Non-powered dams in the US could provide 4GW of hydropower capacity and generate up to 15.2TWh of electricity annually, according to an updated assessment by Oak Ridge National Laboratory (ORNL) and Idaho National Laboratory (INL).
The estimated output would be sufficient to supply more than 1.4 million homes. The assessment covered a subset of more than 2,600 non-powered dams, with an average potential capacity of 1.5MW per site.
Only around 3% of dams in the US currently generate electricity, with most used for water storage, navigation and flood control. Researchers said the existing structures could offer opportunities to add generating capacity without constructing new dams.
Federally owned dams account for 86% of the total potential capacity identified among the candidate sites. The assessment highlighted the upper Mississippi River and Great Lakes regions as particularly promising because of their concentration of dams with relatively high potential capacity.
“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, 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.”
The Olmsted Locks and Dam in Illinois was among the non-powered facilities identified as a candidate for hydropower development.
Previous national studies had estimated theoretical capacity of between 12GW and 30GW at non-powered dams. However, ORNL said those estimates were affected by limited site data and incomplete treatment of the technical and operational factors governing hydropower retrofits.
“This project was really motivated by the need to improve confidence in what’s technically possible,” Hansen said.
The latest assessment used HydroGenerate, an open-source computational tool developed by INL, together with daily streamflow records from sources including the US Geological Survey stream gauge network and ORNL’s Dayflow reanalysis dataset.
HydroGenerate uses long-term hydrological data to calculate design flow and assess the most efficient turbine size for a potential plant. It also incorporates hydraulic head and turbine efficiency to estimate plant capacity and daily electricity generation.
The process is intended to provide a more realistic representation of seasonal water availability and operational constraints at dams that continue to serve navigation, flood control or other purposes.
“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.”
Hansen added: “This tool helps close the gap between theoretical possibilities and realistic potential. Many of these dams already serve other critical purposes, and their operational constraints — such as flood control or navigation — can significantly limit hydropower development. We’ve worked to reflect those limitations in a way that hadn’t been done before.”
The findings have been incorporated into the NPD Hydro resource, which includes two new tools. NPD Insights provides access to the updated assessment and site rankings, while the NPD Toolkit allows users to estimate payback periods and consider potential environmental, community, industrial and grid benefits.
The updated dataset is also available through ORNL’s HydroSource platform, allowing policymakers, dam owners, developers and researchers to examine candidate sites alongside energy infrastructure and water-management information.
ORNL and INL plan to extend the assessment to Alaska and Hawaii and incorporate possible future changes in streamflow. The next phase is intended to examine how long-term variations in water availability could affect the technical potential of individual sites.
“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.”
The research was supported by the US Department of Energy’s Hydropower and Hydrokinetic Office.
