How Reverion generates energy from hydrogen
To play its part in the fight against climate change, Germany must become climate-neutral by 2045 and secure its energy supply exclusively from renewable sources. The pressure to act has also increased as a result of the Ukraine war, as gas has lost its appeal as a transitional technology and - and Germany's independence in terms of energy supply has become massively more important. In view of these new existential threats, the increasingly frequent natural disasters and extreme weather events, the share of renewable energies must rise sharply over the next two decades. At the same time, baseload nuclear and coal-fired power plants are to be completely taken off the grid by 2038 and replaced by wind and solar power.
In this context, long periods without significant solar and wind energy potential pose a particular challenge, so-called dark lulls. During these dark lulls, the output of wind and solar power is only a fraction of the usual average output, so that the energy demand cannot be met even with the help of load management and short-term storage. In Germany, several dark lulls with a length of more than 48 hours occur per year, but in individual cases they can also last for up to ten days. During these periods, long-term energy storage, i.e. energy storage with a storage duration of at least ten hours, plays an essential role in ensuring the stability of the power grid. In addition, long periods usually extend through the winter, during which energy generation will lag behind energy demand in the future.
Long-term energy storage is a central building block for energy autonomy and the achievement of climate targets, and at the same time a growing multi-billion market, which, however, can only be served inadequately with the currently market-ready technologies.
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The Challenge: Store energy and efficiently provide power for more than ten hours without using critical raw materials.
The Challenge will identify breakthrough technological approaches that enable long-term, efficient, and cost-effective energy storage. Key factors are raw material and system costs, self-discharge, storage efficiency, lifetime, energy density, and technical and economic scalability of the project idea.
Teams participating in this Challenge are fully challenged. SPRIND therefore provides intensive and individual support. This includes funding the teams with up to €1 million in Stage 1 of the Challenge and up to €3 million in the 2nd and final Stage. In order to help the teams develop their full potential, SPRIND provides them not only with financial support but also with a coach who accompanies, advises and networks the work of each team.
To enable the teams to concentrate fully on their innovations, we provide funding quickly and unbureaucratically. At the end of the first stage of the Challenge, after one year, the jury decides on the basis of interim evaluations which teams will continue to participate in the Challenge. As finalists, these teams are given the opportunity to drive their project forward for another year and a half and to comprehensively demonstrate their breakthrough.
Thinking one step further: Ideas with the potential for a breakthrough innovation must be brought to market to benefit us all - promising projects in this sense can therefore continue to be supported by SPRIND after the Challenge has ended.
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In November 2023, the expert jury selected the participants for the second and final stage of the 'Long-Duration Energy Storage' challenge. Four teams will each receive up to 3 million euros over the next 18 months for the further development of their long-term energy storage technology.
Reverion
“The new energy world is binary,” says Felix Fischer: "There is either a surplus of electricity or a shortage.” When the sun shines, electricity prices fall; when it doesn't, prices rise, and the rapid provision of stored energy becomes increasingly important.
HalioGen Power
Thin walls protect redox flow batteries from short circuits while allowing ion exchange between the electrolytes: Membranes have been used in batteries for decades. But this could change.
Ore Energy
Iron, air and water: Ore Energy is using these three elements to revolutionise the battery industry. The team's iron-air battery is designed to provide 100 hours of power and to step in when no renewable energy is available.
Unbound Potential
Radically simple design – that's the secret behind Unbound Potential's new flow battery. The company is working on a membrane-less battery to rival lithium-ion batteries.
Science Youtuber Jacob Beautemps introduces the Challenge teams at Breaking Lab
The Jury
Gitanjali DasGupta
Sebastian Scholz
Anna Grevé
Pasquale Salza
Pilar Gonzalez
Nick de la Forge
Do you have any questions about the Challenge? Write to us at challenge@sprind.org.
“The new energy world is binary,” says Felix Fischer: "There is either a surplus of electricity or a shortage.” When the sun shines, electricity prices fall; when it doesn't, prices rise, and the rapid provision of stored energy becomes increasingly important.
Reverion is therefore working on a system that can go from storing energy to supplying it in less than a minute. The company is using a ceramic fuel cell that works at very high temperatures.
“Whenever electricity is cheap, the solid oxide cell operates as an electrolyser and produces hydrogen”, explains Fischer, Reverion's COO. “But - and this is the beauty - at the push of a button, the same system can absorb the hydrogen and use it to generate electricity again.”
DECOUPLING STORAGE CAPACITY AND STORAGE DURATION
The highlight: unlike with batteries, it is possible to decouple storage capacity and storage duration. “We use an energy converter and an independent gas storage system”, explains Fischer. In extreme cases, this means that if the wind blows continuously for a fortnight, for example, Reverion produces hydrogen for a fortnight. “Other batteries would be full after just a few hours, but we can continue to produce hydrogen without any physical limits.”
“Whenever electricity is cheap, the solid oxide cell operates as an electrolyser and produces hydrogen”, explains Fischer, Reverion's COO. “But - and this is the beauty - at the push of a button, the same system can absorb the hydrogen and use it to generate electricity again.”
