Cambridge Consultants: UK must join green hydrogen shift to decarbonise aviation

Green hydrogen is the only viable fuel that can decarbonise the aviation industry, says Nathan Wrench, head of sustainability innovation at Cambridge Consultants – and without urgent action the UK risks losing the energy transition race being spear-headed by Saudi Arabia, the EU (collectively) and Germany.

His study considered both the science of green hydrogen as a fuel, and also the wider consequences of delaying involvement in the hydrogen economy.

“The most impactful companies and technologies of the 21st century will be those that can capture the opportunities of reshaping our energy society,” says Nathan. “In eliminating fossil fuels from the supply chain while increasing energy productivity and availability, the winners and also-rans of this century are already shaping up. Green hydrogen will play a vital role in this energy transition, and those that seek to lead must invest now.”

2020 is turning into a breakthrough year for green hydrogen. The EU unveiled an ambitious post-fossil fuel strategy in July, increasing renewable hydrogen capacity from 1GW today to 6GW by 2024 and 40GW by 2030. Germany’s €40bn green stimulus package has green hydrogen at its core. Saudi Arabia is looking to green hydrogen as a key part of its transition to a post-fossil fuel economy, starting with a $5bn green hydrogen-based ammonia production facility near the border with Jordan and Egypt which will produce 650 tons of green hydrogen daily, enough to run around 20,000 hydrogen-fueled buses.

“In the last few months some countries have decided to put all their chips in this basket and they’re going for it gigawatt style,” says Nathan. “Germany has invested €9bn in this sector. Saudi Arabia has put $5bn just into one facility. It’s like a new race track and you can see right from the start who’s taking it seriously.

“The UK is still at the stage of ‘let’s talk about a pilot scheme’. We don’t have an industrial strategy at the moment because we’re so distracted by other things , but we are capable of it. What we’re doing with wind turbines is truly amazing – truly we’re world class – and the rate of decarbonisation of our electricity supply is pretty good, but we’re not making investments in gas, in heating, in the more difficult industries which need to get the carbon out, like transportation, steel or cement.”

The case for green hydrogen goes beyond the case for hydrogen use in the automotive sector, which has never fulfilled its potential.

“Hydrogen has been spoken of as an energy vector for 50 years and every now and then someone pops up on Top Gear to complain that no petrol stations carry hydrogen,” says Nathan. “It’s always been quite interesting but never quite ready. Now, after 30 years of false dawns, people have been going crazy in the last six months. Saudi Arabia is pivoting towards sustainable energy with its Neom project” – a new smart city project for tourists – “which is 100 per cent fuelled by renewables, and is a net energy exporter of green hydrogen and ammonia.”

Green hydrogen is a very different proposition from the early hydrogen concept.

“Green hydrogen involves taking renewable energy – typically wind power – and add water, H2O, which is split using electrolysis to make hydrogen and oxygen,” says Nathan. “What’s lovely about this process is that there is no carbon involved in this chain and it gives you the promise of strong energy in gaseous or liquid form.”

Meanwhile developing green ammonia is another game-changer. Widely used to make agricultural fertilisers, traditional ammonia production releases 1.5 per cent of global CO₂ emissions. Green ammonia is 100 per cent renewable and carbon-free. By using water electrolysis and renewable electricity, producing ammonia – three parts hydrogen, one part nitrogen – is a zero-carbon fuel.

Ammonia can also be a practical hydrogen energy vector, further reducing CO₂ emissions by allowing for storage at scale. Green ammonia has three advantages. One, there is an existing distribution network, in which ammonia is stored in large refrigerated tanks and transported around the world by pipes, road tankers and ships. Two, ammonia can be burnt in an engine or used in a fuel cell to produce electricity with the only by-products being water and nitrogen. The maritime industry is a likely early adopter. Third, it is a hydrogen carrier: easier and cheaper to store and transport, it can be readily ‘cracked’ and purified to give hydrogen gas when required.

This ‘cracking’ process is the breakthrough the sector needs. Hydrogen can be extracted from ammonia, first by using a catalyst to help decompose the ammonia molecule into a mixture of nitrogen and hydrogen gas. Then, the hydrogen membrane allows hydrogen to pass through it while blocking any other gas. And, if this process takes place on board the aircraft, the sector will have a whole new lease of life, because green hydrogen, unlike conventional hydrogen – remember the Hindenburg – does not leak.

“Aviation is where to go,” says Nathan. “When you’re storing hydrogen as a cyrogenic liquid, even if it’s liquified, in that state it’s still bulkier than kerosene, which is currently used as aircraft fuel, but it’s half the weight. So you can probably achieve comparable ranges in an aircraft but the aircraft requires significant modifications. Hydrogen requires large bulky thermos flasks which won’t go on wings, which is where kerosene is stored.”

Nathan estimates that the use of green hydrogen would push the price of flying up by five to 10 per cent, “but aviation together with the freight industry are fundamentally difficult to decarbonise so a significant redefinition of the industry is needed”. This process would also mean redesigning a new generation of aircraft with fuel storage in the fuselage, which Nathan has concluded would reduce capacity by up to one third.

Of particular interest is that this incredible new fuel can be used for both jet and propeller-based planes.

“For short hops you would have a hydrogen fuel cell for the propellers. Green hydrogen makes electricity for the motor, but for long haul journeys you burn it.”

Recently, the chairman of the Environmental Audit Committee warned that the UK is squandering the opportunity of ‘green hydrogen’. Cambridge Consultants is keen to ensure that the UK does not get left behind.

“Green hydrogen is the emerging fuel that could ultimately usher in a new era of emissions-free flight,” concludes Nathan. “Of course, there are huge engineering challenges to be overcome before this future can be realised.

“Though it’s light, hydrogen is bulky and would require fundamental modifications to plane airframes, not just the engines. And yet, there’s no other energy vector that can hope to shift the emissions of the aviation industry, and both the aviation industry and leading developed nations are now waking up to this fact.”

‘Leading developed nations’ so far doesn’t include the UK. Let’s hope that changes soon. Anyone got any ideas where to start?