The last few days have been windy across northern Europe and turbines have provided a large fraction of power needs from Ireland to Finland. But these storms follow months of unusually European quiet weather, causing wind’s share of electricity supply to fall well below typical levels. This swing between scarcity and abundance illustrates the central question of the energy transition: how can countries cope with the huge variations in electricity supply arising from the unreliability of wind and solar?

The answer is by using hydrogen. When electricity is in surplus, as it was in many countries as Storm Eunice swept over Europe on Friday 18th February, electrolysers can separate water into hydrogen and oxygen. This can soak up the electricity that would otherwise have no productive use. At times of shortage, the hydrogen can then either be burnt in a gas turbine or fed into a fuel cell to generate power.

The standard criticism of this idea is that is wasteful of energy; we will get back less than half the energy initially fed into the electrolyser as the storm blows. But the value of the power used will be very low because of the surplus in the electricity markets. When the hydrogen is turned back into electricity, the reverse will be true because of the shortage of supply. Hydrogen power stations will be generating valuable power. Perhaps even more importantly, conversion to hydrogen is the only way that huge quantities of energy can be economically retained for months at a time. Batteries would be a far more expensive way of achieving very long duration storage.

A national electricity system that continues to invest heavily in renewables, complemented by the development of a hydrogen infrastructure to deal with the variability of supply, is an idea that has not been properly explored. It needs serious consideration now, not least because the continued expansion in renewable electricity sources will make periods of electricity surplus much more frequent.

To give one example, the UK is proposing to add almost 30 gigawatts of electricity from offshore wind by 2030. In the last few days national demand for power in the hours after midnight has been less than this figure. Without taking in account the existing wind capacity of almost 25 gigawatts, and all the other low carbon sources such as nuclear and biomass, wild winter storms will soon overwhelm the UK’s ability to use the electricity generated.

Using hydrogen as the means by which the electricity system provides guaranteed power faces three major obstacles. None are unsurmountable although all are challenging. The first is the requirement to build up sufficient electrolyser capacity. The second is to locate the cheapest and safest means of storing enough hydrogen to cover many weeks use and the third is providing the gas turbine and fuel cells required to balance electricity demand and supply when the wind isn’t blowing.

Let’s look at these issues in turn. Can hydrogen can be generated in sufficient quantities to provide the guaranteed back-up that we require? When the UK has added an extra 30 gigawatts of offshore wind, it will probably need at least 10 gigawatts of electrolysers to convert periods of surplus power into hydrogen. That’s at least twenty times the total global installed capacity today. Nevertheless industry researchers project well over 200 gigawatts by 2040 and every forecast that is issued increases the expected growth rates for electrolysers. New factories to build many gigawatts a year are being constructed around the world and the largest proposed installations are now as much as 800 megawatts, more than today’s global installed base.[1]Although acquiring enough electrolysers to handle surpluses from offshore wind will be challenging, the supply industry is capable of growing at the required rate.

The next question is how the hydrogen will be stored - possibly for very long periods - after it has been generated. Some northern European countries, including the UK, are in the lucky position of having extensive underground salt deposits that can used to create impermeable storage caverns. This is almost certainly the cheapest and safest way of holding large reserves of hydrogen. Researchers recently suggested that Europe has at least 7,000 terawatt hours of potential hydrogen storage capacity, nearly twice the continent’s annual electricity use.[2]

The first salt cavern for storing hydrogen was built in the UK in 1972 and is still operating today.[3] It does not store a large quantity but plans are being developed at sites in Germany and the US for caverns that can hold more than a hundred and fifty gigawatt hours of energy, equivalent to several hours of UK electricity use. As with electrolysers, salt cavern use will need to be increased by many orders of magnitude to enable countries to store months of energy, but the technology exists and is economic.

The last major obstacle to a plan for using hydrogen to balance electricity supply and demand is the need to convert existing gas power stations. The major gas turbine manufacturers now offer products that operate on high percentages of hydrogen in a natural gas mix. Within a few years, 100% hydrogen turbines will be widely available. The cost will not be significantly different from standard natural gas equipment and the operating efficiencies will be very similar.

The UK and other countries can develop large hydrogen-fired power stations. One in the Netherlands is planned to begin operating in 2023.[4] At a much smaller scale, hydrogen can be used to operate fuel cells to deliver power into electricity grids. The most advanced plan is the French territory of Guiana, where a solar farm will produce power during the day, and convert some to hydrogen to be used in a fuel cell to deliver overnight electricity.[5]

The world understands it need to shift rapidly to an energy economy based around renewable electricity. This will be cheaper than gas and coal and emissions will be close to zero. But the variability of electricity supply requires huge storage capacity. Batteries cannot economically provide this. Hydrogen is the only realistic way of dealing with the peaks and troughs of renewable supply. And it would reduce dependence on currently expensive gas and the associated emissions. This idea needs urgent investigation in the UK and elsewhere.

[1] NEL Hydrogen presentation 16th February. https://nelhydrogen.com/quarterly-presentation/

[2] https://www.sciencedirect.com/science/article/abs/pii/S0360319919347299

[3] https://innovation.engie.com/en/articles/detail/hydrogene-souterrain-stockage-sel-cavites-mines/25906/12/1

[4] https://www.nsenergybusiness.com/projects/nuon-magnum-power-plant/

[5] https://www.pv-magazine.com/2021/09/30/large-scale-solar-plus-hydrogen-project-secures-25-year-ppa-in-french-guiana/