Wind and solar farms keep the lights on as long as the weather cooperates. When calm skies and still air settle in for days, though, the result is a wind and solar shortfall that hits both sources at once.
A new study ran that scenario through China’s future power system, hour by hour, and found that these quiet shortfalls can last for weeks at a time.
When people worry about weather knocking out power, they tend to picture hurricanes or ice storms. The threat in this study is far less dramatic – days of thick cloud cover paired with wind so weak the turbines barely spin.
Researchers call these stretches high-impact weather events. The name is a little misleading because the events are not violent.
A long spell of low wind or gray sky might not even qualify as a storm, yet when conditions like these sit over a region for days, wind and solar output both sag at the same time. The grid feels it as a slow squeeze rather than a sudden hit.
That overlap lies at the heart of the problem. A cloudy stretch usually comes with calm air, so the two main clean sources tend to fade together instead of covering for each other.
Xiaofan Yang, a researcher at Beijing Normal University, led an effort to measure how deep that combined shortfall could get across China by 2040.
The team built a detailed model of China’s future grid, then fed it weather data sliced into hour-by-hour pieces across small patches of land roughly 3 miles (5 kilometers) wide. Most earlier work leaned on long-term averages, which smooth over the short stretches that actually strain a grid.
That choice turned out to be the whole point. Hourly data revealed shortfalls that daily averages had been quietly hiding.
Generation deficits came out 10–15% larger once the researchers zoomed in on the hour-to-hour swings, especially in the parched northwest.
The team paired this weather picture with maps of where electricity demand will sit. They ran the model under a range of futures – from aggressive emissions cuts to a high-emissions path where little changes.
The goal was not a single prediction but a sense of how the system bends under stress – and where it cracks first.
Under the high-emissions path, these quiet weather events could choke wind and solar generation for as long as 24 days in a single year – not spread across a decade, but annually.
During the worst stretches, wind output in some inland provinces fell by roughly 40% in the model. Solar dropped by more than a fifth across the northern-central grids.
China’s southwest and northwest – its richest territories for renewables – took the hardest and longest hits. These are the very regions the country is counting on most.
Separate research has found that low-wind spells are already lengthening in northern China and other mid-latitude regions as the planet warms.
Yang and his colleagues point to a real warning shot from 2022. A drought in southwestern China’s Sichuan Basin paired heat and dry air with stubborn cloud cover, knocking local renewable output down by more than a third for weeks.
The model treats that episode not as a fluke but as a preview.
One result cuts against the gloom. Running the same model under deep emissions cuts produced noticeably milder shortfalls – fewer quiet weather events, shorter ones, and a steadier flow of power overall.
The gap between the two futures is large. Annual generation losses from these events came to about 85 terawatt-hours – roughly the amount of electricity Spain uses in a year – under the high-emissions path. Under the low-emissions path, losses fell to roughly 63 terawatt-hours.
In plain terms, the choices made about carbon now shape how reliable a clean grid will be later. The weather problem and the emissions problem are the same problem.
Mitigation does not erase the risk, though. Even in the cleaner future, stubborn trouble spots in the northwest and central grids kept seeing long dry stretches for power.
Some regional shortfalls actually crept up by a few days. Geography is not easy to outrun.
Inner Mongolia and the northwest hold enormous wind and solar resources. They also sit far from the crowded coastal cities that consume most of the power.
The study’s central fix is to close that gap – move electricity across long distances to wherever the weather is still cooperating.
Resource-rich inland zones act as export hubs in the model, pushing electricity east and south when local supply runs short.
Built out and coordinated well, that web of long-distance lines could shift around 605 gigawatts between regions – enough to take the edge off the worst local shortfalls.
Other research points the same direction, finding that a mix of flexibility measures is what keeps a heavily renewable grid steady.
Long lines only help if the weather is patchy, though. When a dim, windless stretch blankets a wide enough area, there is no sunny neighbor to borrow from, and the whole strategy loses its footing. The fix works right up until everyone needs it at once.
The real contribution of this study lies in its resolution. The field already knew that climate change would shift wind and solar patterns.
What no one had pinned down for China, at this fine a scale, was how the timing and spread of these quiet weather spells line up against electricity demand. Daily averages had been undercounting the danger all along.
By zooming into hourly data across a grid three miles wide, the study captures shortfalls that broader models consistently miss.
For grid planners banking on renewables, that granularity could mean the difference between a system that bends and one that breaks.
The study is published in the journal Nature Communications.
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