There is increasing recognition that a UK net zero future will feature a significant role for hydrogen as an energy vector. The UK currently relies heavily on natural gas for heat, industry and power production. If net zero ambitions are to be realised, this must be replaced with either increased electrification (powered by low-carbon sources) or an alternative low-carbon fuel; hydrogen seems to be the leading contender for the latter. But large-scale, clean, hydrogen generation requires a vast amount of low-carbon energy right across the production life cycle, if it is to be helpful for carbon reduction. In this article from our On Hydrogen publication, Dr Will Bodel explores how having advanced nuclear as a balancing technology could enable the generation of substantial amounts of cheaper low-carbon hydrogen whilst also allowing renewable technologies to operate to their full potential.

• Hydrogen is increasingly recognised as a key component for the UK’s net zero future, though it is essential that it is generated using low-carbon energy.
• Researchers at the Dalton Nuclear Institute believe that next-generation advanced nuclear reactors can fuel the low-carbon energy needed for clean hydrogen production.
• Government must take a more integrated approach to the modelling of low-carbon futures and recognise the interconnections between hydrogen, nuclear, heat and renewables.

Many large-scale hydrogen production routes are under consideration, with enough ‘colours’ assigned to them to resemble a paint colour chart, each of them requiring a huge amount of energy. At the Dalton Nuclear Institute, we believe that next-generation advanced nuclear reactors offer a uniquely effective means to do this. Here, we consider two reasons why.

Making nuclear flexible

Firstly, we must consider what an effective net zero electricity grid would look like. The grid will be larger than today’s and made up of low-carbon sources. The only scalable low-carbon options at present are renewables (in the form of wind and solar) and nuclear. In the previous government’s plans for the future, renewables make up the bulk of electricity generation, but these have the drawback of being variable. For the periods where the sun doesn’t shine much and the wind doesn’t blow much, a flexible alternative technology is needed to fill in these gaps and meet the nation’s power demand.

Today’s nuclear plants don’t fit that role very well. While cheap to run, they are expensive to build, which makes the concept of a nuclear power station sitting idle for extended periods, when its power isn’t needed, extremely bad economically. The economics of nuclear plants are therefore optimised by running them at full power, 24/7. In contrast, most of the cost for natural gas power generation is the cost of the fuel. Gas plants are also quick and easy to power up and down, making them ideal for filling in gaps in generation elsewhere.

“Nuclear is inflexible, so delivers baseload power” has long been an established truth for electricity generation but introducing hydrogen production – as well as electricity – to the mix, creates a way to make the output flexible, diverting nuclear output towards electricity or hydrogen production as required. This means reactors can run at full output capacity, and their energy split between the grid or hydrogen production according to demand. Even rapid changes in renewable output can be accommodated by turning the hydrogen production ‘dial’ up and down to divert more or less nuclear energy to that purpose.

Efficiency

The second reason nuclear power is emerging as a preferred route to hydrogen production relates to the way hydrogen is produced. Although hydrogen is abundant on Earth, it doesn’t exist in any significant quantities in pure elemental form, so it needs to be converted from something which contains hydrogen – usually methane (CH4) or water (H2O). Conversion requires a lot of energy in the form of heat and/or electricity.

The vast majority of the world’s hydrogen is currently produced from steam reforming natural gas. This has the downside of producing carbon dioxide in addition to hydrogen – counter-productive when the motivation for using hydrogen is to reduce emissions. Economics are also dependent on gas prices, which in the future may be higher than in the past.

Electrolysis (essentially water + electricity → hydrogen) provides a potential alternative, so long as the source of the electricity is both affordable and low carbon. Electrolysis can be broadly split into low – and high – temperature processes, with the latter particularly relevant for nuclear. This utilises Solid Oxide Electrolyser Cell (SOEC) technology, which is developing rapidly, with operating temperatures expected to reduce to below 650°C. This puts the process well in range of the operating temperature of many advanced reactor designs, including the high temperature gas cooled reactors (HTGR), which the previous UK government committed to demonstrating by the 2030s. For comparison, current light water reactors operate at around 300°C.

High temperature electrolysis is likely to be the cheapest route to hydrogen production, provided the high temperatures it requires are available. This makes it an ideal technology to partner advanced reactors. Such reactors can provide a variable mixture of high-temperature heat and electricity to a hydrogen production facility, in addition to putting electricity into the grid when needed. By delivering vast quantities of high-temperature heat direct to the process, both the additional demand for electricity and the overall cost of the hydrogen production are significantly reduced.

A feasibility report for Department for Business, Energy and Industrial Strategy (BEIS) found overall process efficiencies of over 50% can be achieved for the generation of hydrogen using advanced reactors, compared to efficiencies of less than 40% for low temperature electrolysis. This improvement in overall economics could have a massive impact on the viability of bulk, low-carbon hydrogen production.

Our recent research at the Dalton Nuclear Institute demonstrates how renewables and nuclear working in tandem – alongside a route to hydrogen production – can both reduce emissions by eliminating the use of backup gas-fired generation and save money by reducing the costs of backup plant or expensive energy storage, allowing both nuclear and renewables to operate to their full potential.

Policy recommendations

Reaching net zero will require huge amounts of low-carbon electricity, much of it from renewable sources. Without an effective means of balancing their variable output, we will need a vast over-supply of renewables, which will mean curtailing that output much of the time (turning turbines or solar panels off when demand is lower than the available supply). Having advanced nuclear as a balancing technology not only allows us to generate substantial amounts of hydrogen at a competitive cost, but it also allows renewable technologies to operate to their full potential, without curtailment.

High temperature advanced reactors are particularly suited to generating hydrogen and should be built at scale. These should be equipped for delivering hydrogen and electricity generation for the grid. This would enable them to generate electricity for the grid when output from other low-carbon generators is low. We recommend that government continues to support the delivery of advanced nuclear – at accelerated pace and with full recognition of the wider benefits to achievement of net zero.

Currently, government modelling of low-carbon futures takes a siloed approach – considering heat, hydrogen, renewables and nuclear independently. We recommend a much more integrated view be taken in forward planning, recognising the important interconnections and potential benefits which can result. This will allow renewables and nuclear to work together for a win/win outcome.