Decarbonised grid can be ‘robust and resilient’ in challenging weather

A decarbonised electricity system can be made “robust and resilient” during challenging weather conditions using innovation that are already available or in development, according to new analysis from Regen.

The study, produced for National Grid Electricity System Operator (ESO), modelled hour-by-hour supply and demand on two days in 2035 – the year by which the government has pledged to completely decarbonise the power grid.

The first is a calm and cloudy winter day with high demand and low wind and solar output, and the second is a sunny and windy summer day with high renewable output and low demand.

The winter day is modelled on a mid-January week in 2017, which Regen said would have posed significant challenges for a decarbonised electricity system. Although it was not extremely cold, with temperatures generally staying above freezing in the daytime, a high-pressure system sitting over the east coast led to low winds and cloudy weather, limiting generation throughout the week.

If a similar week occurred during 2035, the report said renewable energy would only be able to meet 40% of demand, which be expected to regularly peak at 80GW. There would be no point at which renewable output would exceed demand.

On the particular day modelled, output from solar, wind and other renewables would peak at up to 8.5GW, 21.7GW and 6.8GW respectively. Gas and biomass generation with carbon capture and storage (CCS) would provide a steady output of 6GW and 4GW throughout the day, whilst nuclear generation would provide 9GW of baseload.

The report said the remaining demand could be met using interconnector imports (up to 18.6GW), low-carbon hydrogen generation (up to 11.6GW) and short and long-duration storage (up to 9.5GW and 4.5GW respectively).

Winter day in 2035

The summer day is also modelled on a week in June 2017 – the time of year when excess renewable could be expected to high – and in particular a Saturday, as demand levels are generally lowest over the weekend.

If a decarbonised electricity system experienced a similar week in 2035, the report said there would be numerous extended periods of excess renewable generation that would be accompanied by very low or negative power prices. Accordingly, electrolysers would be running for the majority of the week, only switching off when prices rise for a few hours at a time.

Interconnectors would export all week, with the levels depending on what is happening in continental Europe. There would no gas or biomass generation although nuclear would provide some baseload generation but at a reduced level due to routine maintenance.

On the particular day in question, generation would exceed underlying demand throughout the day. Wind output would peak at 60.5GW, solar output at 17.8GW and output from other renewables at 4.4GW. Nuclear would provide baseload generation of 6.8GW.

Winter day in 2035 – Supply

Despite maximising the use of the surplus by shifting demand, storing energy (up to 10.2GW), running hydrogen electrolysers (up to 8.5GW) and exporting power via interconnectors (up to 20.9GW), there would still be an excess of up to 19.1GW that would need to be curtailed.

Summer day in 2035 – Demand

Regen said the analysis demonstrates the need for large increases to both dispatchable low-carbon generation to replace fossil fuels, either fuelled by hydrogen or fitted with CCS, and system flexibility from energy storage, electrolysers and interconnectors.

It said policy and financial support mechanisms for dispatchable low-carbon generation should be designed to incentivise flexibility rather than encouraging baseload generation.

The not-for-profit organisation said there will also need to be far greater participation from domestic and business consumers to provide demand-side flexibility enabled by smart technology and markets. It said the value of flexibility must be reflected in market and support mechanisms such as the Capacity Market and the Balancing Mechanism.

Regen said the coordination and integration of data and processes between the planned Future System Operator (FSO) and distribution system operators (DSO) will be vital. It said the FSO’s whole system planning functions and flexibility markets must be integrated with DSO functions.

It said the analysis additionally highlights the value of a diversity of renewable technologies in various locations, such as floating wind in the west of the UK that would be less affected by the weather conditions seen on the winter day.

Commenting on the report, Regen director Johnny Gowdy said: “With energy security firmly on the minds of UK policymakers, a key question is how a decarbonised electricity system based on a high proportion of renewable generation can be operated securely.

“The ‘Day in the Life of 2035’ study takes on that challenge to show that not only is a robust and resilient decarbonised electricity system possible, but it could bring a range of benefits, including protecting consumers from high gas prices and establishing the UK as a world leader in the delivery of low carbon energy.

“Many of the key innovations and technologies that we need to operate such a system are already underway, but getting them to scale in the timeframe required means a step-change in investment.”

Rebecca Hart, strategic investment manager at the ESO, said: “This study brings to life the potential challenges of operating a fully decarbonised electricity system and illustrates clearly how they can be overcome.

“The key message is that it is possible but that we need a whole system approach to making this a reality, with a range of new flexible demand and supply coming from all levels, from domestic consumers right up to hydrogen electrolysis plant.”