Why hydrogen needs nuclear

By 17 September 2020 Comment

Nuclear power can hold the key to an affordable low-carbon hydrogen economy. Neil Murray, the Nuclear AMRC’s business development manager for advanced nuclear technologies, explains why fission’s reliable supply of heat and electricity makes it the ideal power source for sustainable hydrogen production.

Hydrogen has moved to the top of the low-carbon agenda recently, and is increasingly seen as a major component in the drive towards global decarbonisation.

Hydrogen is not itself an energy source, but an energy carrier or vector. Producing hydrogen consumes energy, but it can then be used to replace fossil fuels for transport and heating. It could revolutionise industrial processes such as steelmaking, chemical synthesis, and the production of ethanol and synthetic fuels. In all cases, the only by-product from burning hydrogen is water.

But if we want zero emissions, hydrogen is only as good as how we make it and how we power its production. This brings us to the different classes of hydrogen – grey, blue and green.

Currently, around 70 million tonnes of hydrogen are produced each year for uses such as oil refining, ammonia and methanol production, and transport fuel. About 95 per cent of this is produced from fossil fuels using steam methane reformation, which depends on an energy-intensive catalysed reaction between methane and superheated steam.

This is known as grey hydrogen, and its production releases some 830 million tonnes of carbon dioxide a year – as much as the total emissions of the UK and Indonesia combined. Without carbon pricing, grey hydrogen costs an estimated €1.5/kg, depending on the price of natural gas.

There is growing interest in combining this established process with carbon capture and storage (CCS) to produce so-called blue hydrogen. If today’s nascent CCS technology can be matured and scaled-up, and the cost of emissions is included on the cost of grey hydrogen, then blue hydrogen becomes increasingly competitive.

Both grey and blue hydrogen depend on a finite supply of fossil fuels, whereas the third class – green hydrogen – is powered by renewable energy sources and does not emit CO2.

The leading method for green hydrogen production is electrolysis, where an electrical current splits water into hydrogen and oxygen gases.

Many countries have launched initiatives and strategies to make green hydrogen happen on a grand scale, with grey hydrogen transformed into blue by the addition of CCS.

The European Union, for example, released a hydrogen strategy in July calling for one million tonnes of hydrogen to be produced from green electrolysis by 2024, increasing to 10 million tons in 2030. Within the EU, France is targeting 10 per cent green hydrogen use in industry by 2022, and 20–40 per cent by 2027.

There are two big challenges here: cost and capacity.

Electrolysis is an exciting technology with organisations across the globe developing increasingly large electrolysers, but the efficiency levels have some room for improvement. Electrolysis consumes a lot of energy, with current techniques costing around €3.5–5/kg, depending on the cost of electricity.

That’s not cheap – but with the improvements being made in electrolyser design and the scale-up in production as demand increases, prices should rapidly reduce.

Scaling up electrolysis using current techniques will require a lot of new generation capacity. A recent study calculated that if the US were to move from grey to green production for its 13 million tonnes of hydrogen a year, it would need 74GW of additional low-carbon electricity generation – around 70 current nuclear reactors, or some 25,000 large 10MW wind turbines.

Electrolysis does become much more efficient at high temperatures, but green production requires a low-carbon heat source. This is where nuclear emerges as a potential front-runner.

Nuclear is the only low-carbon source capable of providing both electricity and heat simultaneously, without interruption, in any location. Current light-water reactors can provide steam at up to 300°C, and advanced reactors could provide temperatures of 800°C or higher. That can greatly increase the energy efficiency of electrolysis, resulting in a lower cost for green hydrogen.

Nuclear can also be used as the energy source – again both electricity and high-temperature steam – for the steam methane reformation process, therefore it represents a very real low-carbon option for the scale-up of blue hydrogen production as well as green.

In its latest annual report, the UK’s Nuclear Innovation and Research Advisory Board (NIRAB) highlighted a process known as thermochemical water splitting as the prime candidate for producing green hydrogen from nuclear.

Thermochemical water splitting uses high-temperature heat (500–2,000°C) to drive a series of chemical reactions that produce hydrogen through a closed-loop process that consumes only water and power.

This is arguably where nuclear could realise its full potential. Only nuclear and concentrated solar power can produce such high temperatures, and only nuclear can do it around the clock in all locations and all conditions.

The next generation of advanced modular reactors are ideally placed to produce hydrogen by this method, thanks to their high output temperatures and their compact size which allows them to be located alongside existing facilities. Thermochemical water splitting still requires some development, but represents a credible and highly cost-competitive route for producing industrial quantities of green hydrogen.

There are a lot of challenges involved – from reducing the construction and manufacturing costs of new nuclear plants, to regulatory hurdles for co-generation – and the Nuclear AMRC is working with partners to tackle these.

Modular manufacturing means that new high-temperature reactors will largely be produced to a drumbeat in factories, then transported to and assembled on-site with repeatability and precision. Prices will be considerably lower, thanks to economies of scale and experience. We are placing advanced manufacturing and best practice at the heart of each nuclear project, delivering the technologies to unlock the full benefits of nuclear.

We need to move swiftly and with purpose if we hope to achieve global decarbonisation. Grey hydrogen production is no longer sustainable, so we must move quickly to develop the infrastructure for a hydrogen industry made of green and blue, powered by a low-carbon mix of energy sources –  including wind, solar, hydro, tidal and, of course, nuclear.

  • The Nuclear AMRC is actively supporting projects on hydrogen production and nuclear co-generation. To find out more about how we can support your project, contact neil.murray@namrc.co.uk