Professor Schmidt, you head the PSI Energy and Environment Research Division, and Professor Pautz, you oversee the Nuclear Energy and Safety Research Division. What are the differences between your two fields of research, and what do they have in common?

Thomas J. Schmidt: The Energy and Environment Division does research on the production, conversion, and storage of energy from renewable sources, as well as addressing the consequences our energy use has for the environment and atmosphere. Our research does not cover nuclear energy, however.

Andreas Pautz: That is our expertise. But we do have some common ground: We always work within the context of Switzerland’s Energy Strategy 2050. During this transition phase, we both have important tasks to perform: The Energy and Environment Division needs to push forward with renewables, while we have to solve the problem of how to ensure that nuclear power stations continue to operate safely up into the 2040s – possibly even well beyond – and lastly, how to safely dispose of radioactive waste. We play our part in maintaining high safety standards throughout and minimising the nuclear legacies for future generations to deal with.

So, you don’t see each other as rivals, championing different energy sources?

Schmidt: Not at all. We work closely together and in doing so have to keep an eye on time scales when it’s time to replace one technology with a different one.

Pautz: Exactly, our aim is to ensure optimal interplay with a view to avoiding potential environmental impacts as much as possible and minimising costs. We look at this purely from a scientific angle; we are not engaging in political discussions. The decision not to limit the lifetime of existing nuclear power stations effectively makes them an integral part of the country’s energy strategy. By the way, there is no other scientific institute in Switzerland where so much energy research is conducted as at PSI, in other words, where so many researchers are concentrated in such a small space.

Do you also work on joint projects?

Pautz: Certainly. For example, we work together on the SURE project, whose aim is to determine how we can build a secure and resilient energy supply for the country over the coming years. This involves much more than just minimising CO2 emissions, but includes other aspects such as reliability of supply, network stability, and defence against external and internal threats. In addition, we are working together on net-zero, that is, on technology development and modelling for a society whose bottom line in terms of greenhouse gas emissions is zero. In this connection, we will be leading and coordinating a competence centre of the ETH Domain, beginning in autumn 2022.

Schmidt: We carry out this research in a joint PSI lab, the Laboratory for Energy Systems Analysis. This specialises in holistic analyses of the entire energy system. Transport, industry, private households, electricity generation – everything comes together here. Aside from that, though, there is a whole series of other subject areas in which synergies arise. These include materials aspects, the formation and spread of aerosols, flow processes in porous media, disposal and recycling processes, and much more.

Is more scientific objectivity necessary in the discussions about the energy transition and the various ways of achieving it?

Pautz: More objectivity in the energy debate would be extremely helpful. We simply need to carefully weigh the new facts that we have today – for example with regard to the increasingly visible consequences of climate change or the unfortunate lack of speed in the expansion of renewable energy and storage technologies. Due to the military conflict in Ukraine, which has made us aware of our dependency on fossil fuels, the issue of security of supply has come into focus in a massive way. In view of these new realities, I am pleading for an open debate on technology that does not exclude any form of energy, not even nuclear power. There need to be an evaluative thought process.

Schmidt: This also underlines the importance of the holistic approach we adopt at PSI in order to understand energy systems as a whole. Only a few other places in the world follow this approach.

Is it difficult for you to attract young scientists in your area of research?

Schmidt: No. Our international outlook helps: People from around 45 different countries work in the Energy and Environment Division.

Pautz: I can confirm that for my division as well. We have a very good  international reputation and thus strong demand. Together with EPFL and ETH Zurich, we offer a master’s course in nuclear engineering, for example. On average, 15 new students start every year, and the trend is upward. This year more than 25 are starting. It is also very gratifying that in the past three years more and more Swiss students have chosen nuclear engineering as their subject. This shows that nuclear energy is not an obsolete model internationally, and that the subject also motivates young people in Switzerland.

Is the criticism “Switzerland wants to discontinue nuclear energy, so why is PSI still doing research on it?” something that you hear often?

Pautz: Hardly ever. No one disputes that specialists are needed for the next 25 years at least, partly to solve the problem of radioactive waste disposal. The need for Switzerland to maintain its nuclear expertise is also widely recognised in political circles. When it comes to nuclear technology, Switzerland should also be able to defend its position as a global player and draw on a deep pool of know-how. This is only possible, however, if we continue to do research on important issues relating to nuclear safety, and on the sustainability aspects of this form of energy.

What has changed in your field of research over the past years, and what do you expect for the future?

Schmidt: Amongst other activities, we have reduced our research into combustion technology. Although this used to be an important topic, it now has a limited future. On the other hand, we have taken on several new topics, such as hydrogen production. Another issue that has become more important is the impact of our energy use on the climate. For example, what effects do aerosols have on the atmosphere and on human health?

Pautz: The long-term operation of nuclear power stations tops our agenda, as well as the final disposal of nuclear waste and the dismantling of decommissioned plants. Since it became clear that Switzerland plans to phase out nuclear energy, we have suspended activities that are related to constructing new power stations, such as the development of new fuels. We are only marginally involved in investigating new safety systems. In the future, I’d really like to see collaborations between industry and research become much more international. We want to continue to capitalise on PSI’s strong international reputation in nuclear energy research.