How do we use hydrogen as a fuel?

With temperatures soaring in some places, our love affair with fossil fuels is going to have to come to an end pretty soon. And hydrogen is regarded by some as a strong contender. Others are less convinced. Kicking off our investigation, Will Tingle…

Will - Hydrogen. The most abundant element in the known universe. And you're probably familiar with its work in water and every molecule of every living thing ever. But in the right conditions, hydrogen is a source of renewable energy. And if it is the most common element in the universe, surely harnessing it as a fuel source sounds like a no-brainer. In fact, hydrogen fuelled projects have been in the pipeline for many decades now. The first hydrogen powered car was the Chevrolet Electrovan made back in 1966, and hydrogen power has been in the news spotlight in every decade since.

TV Presenter - 'In two weeks time, this van will be the first working vehicle in the world to be sold running on hydrogen.' 'It may be the future of driving for all of us, and it's already here.' 'Buses that run on hydrogen are being introduced to try to help cut emissions in the capital. The vehicles, which cost 10 million pounds, produce no pollution or carbon dioxide and will be on our roads by 2010.'

Boris Johnson - 'We want to be the Klondike of carbon capture and storage. The Qatar of hydrogen! I think Qatar may already be the Qatar of hydrogen... But we want to be with you!'

Will - As the underlying technology has developed, so too have hydrogen based projects, more recently companies have been looking into hydrogen powered trains. I spoke to Jochen Steinbauer, head of platform development at Siemens Mobility, about the upcoming launch of their H2goesRail project, a joint venture with Deutsche Bahn, which has fitted trains with hydrogen fuel cells instead of diesel engines and plans to put them on mainline railways.

Jochen - At the moment, the first demonstration train is running in our Siemens test centre, but the first test operation on public lines with our first demonstration train will be in September in Bavaria and this will be a really great event.

Will - But why did they choose hydrogen in the first place when electrically powered trains are already so widespread and proven? What advantages does hydrogen have?

Jochen - The hydrogen trains, with a range of almost 1000 kilometres, provide a certain flexibility in the operation compared to battery trains, which have a range of 80, maximum 100 kilometres. There's a certain restriction in the operation, so you have to have a continuous system or special charging stations but, for the hydrogen train, you're completely flexible.

Will - And whilst flexibility is always good with public transport, Jochen is also very impressed with how the trains themselves run.

Jochen - The hydrogen trains, with a range of almost 1000 kilometres, provide a certain flexibility in the operation compared to battery trains, which have a range of 80, maximum 100 kilometres. There's a certain restriction in the operation, so you have to have a continuous system or special charging stations but, for the hydrogen train, you're completely flexible.

Will - And whilst flexibility is always good with public transport, Jochen is also very impressed with how the trains themselves run.

Jochen - The performance of the train is, from my perspective, important. The train has 1.7 megawatt in power, and the diesel train has an average of 0.6 megawatts. So we provide a higher acceleration and a higher top speed of 160, so degraded wattage for our customers is shorter for travel times and more comfortable. So the potential in hydrogen technology is huge and therefore I strongly believe that these hydrogen trains have a great future.

Will - Strong words from Jochen Steinbauer there. But before we get carried away with the excitement, we should probably attempt to understand the chemistry. How does hydrogen fuel work and where does the hydrogen come from in the first place? I spoke to the business editor of Chemistry World, Phillip Broadwith.

Phillip - At the moment, the vast majority of the hydrogen that we use comes from fossil fuels in the process of refining oil and in the process of cracking to make different oil products. You can release some of that hydrogen as hydrogen gas, we can make it renewably using electricity to take water, which is hydrogen and oxygen, and electrically split that molecule apart and recombine it to make hydrogen - h2 gas - and oxygen.

Will - Is that where the different terms of hydrogen come from when we speak about 'green hydrogen' and 'blue hydrogen?' Is that because that's the different ways in which they are made?

Phillip - That's absolutely right. All the hydrogen is the same, but we classify it by where it comes from because that has, from an environmental point of view, an influence on the amount of emissions that are associated with producing it. But generally the main ones are black or grey, which come from fossil fuels. Blue is from fossil fuels but with the carbon captured and stored and green from renewable sources.

Will - So once we've pulled our hydrogen apart one way or another, what goes on inside a hydrogen fuel cell that gives us this energy?

Phillip - So our hydrogen fuel cell is basically the opposite process to the electrolysis that we were using to make the hydrogen with electricity. It takes hydrogen gas, h2, and oxygen gas, o2, and recombines them in a way that generates electricity. So instead of just burning the hydrogen in air to make water, you can do the same chemical reaction but inside a fuel cell which allows those atoms to combine together to make water. And instead of making heat, it makes electricity. The reason it can do that is because chemical reactions involve transmitting electrons between molecules. And if instead of transmitting those electrons directly in a kind of combustion process, you transmit them in a way that makes them go round a circuit, they can produce electricity and do electrical work.

Will - If we are using and burning hydrogen gas the same way we use natural gas, can we just send the hydrogen down the same pipes that we use to pump gas into our homes?

Phillip - Well, we absolutely could. That is technically feasible. Whether we should or not is a completely different question. So it all comes down to how much energy it takes to generate the hydrogen to transport it, and then how much energy you get out at the other end. Everybody says the energy density of hydrogen is much better than the energy density of natural gas. And if you consider it by terms of weight, then yes, it is. If you consider it in terms of volume, natural gas has much more energy per unit volume. The problem with heating homes is that if you compare it to using natural gas, it's much less efficient. And if we wanted to do that with renewable hydrogen, with green hydrogen, it would take more renewable electricity than we currently generate for the whole country to heat everybody's homes using hydrogen. And partly that's because each step of the process we lose some energy. Not all of these processes are a hundred percent efficient. So we generate some renewable electricity, we use that to make hydrogen which has a process of efficiency of about 80%. We might lose 20% of the energy that we'd had as electricity in making hydrogen. We then have to transport that hydrogen which takes some energy and then we have to burn that hydrogen in a boiler to heat water to heat our houses. That's not a particularly efficient process.

Will - If hydrogen can't be pumped down the same gas pipelines as the ones we were using before, how best to transport it, if at all?

Phillip - The best way to transport it is a pipeline because that doesn't require you to compress the hydrogen, which loses lots of energy. It doesn't require you to cool it or anything like that. But whether we need to transport hydrogen at all depends on what we're going to use it for. The vast majority of the hydrogen that's used at the moment is used in chemical processes, it never leaves the compound or plant where it's made. Partly that's because we are making it in places that process fossil fuels and therefore produce the hydrogen and then it gets used in various chemical processes. But partly it's because of that difficulty in transporting hydrogen.