“Moderate” is the new “extreme” impact of weather on the development of renewable energy networks | News

How changing our perception of extreme weather can help plan for a reliable power system using wind and solar energy

Photo of a wind turbine looking up from the base of the turbine to the blades against a hot, smoky sky.
In a first-of-its-kind analysis, NREL researchers examined how various extreme weather events could impact the operation of the U.S. power system as wind and solar power make large contributions to the future energy mix. Photo from Getty Images

From severe storms to recent unprecedented cold and heat waves, extreme weather events are impacting utilities, grid operators and, ultimately, customers like never before. At the same time, the energy sources powering the grid are evolving, including a greater percentage of renewable sources.

This evolution of both weather and the power grid raises new questions about the intersection of extreme weather with the electrical grid, and how to maintain and increase grid reliability as the share of weather-dependent renewable energy increases. In a first-of-its-kind study, analysts from the National Renewable Energy Laboratory (NREL) and Sharply Focused created model scenarios to answer these questions and change the way we define “extreme weather.”

“Our study examined two questions,” said Marty Schwarz, NREL power systems engineer and co-author of the report. “First, we examined whether rising levels of wind and solar power impede the reliable operation of the power system during extreme weather events. Second, we assessed whether these renewable technologies influence what types of weather events we consider “extreme” based on their impact on grid operations.”

Understanding the future through the past

To generate the 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 mass power system. ReEDS modeled what the system could look like in 2024, 2036 and 2050, showing variable levels of renewable energy generation of 17%, 50% and 65% of annual demand, respectively.

Analysts also collected historical weather data and records from selected weather events from 2007 to 2013, along with wind and solar resource availability modeled from the NREL Wind Integration National Dataset (WIND) toolkit, the National Solar Radiation Database (NSRDB) and historical electrical load profiles. This data identified weather events that modelers, utilities and regulators need to consider in their long-term planning.

Weather events from historical data are divided into two broad categories: 1) “high-impact events,” such as cold waves, mid-latitude storms, heat waves, and tropical systems; and 2) “planning challenging events,” including periods of low renewable energy resource availability and high electricity demand, as well as high resources and low demand.

With ready-made scenarios for future networks and a variety of historical weather data, analysts set out to see how the two networks could interact.

Setting a New Perception of ‘Extreme’

When we think about extreme weather today, we naturally imagine events that cause major disruptions to our daily lives and are headline-worthy – which is what’s on our minds right now as we enter hurricane season. However, NREL found that the impact of extreme weather events on the power grid does not increase as more wind and solar power are added to the grid.

This is because wind and solar energy remain available even during extreme weather events due to the meteorology of the events themselves. A heat wave, which places greater strain on the grid through the use of fans and air conditioning, also often coincides with sunny days that enable high levels of solar power generation. Likewise, a strong winter cold front that increases heating demand also creates strong wind gusts that can drive wind generators to meet those needs.

On the other hand, analysts have found that moderately severe, but not extreme, hot/cold weather conditions occurring simultaneously with long periods of weaker wind and solar resources could be the new “extreme” weather in terms of impacting power system operations.

“These findings are detailed and limited to the weather that occurred in the historical dataset and the future network infrastructure being considered, but nevertheless lead to an overarching conclusion,” Schwarz explained. “This means that the most concerning weather events for the future grid are different from what happens today.”

Ultimately, the analysis led to eight key conclusions, which are presented in the research report.

Navigating the calm after the storm

The changing perception of extreme weather events that emerged from the findings illustrates the lull in wind that often occurs after a cold front passes through a region. During the winter months, when solar energy levels are already low, the future grid will rely more on wind energy. Generally, a lot of wind is produced in the immediate vicinity of cold fronts, but these fronts are often followed by a lull in wind of varying strengths, with persistent cold causing sustained heavy loads as people heat and light their homes.

Evolution of the February 2011 cold wave, showing temperature across the country (right) and historical electrical load in selected regions (left).

Evolution of the same 2011 cold wave, showing total electricity production for selected regions (top left), wind resources (top right), historical load for the same selected regions (bottom left), and photovoltaic resources (bottom right).

The sample size of weather events included in the study suggests that the calm days following a cold wave may be the most important weather conditions for planners to consider when determining the power requirements of future systems relying on high levels of variable renewable energy generation.

System planners, policymakers and researchers can use the findings to test the weather resilience and resource adequacy of future power system infrastructure. The analysis can also be used to test the performance of integrated resource plans or to examine the trade-offs and benefits between different policy options.

Looking towards the horizon

Analysts behind the study cautioned that despite its limitations, its findings are important for a comprehensive understanding of the impact of extreme weather – what happens not only at the peak of a storm, but also after it and for planning for periods of low renewable energy production. because the grid is powered by more renewable energy.

These preliminary results should then be applied to additional power system scenarios and even more weather conditions beyond the study’s limited sample of 2007–2013 weather events. Analysts are particularly interested in studying more recent weather events that can capture the impact of climate change on weather patterns.

“We hope this preliminary study will help us better understand extreme weather events on an increasingly renewable grid,” Schwarz said, “and prepare us to continue working toward accurate planning and robust reliability of tomorrow’s power system.”

Access the full study to see all eight findings and learn more about NREL’s energy analysis and grid modernization research.

This work was funded by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy and the Office of Hydropower Technology.