Energy transition

Sven Linow is a friendly guy. He speaks with a calm voice, which lends even greater weight to his description – crystal clear – of the uncomfortable truths already facing us. Diluting the facts would not be appropriate for the issue at hand: it’s a matter (for him) of protecting the climate. As Professor of Thermodynamics and Environmental Engineering, Linow wants to impart “energy literacy”. He thinks and acts beyond the boundaries of his subject area and makes an important contribution in many ways, including to “Scientists for Future”. A conversation about our future energy supply, sufficiency and small disasters.

Interview: Daniel Timme, 1.4.2025

impact: Professor Linow, you already gave us an impact interview in 2021 on climate protection. Have we here in Germany set off in the right direction since then?

Professor Sven Linow: Certainly not at the political level. The campaign in the run-up to Germany’s federal elections avoided the important issues facing us in the future. Unfortunately, climate protection is often presented as a “green” topic. But it’s not: climate protection affects us all – regardless of what we think and who we vote for. To scientists it is very clear why we are seeing this massive rise in temperature and what it means for us: it’s pulling the rug from under our feet and our economic system. Although we are reaching biophysical limits, we continue nevertheless to plan further growth and talk about more and more. That’s not going to work.

impact: You’re flying the flag for energy literacy, which helps people to live in a more sustainable way. What does this mean for your teaching?

Linow: We look at things through the lens of “energy, cost and effort”. I take this systemic approach in the environmental engineering course as part of the Bachelor’s degree programme, for example. Climate protection, biodiversity and some other topics will have an impact on our students’ lives – whether we like it or not. In the final analysis, it’s about the future. It’s our job as a university to shape the future by educating young people. A hundred years ago, you could go to the railway station, watch a steam engine at work and understand the technology. Nowadays, we need, on the one hand, a broad overview of complex systems that are difficult to grasp and, on the other hand, very specific and detailed knowledge. That’s what makes teaching more difficult today.

impact: In your opinion, how should the energy transition look if we are to significantly reduce our carbon emissions? How can the heat, mobility and electricity transition succeed?

Linow: The main message is that our future energy supply will be electrical. You have named the three pillars. As far as the electricity transition is concerned, we’re on the right track and it’s the least of our problems. Renewable energies – wind power and photovoltaics – are the most inexpensive options. We will easily manage the electricity transition in Europe in ten to 15 years – and will have transformed large parts of our industry in the process.

impact: Well, that gives cause for hope! What about mobility and heat?

Linow: When it comes to the mobility transition, we’re trying to treat the symptoms. The number of cars in Germany continues to rise. We are tying up ludicrous resources in ever larger, heavier and more powerful cars, which then spend most of their time either parked in the garage or in a traffic jam. Sufficiency would be the key to solving this: the average driving distance in Germany is 2.5 kilometres. A major problem is the high cost of housing in inner cities. Many people cannot afford it, move out into the countryside and commute to work every day by car. The following approach could offer a solution: the place where I live must also be where my work is, where my friends are and where my whole life takes place. The reduction in traffic as a result would contribute to the transition.

impact: It seems there is still a long way to go. What’s the situation with the heat transition?

Linow: The heat transition is a tough nut to crack. Many options that people like to talk about will not work or not on a large scale. Hydrogen will always be too expensive. Its production is costly and energy-intensive, losses are high, and transport is incredibly expensive. What’s more, hydrogen is an indirect greenhouse gas. We haven’t got enough biomass and waste to come even close to covering our energy demand. And we certainly don’t want to increase the amount of waste we produce in order to keep warm. Apart from which, that would again release a lot of carbon emissions. Biomass will be a niche solution. Heat pumps of all sizes will remain the standard solution – where possible in combination with heat from industrial processes or data centres.

impact: Is the heat transition primarily a social process or does politics need to steer it via incentives, subsidies and regulations?

Linow: Both. If people earned enough money, it would be possible to dispense with a lot of subsidies and regulations. Construction, like so many things, has become very expensive. The typical housebuilder is on the verge of bankruptcy. And then on top of that, heating systems also cost even more than they used to... You have to bring the population on board with their anxieties, worries and problems. Politics and the media are partly responsible for people’s doubts and resistance. Yes, the heating transition is a social process. It means more than just replacing my heating system. It’s about sufficiency on a large and a small scale, about questions such as: What are commensurate living conditions? What do we really need for a good life?

impact: Let’s please stay for a moment with the technical aspects of the heat transition.

