‘Moderate’ is the new ‘extreme’: Weather’s impact on growing renewable 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. 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. In a first-of-its-kind study, analysts from the National Renewable Energy Laboratory (NREL) and Sharply Focused modeled scenarios to understand the answers to these questions and change the way we define “extreme weather.” “Our study investigated two questions,” said Marty Schwarz, NREL power systems engineer and co-author of the report. “First, we examined whether increasing levels of wind and solar make it more challenging to reliably operate the power system during extreme weather events. Second, we evaluated if these renewable technologies change what types of weather events we consider ‘extreme’ based on their impact to grid operations.” Understanding the future through the past To generate scenarios used in the study, analysts turned to NREL’s publicly available flagship 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. 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. Charting a new perception of ‘extreme’ When we think of extreme weather today, we naturally imagine the events that cause major disturbances to our daily lives and are worthy of front-page news—which is front-of-mind now as we enter hurricane season. However, NREL found the power grid impacts of extreme weather events do not increase as more wind and solar are added to the grid.