In a first-of-its-kind study, analysts from the National Renewable Energy Laboratory and consulting firm Sharply Focused examined whether increasing levels of wind and solar make it more challenging to reliably operate the power system during extreme weather events and if these renewable technologies change what types of weather events are considered “extreme” based on their impact to grid operations.
“From severe storms to recent unprecedented cold and heat waves, extreme weather events are impacting electric utilities, grid operators, and ultimately customers like never before. At the same time, the energy sources that power the grid are evolving, integrating higher percentages of renewable sources,” NREL said.
“This evolution in both weather and the power grid is raising new questions about the intersection between extreme weather and the electric grid -- and how to maintain and enhance grid reliability as the share of weather-driven renewable energy increases,” it said.
To generate scenarios used in the study, analysts turned to NREL's publicly available capacity-planning model for the power sector -- the Regional Energy Deployment System (ReEDS) -- which simulates the evolution of the bulk power system.
ReEDS modeled what the system could look like for the years 2024, 2036, and 2050, showing variable renewable generation levels of 17%, 50%, and 65% of annual demand, respectively.
Analysts also gathered historical weather data and records from select weather events between 2007 and 2013, along with wind and solar resource availability modeled from NREL's Wind Integration National Dataset (WIND) Toolkit, National Solar Radiation Database (NSRDB), and historical electrical load profiles. This data identified weather events that are essential to modelers, utilities, and regulators to consider in their long-term planning, NREL said.
Weather events from the historical data were slotted into two broad categories: 1) "high impact events," such as cold waves, midlatitude storms, heat waves, and tropical systems; and 2) "events posing planning challenges," including periods of low renewable energy resource availability and high electricity demand, as well as high resource and low demand.
With their future grid scenarios in place and a variety of historical weather data, the analysts set out to test how the two could interact.
NREL found the power grid impacts of extreme weather events do not increase as more wind and solar are added to the grid.
“That is because wind and solar power remain available even during extreme weather events due to the meteorology of the events themselves. A heat wave that triggers a higher grid load from the use of fans and air conditioning also often coincides with sunny days that enable high levels of solar generation. Similarly, a strong wintertime cold front that increases the need for heating also brings strong wind gusts that can power wind generation to meet those needs,” NREL said.
On the other hand, analysts found that moderately severe, but not extreme, hot/cold weather conditions occurring concurrently with extended periods of low wind and solar resources could be the new "extreme" weather when it comes to the impact to power system operations.
"These findings are specific and limited to the weather that occurred in the historical data set and to the future grid infrastructures considered, but they do point to an overarching conclusion," Marty Schwarz, NREL power systems engineer and coauthor of the report, said. "Which is that the most concerning weather events to the future grid are different than the concerning events of today."
The analysis ultimately informed eight key findings which are outlined in the study report.
