“Energy Droughts” in Wind and Solar Can Last Nearly a Week, Research Shows
The researchers found that energy droughts can occur in any season across the continental U.S., though they vary widely in frequency and duration. In California, for instance, cloudy and windless conditions might last several days, whereas the same conditions might last for only a few hours in Texas. Utah, Colorado, and Kansas experience frequent energy droughts both over several-hour timescales as well as several-day timescales. The Pacific Northwest and Northeast, meanwhile, seem to experience energy droughts that last several hours more frequently than several days. The different timescales (hourly versus daily) will help inform the energy drought’s impact on the grid—will it last just a few hours, or several days?
Overall, researchers found that the longest potential compound energy drought on an hourly timescale was 37 hours (in Texas), while the longest energy drought on a daily timescale was six days (in California).
Energy Drought at Peak Demand
Simply knowing the where and how of energy droughts is just one piece of the puzzle, Bracken said. He also stressed that a drought of solar and wind power won’t necessarily cause an energy shortage. Grid operators can turn to other sources of energy like hydropower, fossil fuels, or energy transmitted from other regions in the U.S.
But as the nation aims to move away from fossil fuels and rely more on solar and wind power, grid operators must understand whether energy droughts will occur during times when the demand for electricity might exceed supply. Climate change brings hotter summers and more intense winter storms, and these are times when not only people use more energy to stay safe (for cooling or heating), but access to electricity might mean life or death.
To understand the possible connection between energy droughts and energy demand, the team mapped their historical, hypothetical generation data onto 40 years of historical energy demand data that also covered real power plants across the continent.
The data showed that “wind and solar droughts happen during peak demand events more than you would expect due to chance,” Bracken said, meaning that more often than not, windless and cloudless periods occurred during times when demand for power was high. For now, Bracken isn’t certain that the correlation means causation.
“This could be due to well-understood meteorological phenomenon such as inversions suppressing wind and increasing temperatures, but further study is needed,” Bracken said.
Energy Storage for Energy Droughts
Studying patterns in the frequency and duration of energy droughts will also help inform the deployment of long-duration energy storage projects, said Nathalie Voisin, an Earth scientist at PNNL and coauthor on the paper. The paper is the first to provide a uniform standard of what a compound energy drought is and how long it can last in different parts of the country.
“We’re providing insight on how to adequately design and manage multi-day storage. So when you know an energy drought is going to last for five hours or five days, you can incentivize storage to be managed accordingly,” Voisin said.
Next, Bracken and the team will extrapolate weather and demand data into the future to see how climate change will affect the frequency and duration of energy droughts. The team plans to model energy droughts all the way to the end of the century combined with evolving infrastructure.
JoAnna Wendelis Media Relations Specialist at Pacific Northwest National Laboratory. The article was originally posted to the website of the Pacific Northwest National Laboratory.
