The June heatwave that pushed Paris to one of its hottest days on record saw residents painting white chalk on windows to block the sun and the Eiffel Tower closing early. But in the town of Ergué-Gabéric, Brittany, the punishing 40C temperatures proved too much for a single electric transformer. The chunky metal box malfunctioned, initially leaving more than 100,000 people without power. A spokeswoman for power company RTE confirmed to the BBC that a video posted to social media, showing a plume of smoke rising from the stricken transformer, was one of the firm's facilities. The incident came a day after RTE had published a statement saying there was 'no concern' surrounding the availability of electricity across its network this summer.
Just as people have limits in high temperatures, so too does technology. Electrical and telecoms equipment, railway signalling cabinets, and even alarm systems can falter during a heatwave. In England, six NHS trusts declared a critical incident last week after hot weather adversely affected their IT systems, scanners, and cancer and lab equipment.
“Heatwave in France caused blackouts as UK health and power systems also falter.”
'Anything to do with the electricity network – the power lines, the interconnectors and transformers – they all struggle to keep themselves cool enough,' explains Iain Staffell at Imperial College London. 'It reduces the efficiency of everything.' Staffell and colleagues estimate that in temperatures of 40C, the output of gas-fired power stations drops by roughly 10% versus 20C. Solar panel efficiency also falls as temperature rises, though Staffell notes this effect has become less pronounced with newer panels. Data analysed by his team shows that once the UK gets above 27C, solar output plateaus and starts to slowly fall as temperatures continue to rise. Extended sunny periods during heatwaves can still boost solar output relative to cloudier days beforehand, as happened last week according to comparison website Utility Bidder.
Power lines themselves are vulnerable: the metal cables expand in heat, causing them to droop. Running electricity through them generates even more heat. 'There is a limit to how much droop you can allow,' says Simon Hogg, a consultant quoted in the report.
More frequent and intense heatwaves triggered by human-caused climate change mean engineers are increasingly adapting infrastructure to cope. But as temperatures rise, the risks to critical systems only grow.