A Comparison of the Environmental Effects of Open-Loop and Closed-Loop Pumped Storage Hydropower

A Comparison of the Environmental Effects of Open-Loop and Closed-Loop Pumped Storage Hydropower.

April 13, 2020

Cover of report "A Comparison of the Environmental Effects of Open-Loop and Closed-Loop Pumped Storage Hydropower"

Pumped storage hydropower (PSH) is a type of energy storage that uses the pumping and release of water between two reservoirs at different elevations to store water and generate electricity (Figure ES-1). When demand for electricity is low, a PSH project can use low cost energy to pump water from the lower reservoir to the upper reservoir for storage. When demand for electricity is high, a PSH project can release water from the upper reservoir through a powerhouse to generate electricity. Traditionally, this meant that PSH plants generated power during the day and pumped at night, with modest diurnal or seasonal variation.

Today, PSH pumping operations are changing to facilitate the integration of the tremendous growth of variable renewable energy (VRE) generating resources, especially wind and solar, on the U.S. grid. PSH facilities are often a least cost option for high capacity (both energy and power), long-duration storage, and can provide the flexibility and fast response that a high-VRE-penetration grid requires. PSH faces its own set of challenges in construction and operation, however, including high initial capital costs, long construction timeframes, uncertainty in revenue streams (similar to all storage), and potential environmental impacts. The U.S. Department of Energy’s (DOE) HydroWIRES initiative includes research to address each of these challenges. This report focuses on potential environmental impacts: specifically, the degree to which impacts can be reduced by using closed-loop pumped storage systems as opposed to the traditionally more common open loop systems.

Download the report:

A Comparison of the Environmental Effects of Open-Loop and Closed-Loop Pumped Storage Hydropower (1.6 MB)

With the potential for growth in closed-loop PSH capacity, project developers, regulators, resource agencies, and other stakeholders should understand the environmental effects of these projects when compared to open-loop PSH systems, as well as measures to avoid, minimize, and mitigate those effects (when we refer to “effects” or “impacts” we are referring to adverse effects or impacts unless noted otherwise). Importantly, because all the PSH projects constructed in the United States to date are open-loop, the potential environmental effects of closed-loop systems are not as well-documented as the effects of open-loop systems.
To address this knowledge gap, the DOE Water Power Technologies Office, under its HydroWIRES Initiative, has prepared this report to (1) compare the potential environmental effects of open-loop PSH projects with those of closed-loop PSH projects; (2) describe how these effects are being avoided,
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minimized, or mitigated at existing projects in other countries and proposed projects in the United States; and (3) discuss the relative significance of the environmental issues.