On Wednesday 16 September, the Environment and Climate Change Committee hosted an evidence session on Dunkelflaute and the risks of electricity intermittency.
Dunkelflaute – dark doldrums in German – is a weather period with little or no wind and solar power generation because wind speeds are low and there is little or no sunlight.
The verbal evidence session is complemented by an inquiry on the same topic. The inquiry will consider how the UK can maintain a secure, affordable and low carbon electricity supply during Dunkelflaute events, and include an assessment of current UK preparedness for such events, future plans, and policy and regulatory gaps. The deadline for written submissions is Wednesday 14 October.
Keith was joined on the panel by Jon Saltmarsh, Chief Technology Officer of Energy Systems Catapult and Dr Emily Wallace, Fellow in Weather and Climate Extremes and Impact at the Met Office.
The session addressed the meteorological conditions that cause Dunkelflaute, the energy system impacts, the technology options that can ensure that demand for energy can still be met and the different commercial incentives that might drive – or fail to drive – sufficient investment in those options.
Keith emphasised that risk of not meeting demand arises regardless of the source of energy. In an energy system that draws most of its energy needs from renewables, there is clearly a dependency on the weather and a need to plan for the wide range of weather conditions that might arise. However, he highlighted that risk also exists in systems using fossil fuels, and not just in respect of geopolitical shocks that affect the prices of fuels. For example, the last time that electricity supply was rationed in Britain – through the use of ‘rota disconnections’ – was when coal production was disrupted in the early 1970s.
Keith argued that policymakers need to make a judgment about what level of risk of not meeting demand can be tolerated. That needs to be informed by modelling that takes adequate account not just of how weather affects available production and demand in Britain, but also in neighbouring countries with which our system has interconnections, and how demand for energy responds to increases in prices as supply margins get tighter.
He suggested that we might quantify the difference between demand for electricity and the energy available from renewables in 24 hour, 1 week, 2 week and 4 week periods. This could be used to assess the costs and benefits of options that allow Great Britain to meet those levels of ‘residual demand’ in 95% or 99% of cases, given the long-term variability of weather.
However, he also noted that the variability of a large base of renewable generation capacity presents opportunities as well as risks: over short periods, surplus of available production relative to demand could encourage a shifting of use of energy in time. Over longer periods, green hydrogen might be manufactured, which could then be stored in large quantities to help meet demand for energy during Dunkelflaute. The nation’s wind fleet could also be a very good complement to energy resources in other countries. For example, when it’s windy in Great Britain, we can export surplus electricity to Norway, allowing Norwegian operators to leave water in hydropower reservoirs. When it’s less windy here, we can import hydropower from Norway.
The session concluded by noting that a very large amount of molecule-based storage capacity needs to be developed that stores fuels produced or usable in a low carbon manner, of the order of tens of terawatt-hours. That represents a major challenge. In practice, Keith argued it will be met in stages that give an opportunity for learning by doing in respect of both technologies and business models.