In the decades since, there have been waves of interest in using hydrogen more extensively, due to its specific characteristics.
“Hydrogen has excellent gravimetric energy density - the amount of energy it stores relative to weight,” says Tony Roskilly, professor of energy systems at Durham University and lead on Network-H2, the hydrogen-fuelled transportation research network.
“It has about three times the specific energy density of petrol or diesel. When you convert it in a fuel cell to produce electricity, it does not release any carbon dioxide (CO2) into the atmosphere. It is also the most abundant element on earth and a good form of energy storage, although its volumetric energy density is low. There are challenges producing it, because it is bound to other elements, and storing it for use.”
In the past, enthusiasm for hydrogen has proved overblown. This time the world looks different, with more governments committing to the net zero target.
“In 2008, the UK committed to an 80 per cent reduction in carbon emissions by 2050, so all the hard-to-abate sectors assumed they would fall into the ‘other’ segment. That’s no longer the case. Everyone knows there is nowhere to hide,” says Nigel Brandon, professor at Imperial College, London, the electrochemical engineer leading the UK’s hydrogen and fuel cell research hub, H2FC SUPERGEN. “That brings an energy carrier like hydrogen onto the table, because it is potentially the most cost-effective way of abating carbon emissions in areas that are difficult to address, like heavy industry.”
Meanwhile, there have been encouraging advances in the design of fuel cells, making them more efficient and durable. Other developments, like the fall in the cost of power generated by renewables, are also changing hydrogen’s prospects.
“Harnessing green energy has been a wonderful success,” says Upul Wijayantha, professor of physical chemistry at Loughborough University, whose research career has encompassed developing ways to split water using solar energy in the UK and US. “But renewables are intermittent. We cannot anticipate exactly how much energy will be generated when the sun shines or the wind blows, so we cannot anticipate the capacity of the batteries needed to store it. What do you do if you generate more energy than you can store? Use the excess to generate hydrogen.”
But generating hydrogen from renewables does not solve the challenge unless viable options are developed to store and transport it to suit end users.
Another issue is where the hydrogen will come from. Today, both natural gas and coal are major sources. “The cheapest way to produce hydrogen is by steam methane reforming at a high temperature, which creates grey hydrogen and CO2. Around 95 per cent of the hydrogen we use now is produced this way,” says Rick Stathers, senior environmental, social and governance (ESG) analyst and climate lead at Aviva Investors.
“Blue hydrogen is an alternative: it also involves steam methane reforming, but the carbon is captured or utilised,” adds Stathers. “But industrial carbon capture is an early stage technology, and there is comparatively limited capacity to carry it out.” (More on carbon capture and sequestration (CCS), here.)
“We need to be clear-eyed about this,” says Max Burns, senior research analyst for industrials at Aviva Investors. “Cheap and plentiful natural gas from the US, Russia and the Middle East is a likely feedstock for hydrogen, but this does little to reduce greenhouse gas emissions. Until we perfect CCS, blue hydrogen is really ‘greyish’ hydrogen with dubious green credentials. The timeline for widespread hydrogen uptake is likely to be extended.”
Green hydrogen is the optimal option from an environmental perspective, produced from splitting water using renewable electricity. “We only produce a very small amount of hydrogen in this way now; it is less than five per cent overall and not cost effective at the moment,” says Stathers.
The question then is: How rapidly could the economics of green hydrogen production change? “The consensus is that green hydrogen could reach cost parity with hydrogen produced from fossil fuels and CCS by around 2030,” says Stathers.4 “It could be the cheapest form by 2050. That implies a potential cost reduction of 60 to 70 per cent in the next 30 years. But the cost curve could change faster: that depends on policy factors like the price of carbon and how the market develops.”
To be effective at network scale, hydrogen needs to be stored in pressurised tanks or in geological sites underground. In Europe, meaningful amounts could be stored in underground salt caverns5, in cavities as tall as the Eiffel Tower.6 There are already sites of this type in operation. “We store hydrogen in that way to provide strategic reserves for petrochemical operations,” Brandon explains.
Other challenges include distribution and safety. Diatomic hydrogen is small and liable to escape, but work on whether it would be possible to use the existing gas network is ongoing.
“Further work is needed, but the upgrade of our gas networks has been going on for years on a rolling basis,” says Roskilly. “All our old cast iron pipes are being replaced or relined with polyethylene pipes. Once this is done, there should be no issues for the transport of hydrogen. The upgrades are well advanced.”
When it comes to safety, Roskilly believes hydrogen is “as safe or safer than the other fuels we use, either for transport or in our homes. There are safety risks, but these can be managed, just as we do for natural gas. And there is no risk of carbon monoxide poisoning when hydrogen is used in a boiler.”
If hydrogen’s role changes from being one chemical in the industrial mix to an energy source and store, the implications could be game changing.
“From an investment perspective, you can gain exposure to the hydrogen theme through a combination of renewable energy companies, pure play fuel cell and electrolyser producers,” says Stathers.
“European industrial gas producers are expecting meaningful revenues from blue hydrogen within about five years. We also expect to see demand for particular chemicals like polysilicon jump: it’s a critical component in solar cells, and demand could grow to fuel hydrogen production and the production of low-carbon electricity,” he adds.
In transport, the greatest potential is thought to be in areas that are hard to electrify, including long-distance freight, trains and shipping. (Conversely, battery electric vehicles are cheaper and likely to be adopted faster in the small car market.)
Another route is through the companies that will allow hydrogen to be integrated into the wider energy system. “Managing the grid is going to be a big challenge for the future,” says Richard Howard, research director at the energy analytics group, Aurora Energy. “The whole spectrum of technologies that help to run a stable system safely will become increasingly important, surprisingly quickly.”
Hydrogen was dismissed as an energy option a little over ten years ago, when then US energy secretary Steve Chu said it would take ‘four miracles’ to make it a contender.7 Cost, the inadequacy of fuel cell technology, lack of high-density storage and distribution infrastructure were all obstacles in his view.
A decade later, there has been progress in all areas, some more than others. Most striking of all, perhaps, is that energy consultants are asking what happens in the future when excess renewables take the cost of energy to almost nil. This scenario is someway off, but worth contemplating for those keenly awaiting cheaper green hydrogen.
- ‘World first: An offshore pilot plant for green hydrogen’, TNO, 2020
- ‘The world’s first offshore green hydrogen plant’, Neptune Energy, 2020
- J. B. S. Haldane, ‘Daedalus of science and the future’, Cambridge University, February 4, 1923
- Source: Aviva, UBS, CSIRO, BNEF, Hydrogen Council, Merrill lynch, Parkinson et al, as at August 2020
- Howard B. J. Stone, Ivo Veldhuis and R. Neil Richardson, ‘Underground hydrogen storage in the UK’, Geological Society, 313, 217-226, January 1, 2009
- ‘Hydrogen caverns are a proven, inexpensive and reliable technology’, cH2ange, February 8, 2018
- Kevin Bullis, ‘Challenging Chu on hydrogen fuel cells’, MIT Technology Review, June 19, 2019