployment of photovoltaics

A comparison of the different scenarios confirms the importance of expanding the deployment of photovoltaics in Switzerland. In the Nexus-e reference scenario, the main scenario used by the ETH researchers based on economic optimisation, electricity from hydropower and photovoltaic (PV) systems will cover most of the future electricity demand, while other renewable energies such as biomass and wind power will play a lesser role. This result is comparable with the “Energy Perspectives 2050+”, the net-zero scenarios from the federal government.

In the comparative scenarios, on the other hand, in which photovoltaics use is not expanded to the extent that would actually be technically and economically feasible, it would be difficult for Switzerland to meet future electricity demand from its own production. If the rate of expansion of solar energy were to remain at the current level, the supply of electricity in 2050 would fall well short of demand due to the phase-out of nuclear power, and Switzerland would have to import large amounts of electricity.

Even in the Nexus-e reference scenario, the strong expansion of photovoltaic systems would only offset the phase-out of nuclear power in the long term. This would necessitate high electricity imports, especially around 2040, once the nuclear power plants are no longer in operation. Towards 2050, wind power, pumped storage and gas-fired power plants (including the storage of greenhouse gases emitted) could make all the difference when it comes to Switzerland meeting its electricity needs.

Electricity trade with Europe

The supply of electric power will also be influenced in no small part by the framework conditions for electricity trade with Europe: “As long-term restrictions on electricity trading could affect the security of supply in Switzerland, it might make sense to invest in wind power and gas-fired power plants from 2040,” said Hug. Gas-fired power plants could serve as flexible electricity production units that can also generate electricity at short notice and on a seasonal basis, for example in winter. Depending on the scenario, they are an option or a necessity. The resulting CO₂ emissions, however, would have to be captured and stored in every case.

Cooperation and sector coupling

When it comes to actually reducing greenhouse gas emissions in the long term and optimising the energy system as a whole – and here the representatives from science and business were in agreement – cross-sectoral cooperation and value chains will play a crucial role in the future. “The growth of renewable energy technologies goes hand in hand with the coupling of sectors,” said Annegret Stephan, economist in the ETH “Sustainability and Technology” research group.

Using the example of energy planning that jointly examines the electrification of buildings and mobility, Kristina Orehounig, head of the Urban Energy Systems Laboratory at Empa, highlights how such sector coupling can work at neighbourhood level. How exactly sector coupling and flexibility can contribute to a climate-neutral energy system in Switzerland is being investigated by researchers in the SWEET PATHFNDR research consortium led by ETH Zurich, which was launched in May. The symposium provided a vivid demonstration of Vanessa Wood’s opening words – namely that a sustainable energy future is everyone’s business, and everyone needs to play their part.