Throughout July and August 2022, the British energy system was under severe strain. Not only had wholesale gas prices pushed the energy mix into an increased state of tension, but scorching heatwaves further strained both capacity and the networks.
According to the Met Office, on the 19 July, 40.3°C was recorded at Coningsby (Lincolnshire), setting a new UK and England temperature record by a margin of 1.6°C. Multiple locations across England also exceeded 40°C.
Heatwaves impact the energy system – supply and demand – in numerous ways. With high temperatures comes increased demand for electricity. For instance, air-conditioning sees a dramatic increase in its usage, adding further pressure on the energy grid, while many appliances have to work harder in order to function amid high temperatures. The result is a surge in energy demand.
Meanwhile, higher temperatures can squeeze electricity supplies by reducing the efficiency and capacity of traditional thermal power plants, such as coal, natural gas and nuclear, according to the International Energy Agency (IEA).
Extreme heat can also reduce the availability of water for cooling plants or transporting fuel, forcing operators to reduce their output. In some cases, it can result in power plants having to shut down, increasing the risk of outages.
With heatwaves set to become increasingly common even in mild countries like the UK as climate change becomes more aggressive, how will the system react? And what preparations have been made to manage these?
Does heat affect energy generation?
High temperatures broadly can have a negative impact on electricity generation in the UK. One of the primary issues is the sharp increase in the temperature of the water used as coolant, making it less efficient.
Power stations consume water for two main reasons: to turn into steam to drive generation turbines, and to cool down machinery. This water must be at the correct temperature otherwise the efficiency can radically decrease for power generation, a struggle during a heatwave when the rivers and other natural water bodies often relied on for this function start to heat up.
Another aspect that affects energy generation is the need for water to be cooled before it can be released back into the wild, to ensure it does not have a negative impact on wildlife.
To achieve this, cooling towers must work harder to reduce the temperature of water before it is released. The result is a drop in efficiency levels due to it requiring more power output to reduce the water temperature to optimal levels.
While a lot of generation struggles during heatwave, the sunnier weather does boost solar energy production. Generation from solar hit a peak of 7.77GW by midday on 19 July according to Sheffield Solar’s PV Live website, more than six times the capacity of the country’s largest nuclear power station, the 1.36GW Heysham 2 plant in Lancashire.
Over the entirety of 19 July, solar provided around 66.9GW, or 8.6% of the UK’s power needs. Whilst over seven days days during the heatwave, solar supplied about 9% of the country’s power. This is a significant jump from the 4% average solar contributes over the course of the year.
However, the heat does still impact solar, which operates most optimally at 25°C. Any increase can have an impact on the generation output of solar. For every degree either side of that figure, efficiency is lowered by around 0.5%.
Newer solar modules do, however, have improved performance, with a variation in efficiency of only 0.35% per degree, according to manufacturers. Panel temperatures depend on a combination of the ambient temperature, radiative heating from the sun and the cooling effect of the wind.
Therefore, for solar panels to lose 20% efficiency – the level considered significant – it would require them to reach 65°C.
With each degree over 20°C, demand in the UK rises by around 350MW according to Drax Electric Insights. Therefore as gas, nuclear and solar all see their efficiency fall, the system is strained amid sunny spells. Research from Cornwall Insight revealed electricity system margins in Great Britain were tight during the record-high temperatures in both July and August, with demand very close to overtaking supply.
It is also the case that the National Grid ESO’s one hour forecast for de-rated margin (the difference between available generation and demand) was negative for two hours on 18 July meaning demand was forecast to outstrip supply further reinforcing the heavy demand for energy during the heatwaves.
The impact of heat on the energy network
Physical infrastructure can also be significantly affected by higher temperatures. When materials get hot, they tend to expand and this is what happens within overhead power transmission cables that are often clad in aluminium, which is susceptible to heat expansion.
When this happens, lines can slacken and sag, increasing electrical resistance in the cables and leading to a drop off in efficiency.
Transformers can also be impacted due to the heat they give off as a by-product. To maintain safe levels of operation, the technology must maintain its power rating, which is much harder to achieve when ambient temperatures rise. As indicated, higher temperatures can have drastic impacts on the physical infrastructure within the UK.
When asked how heatwaves directly affect the energy and infrastructure, Dan Clarke, head of innovation at Energy Networks Association (ENA), highlighted that the infrastructure can withstand significant temperatures, and is used safely globally.
“Infrastructure in the UK is built to international standards and can operate in countries like Saudi Arabia and Australia – environments with much higher temperatures than we see in the UK,” said Clarke.
This showcases how minimal the impact can be on the energy network of heatwaves, limited to minor efficiency reductions.
Beyond physical infrastructure, managing of the networks is impacted by higher temperatures as the health and safety of workers is pushed.
“One tangible impact of hot weather is on operational teams who must wear heavy-duty protective clothing required to keep themselves and customers safe,” said Clarke.
“Network companies work hard to ensure staff stay hydrated and avoid fatigue while working in extreme heat and, wherever possible, working at the height of the sunshine is avoided.”
This could have an impact on the energy network for multiple reasons, including hampering the upgrades and maintenance works often undertaken over the quieter summer months.
Alongside this, maintaining the health and safety of workers during these months is paramount for ensuring the energy network is able to be maintained and improved. Should the frequency of heatwaves increase, it can be assumed vital repairs may not be able to take place during these usually quieter months.
How to prepare for future heatwaves?
In order to prepare the UK for seemingly inevitable heatwaves in the coming years, the energy industry is exploring innovative technologies that can better forecast weather, allowing more funds and energy to be allocated in times where demand is expected to soar.
“All network operators invest in extensive forecasting services and work with relevant public authorities to develop the clearest picture possible,” said Clarke.
“Network companies remotely monitor equipment throughout the year, including during extreme weather events.”
Improved forecasting can support the UK’s energy networks in several ways. Companies and UK infrastructure can prepare for spikes in energy usage and thus cater for the growing demand.
As well as this, monitoring the performance of the existing network can allow companies to understand possible faults and areas to increase technological innovation.
National Grid ESO, has already implemented practices to closely monitor the system, meaning the energy grid did not “experience anything unexpected” across the heatwaves in both July and August.
A spokesperson for National Grid ESO said: “The ESO has the relevant tools and experience to deliver safe and secure system operation at national transmission level. Our control room engineers are used to managing heatwaves and our demand models account for varying temperatures.”
As the energy system becomes increasingly flexible, newer technologies are also stepping up to the plate to support these surges in demand. Battery energy storage systems (BESS), for example, could not only be vital in transitioning to a net zero society, but could also play a huge role in mitigating the impact of heatwaves.
BESS systems can store energy for when it is needed by the grid when coupled with intermittent energy generation such as wind and solar. This can help mitigate the effects of heatwaves, ensuring there is enough energy for sudden spikes in demand.
Alongside this, many operators are exploring opportunities to integrate new technologies to support network resiliency.
“Operators are working hard to anticipate future challenges to network resilience and ensure solutions are in place to deal with them,” said Clarke.
“This work includes investing in a host of innovation projects, many of which are focused on ensuring the continued resilience of the system at the least cost to the consumer. Networks are already deploying innovative technologies, like drones to monitor equipment during extreme heat.”