Despite their small sizes, streams across the United States have the combined potential to generate significant amounts of energy if hydropower facilities of the proper scale and functionality are constructed, according to a new report. Courtesy of Ryan A. McManamay
A new federal publication lays out the significant hydropower potential of streams located across the United States.
May 13, 2014—Hydropower currently supplies the United States with approximately 7 percent of its electricity, but there is a wealth of untapped streams across the nation that could supplement that supply, according to a new report prepared for the U.S. Department of Energy by the Oak Ridge National Laboratory in Tennessee.
As part of its efforts to explore the potential of renewable energy generation in the United States, the Department of Energy commissioned the report, New Stream-Reach Development: A Comprehensive Assessment of Hydropower Energy Potential in the United States. Prepared by the Oak Ridge National Laboratory in Tennessee from 2011 to 2014, the publication was released to the public on April 29 along with its raw datasets, which engineers and researchers can further analyze themselves.
“We have previously heard comments that hydropower was ‘tapped out,’ or that since we’ve had hydropower in the United States for over 100 years, all of the promising sites have already been developed and the only remaining sites would be in areas where development is legally prohibited,” says Shih-Chieh Kao, Ph.D., a research scientist at Oak Ridge National Lab (ORNL) and the principal investigator for the report. “Some people may be surprised to learn that there is 65 GW of new hydropower potential in undeveloped stream reaches [in the United States].”
As part of the study, over 3 million stream reaches, defined as 150 m long segments of streams, were analyzed. The report found that the Pacific Northwest has the highest potential for new stream-reach hydropower resources, offering the potential for 17 GW of hydropower. The Missouri River Basin ranked second, with a potential 11 GW of currently untapped power.
The undeveloped potential of “nonexcluded” areas—those locations that have not been excluded from hydropower development by federal legislation protecting such areas as national parks, wild and scenic rivers, and wilderness areas—is equivalent to about 128 percent of the current U.S. hydropower production, according to the ORNL website. (For example, read “Yosemite Waterway Restoration Plan Approved” on Civil Engineering online.)
“We wanted to move beyond a thought process of reacting to potential development, and say, ‘Well, if we’re going to develop hydropower, where is it, and what are its characteristics? And how likely is it that it could develop?’” says Brennan T. Smith, Ph.D., P.E., M.ASCE, the program manager for water power research in the Energy-Water-Ecosystem Engineering Group at ORNL. “This was very much an assessment across all streams, to look at their potential hydropower, how they might be developed in a sustainable way, and then recognize that across all those streams, that projects supporting any given perspective on sustainability…might rank out differently.”
The result, Smith notes, is a “nationwide accounting of all that potential and a whole host of attributes that enable a variety of stakeholders to rank that potential and have rich discussions about what is the best, for example, ten percent of this resource to be developed, and correspondingly, what’s the worst 10 percent that we might want to set aside for now and only come back to down the road, once we’ve looked at the better sites.”
The assessment contained three main components, according to Kao. One part focuses on hydrologic regions—river basins—to determine the capacity and energy potential of stream reaches. The second analyzes the topography of promising stream reaches to estimate the storage capacity of potential reservoirs and determine the characteristics of potential reservoir inundations. And the third assesses the attributes of each stream-reach and presents data on their natural ecological systems, the social and cultural settings in which they are located, and any local policies, management, and legal constraints that may affect them—all of which can be measured against their energy-generating potential.
While the data was gathered by hydrologic region, it can be broken out in a number of different ways—for example, by state boundaries or by federal versus nonfederal land, Smith notes. (The raw data is available for download on the ORNL website.)
The DOE commissioned the study because it realized that “an analysis and a series of data [were] needed to enhance the discussion about opportunities to develop hydropower in the country,” says Hoyt Battey, a program manager for market acceleration and deployment within the wind and water technologies office at the Department of Energy, and the project manager for the assessment. Prior to the assessment, Battey says, “We really didn’t have rich sets of detailed and dynamic data that we could use to make people consider opportunities that they may not have realized existed.”
The current research builds on a 2012 report that focused on opportunities to develop hydropower on existing, nonpowered dams within the nation. “That was a study in a very similar vein,” Battey notes. “People had talked about opportunities to [develop new hydropower], but couldn’t really quantitatively specify what those opportunities were, or where they were located, and how realistic those opportunities may be.” The current report offers that information for new, untapped hydropower development opportunities in streams and rivers across the nation, he says.
The current study is unprecedented both for its identification of untapped potential hydropower locations and for its examination of the seasonality of water availability in all locations, Smith notes. “All the previous resource assessments were annual averages based on a total annual water quantity,” he says. “But when you are sizing hydroplants and looking at potential capacity, knowing—for example—the summer and winter differences in water availability is important for the economics and sizing, and this study does that as well.” The availability of new tools and geospatial datasets covering topography, hydrology, and environmental characteristics over the last 10 years have made the current study possible, Smith and Kao both note.
While many people argue that hydropower potential has been exhausted in the United States, the current study highlights “that there is further opportunity, and that this warrants further discussion, investigation, and consideration as a the nation tries to evolve its energy portfolio,” Battey says. “That’s a pretty key finding for me.”
Smith agrees: “This is not your father’s hydropower,” he says. “It’s not as high and as massive—these are not huge dams.” Instead, these would be “smaller projects that can and will have to be developed innovatively to be sustainable and to have a smaller footprint than some of the hydropower that’s been developed in the past,” Smith says.
The next step for ORNL is to develop a breakdown of the costs associated with developing hydropower in the locations identified by the report. “We’re thinking in terms of initial cost and dollars per kilowatt of capacity that can be developed, but also in terms of dollars per kilowatt-hour of energy that they will produce,” Smith says. This will help project planners make informed decisions, he points out. “We’ve given them the fact that, yes, there’s resources available. Next, we need to tell them [what is] available at what price and [at] what type of development mode.”
The researchers caution that the current report was conducted at a “reconnaissance level” and on-site assessments would still need to be undertaken at specific sites to determine whether local conditions might preclude such developments.
In addition, “in order to utilize these significant, undeveloped resources, the environmental sustainability of future hydropower development should be emphasized,” Kao says. This includes research that the DOE and others are doing to create environmentally friendly technologies, such as fish-friendly turbines, sensor fish devices, and water-use optimization tools, he says. (Read “Team Focuses on Making Dams Safer for Fish” on Civil Engineering online.)