Natural hydrogren

It is also possible to find hydrogen in the wild, often alongside natural gas and other hydrocarbons, which can complicate its extraction and green credentials. And as far as we know, it is not abundant. “Natural hydrogen occurs in very small pockets around the world, and will have a limited role relative to blue and green hydrogen,” says Dr Sunny. 

But other options are available, such as generating hydrogen from biomass. That could mean crops grown as fuels, or biowastes such as wheat straw or wood residues from forestry. Like blue hydrogen, creating hydrogen from biomass will have to be coupled to carbon capture and storage if it is to be carbon neutral. The bonus is that this is not ancient carbon from fossil fuels, but carbon newly extracted from the atmosphere. 

“Biomass as an energy source provides not only the benefit of hydrogen that will go on to displace natural gas, avoiding carbon emissions, but when properly treated it will help achieve negative emissions,” Dr Sunny explains. 

The technology to produce hydrogen from biomass is essentially the same as that used to turn coal into gas. But further development will be needed if it is to operate at scale. “We need to understand which kinds of biomass work well, how you best operate the processes, how you handle the solids. All those questions need to be ironed out, but the technology itself is widely understood.” 

Displacing other possible uses for the same scarce biomass should not be a concern. “If you look at all the potential products you can get from tonne of biomass, making hydrogen turns out to be one of the best,” Dr Sunny says. “Gasifying it to produce hydrogen means that you get more of the energy than if you were to turn it into a liquid fuel or simply burn it.” 

Industrial applications

Instead of our energy system transitioning from hydrocarbons to hydrogen, as Jeremy Rifkin envisioned in 2002, the future is now expected to be electric. This offers a more direct connection with renewable energy sources that produce electricity in the first place. “Making hydrogen, you pay a penalty in both efficiency and cost,” explains Professor Brandon. “So, if you can use low-carbon electricity directly, that is what you should do.” 

Meanwhile there have been dramatic advances in technologies that make electric power viable in sectors once considered good prospects for hydrogen power. “Advances in battery electric vehicles mean that we are not looking seriously at hydrogen as a transport fuel in the near term for things like light-duty vehicles, cars and vans,” says Professor Brandon. “But there is still an open discussion about how you fuel trucks, ships and aircraft.” 

Domestic heating is another area where hydrogen is no longer seen as having a major role. “It’s a lot more efficient to use electricity to heat homes directly via heat pumps, for example, than to use green hydrogen,” says Dr Richard Hanna in the Centre for Environmental Policy. In 2022, he co-authored a report for Imperial’s Energy Futures Lab on the future of home heating, which placed hydrogen low down the list of viable solutions. 

There is now a broad consensus that hydrogen will struggle to find a place in these applications, given the alternatives available. For example, both domestic heating and hydrogen cars find themselves at the bottom of the Hydrogen Ladder produced by influential energy analyst Michael Liebreich. 

With both green and blue hydrogen likely to be scarce in the coming years, we will have to think strategically about where best to use the resource we have. Experts at Imperial think that industry should be first in line. 

For example, green and blue hydrogen can substitute for grey hydrogen in sectors where the gas is needed in its own right rather than as a source of energy. These include the chemicals industry, where hydrogen is a feedstock, and steel-making, where hydrogen can be used as a reducing agent in the production of iron. “They are a good place to start, because we can replace hydrogen from coal and gas with hydrogen from renewables,” says Professor Brandon. 

Similarly, hydrogen can replace natural gas as an energy source in industrial plants, decarbonising processes that are often hard to electrify. “Hydrogen can be a drop-in replacement that results in minimum disruption to the way industries today operate,” says Dr Sunny. 

That said, adjustments to turbines will be necessary. “The combustion process needs to be adapted, the way injection happens, the way vaporisation of hydrogen happens, and the temperatures required,” says Professor Martinez-Botas. “This doesn’t require a fundamental change in the technology, but you do need to pay attention to the components, their behaviour and safety.” 

For example, adjusting the air supply will determine whether or not the engine burns hydrogen cleanly. “If you want to avoid the production of nitrogen oxide emissions, then you have to handle both the hydrogen and the air supply in an optimal way,” he says. “Then you can be sure that the output is mostly water vapour, and there is no need to further treat the exhaust gases.” 

Decarbonisation pain-points 

The use of hydrogen in transport is more finely balanced. Battery electric vehicles may have put hydrogen largely out of the picture when it comes to cars and light delivery vehicles, but it may still make sense for other modes of transport where recharging times, range or payloads are an issue. 

“Heavy duty vehicles, like trucks and buses, and beyond that shipping and aviation, are the big pain points in terms of the energy transition,” says Dr Reshma Rao from the Department of Materials and the Grantham Institute. “Since there are only so many lithium-ion batteries you can put into something that moves, either hydrogen or one of the hydrogen carriers, like methanol or ammonia, will play a key role in helping decarbonise those sectors.” 

