Hydrogen is the fuel of the future. It can be used at sea, rail or road. In heavy industry, H2 is a viable alternative fuel to oil, gas and coal. If it was obtained during electrolysis using wind energy or solar power, it burns green even at temperatures of 1600 degrees Celsius in steel production, so it does not cause any further CO2 emissions. The federal government is convinced: it has planned or already agreed hydrogen partnerships with several African countries, Canada, Kazakhstan and Saudi Arabia. A crowd of advocates that impresses Roel van de Krol after many years of waiting. "Hydrogen is really supported by everyone," says the director of the Institute for Solar Fuels at the Helmholtz Center Berlin. In ntv's "Climate Laboratory" he also warns of an important bottleneck in the expansion of electrolysis capacities: we need large quantities of the rare precious metal iridium. Is there enough of that? "Right now we don't know."
ntv.de: Microsoft founder Bill Gates says hydrogen is the "Swiss army knife of decarbonization". Tesla boss Elon Musk thinks hydrogen is the "stupidest thing" he can imagine for energy storage. Who is right?
Roel van de Krol: Both a bit. When you think of renewable energy, you think of wind or solar. They deliver electricity, which is best used right away, because then you have the lowest losses. But that's not possible because we don't have any sun at night. Therefore, we have to temporarily store the electricity generated during the day in order to be able to use it at night.
The known problem.
Exactly. But the storage capacity of batteries is not sufficient for this. You can drive 500 or 600 kilometers with it, which is great. If we want to power a city for a whole night, we need alternative storage methods. Chemical fuels are simply unbeatable when you look at the energy density - i.e. how much energy they contain per kilogram or per liter.
Do you mean, among other things, hydrogen?
Hydrogen is one of them, exactly. This is the simplest chemical storage material imaginable. The advantage of hydrogen is that when you burn it, no CO2 is released, just water. If you convert water into hydrogen and oxygen and then use hydrogen as a fuel, you have a closed cycle. This makes hydrogen very attractive compared to other chemical fuels, where CO2 is released again. That's why there's so much interest in it.
Sounds like Bill Gates is right. Why, then, does Elon Musk call hydrogen the "stupidest" energy storage device he can think of?
For cars, he's right, because the batteries are enough for that. Then of course it would be "stupid" to use hydrogen because energy is lost in the splitting of water and also in the reverse reaction when you turn hydrogen into electricity. With batteries, the losses are very small. You only lose a few percent of the energy in the form of heat when charging and discharging. When producing and consuming hydrogen, you lose easily 30 to 40 percent of the energy. From this point of view, Elon Musk is right. But you can't store all energy in batteries, so Bill Gates is right.
Bill Gates thinks more of heavy industry?
In heavy industry there are processes that are difficult to electrify. You can't do that with electricity, you need an alternative. Hydrogen has its advantages and disadvantages, but it is actually one of the most promising energy carriers.
So it is correct when you hear: Hydrogen is the fuel of the future. With it we can replace oil, gas and coal.
I would put it this way: Hydrogen is the best we can imagine at the moment. It's not perfect, but we don't have anything that works better.
What's the big catch when you say hydrogen isn't perfect?
The catch is the energy lost when you break down water into hydrogen and turn it back again. That's 25 to 30 percent per conversion step. That's remarkable. The second disadvantage is that although hydrogen has a very high energy density per kilogram, it has a very low density per liter, i.e. volume. If a truck wants to take hydrogen with it, you have to compress the hydrogen up to 700 or 800 bar. There are technically mature solutions for this. But energy is also lost when hydrogen is compressed.
That means you either have an extreme amount of space and huge memories that can hold the large volume, even if it doesn't weigh much. Or one expends energy to compress it?
Exactly. In mobile applications, however, you have to compress hydrogen, otherwise you can't carry it with you. There's no way around it.
Is producing hydrogen as problematic as storing it?
Technically not. Electrolysis has been used for more than 100 years. The process can still be improved, but the technology is mature, mature and applied on a large scale.
Can you explain the process again in layman's terms?
Electrolysis is the experiment in which you put two electrodes in a barrel of water and apply an electric voltage. This current causes the water molecule to be broken down into a hydrogen molecule and an oxygen molecule. You can collect these gases separately and you have hydrogen.
