ENERGY SECURITY“Energy Droughts” in Wind and Solar Can Last Nearly a Week, Research Shows

By JoAnna Wendel

Published 15 December 2023

Understanding the risk of compound energy droughts—times when the sun doesn’t shine and the wind doesn’t blow—will help grid planners understand where energy storage is needed most.

Solar and wind power may be free, renewable fuels, but they also depend on natural processes that humans cannot control. It’s one thing to acknowledge the risks that come with renewable energy: the sun doesn’t always shine and the wind doesn’t always blow, but what happens when the grid loses both of these energy sources at the same time?

This phenomenon is known as a compound energy drought. In a new paper, researchers at Pacific Northwest National Laboratory (PNNL) found that in some parts of the country, these energy droughts can last nearly a week.

“When we have a completely decarbonized grid and depend heavily on solar and wind, energy droughts could have huge amounts of impact on the grid,” said Cameron Bracken, an Earth scientist at PNNL and lead author on the paper. Grid operators need to know when energy droughts will occur so they can prepare to pull energy from different sources. On top of that, understanding where, when, and for how long energy droughts occur will help experts manage grid-level battery systems that can store enough electricity to deploy during times when energy is needed most.

The team published the findings October 31 in the journal Renewable Energy and will be presenting at this week’s annual meeting of the American Geophysical Union.

Hunting for Cloudy, Windless Days
In the past, researchers studied compound energy droughts on a state or regional scale. But not much has been studied on a nationwide scale. To find out more about the risk of energy droughts over the entire continental U.S., the researchers dug into weather data and then used historical energy demand data to understand how often an energy drought occurs when that energy is needed the most.

The team examined 4 decades of hourly weather data for the continental U.S. and homed in on geographical areas where actual solar and wind energy plants operate today. Weather data included wind speeds at the height of wind turbines as well as the intensity of solar energy falling on solar panels. Times when the weather data showed stagnant air and cloudy skies translated into lower energy generation from the wind and solar plants—a compound energy drought.

“We essentially took a snapshot of the infrastructure as of 2020 and ran it through the 40 years of weather data, starting in 1980,” Bracken said. “We are basically saying ‘here is how the current infrastructure would have performed under historical weather conditions.’”