Hydropower can go beyond massive Earth-altering infrastructure. Despite a growing trend of dam removal to preserve and restore native ecology and ways of life, small hydropower projects have the potential to contribute more to a renewable energy future because they can be reliable, flexible and cost-effective, according to a study by the University of Maine.

Small hydroelectric projects are defined by the US Department of Energy as those producing less than 60 MW, although the exact classification of subclasses in the “small” range may be debatable. UMaine researchers Sharon Klein, an associate professor in the School of Economics, and Emma Fox, a former Klein graduate student, have classified the cost and performance measures used to evaluate different types of small hydropower projects and compared the results of these measures in 13 different studies on small hydroelectricity. projects carried out in several countries on four continents.

“This literature review was an important first step in the research we conducted for the National Science Foundation, funded by The future of dams project. We were creating a benefit-cost model of small hydropower in New England and wanted to know what other researchers were doing. It turned out that no one had yet published a full review of the metrics we were looking to calculate, and it took a lot of work to harmonize the data from multiple studies so they were comparable,” Klein says.

Klein and Fox identified four major types of small hydropower design: reservoir-based dams, which block the flow of water downstream and release it through turbines; run-of-the-river, which may involve a dam but channels water from the stream to the turbines in such a way as to ensure that the flow downstream is equal to the flow upstream; pumped storage dams, which draw water from a lower reservoir to an upstream holding reservoir and release it through turbines to meet peak demand; and in-stream turbines, which are placed directly in the water flow and do not require a diversion or restraint of the river.

Each style has its pros and cons. Some styles of small hydro projects, such as run-of-river turbines and in-stream turbines, may be less disruptive to fish habitats and passage, but more conventional styles like reservoir-based dams are generally more reliable.

“There are so many different styles of small-scale hydroelectric dams and so little consistency in the literature on evaluating benefits and costs for these generating assets,” Fox said. “It was difficult to find points of comparison.”

Still, the data showed promising general trends in small hydropower projects, such as decreasing energy cost and increasing benefit-cost ratio with increasing electrical capacity. However, the researchers also found a lack of consistency in the details, assumptions, definitions, and data entries reported across the studies, making it difficult to compare them effectively.

The researchers conclude that although small hydropower projects can still contribute to the renewable energy market, scientists will need more publicly available and user-friendly cost estimation tools with site-specific input data in order to put them into perspective. effectively implemented.

“Because the impacts of small hydropower are so site-specific, our study really highlights the need for further investigation of the costs and benefits of small hydropower – not only financial, but also cultural and ecological – in more of places that use consistent and comparable measurements, assumptions, and inputs,” says Klein.

The research was supported by the National Science Foundation Research Infrastructure Improvement, the U.S. Department of Agriculture’s National Institute of Food and Agriculture, and the U.S. Geological Survey.

The study is now available online and will be published in Renewable and Sustainable Energy Reviews in November 2022.

Contact: Sam Schipani, [email protected]