Publication: Hydro Review
Issue: September 2017

Recent small low-head hydropower development in the U.S. has occurred at non-powered dams and irrigation canals, a significant break from historical development at sites without existing hydraulic and dam structures. The latter is termed greenfield development or new stream-reach development (NSD). These sites are the bulk of the existing technical hydropower resource potential in the country. The financial viability and feasibility of NSD is influenced by: development risk and uncertainty associated with the cost and duration of the licensing process, the cost of site-specific design and customization of equipment and structures, and evolving environmental constraints on design and operation.

Sustainable hydropower development must address these challenges with new thinking and transformational technology and facility design. The resulting hydropower deployments will necessarily feature significantly reduced costs, smaller physical and environmental footprints, and greater stakeholder acceptance than conventional hydro. Oak Ridge National Laboratory is leading a multi-year research and development effort to accelerate the progress of small hydropower development toward this end.

Small hydropower by the numbers

This article defines small hydropower projects (SHP) as having less than 10 MW of capacity. There is about 3.8 GW of SHP capacity in the U.S from more than 1,700 plants with roughly 3,500 units (see Figure 1). The SHP population represents 73% of all hydropower plants but only 4.7% of installed capacity. However, SHPs remain a valuable contributor to U.S. renewable energy supply. In 2015, SHPs generated 13.6 million MWh of energy, roughly equivalent to the aggregated outputs of the landfill gas, geothermal and small-scale solar PV sectors.

U.S. SHPs have median and mean capacities of 1 MW and 2.14 MW, respectively, and tend to be low- to medium-head (median of 23 ft, majority less than 100 ft). One in five SHPs are in canals or conduits; most others for which data are available are run of river (see Figure 2). The first SHP on record began operation in 1891, and SHPs played an important role in U.S. electrification to 1930. About half of operating SHPs were commissioned in a second development wave in the 1980s. SHPs are present in 46 states, with more than half of SHP capacity in California, New York, Idaho, Wisconsin and Michigan (see Figure 3).

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