Modelling the energy transition

Switzerland’s energy system will undergo a fundamental transformation in the coming years. The Energy Act went into effect in 2018 after Switzerland voted to phase out nuclear energy and generate more power with decentralised, renewable energy sources. In 2019, the Federal Council also set the target of reducing Switzerland’s net emissions to zero by 2050.

Solar power will play a key role in achieving this. It’s also clear that this transformation will call for flexible technologies that can convert and store energy efficiently and make it available when required – in a matter of hours or seasonally. However, exactly how these ambitious goals will be met remains unclear.

This has raised unresolved questions relating to policies, industry and society at large. What are the appropriate policy measures to ensure a smooth transition from nuclear energy to renewables? Which flexible technologies can best balance the fluctuations in power production from photovoltaics – pump storage, dams, battery storage, solar-generated hydrogen or flexible consumers? How can more people be motivated to invest in the technology driving this transformation? And how can we minimize systemic risks in the future energy infrastructure?

Solutions for a complex system

To answer these questions and understand the different pathways towards carbon neutrality, computer models can be a big help. This is why an interdisciplinary group of researchers at ETH Zurich’s Energy Science Center is developing the Nexus-e platform for modelling energy systems. The first version of Nexus-e was completed at the end of 2020. The pilot project was co-financed by the Swiss Federal Office of Energy (SFOE) and participating ETH professorships.

The common goal of the project is to develop a suitable tool that can holistically represent the complex Swiss power system. This will enable in particular an evaluation of the roles of centralised and decentralised technologies, and the economic and political factors affecting a future electricity grid with increasing flexibility demand.

“In order to find future solutions, there is a need for greater flexibility. We want Nexus-e to serve as a platform that can be used to model various scenarios and thus facilitate the transformation of the energy sector in the coming decades,” says Marius Schwarz, project manager of Nexus-e.

Toolbox for the energy transition

As the energy sector is very complex, only a few attempts have been made to model the relationships between the individual components of the entire system. The purpose of Nexus-e is to close this gap. “The key factor is the platform’s transparent architecture, which allows components of the energy system to be easily connected in the form of modules via clearly defined interfaces,” explains Schwarz.

More specifically, the platform currently combines five energy modules to incorporate knowledge and methods from various disciplines, such as electrical engineering and macroeconomics. These five modules represent the overall Swiss economic structure and the electricity market, investment in decentralised and centralised energy sources, network security and grid expansion. The modular approach makes it possible to map the energy system and the interaction of its components much more extensively than conventional, isolated simulations of sub-systems.

Illustrative test scenarios

To demonstrate the potential of Nexus-e, during the first project phase the researchers ran three scenarios for the transformation of the Swiss power system by 2050. The simulations suggest that phasing out nuclear energy could be achieved with considerable investment in new photovoltaic systems. Wind energy, on the other hand, could play a key role only if costs were reduced significantly. With hydropower, Switzerland is in a good position to balance out the daily and seasonal fluctuations in power generated by photovoltaics.

“Since the underlying assumptions are still subject to considerable uncertainty, these test results are primarily illustrative and should not be seen as official forecasts,” emphasises Schwarz.

A catalyst for interdisciplinary research

Nexus-e also serves as a modelling infrastructure that can be used in research and education on an ongoing basis. Christian Schaffner, Executive Director of the Energy Science Center, says: “The Nexus-e platform will allow students and researchers to study complex problems and new phenomena more efficiently.” This way, individual aspects of the total system can be studied in greater detail and more easily.

In turn, the modelling platform simplifies interdisciplinary research within the university. Nexus-e is already being used as a basis for several ETH projects, and thus will be further developed in specific ways. One example is the CH2040 research project, in which the Nexus-e team and Anthony Patt’s Climate Policy Group are investigating to what extent a decarbonisation of Switzerland by 2040 is technically and financially feasible.

Another collaboration with Marco Mazzotti’s Separation Processes Laboratory is using Nexus-e to study the extent to which energy from biomass combined with carbon capture and storage could reduce emissions, and the economic and ecological significance of this for the Swiss energy system.

Detlef Günter, Vice President for Research at ETH Zurich, is delighted about the intensified partnership between professors and departments: “Nexus-e is showing, quite impressively, what an interdisciplinary approach can achieve. I’m convinced that interdisciplinary collaboration is the only way to develop sound, feasible solutions – particularly with challenges such as the energy transition.”

Creating a workable testing environment

Schaffner and Schwarz say that the new modelling platform will also be used and further developed by interested parties outside the university. Their vision is to make Nexus-e a generally recognised, practical testing environment. “We are open to new partnerships in the academic arena and also with policy makers or industry stakeholders that want to use Nexus-e,” says Schaffner.

This is why those working on the Nexus-e project are striving to make access to the platform as simple and efficient as possible. The team has already succeeded in reducing the time needed to run simulations from a matter of days to a few hours. The next step is to open up the platform fully, and support external users and developers in working with Nexus-e.

Involved research groups

• Power Systems Laboratory
• Research Center for Energy Networks (FEN)
• Reliability and Risk Engineering Laboratory (RRE)
• Chair of Energy and Public Economics (EEPE)
• Energy Science Center (ESC)