Research & Development

Royal Society / UK Report Highlights Potential Of Nuclear Cogeneration

By David Dalton
9 October 2020

Heat from reactors, much of which is wasted, could be used for domestic heating and hydrogen production
UK Report Highlights Potential Of Nuclear Cogeneration
The Sizewell C project is investigating using some of the heat for cogeneration. Courtesy EDF Energy.
Nuclear energy has the potential to help the UK to achieve net-zero carbon emissions by 2050, not only through the generation of low-carbon electricity but by more fully using the heat generated by a reactor, the Royal Society has said in a policy briefing.

The briefing considers how the use of nuclear energy could be expanded to make the most of the energy produced by nuclear plants and also to have the flexibility to complement an energy system with a growing input of intermittent renewable energy.

Nuclear “cogeneration” is where the heat generated by a nuclear station is used not only to generate electricity, but to address some of the “difficult to decarbonise” energy demands such as domestic heating and hydrogen production. It also enables a nuclear plant to be used more flexibly, by switching between electricity generation and cogeneration applications.

The society warns, however, that there are no existing nuclear cogeneration installations in the UK and it would be economically challenging to convert current nuclear plants to support cogeneration.

Planned new-build nuclear plants are designed primarily for the generation of electricity, but the designs could be modified to make use of the various benefits of cogeneration. In the case of Sizewell C, the potential for cogeneration is already under consideration.

The briefing explores the additional uses of nuclear energy beyond electricity, such as using high temperature heat to fuel processes directly, such as chemical synthesis, or low temperature heat for district heating. It considers how a nuclear plant can be used flexibly, switching from the production of electricity when needed to another application when electricity demand is low. This would allow nuclear energy to sit more comfortably within an energy supply dominated by intermittent renewable generation.

The principle focus of the briefing is heat. Nuclear reactors produce heat on a vast scale. A typical nuclear power station produces around 3.4 GW of heat – equivalent to about 100,000 domestic gas boilers – which is used to generate around 1.2 GW of electricity. Currently, around 65% of the energy is lost in the conversion as waste heat.

The current generation of UK nuclear power plants produce large amounts of electricity, but operate at a constant output and have, to date, provided only baseload electricity. This was not a problem when electricity demand fluctuations could be met by switching on and off gas-powered stations.

However, with increasing proportions of generating capacity delivered by intermittent renewable energy, coupled with the need to reduce gas-fired generation, greater flexibility from nuclear generation will be required if it is to remain an important part of the UK’s energy mix.

Case Study: Sizewell C

The proposed Sizewell C nuclear power station, where two Generation III EPR units are planned, would produce enough electricity to meet 7% of the UK’s electricity demand. The Sizewell C project is also investigating using some of the heat for district heating networks, process heat demands within industrial applications or agriculture, and to increase the efficiency of low-carbon fuel production.

In particular, the possibility of making hydrogen using nuclear energy is being explored. EDF is seeking to establish a pilot electrolyser project at the existing Sizewell B nuclear power station in the short-term. The hydrogen produced would meet the station’s internal demand (for example, in certain cooling mechanisms), power elements of the construction of Sizewell C (buses, excavators and forklifts), and feed into several other applications in the local area.

Ultimately, if successful, a large-scale, high efficiency steam electrolyser could be constructed at Sizewell C, as part of a regional energy hub.

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