The device, which aims to help make emission-free mobility a breakthrough, is as big as a refrigerator and transforms the local garage into an eco-fuel pump. The mini hydrogen filling station was developed by scientists at the Polytechnic University in Lausanne, Switzerland (EPFL) and will one day enable homeowners not only to store high-energy gas, but also to produce it themselves.
Hydrogen has many prerequisites for a dream mix of the energy turnaround: it is obtained in an electrolyzer that activates water (H2O) so that hydrogen (H2) and oxygen (O) separate. In a second step, the hydrogen can be processed to synthetic natural gas, gasoline, diesel or kerosene and is therefore versatile. Fuel cell vehicles run on pure hydrogen completely pollutant-free and climate-neutral when it is generated by electrolysis with wind or solar power. In terms of weight, it contains almost three times more energy than gasoline, so cars carry a full tank of fuel several hundred kilometers. And wind and solar power can be stored in it for almost indefinitely without losing energy.
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If only it were not its extremely low density. Gaseous hydrogen takes up a lot of space - one kilogram has a volume of about twelve cubic meters. To be able to store, transport and refuel it, it has to be heavily compressed or liquefied. This is very expensive and consumes a lot of electricity.
With their new development, the researchers from Switzerland now want to solve a problem that is currently slowing down electromobility: the lack of charging infrastructure. There are currently around 90 hydrogen filling stations in Germany. However, according to estimates of the consulting firm Ernst & Young, at least 1000 filling stations are needed nationwide for the technology to prevail. Just a few hundred private basement petrol stations can quickly make a big difference. "Our system is the size of a refrigerator," says Professor Andreas Züttel from the EPFL Materials Laboratory for Renewable Energy. "Private individuals can use it to build their own small gas station."
Gas station the size of a refrigerator
At the heart of the newly developed system is a metal hydride, which absorbs the hydrogen molecules like a sponge. "When you add heat, the gas pressure in the reservoir increases, which compresses the hydrogen," explains Züttel.
In this way, can be produced exactly the pressure level that is necessary for the refueling of the vehicles. At the same time, the pressure increases exponentially as the temperature rises - fed by a boiler. Electricity is not necessary for saving and compacting. An electrolyzer ensures a steady supply of hydrogen. The plants only need electricity and water. The inhabitants can generate the electricity for the electrolysis with a photovoltaic system on their roof.
It will take a while until the system hits the market. The research team has partnered with partners to produce prototypes that are now being tested in practice.
Long-term storage for wind and solar energy
The hydrogen storage is not only interesting for traffic, say the EPFL experts. It could also serve as a long-term storage for solar and wind energy.
The Swiss scientists also want to couple their storage with fuel cell heaters, such as those offered by Viessmann or the Bosch subsidiary Buderus. Such plants today extract the necessary hydrogen from natural gas. This is not climate friendly.
That changes when the hydrogen is supplied by an electrolyser, which is powered by electricity from a photovoltaic system on the house roof. Homeowners could use the summer sun to produce hydrogen and then store it in storage until the days get colder.
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"In contrast to battery storage, there is no self-discharge over time as the system is closed and no hydrogen is lost," says EPFL researcher Züttel.
At the same time the electrolysis avoids possible bottlenecks in the networks, which arise when in high sunshine large amounts of solar power flow into the pipes.
"Households do not bring the mass"
However, Michael Sterner, professor of energy storage and systems at the Ostbayerische Technische Hochschule Regensburg (OTH), is less convinced of this concept. "In order to achieve the Paris climate goals, we need a hydrogen economy on an industrial scale, for example in refineries or in the steel industry, because households are unfortunately only 'hobbyists' and do not bring the mass," says the scientist.
In addition, electrolysers for private use are enormously expensive. "It's only for people who are willing to put tens of thousands of euros on the table," explains Sterner. Also, the cost of the memory will be high, since they, at least initially, must be made largely by hand.