DECOUPLING STORAGE CAPACITY AND STORAGE DURATION
The highlight: unlike with batteries, it is possible to decouple storage capacity and storage duration. “We use an energy converter and an independent gas storage system”, explains Fischer. In extreme cases, this means that if the wind blows continuously for a fortnight, for example, Reverion produces hydrogen for a fortnight. “Other batteries would be full after just a few hours, but we can continue to produce hydrogen without any physical limits.”
The system's energy converter, the ceramic fuel cell, is located in a container. The hydrogen can be compressed or liquefied in a separate unit. "This gives you a high energy density. So you need relatively little space to store a lot of energy”, explains Fischer. The hydrogen can be stored directly on site, but it is also possible to connect the system to the natural gas grid. This means that the hydrogen can be transported away in large quantities and used directly in industry, for example, or it can be converted back into electricity at another location using Reverion.
MORE EFFICIENCY THROUGH SUPERIOR SYSTEM COMBINATION
The ability to quickly switch between storage and power generation modes is not only practical, but also much more energy efficient than two separate systems. “If you had two different stand-alone solutions, an electrolyser and a fuel cell unit, the electrolyser would always need a start-up phase. It has to warm up first. With high-temperature electrolysis, this takes a long time; with a cold start, you would have to wait for hours,” says the 36-year-old. Fuel cells also need a certain amount of start-up time. “Because all our components are running all the time, we don't have this problem. All we have to do is flush the gas lines and change two or three valves. Electrically, the changeover takes place in milliseconds,” explains Fischer.
The ability to quickly switch between storage and power generation modes is not only practical, but also much more energy efficient than two separate systems. “If you had two different stand-alone solutions, an electrolyser and a fuel cell unit, the electrolyser would always need a start-up phase. It has to warm up first. With high-temperature electrolysis, this takes a long time; with a cold start, you would have to wait for hours,” says the 36-year-old. Fuel cells also need a certain amount of start-up time. “Because all our components are running all the time, we don't have this problem. All we have to do is flush the gas lines and change two or three valves. Electrically, the changeover takes place in milliseconds,” explains Fischer.
No wonder there are already some interested parties. In addition to solar and wind farms, breweries are also interested in Reverion's system. A perfect use case for Reverion. Breweries that have a solar system on their roof and do not produce at the weekend can use the Reverion system to store sunlight at the weekend and use the electricity themselves on Monday morning when it is still dark. If the breweries were to sell the electricity to the grid at the weekend instead, it would hardly be worth anything.
"I never wanted to start a company because I wanted to be a founder, but because I wanted to do something meaningful with my time. That is my intrinsic motivation”, says Fischer. He tells us about his team: “What sets us apart is that we are very passionate about finding technical solutions to a very acute problem.”
I never wanted to start a company because I wanted to be a founder, but because I wanted to do something meaningful with my time.
LOW ENERGY LOSSES THROUGH HEAT INTEGRATION
The key to success is heat integration, and that's something Reverion takes very seriously. Waste heat is always used sensibly: “This also increases the efficiency of the electrolysis even further.” Another innovation is the generation of electricity. “Generating electricity from hydrogen is relatively simple from a technical point of view, but it is usually not very efficient”, says Fischer and continues in a mysterious manner: “We have found a way to change that.”
“The combination of technologies we have discovered gives us a round-trip efficiency of 75 percent,” says Fischer, admitting: "We cannot store energy without losses, but our energy losses in the conversion and reconversion of electricity into hydrogen are lower than almost anything else that has been achieved so far.”
The key to success is heat integration, and that's something Reverion takes very seriously. Waste heat is always used sensibly: “This also increases the efficiency of the electrolysis even further.” Another innovation is the generation of electricity. “Generating electricity from hydrogen is relatively simple from a technical point of view, but it is usually not very efficient”, says Fischer and continues in a mysterious manner: “We have found a way to change that.”
“The combination of technologies we have discovered gives us a round-trip efficiency of 75 percent,” says Fischer, admitting: "We cannot store energy without losses, but our energy losses in the conversion and reconversion of electricity into hydrogen are lower than almost anything else that has been achieved so far.”
SCALING: SERIES PRODUCTION IN SIGHT
The first 100-kilowatt system is scheduled to be tested in continuous operation by the end of 2024. “After that, we want to scale up by a factor of 10. That should be possible within a few weeks, because it doesn't require any further leaps in innovation, just very clean, traditional engineering work,” explains the trained energy and process engineer.
Scaling also plays an important role at Reverion in terms of personnel: within two years, the original team of five has grown into a company with more than 100 employees. The impetus for Reverion came from Dr Stephan Herrmann, who did his doctorate in the same department as Fischer. Fischer recalls: “We realised that solar systems alone were not enough for the energy transition. There was a gap we had to fill.” Herrmann and Fischer felt the urge to take matters into their own hands.
The first 100-kilowatt system is scheduled to be tested in continuous operation by the end of 2024. “After that, we want to scale up by a factor of 10. That should be possible within a few weeks, because it doesn't require any further leaps in innovation, just very clean, traditional engineering work,” explains the trained energy and process engineer.
Scaling also plays an important role at Reverion in terms of personnel: within two years, the original team of five has grown into a company with more than 100 employees. The impetus for Reverion came from Dr Stephan Herrmann, who did his doctorate in the same department as Fischer. Fischer recalls: “We realised that solar systems alone were not enough for the energy transition. There was a gap we had to fill.” Herrmann and Fischer felt the urge to take matters into their own hands.
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