Decarbonising electricity in the UK is far from straightforward. Government plans for the nation’s future electricity supply rely heavily on renewables, supported by gas power during periods of low renewable output. In this article, Professor Juan Matthews considers how nuclear energy can provide an alternative to gas power and support a future renewables-heavy grid, and how this could reduce emissions and save money.
- Electricity demand could double by 2050 as the UK attempts to decarbonise. This future supply is anticipated to come from renewables which require standby capacity.
- Our standby capacity is currently planned to be gas generation. Nuclear power could provide an alternative, but it requires cogeneration to be maximally effective.
- The government should think beyond nuclear’s use as only a baseload generator and consider the whole energy system when developing energy strategy.
In March 2024, the last government announced the need for continued use of unabated natural gas to support renewables for electricity generation. This would mean construction of dedicated new natural gas power stations. This policy was consistent with the Department of Energy Security and Net Zero’s (DESNZ) current “High Electrification” scenario, which details what the future energy generation mix may look like. This scenario requires a large capacity of unabated gas power – 84 GW compared to the current capacity of 35 GW. Such a high level of gas capacity is needed as solar is only available for up to 11% of the time and wind for 35-45% of the time – we can go for weeks with low generation levels.
Supporting renewables
To achieve net zero, electricity demand may double to supply electric cars and heat-pumps, as well as contributing more to industry. The DESNZ scenario envisages 90 GW of solar and 151 GW of wind capacity by 2050. The large unabated gas capacity is needed to complement renewables to meet demand, and to ensure there is sufficient power when renewable output becomes very low. However, the High Electrification scenario anticipates that this unabated gas capacity would only be used around 1.2% of the time. This is wasteful, and the cost of the supporting electricity would be high, because interest costs for financing the power plant must be recovered whether the plant is operating or not.
Maintaining the gas plants would add about £10 billion a year to electricity generation costs and result in substantially higher CO2 equivalent emissions. Replacing unabated gas with gas plus carbon capture and storage would increase costs but not make much impact on emissions, as the low usage means that most of the carbon emissions derive from the construction of the power stations – not the fuel use. The scenarios also include 35-55 GW of hydrogen fuelled generation, which is only used for around 2.2% of the time.
Batteries are useful to support solar power particularly to spread the availability of power over the day or to charge electric vehicles after sunset, but they are too expensive to store large amounts of electricity for days. Pumped hydro storage is also a useful storage method, but there are few suitable sites available for expanding the current capacity. Finding around 100 GW of new pumped storage capacity would not be plausible.
Could nuclear power help?
Yes, with some provisos. Cogeneration – using nuclear energy to deliver both electricity and heat, depending on what is needed at a given time – will be key to achieving much-needed flexibility, as will effective energy storage. Batteries aren’t the only way to store energy; the high temperatures nuclear power uses to make electricity means that storing the heat is an effective alternative that also allows the possibility of increasing the effective power capacity.
Nuclear power stations are currently operated at full capacity, delivering baseload electricity supply to keep costs low, as the economics requires they are used as much as possible. This has given nuclear power the reputation of being inflexible. At the Dalton Nuclear Institute our recent report outlines a simple but effective solution: use nuclear mainly for the provision of heat and power for a range of applications (for simplicity we focus on hydrogen production), and cheaply power the grid when necessary. This enables the nuclear plant to be operated at full power, keeping costs low, and supporting the grid when demand is high but wind and solar power are not available. Our “Flexible Nuclear” scenario shows that nuclear cogeneration is both substantially cheaper than using gas and lowers emissions of CO2. Savings of up to £14bn per year are possible with this approach.
Any type of reactor can be used, but potential for cogeneration varies between designs. Cogeneration plans already exist for the Sizewell C plant and new small modular reactors. The last government was also committed to demonstrating advanced high temperature reactors by the early 2030s, which would expand the range of cogeneration possibilities. There is a need to reduce the costs of nuclear, and a way to achieve this would be to “fleet build” – that is, building many identical stations so savings are made from replication. By moving to smaller modular reactors, the effect of learning rate is greater as more reactors are built, whilst also offering savings on factory construction and shorter build times.
To enable nuclear power to play the defined role in supporting renewables, up to 30 GW of advanced nuclear plants is needed over and above the 24 GW announced by the then government in January 2024. This is ambitious, but partial implementation could still help reach net zero, and a focus on “fleet build” would make things easier and cheaper. Some of the hydrogen produced by cogeneration would be used to provide additional grid support. As in the DESNZ High Electrification scenario, most of the electricity supply will come from wind and solar power, but with assistance of nuclear power.
Policymakers must consider the whole energy system when strategising and making decisions. Big decisions in one area almost always impact everything else in the system. This impacts nuclear as much as other generation types, as using nuclear only for “baseload” generation as we’ve done in the past, will have detrimental impacts elsewhere in the system.
Policy Recommendations from the Flexible Nuclear scenario:
1. Build identical copies of plants
Government, working through Great British Nuclear, should strive to improve the economics of nuclear energy by encouraging fleet build of nuclear plants, with minimal delays, and which are then operated as much as possible.
2.Always consider the “whole system”
Planning around energy (not just electricity) infrastructure delivery should be fully co-ordinated to ensure the UK has a functional whole system. Government’s future energy strategies should include full appreciation of effects at the whole system level, comprising generation, transmission, and storage, which must all be developed in parallel. Ultimately, we need an integrated system where nuclear and variable renewables work in harmony through cogeneration and energy storage. Using reactors with thermal storage could also contribute to solving the problem of nuclear inflexibility and government should prioritise research to investigate this opportunity.
3.Embrace cogeneration
Government assessments of the impact of new nuclear capacity should recognise and incorporate cogeneration applications (including hydrogen production). These applications ensure maximum usage can be achieved to keep costs low and provide grid support when renewable output is low.
4.Think beyond baseload generation
Nuclear energy should not be restricted to delivering only baseload electricity generation. The possibility of locating new nuclear on existing or purpose-built industrial parks to maximise the opportunity for cogeneration must be explored.
