NREL develops tool to estimate emissions from closed-loop pumped storage

NREL pumped storage
This digital mock-up showcases a pumped storage hydropower plant in action. This form of renewable energy stores electricity efficiently and boasts the lowest greenhouse gas emissions among grid-storage technologies. (Image from IKM 3D)

The National Renewable Energy Laboratory (NREL) has developed a “first-of-its-kind” tool that enables hydropower operators and developers to estimate the greenhouse gas emissions associated with building and operating closed-loop pumped storage hydropower (PSH) facilities.

Closed-loop PSH, in contrast to open-loop PSH, is not continuously connected to a natural, outside water source. 

With PSH, GHG emissions can be part of the equation due to diesel-powered construction equipment, the use of concrete and steel, and the local grid electricity mix powering the pump to move water to the upper reservoir, NREL said. 

In 2023, an NREL research team published a study showing that PSH is the lowest emitter of GHGs compared to four other grid-storage technologies — compressed-air energy storage (CAES), utility-scale lithium-ion batteries, utility-scale lead-acid batteries and vanadium redox flow batteries. PSH and CAES are designed for long-duration storage, while batteries are intended to be used for a shorter time frame.

The NREL team used data and methods from the 2023 study to create the Pumped Storage Hydropower Life Cycle Assessment tool. PSH developers and anyone interested in PSH deployment can use this web-based, interactive application to determine the GHG emissions of a PSH facility over its lifetime. Lifetime emissions vary depending on numerous site-specific factors, such as construction materials, components and especially the grid electricity mix used to operate the facility.

Users can input specifications for PSH facilities at varying levels of detail. Examples of specifications include the reservoir volume, dam material and dimensions, number and capacity of turbines, and length of the transmission line that connects the PSH system to the grid. Users can compare different PSH scenarios side-by-side and view the emissions by component, material and life-cycle phase. This is meant to help users determine the sites, specifications and configurations that minimize emissions.

Although likely a low source of emissions, closed-loop systems using groundwater to fill and replenish their reservoirs could potentially have greater impacts on geology, soils and groundwater quantity and quality than open-loop systems, which use surface water, according to the Pacific Northwest National Laboratory (PNNL)

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