Redefining Extreme Weather: Ensuring Grid Reliability In A Renewable Energy Future

Recent severe storms and unprecedented cold and heat waves are affecting electric utilities, grid operators, and customers more than ever before. Simultaneously, the energy sources powering the grid are evolving, with higher percentages of renewable sources like wind and solar being integrated. This dual evolution in weather and the power grid raises new questions about how to maintain and enhance grid reliability as weather-driven renewable energy increases.

Analysts from the National Renewable Energy Laboratory (NREL) and Sharply Focused conducted a study to explore these questions. Marty Schwarz, an NREL power systems engineer, explained the study’s focus: examining if increasing levels of wind and solar make it more challenging to operate the power system during extreme weather events, and whether these renewable technologies change the types of weather events considered “extreme” based on their impact on grid operations.

To generate scenarios, analysts used NREL’s Regional Energy Deployment System (ReEDS) model, which simulates the evolution of the bulk power system. ReEDS modeled what the system might look like in the years 2024, 2036, and 2050, showing renewable generation levels of 17%, 50%, and 65% of annual demand, respectively. Analysts also gathered historical weather data and records from events between 2007 and 2013. They used wind and solar resource availability data from NREL’s Wind Integration National Dataset (WIND) Toolkit, National Solar Radiation Database (NSRDB), and historical electrical load profiles to identify weather events essential for long-term planning.

The historical data categorized weather events into two broad categories: “high impact events,” such as cold waves, storms, heat waves, and tropical systems, and “events posing planning challenges,” including periods of low renewable energy resource availability with high electricity demand, and high resource availability with low demand.

With future grid scenarios and historical weather data in hand, the analysts tested how these elements could interact. They found that the power grid impacts of extreme weather events do not increase as more wind and solar are added. This is because wind and solar power often remain available during extreme weather events. For instance, a heat wave that triggers high grid load from air conditioning also brings sunny days that enable high solar generation. Similarly, strong winter cold fronts that increase heating needs also bring strong wind gusts for wind generation.

However, moderately severe weather conditions, though not extreme, occurring with extended periods of low wind and solar resources, could be the new “extreme” weather concerning power system operations. These findings, though specific to the historical data and future grid infrastructures considered, suggest that the most concerning weather events for the future grid are different from today’s concerning events.

An example of the changing perception of extreme weather is the wind lull that often follows a cold front. During winter, when solar power is low, the grid relies more on wind power. While wind generation is abundant near cold fronts, a wind lull usually follows, with continued cold causing high loads as people heat and light their homes. This wind lull following a cold wave may be crucial for planners to consider when determining capacity needs for future systems with high levels of variable renewable generation.

System planners, policymakers, and researchers can use these findings to test the weather resilience and resource adequacy of future power system infrastructure. The analysis can also help test integrated resource plans and explore trade-offs and benefits between different policy options. Despite the study’s limitations, the findings are important for understanding the holistic impact of extreme weather—not just during the storm’s peak but also after, and for planning low renewable output periods as the grid becomes more reliant on renewable energy.

The analysts suggest further applying these initial results to more power system scenarios and weather conditions, especially recent events that capture the influence of climate change on weather patterns. Schwarz hopes this study will advance understanding of extreme weather events on the increasingly renewable grid and aid in accurate planning and robust reliability for the future power system.