Professor Brandon agrees. “After electrons, hydrogen is the next building block of the fuels of the future, whether that is hydrogen directly or other hydrogen carriers,” he says. 

Hydrogen is also likely to have a role balancing supply and demand for renewable energy. New technologies such as the hydrogen flow batteries being developed by Imperial spinout RFC Power are designed to help even out electricity supply from intermittent sources such as solar and wind power. 

“That’s looking at developing local energy storage solutions in the 8–24 hour range, which is presently beyond the capability of batteries,” says Professor Brandon, who co-founded the company with Professor Anthony Kucernak in the Department of Chemistry. RFC Power has been working with Shell’s GameChanger programme to further develop the technology, and with leading renewables company Ørsted to explore options for its pilot deployment. 

But hydrogen could also provide a longer term energy buffer for the whole country. “With a high electricity renewable system, you end up with a concern about what happens in the winter when power use for heating peaks, and you can store hydrogen at scale much more easily than you can store electricity,” says Professor Brandon. 

Storing large volumes of hydrogen for months or longer will be challenging. “When we think about rolling out hydrogen at scale, we’re talking about levels of hydrogen storage that are much greater than we have ever had to achieve for natural gas,” says Dr Sunny. 

Geological reservoirs, such as depleted oil and gas fields, which have been used for storing natural gas will often be unsuitable for hydrogen. “Hydrogen is a small molecule and it will pass through cracks in the rock, so you don’t necessarily have good control over whether it will stay where you inject it,” Dr Sunny says. Salt caverns might be a better alternative, but these are only available in areas with a very specific geology. 

The supply of green hydrogen is limited by the availability and cost of renewable energy, and the availability and performance of the electrolysers that produce the gas. This is proven technology, but work is still needed if it is to be deployed at scale. “There are challenges making bigger, better, cheaper and more efficient electrolysers,” Professor Brandon says. 

Among the companies working on these issues is Ceres Power, which was spun out from Professor Brandon’s lab at Imperial in 2000. Its solid oxide fuel cells are now being deployed at scale and its megawatt-scale electrolyser for producing green hydrogen was recently installed for Shell in India. It is currently working with engineering group AtkinsRéalis to design a commercial multi-megawatt modular hydrogen production system. 

Professor Brandon’s work with solid oxide fuel cells and electrolysers continues. “We are exploring options for different structures, different ways of making cells, and different materials, to see if they give us functional benefits, both in performance and lifetime,” he says. 

When it comes to proton exchange membrane (PEM) electrolysers, a significant hurdle is the platinum or iridium needed for their catalysts. Already scarce, these metals are mined in a limited number of countries, often in regions where geopolitical tensions make supply challenging. Their extraction also has environmental impacts that do not sit well with the goal of producing clean energy. 

Reducing these rare metals in PEM electrolysers would help boost their scalability. This is a question Dr Rao is pursuing with respect to iridium. “We are breaking this problem down to the atomic scale, and trying to see which atoms in the catalyst are necessary for the reaction to happen, and which can be replaced with something that is much more earth-abundant,” she says. 

Another option is to look for alternative catalysis systems that do not need rare metals at all. In photosynthesis, for example, plants split water to make hydrogen and oxygen, before building the hydrogen into carbohydrates. “The enzyme that does this in plants relies on manganese, which is much more abundant than the materials we use at present, but we still haven’t been able to use manganese as a catalyst, even at the laboratory scale,” Dr Rao says. 

A further technical challenge is that most current electrolysers need ultra-pure water to function, which means expending resources on purification. “We are thinking of ways to have catalysts that are more tolerant and resilient to contaminants in water,” says Dr Rao. “The dream is that you can take seawater or sewage water and use that to make hydrogen. That could really make this technology available globally. But now even tap water is orders of magnitude more contaminated than what you can put in an electrolyser.” 

Hydrogen hubs

One of the attractions of hydrogen as an energy carrier is that it seems easy to move around, but the reality is more complicated. Hydrogen has a low energy density, much lower than natural gas, and so must be compressed and piped at high pressures for supply to be efficient. Most natural gas pipes are not up to the job, so a new high-pressure gas network will be needed, complete with appropriate safety systems. Then, on arrival at its destination, the hydrogen needs to be expanded again before it can be used. 

These transitions add significant energy costs to the use of hydrogen, for example in fuel cells. “The auxiliaries, such as the compressor, the pump and the expander, account for possibly 20–25% of the energy needed to run that fuel cell,” says Professor Martinez-Botas, who has a significant project at the moment looking at fuel cell deployment. “So, you need compression technology that works efficiently, and expansion technology that can recover some of that energy effectively.” 

The solution is to avoid moving hydrogen around too much, and have hydrogen production and use as close together as possible. “What I envisage in the near term is local hydrogen hubs, operating in a similar way to today’s petrochemical sites,” Dr Sunny says. These hubs will both produce and use green and blue hydrogen. “We will then see these hubs expand so that they supply an additional series of users who are clustered nearby.” 

