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China’s vast electrical grid buzzes with more renewable energy than that of any other country, but this system is also becoming more vulnerable to power shortages caused by unfavourable weather. The need to ensure a reliable power supply could push China’s government to use more coal-fired power plants.

China’s energy system is rapidly getting cleaner, with virtually every month setting new records for wind and solar energy generation. The country’s overall greenhouse gas emissions – the world’s highest – are expected to soon peak and begin to decline. Wind, solar and hydropower currently make up about half of China’s power generation capacity, and are expected to increase to almost 90 per cent by 2060, when the country has pledged to reach “carbon neutrality”.

This growing reliance on renewable energy also means the country’s power system is increasingly vulnerable to changes in the weather. Intermittent wind and sun can be supplemented by steadier hydropower, produced by huge hydroelectric dams concentrated in southern China. But what happens when a wind and solar slump coincides with a drought?

at Dalian University of Technology in China and his colleagues modelled how power generation on the increasingly renewable grid would respond to these “extreme weather” years. They estimated how the country’s current and proposed future mix of wind, solar and hydropower would behave under the least favourable weather conditions seen in the past.

They found that the future grid would be substantially more sensitive to changes in the weather than today. In the worst case weather scenario, power generation could decline by as much as 10 per cent, leading to power shortages. In 2030, a year with the least favourable weather would result in an energy shortage of more than 400 terawatt-hours, nearly 4 per cent of total energy demand. “That’s not a number that anyone can just ignore,” says at the Asia Society Policy Institute in Washington DC.

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In addition to an overall lack of power, droughts could specifically limit the amount of hydropower available to smooth out irregular wind and solar generation. This could also lead to power shortages. “It is essential to equip the power grid with a proper proportion of stable power sources that are less affected by meteorological factors to avoid large-scale extensive electricity shortages,” the researchers wrote in their paper.

One way to help would be to move surplus electricity between provinces more efficiently. Expanding the transmission infrastructure to do so could eliminate the risk of power shortages on today’s grid and cut the risk in half by 2060, the researchers found. Adding tens of millions of kilowatts of new power capacity, whether using batteries or other methods, would also mitigate against hydropower droughts, they found.

The amount of additional storage China will need to add in order to achieve carbon neutrality “will be an astronomical number”, says Li.

While these changes will be difficult, adding that much storage is feasible given the huge volume of batteries already being produced in China, says at the Centre for Research on Energy and Clean Air in Finland. He says the country is also building 190 gigawatts of pumped hydro power capacity, which can provide longer-term energy storage by pumping water above a dam using surplus electricity, then releasing it when more power is needed.

However, to date, power shortages have mainly spurred China’s government to build more coal-fired power plants. In 2021 and 2022, for instance, hydropower droughts and heatwaves raised power demand enough to cause severe blackouts, creating political pressure for a . In 2023, record-low hydropower generation led to record-high emissions.

China’s president Xi Jinping has said coal power would peak this year, but entrenched political support for the power source makes this a difficult prospect. “If China suffers another round of those episodes, more coal-fired power plants should not be the answer,” says Li. “It’s just hard to phase out coal; China loves coal.”