Linow: We need first to minimise heat loss in buildings through better insulation. Then sufficiency: Where do I really need it to be how warm? Does it have to be 25 °C throughout my flat the whole time and does adjusting the temperature by opening the window really make sense? Or is 19 °C in my kitchen or living room enough when I’m in there? These are huge differences! The heat pump will be the standard heating system for most people – whether as an air-source heat pump or in combination with a cold local heating network. Neighbours can join forces to finance the geothermal boreholes, which are expensive. The technology is there, you can buy it.

impact: What have you got to say to those people who continue to back fossil fuels or claim that renewables will never be able to completely cover our energy demand?

Linow: Behind this are either huge economic interests or else cluelessness and the hope that we don’t need to change. But that’s rubbish. With our current lifestyle, we externalise the costs. We don’t include the effects of using oil and gas, the climate costs, in the calculation. Not to mention the sacrifice zones in the Global South. Until 150 years ago, we also managed to meet our energy demand without fossil fuels. From a technical perspective, using renewables to cover that demand is unproblematic. However, if we continue to squander energy on such a large scale, we will have to blot large parts of the landscape with wind turbines. That is why sufficiency – reducing consumption – is so important, regardless of whether for heat, mobility or electricity.

impact: What role can oil, gas and coal still play?

Linow: Europe’s, Germany’s and Hesse’s goal is to be carbon neutral by 2045. To achieve this, we need to stop using fossil fuels as quickly as possible. Calculations vary, but they will be exhausted in 50 to 100 years anyway. We need to be honest with ourselves. Natural gas is almost as harmful to the climate as coal because it releases methane when burned. To slow down global warming, we shouldn’t burn the remaining fossil fuels at all. Science knows that – and so does industry. In Darmstadt, Entega will likely switch off the gas network in 2045. That’s the logical consequence of the targets we’re obliged to meet. The bad news is that energy is already expensive today – and will become even more expensive in every conceivable scenario in the future. We need to get used to that.

impact: Why is there no future for nuclear power in Germany?

Linow: There are four reasons. Firstly, nuclear power is unbelievably expensive – much more expensive than wind power. Secondly, the risks and the issue of final storage remain unresolved. Thirdly, construction and operation are incredibly expensive and more or less impossible to achieve in practice. There is no one in Europe who could build a nuclear power plant. Who can supply the huge steel castings for the reactor pressure vessels? And fourthly, it would take far too long before a nuclear power plant in the planning today could go into operation because we also have a considerable problem as far as know-how is concerned. In short: if I have a functioning infrastructure, I can build on it – this applies for Russia and China. But even France has enormous problems with this.
 
impact: What about hydrogen or nuclear fusion?

Linow: Laser-based nuclear fusion, hydrogen for heating or Carbon Capture and Storage (CCS) – these are very nice, but very expensive promises. If we were able to implement them, it would be ridiculously expensive. We need hydrogen derivatives such as methanol and ethanol as raw materials in the chemical industry and for e-fuels in ocean-going vessels. So far, laser-based nuclear fusion has at most succeeded in the laboratory on a very small scale. The underlying technological issues have been unresolved for 70 years. Internal energy consumption is so high that it is questionable whether any energy can be given off at all. And if it is possible, we lack the required amounts of precious metals. Such supposed “options” are at a very low Technology Readiness Level. They are not practicable and available in the short and medium term. They won’t help us to solve the problems that we need to solve now.

impact: You’re the chairperson of the Scientific Climate Council of the Hessian State Government. Do people listen to you?

Linow: The Scientific Climate Council could be a wonderful instrument. Unlike many other interest groups, we are independent. So all I can say is that we invite the State of Hesse to make use of its excellent tools.
 
impact: That doesn’t sound particularly hopeful. Do you dare to predict how this will all turn out?

Linow: I’m afraid that we will no longer achieve transformation by design and that it will be more a case of transformation by disaster. Something will happen that puts us on the right track. Hopefully, the disaster will be so small that we can still cushion it and make structural use of it. We’re already experiencing right now how the peace order in the North Atlantic is on shaky ground. What is happening now will stir up a lot more. The climate issue is closely interwoven with geopolitics: energy, raw materials. But independently of that, it cannot simply be brushed aside.