That might mean small-scale industry, or possibly commercial transport fleets running on hydrogen. Proximity to a hydrogen hub might also tip the balance for domestic heating. “There might then be some potential for either 100% heating through hydrogen boilers, or possibly hybrid systems where they might be appropriate for difficult-to-heat properties,” said Dr Hanna. “But that is going to be quite niche.”

Electricity networks

In order for green hydrogen to be integrated into industrial and other systems, producers will have to solve the problem of intermittent renewable energy. Storing hydrogen to use when there are dips in current is one approach, but this may not be enough to guarantee supply. An additional safeguard is to bridge the gaps with green electricity drawn from the grid. 

The challenge here is getting a grid connection, with lengthy waiting lists already common. “This is a key barrier to scaling up hydrogen at the rates that we would like to see,” says Dr Sunny, who is working on a project that looks at alternative connection models that might avoid these bottlenecks. 

What takes time is building in network capacity and reinforcements to ensure the contracted power is available at all times. A flexible grid connection might not have these guarantees, but the risk of interruptions might not be a deal-breaker for the hydrogen producer. “The question is: do you have enough hydrogen in storage to meet demand? Can you operate in an intelligent way in order to get your electrical connection two or three years sooner, and still meet the needs of your clients?” 

Dr Sunny is working with UK energy regulator Ofgem and distribution network companies on this question. The initial results are encouraging. “Some of these solutions involve understanding the local grids better and building in control systems necessary to trade different kinds of connection, and to better understand whether a flexible connection makes sense,” he says. 

Addressing the technological challenges involved in integrating hydrogen into the energy system will only take us so far, however. “You can achieve some reductions in costs from technological innovations, but not to the point where hydrogen is competitive with natural gas,” says Dr Oluleye. “This is where you need policy, such as market-shaping mechanisms, and private finance to get hydrogen to scale.” 

She works on these economic questions, asking how hydrogen can be deployed and scaled-up cost-effectively. “It’s about how we reduce the price of hydrogen so that it is close to that of natural gas, the business-as-usual source of energy,” she says. “And that economic challenge is still very big.” 

In order to address this, Dr Oluleye has developed a comprehensive framework that helps assess policies and inform decision-making, taking into account technological breakthroughs, changes in policies and markets, and private investments. “My research shows how we can blend these themes, achieve hydrogen commercialisation, and get us over the ‘valley of death’ where new technologies so often fail on their way to the market,” she says.

Where significant uncertainties remain, we must be able to adapt. “There is huge potential in some green hydrogen technologies that look very expensive at the moment, and that’s where flexibility would help, so that we can embed them when they make sense economically,” says Dr Michel-Alexandre Cardin in the Dyson School of Design Engineering.

His work applies the theory of real options analysis to engineering design practice, making it possible to put a value on flexibility when building a system under uncertain conditions.

For example, building a hydrogen production plant is a major undertaking, yet at present it is impossible to predict how strong the demand for hydrogen will be once it is finished, several years down the line. So, is it better to build a 2-gigawatt plant that might fall short of demand, or 4-gigawatt plant that might have unnecessary and expensive overcapacity?

Dr Cardin’s approach points to a smarter third choice: start small, but build in the flexibility to scale up if required later on. This requires an entirely different design of hydrogen plant, and planning tools that can put a value on this flexibility. “Traditional investment evaluation methods, such as discounted cash-flow analysis, don’t do that.”

While the challenges should not be underestimated, experts at Imperial are broadly positive about the prospects for developing hydrogen as part of the future energy system. “We have identified where the bottlenecks are, and we know which materials challenges are most critical to unlock the hydrogen economy,” says Dr Rao. “The pace and interdisciplinarity of research to find novel solutions and the strong partnerships between academia and industry make me optimistic about the future of green hydrogen production.” 

Professor Brandon is also optimistic about the potential for hydrogen and its carriers to contribute to a low-carbon economy. “The world will need green fuels and chemicals, and the easiest one to make is hydrogen, be this green or blue,” he says. “While we need to drive down cost and scale-up hydrogen production, I cannot see a world in which hydrogen does not have a role to play in some form.” 

Dr Oluleye thinks that progress will not be long in coming. “I am optimistic that blending internal interventions, based on technological breakthroughs, and external interventions from market-based policy, market shaping mechanisms and private finance can make hydrogen competitive, and the resulting demand-pull from heavy industrial sectors can trigger positive tipping points for the rest of the economy,” she says. 

Professor Martinez-Botas, however, sounds a warning note, adding that it is important to consider equity in the new hydrogen economy. “Whatever changes in fuel and technology take place, they need to be accessible to everyone, from the highest to the lowest,” he says. That could be challenging in a situation where hydrogen is in short supply, yet less sustainable technologies are forced out of the market by regulation.