Why heat waves heighten the risk of blackouts
When extreme heat hits, people turn to AC, but what if the grid fails? From France to the US, heat waves are pushing power systems
When extreme heat hits, people turn to AC, but what if the grid fails? From France to the US, heat waves are pushing power systems to the limit, raising blackout risks and energy prices when electricity is needed most. In late June, a heat wave in France left nearly 70,000 households without power after a transformer failed under high temperatures. For about 24 hours, as the mercury hovered near 40 degrees Celsius (104 Fahrenheit), residents in parts of Brittany sweltered in deadly heat without fans or air conditioning. Then as the United States baked in extreme heat in the run up to its 250th birthday celebrations, federal authorities issued blackout warnings. Grid operators were allowed to order large energy users, such as data centers, to switch to backup generators to maintain power to homes and emergency services like hospitals. Power grids worldwide are struggling under intense heat waves and other extreme weather events — and in the US, outages are already happening. Heat-season power outages in the country, some linked to hot temperatures, rose about 60% over the past decade compared with the 2000s, according to data from the nonprofit Climate Central. Having no access to cooling in heat waves is especially dangerous for children, the elderly and those with chronic illness. Extreme heat in the run up to the United States' 250 birthday prompted federal authorities to declare a blackout warning Image: Cheney Orr/REUTERS That trend is expected to continue as human-induced climate change drives longer, more frequent and intense heat waves, making it crucial for energy networks to adapt. "As it gets hotter, things stop working quite so well," said Iain Staffell, associate professor of sustainable energy at Imperial College London. That means one "should expect faults to be more common at these very high temperatures." "I think we do need to adapt the power system to cope with the changing weather," added Staffell, referring to Europe, which is warming much faster than the rest of the world. Why are heat waves a problem for power networks? When heat waves hit, electricity demand surges as people turn to ACs, fans and other cooling devices for relief.
That strains the power grid, especially later in the day when heat lingers but solar power starts to fade. At the same time, the infrastructure that keeps electricity flowing — from power plants to transformers — is vulnerable to heat stress. Transmission lines moving power across the country expand as temperatures rise, for instance. This causes them to sag, sometimes enough to brush against trees or other obstacles, increasing the risk of short circuiting or outages. "The grid operator has to reduce the amount of power that flows down these wires in the very hottest temperatures to make sure everything remains safe," said Staffell. Some nuclear power plants in France and Switzerland reduced output or switched off reactors due to the June heat wave Image: Lionel Bonaventure/AFP Heat and sagging lines were contributing factors in 2003 when around 50 million people across the northeastern US and parts of Canada were left without power during high temperatures. It was the largest blackout in North American history. While grid operators have since introduced safeguards to prevent a repeat outage of that scale, experts say extreme weather still poses a threat. Thermal power plants are not immune either. In extreme heat, cooling in coal, gas and nuclear plants becomes less effective, meaning operators sometimes have to reduce output. "Efficiency of coal and gas as well as nuclear power stations falls by roughly 1% for every degree it gets hotter," Staffell said — so they're 10% less effective at 35 C than at 25 C. During Europe's heat wave in June, several nuclear facilities in France and Switzerland had to reduce output or temporarily shut down because the rivers they use for cooling had become too warm. Regulations require plants to limit the temperature of discharged water to protect ecosystems and aquatic life. Renewable energy sources are affected as well. Low water levels can hamper electricity production from hydropower, for instance. And solar panels become slightly less efficient in high temperatures, while wind speeds often drop during heat waves, reducing their output. The hidden problem with solar (and how to solve it) To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video These factors, taken together, can contribute to grid instability, with operators needing to source energy from elsewhere if the mismatch between demand and supply becomes too tight.
The BriefWire