As a water resources engineer at the Department of Energy's Oak Ridge National Laboratory, Carly Hansen studies dams, river basins and the data needed to understand how those systems behave. She is a key researcher supporting ORNL's work on non-powered dams, identifying existing dams that could support hydropower without compromising the purposes they already serve.
Non-powered dams (NPDs) are one of several untapped sources of hydropower that fly under the radar, which are being highlighted as part of a series called "Hidden Hydropower." Although dams are often associated with electricity, only about 3% of dams in the United States are used to generate power. Most were built for other purposes, including navigation, flood control, irrigation, water storage and recreation.
A recent ORNL-led assessment conducted with Idaho National Laboratory took a closer look at a subset of more than 2,600 non-powered dams and identified 4 gigawatts of potential hydropower capacity. The assessment used improved streamflow data and site-specific modeling to pinpoint the best facilities for potential hydropower development.
In the following Q&A, Hansen explains why these opportunities can be hard to recognize, and how researchers are using new data to pinpoint which sites warrant additional study and investment.
Q: What makes non-powered dams a hidden hydropower opportunity?
A: These dams are hidden opportunities because the infrastructure is already there, but electricity generation was never the reason it was built. Many non-powered dams were built for purposes that are still important, so the dam is not going anywhere. The question becomes whether that same infrastructure can also support hydropower without disrupting the functions it already serves.
That is what makes this different from building a new dam. We are not starting with a blank slate. We are looking at existing water infrastructure and asking whether there is unused energy potential that can be responsibly captured.
Q: Why can hydropower potential at existing dams be hard to recognize?
A: People often picture hydropower facilities as very tall dams with large differences in elevation from one side to the other, but some of the biggest opportunities we found are not necessarily those classic high-head dams. Many are locks and dams on large river systems, including along the Mississippi River and in the Ohio River Basin.
Those structures may not have the highest hydraulic head, or difference in water elevation that creates pressure and potential energy, but they can still have enormous flow rates. Part of the challenge is recognizing that hydropower potential can come from different combinations of flow and hydraulic head, and that a site that does not look like a traditional hydropower facility may still be worth evaluating.
Q: What makes a non-powered dam a good candidate for hydropower development?
A: At the most basic level, you need enough flow and enough hydraulic head to generate power cost-effectively. But for existing dams, the question is more complicated than that. These structures already have operating purposes, and hydropower has to fit within those constraints.
Site conditions matter too. Even if the head and flow look promising, a project may run into land access issues, environmental concerns, complicated geology or other physical constraints that make development impractical.
That is why gathering better data is so important. We're trying to go beyond identifying theoretical potential to help narrow the list to sites where further study is actually worth the time and investment.
Q: Why focus on existing dams instead of building new hydropower infrastructure?
A: In the United States, building new water-regulating structures is often very difficult to justify. Many of the best sites were developed a long time ago, and new dams can face major environmental, social and permitting challenges. Retrofitting existing dams can also be cheaper in many cases.
These projects still require careful engineering, environmental review and coordination with dam owners and other stakeholders. But the infrastructure isn't going anywhere in most cases, so it makes sense to ask whether it can provide additional value.
Q: Did anything surprise you as you studied non-powered dams across the country?
A: One of the biggest surprises has been the complexity of the infrastructure data itself. There are many different organizations tracking dams and water infrastructure, but the information is not always complete or consistent. A lot of facilities are just missing from national datasets, and different datasets may represent the same site in different ways.
This is actually a big hindrance to our ability to provide a thorough assessment of NPDs, because the quality of the assessment depends on the data going into it. To understand hydropower potential, researchers need confidence that they are describing the right structure, using the right streamflow information and accounting for how the system actually operates.
Q: What questions are ORNL researchers working on next?
A: One major question is how future water availability could affect hydropower potential at these sites. Our recent assessment was based on historical streamflow data, which gives us a stronger baseline than previous national estimates, but water availability and usage are constantly changing, and we still have work to do.
Now we're looking at projected streamflow data to get a better understanding of how changing water availability, seasonal patterns and water use could affect potential hydropower generation. In some systems, future conditions could reduce potential, and they could increase in others. The goal is to give decision-makers a clearer picture of what these opportunities may look like over the long term.
The NPD assessment was funded by the Department of Energy's Hydropower and Hydrokinetic Office.
Learn more about the NPD assessment here .
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science . - Galen Fader
