Sizewell C: maximizing the value of nuclear power

Sizewell C is the 3.2GW nuclear power plant planned to be constructed in Suffolk on the UK’s east coast - adjacent to the existing Sizewell B nuclear power plant. The project has been approved by the UK Government and recently received a positive final investment decision (FID). Site preparation works are already underway.

The project will replicate the design and operation of Hinkley Point C, currently under construction in the south-west of England, in Somerset. Both plants will create thousands of jobs and generate enough low-carbon electricity to power over six million homes for over 60 years.

To provide maximum benefit to society, existing and future power generation assets should be utilized to their full potential. Optimal energy system design integrates a diverse mix of generation technologies to meet a nation’s energy demands.

In the UK, plans to further decarbonise the grid involve increasing the proportion of wind and solar renewable generation significantly on the system. An increased proportion of weather-dependant and intermittent renewable generation poses a new set of challenges to balance demand and supply, as well as grid stability.

Nuclear will play a key baseload role in such a system, reducing overall system cost and providing high capacity factor and weather independent power. There are multiple additional benefits from having nuclear as a part of a diverse mix in terms of jobs and growth, energy security, carbon emissions, minimising infrastructure intrusion and managing overall system engineering delivery and operational risk.

However, the large-scale deployment of new wind and solar generation and their variability will mean that more flexibility will be required to balance the system efficiently and minimise curtailments and wasted power. In the UK this is expected to be most pronounced in the summer period when solar generation is at its highest and energy demand at its lowest – a seasonal pattern referred to as minimum summer demand.

Sizewell C plans to develop the capability to power off-grid applications and maximise the value of the generation asset to the energy system, electricity consumers and society by being able to maintain power generation at full capacity while reducing the amount of electricity exported to the grid when required and diverting energy to other non-grid uses.

Sizewell C could power off-grid uses with energy in the form of heat as well as electricity. The heat could be harnessed through a nuclear cogeneration process that would involve steam-extraction prior to the ‘steam-to-electricity’ conversion process in the generation cycle.

Heat from a nuclear power plant is particularly valuable. Its clean, low-carbon properties can help decarbonise industrial processes or power clean technologies such as hydrogen production or direct air capture more efficiently which can lead to further benefits and value to society.

Interview: Fred Chung, Head of Energy Strategy, Sizewell C

Nuclear power plants have been able to adapt to varying grid demand by reducing output to the grid by ‘load-following’ (e.g. in France). What is novel about Sizewell C’s proposed approach to provide flexibility?

Although nuclear power plants can generally regulate the amount of energy produced to a limited extent, this is not their optimal operational mode. As is the case for many machines, the cost of operating the plant does not decrease proportionally with production. By maintaining full production capacity, we can maximise the utility of the generation asset as well as provide some flexibility to the energy system. Also, in France for example, the large fleet also allows for outage planning to manage overall generation.

How can Sizewell C’s plans deliver benefits beyond helping to balance the energy system through flexibility?

Sizewell C’s plans for an energy-hub ready power plant can enable technologies such as water desalination plants to ‘soak up’ power that would otherwise be surplus to the system and produce valuable commodities and products with this energy.

In addition, heat from the nuclear power plant can make hydrogen and carbon capture cheaper for industry and consumers. Technologies such as solid-oxide electrolysers (SOEC) and the type of heat-driven direct air capture technology that Sizewell is developing locally, could take advantage of our heat to help difficult-to-decarbonise sectors such as aviation achieve their ESG goals.

How much heat can the plant supply and is there an impact to electricity production?

Sizewell C will produce 3.2GW of electricity (enough to power 6 million homes in the UK) from 9GW of steam and the extraction of a small proportion of this heat (e.g. around 400 MWth) can provide significant industrial and decarbonisation opportunities while decreasing the electricity production by only approximately 3%.