But you need a lot of electricity for this, which of course has to come from renewable energies if you want to produce green hydrogen. But there is also blue, grey, red hydrogen and other colors. How are they different?
Green hydrogen is the preferred route. It is made with electricity from renewable energy sources. With gray hydrogen, the electricity comes from fossil fuels and steam reforming. Around ten tons of CO2 are released into the atmosphere for every ton of hydrogen.
Ten tons of CO2 for one ton of hydrogen?
Yes. The blue hydrogen is actually the same as gray hydrogen. The energy is generated from methane by steam reforming. Around 90 percent of the ten tons of CO2 that are produced in this way are intercepted and stored. This is CCS, Carbon Capture and Storage.
During steel production, fuels are burned at 1600 degrees Celsius. If we use green hydrogen, would there really be no additional CO2 being blown into the atmosphere?
If we use green hydrogen, not in principle.
But that's the crux. We just don't have enough green hydrogen for everyone right now, do we?
Of course not at the moment. For 2021 it was calculated that only 0.03 percent of the hydrogen used was green.
Very little.
Yes, but the industry is growing rapidly. Of course there are no figures for this year yet, but maybe we are already at 1 percent. The electrolysis capacity is massively expanded. The federal government has the ambition to achieve a capacity of 10 gigawatts by 2030.
We not only need more electrolysis capacity for this, but also significantly more solar and wind energy - which of course cannot then be used to supply German households.
It's an either/or question, exactly: you generate electricity and feed it immediately into the grid, or you use it to produce hydrogen. But the idea is that hydrogen is only produced when the power grid no longer needs electricity.
Do we have to produce more electricity than we use?
Yes, but we already reach an overcapacity of wind energy and solar power several times a year. At such moments, we even have to pay extra to export the electricity to France. Instead, it would of course be wise if we produced green hydrogen with this overcapacity.
Is this the last remaining challenge? We just have to expand solar and wind energy to a level that is sufficient for both the power supply of private households and the production of hydrogen?
That goes hand in hand. It makes no sense to expand solar and wind power without expanding electrolysis capacity.
And if that works, would we have enough green hydrogen for the steel and chemical industries, or would we have to import more hydrogen from abroad?
In Germany we don't have enough sun and wind to cover our entire energy needs. This applies to all of Europe and also Asia. These are the two continents that depend on energy imports.
In order to expand the electrolysis capacity, we need many electrolysers. There, in turn, a lot of iridium is needed, a rare and expensive raw material. Have we had enough of this?
There are two types of electrolysers: The first type is alkaline electrolysis, which we have known for 120 years. This works with iron and nickel electrodes. We have enough of those, that's no problem. However, these electrolyzers must be operated continuously. Not 100 percent, 10 percent is enough. But of course that is not compatible with the fluctuating supply of solar energy and wind power. If no current is applied, these iron and nickel electrodes simply dissolve.
This second type of electrolyzer was developed for this purpose. Polymer electrolyte membrane electrolysis (PEM) can deal with the fluctuating supply. However, this variant is dependent on the precious metals iridium and platinum. Many research groups are working on an alternative, but at the moment there is none.
That sounds like a very tight bottleneck that we have to overcome.
Yes, that can be problematic. At the moment we don't know what will happen when we build these electrolysis capacities. Nobody can predict that. There was also a large demand for platinum for catalytic converters for cars. This problem was solved back then by recycling. This will also be necessary for electrolysis. But there are calculations that show that we should have enough, even if it's running out.
When do you estimate that we will use hydrogen on a large scale? We need more solar power, more wind power and a lot more electrolysers. When can we use the fuel of the future?
Unfortunately I can't answer that. But I am impressed by the mass of advocates. It's not just one or two people or companies dealing with hydrogen. Everyone really supports that. In the Netherlands, for example, Tata Steel wants to use hydrogen instead of fossil fuels from 2030. Thyssenkrupp has similar plans, as do many other companies.
Clara Pfeffer and Christian Herrmann spoke to Roel van de Krol. The conversation has been shortened and smoothed for better understanding.
