Ricardo-led research supports UK government to build energy resilience during heatwaves

In 2009, a severe heatwave exposed acute vulnerabilities in the electricity system of Melbourne, Australia. On Friday, 30 January, three consecutive days in which temperatures exceeded 43 ˚C caused localised power outages and unannounced pre-emptive load shedding. A minor explosion at an overheated substation triggered failures across multiple transmission lines. Roughly half a million households lost power – the cascading impacts were widespread. City traffic lights failed, rail services were cancelled, and several commercial buildings were evacuated due to tripped alarms. Financial losses from the heatwave were estimated at $800 million, mainly due to power outages, transport service disruptions and response costs. The heatwave as a whole contributed to over 400 deaths. It is unclear whether the cascading effects of the power outages to cooling, communications, transport and emergency services contributed to this loss of life.

This heat-induced power failure in Melbourne was extreme. However, the increasing strain that extreme heat is placing on electricity systems is being felt broadly around the world, for example, in Washington State and China. Even in the UK, extreme heat is becoming more common, with temperatures exceeding 40˚C in July 2022.  

In this context, the Ricardo-led Climate Services for a Net Zero World (CS-N0W) research programme conducted research on behalf of the UK Department for Energy Security and Net Zero (DESNZ) to assess the vulnerabilities of different components of the energy system to extreme heat and the potential impacts that temperatures at different levels of global warming might have on those components. This type of analysis is a fundamental step for the government to take proactive measures to increase energy resilience.

The study began by reviewing scientific literature on the vulnerability of different energy system components to extreme heat. The team qualitatively rated the vulnerability of 28 components across five different categories – electricity generation, power network components, energy storage, natural gas infrastructure and hydrogen. Overall, no components were rated ‘extremely vulnerable’. Four components were assigned the second highest rating, ‘vulnerable’, all from the power networks category: 

• Transmission & distribution transformers. High temperatures can reduce the electrical current-carrying capability, lead to faster degradation of insulation and cooling oil and can cause failure of the unit. In the UK, transformers are typically designed for ambient temperatures of up to 40°C.
• Service lines and connections. High temperatures can reduce current-carrying capability and lead to excessive sag and loss of tensile strength.
• Switchgears, circuit breakers, and other protection devices. High temperatures accelerate component degradation, impair insulation, and reduce mechanical strength, leading to potential malfunctions and operational difficulties.
• Distribution underground cables. High ground temperatures impair the ability of underground cables to dissipate heat from the conductor, reducing current-carrying capacity. 

Next, the study examined the maximum temperatures to which these components are expected to be exposed in future decades across the UK under Global Warming Levels of 1.5°C, 2°C, and 2.5°C. As expected, the highest temperatures in all scenarios are concentrated throughout England and parts of Wales. Under global warming of 2.5°C, the south of England is projected to be exposed to temperatures of up to 42°C, with the rest of the UK (excluding coastal areas) projected to experience maximum temperatures of up to 36°C.

The team qualitatively assessed and mapped the potential impact to different types of components at those temperatures. At the highest temperatures projected, the study found that ‘vulnerable’ components could suffer from impacts classified as ‘medium’ and ‘medium-high’. Examples include a reduction in current-carrying capability and an increase in the frequency of faults. 

Importantly, our findings on the vulnerability of specific energy system components to extreme heat cannot be interpreted as vulnerabilities in the electricity grid as a whole. The UK electricity system is generally highly successful at delivering a reliable supply of electricity. Resilience at the system level is enhanced through measures like reserve generation and transformer capacity, grid reinforcement to enhance load carrying capacity, reactive power and voltage controls, demand management via interruptible demand-side contracts, and routine monitoring and maintenance. These measures usually ensure that component faults do not result in supply interruptions, and that when they do, they are localised.

Even so, when an electricity system is under strain, as illustrated in the Melbourne example, rare component level faults can have cascading effects that lead to the loss of multiple system elements. Numerous component faults within a short space of time can also lead to severe network disturbances. Further research is required to model redundancy and interdependencies in the UK power grid to assess vulnerability and resilience to extreme heat at a system level.

Historical data indicates that the UK electricity grid has at least some system-level vulnerabilities to extreme heat that warrant further investigation. During the 2022 heatwave, extreme temperatures caused some assets to overheat, leading to almost 15,000 properties in Yorkshire, Linconshire and the North East losing electricity, some of them overnight. Power plants and transmission lines operated at reduced efficiency, with some transmission lines visibly sagging. Northern Powergrid reported an abnormally high number of faults, which caused delays in the power being restored. In addition, the UK came close to a shortfall in electricity supply, not as a result of power plant failures, but rather the degraded output of power plants as extreme heat hindered their cooling systems. Wholesale electricity prices surged as the UK was forced to import power from Europe at a high cost.

Managing the strain caused by heatwaves will become more challenging as more households in the UK adopt air conditioning. Currently, approximately 5% of UK households have air conditioning. In the future, as people adopt active cooling technologies, extreme temperatures may cause spikes in electricity demand, exacerbating the strain placed on power network components and the risk of supply shortfalls.

This study provides a valuable foundation for DESNZ to ensure that adaptive measures are incorporated during grid upgrades. Common adaptation measures across the components include upgrading cooling systems, insulation, ventilation and shading of vulnerable assets; selecting components with more heat-resistant materials; and incorporating automated monitoring and controls that can reduce allowable currents, switch on cooling systems and facilitate faster response times. 
 
Ultimately, this type of vulnerability and exposure analysis should become commonplace to planning of critical infrastructure around the world. The lifetime of energy components is often several decades, and the climate conditions they will be exposed to in the future will be different than those they face today. It is essential that decisions regarding their design factor in future climate conditions, not historical ones.