The U.S. is sitting on a gold mine of untapped hydropower potential

The United States is not using nearly as much hydropower as it could be, new research has found. Researchers at the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) and Idaho National Laboratory (INL) issued an updated assessment of hydropower technical potential across the U.S., finding that as much as 15.2 terawatt-hours of electricity could be generated annually at non-powered dams. Only three percent of dams in the U.S. have been used for hydropower generation, with the rest serving other functions like water storage, navigation, and flood control. The remaining non-powered dams (NPD) “present an opportunity for domestic energy production,” ORNL said. ORNL’s previous assessment found potential capacity of four gigawatts (GW) across more than 2,600 NPDs, with individual facilities averaging 1.5 megawatts (MW). Federally owned dams account for 86% of this total potential capacity, and the upper Mississippi River and Great Lakes are “particularly promising” for hydropower development given the large number of projects with high potential capacity, ORNL said. “The potential is heavily concentrated in large, federally owned dams, but we also see many opportunities for utilities and local or state agencies,” said ORNL’s Carly Hansen, the project’s principal investigator and lead author of the report. “This refined data will help decision makers focus their efforts on the sites with the greatest possible capacity.” Past assessments estimated the nation’s capacity of NPDs between 12 and 30 GW, but ORNL argues these estimates were “hindered by a lack of detailed data and an incomplete representation of technical factors relevant to hydropower retrofits.” The recent assessment, on the other hand, aims to address this gap by including “more sophisticated methodologies and detailed datasets” to offer a clearer picture, ORNL said. “This project was really motivated by the need to improve confidence in what’s technically possible,” Hansen said. For the latest assessment, researchers utilized a tool developed by INL called HydroGenerate, combined with daily records of streamflow. After analyzing long-term hydrological data, HydroGenerate calculates the design flow, hydraulic head, and information on turbine efficiency to calculate information like expected plant capacity and daily electricity generation. These tools have allowed for more accurate projections of operational constraints and seasonal variations in water availability and movement, ORNL argues. “By using HydroGenerate, we are considering different types of turbines suitable to the conditions of the flow and hydraulic head at each site,” said INL researcher Juan Gallego-Calderon. “The tool is also offered as an open-source package so stakeholders such as researchers and project developers can use it to verify their own feasibility assessments.” ORNL and INL researchers plan to add future streamflow variability into the model to capture long-term impacts of changing water availability on these potential resources, and the next phase will extend to regions like Alaska and Hawaii. “Hydropower development takes time, often decades, so we need to consider what future water availability might look like,” Hansen said. “In some regions, increasing precipitation could even create greater potential for hydropower in the future.”