PNNL Report Says Hydropower Can Still Perform During Extreme Droughts

by Peter Maloney
APPA News
October 8, 2022

Even during the severe droughts of the last two decades, hydropower has sustained 80 percent of average power generation levels, according to a report by researchers at the Pacific Northwest National Laboratory (PNNL).

“That’s a noticeable dip — but it’s still a lot of renewable energy,” Sean Turner, water resources modeler at PNNL and main author of the report, said in a statement.

The megadrought in the Southwest is the driest and longest in the last 1,200 years, depleting water reservoir levels to critically low levels over the past 22 years and has raised concerns among policymakers and system planners over the reliability of the electric grid.

Droughts particularly affect hydroelectric power dams, as well as some thermoelectric power plants that require large amounts of water for cooling. But drought rarely impairs hydroelectric power across all regions of the Western United States simultaneously.

In the last 20 years, there has not been a drought that has affected all major hydropower generation regions at once, the report said, noting that current river flows and reservoir levels in California and the Southwest are low due to ongoing drought, which affects hydropower generation in those regions, but the lion’s share of hydropower generation in the West is dispatched to the grid from the Northern Cascades and Columbia River Basin, in Washington, Oregon, Idaho, and British Columbia.

“The current drought is severe but it’s nowhere close to being the worst hydropower generation year for the West and water resource conditions are actually above average right now in the Northwest,” Turner said.

The report combined 20 years’ of annual power generation data from more than 600 hydroelectric power plants with historical precipitation data from eight hydropower climate regions of the Western United States and used the data to extrapolate hydropower generation as far back as 1900.

The findings were published in a retrospective report funded by the Water Power Technologies Office within the Department of Energy’s (DOE’s) Office of Energy Efficiency and Renewable Energy.

Meanwhile, another PNNL researcher is investigating how well hydropower dams perform during heat waves and exceptional load demand. PNNL power systems modeler Konstantinos Oikonomou that a heat wave can actually create favorable conditions for hydropower plants.

Rapid snowpack melt during a heat wave can help reservoirs fill with water, which can allow hydropower plants to meet increased load demand, Oikonomou said.

To further test their results, PNNL hydrologists and power system modelers simulated the effect of compound heat waves and droughts on the power grid and found that regional interconnections are critical to manage extreme events.

Oikonomou’s research is now focused on creating a new framework for simulating grid behavior under extreme weather conditions, such as compounding droughts and heat waves, and under occurrences like faulty transmission lines.

“This information will help power plant operators and system planners explore mitigation strategies to fortify the grid against outages,” Oikonomou said.