In August 2021, hydrogen was on the up. For several years, its role in the future energy mix had been growing. The government released the UK Hydrogen Strategy, spelling out the fuel and energy vector’s potential contribution to ‘net zero’ goals and a more sustainable future.
Then, in February 2022, Russia invaded Ukraine. The war upended European energy supplies and global energy markets, and had “major ramifications” for how the government thought about hydrogen, according to Ian Graffy, senior policy advisor at the recently-created Department for Energy Security and Net Zero. The government’s British Energy Security Strategy, published in April 2022, doubled the ambition for hydrogen production to 10GW by 2030.
Achieving that goal will involve overcoming huge challenges. Countries around the world face similar barriers.
Those issues – and some solutions – were discussed at Engineering Challenges in the Hydrogen Economy 2023, an IMechE event held at the Tottenham Hotspur Stadium in London last week (14-15 March). Here are five of the challenges discussed during the first day, and five potential solutions.
Challenge: We need to produce more hydrogen – without generating carbon dioxide
Potential solution: Nuclear-powered hydrogen production
Boosting energy security, bringing economic opportunity and helping meet legally binding net zero targets, “we know that hydrogen has a major role to play in the UK’s energy future,” said Graffy. It can also cut carbon from hard-to-decarbonise industries, he added, with demand in industry, power, heat and transport.
Models in the Net Zero Strategy show that hydrogen could represent 20-35% of final energy demand in 2050. “That’s really substantial,” Graffy said. “That’s in the region of the current electricity usage today, which is about 330TWh. But we’re going from zero to a really, really large number and we need to act now.”
That huge increase in production needs to be as green as possible. Electrolysis powered by renewable energy has received significant coverage, but several of the event sessions focused on production using nuclear energy.
Nuclear power plants are a promising option because they can generate reliable, low-carbon electricity 24/7 for 60 years or more, said Allan Simpson, technical lead for nuclear enabled hydrogen at the National Nuclear Laboratory. If Hinkley Point C was used to power conventional electrolyser technology, he said it could produce enough hydrogen for 40,000 hydrogen buses or heat a million homes, “changing the paradigm” of how we use hydrogen.
Hinkley Point C developer EDF Energy also featured at the IMechE event. Development manager Peter Smith told attendees that the company had recently completed a feasibility study on demonstrating solid-oxide electrolysis integrated with nuclear heat and electricity, providing low-carbon hydrogen. The process, which the firm is demonstrating with industrial partner Hanson, could prevent hundreds of thousands of tonnes of carbon emissions from asphalt and cement producers.
Challenge: We need to balance supply and demand
Potential solution: Storage in salt caverns
“There’s not a ‘golden goose’ solution to hydrogen storage in my opinion, it’s very project specific,” said Stuart Doherty, senior process engineer at Atkins SNC-Lavalin. “Hydrogen storage is actually really hard because of the chemical composition of hydrogen, it has very low energy density, so compared to natural gas for example, it’s actually quite hard to store. It’s a small molecule, which makes it hard to contain as well, it’s not easy. Additionally, it’s got a very low freezing point.”
The UK has a bigger problem than some other European countries, he said, because storage is lagging behind production. This is particularly important because we need to balance supply and demand levels.
“In a perfect world, supply would balance out demand, but obviously the hydrogen economy is going to be very complex, with lots of different producers, small producers, electrolytic, blue, and the same with demand – there’s going to be lots of different small demands, from heat, from power,” he said.
With electrolytic production of hydrogen from wind energy, for example, days without wind will reduce supply but demand might remain the same. Storage can balance those peaks and troughs.
There are lots of potential storage options, Doherty said. Pipelines are perhaps the most obvious option, but higher pressure would be needed due to hydrogen’s lower energy density. Above-ground vessels are another option, but the lower energy density would either require a larger footprint or thicker walls for high-pressure vessels.
Underground storage in aquifers, reservoirs and salt caverns, could provide a more promising option, he said. Atkins is focused on salt caverns, in which wells are drilled, water is leeched down to dissolve the salt, and the cavern is formed. The proven technology can store large volumes, without concerns about above-ground footprint.
There are some drawbacks however, meaning all options need to be explored to maximise hydrogen’s contribution to the energy mix. It might take two years to build a cavern, and building and operation is not cheap. Reactions between the gas and cavern walls can cause issues, while the UK’s geology means there are fewer opportunities than in northern Germany, for example, where there are ample sites for underground storage.
Challenge: We need to get hydrogen where it is needed
Potential solution: Distribution by road
Pipelines might seem like the obvious choice for hydrogen distribution, but land use and high costs can make it impractical for relatively short distances, said Stephen Livermore, senior systems modelling engineer at hydrogen engineering company Lifte H2.
The company, which aims to reduce barriers for hydrogen projects, has instead explored two different options for road transport of green hydrogen.
The first was a road trailer that transports hydrogen to refuelling stations, which has high capital costs but low transport costs. The second option was a road trailer that can directly refuel fleet vehicles at a location. The mobile refueller cannot carry as much hydrogen, however, and cannot be completely emptied.
The mobile refueller is cheaper at distances below 170km, Livermore said, after which the other option is preferable.
The Lifte H2 case study just focused on cost, meaning other parameters – such as safety – need further consideration. Truck drivers would need to be specially trained to transport the flammable gas, Livermore said.
Challenge: We need storage options for hydrogen aircraft
Potential solution: Composite tanks
Hydrogen is the most promising short-term fuel option for zero-carbon aviation, according to the Aerospace Technology Institute – it can be produced with renewable energy and the only emission from its use is water. Sustainable Aviation Fuels (SAF) might need unsustainable amounts of agricultural land, while batteries are not predicted to become feasible for several decades.
Despite some promising demonstrations, technology for hydrogen aviation is far from proven. Engineers at the National Composites Centre (NCC) believe their speciality could have a big role to play, said head of hydrogen technologies Marcus Walls-Bruck.
Composite materials could be suited for cryogenic storage on aircraft thanks to their typically low mass – a key feature for any aerospace application.
“The headaches are pretty significant,” however, Walls-Bruck said. Many different components and interfaces are needed, and the temperature ranges involved can be massive – the outside of a tank could be at ambient temperature while the inside is at -253ºC. Those extreme differences are challenging for composites, which can have large temperature differentials between their component materials. That can lead to ‘micro-cracks’, threatening the integrity of a tank and risking dangerous accidents.
The NCC aims to fix that problem. The centre is exploring tougher materials and is designing and building vessels, which it aims to test with liquid hydrogen soon.
Challenge: We need to improve efficiency of offshore electrolysis
Potential solution: Capturing waste heat
One of the neatest solutions for green hydrogen production could be to use renewable electricity where it is generated, at solar installations or offshore wind farms. Working at sea raises some costs, said Iain Scott, business development manager at water, energy and waste management firm Veolia, but it also brings some enticing advantages.
The main draw is the ready supply of seawater, which can be split through electrolysis into oxygen and hydrogen. The seawater first needs to be converted to freshwater, however. Using PEM electrolysis, one of the most mature technologies, also leads to 20% of power generation being lost as heat.
Veolia set out to tackle that issue with a system that captures waste heat and feeds that energy back into the process, improving efficiency. The process can reduce the power requirements quite dramatically, Scott said, while also reducing costs.
Extracted from IMechE website, read more here