The primary benefit cited for increasing energy storage capacity typically points to greater penetration of renewable energy sources in power grids. As an additional plus is decarbonization at the grid scale, researchers from the U.S. National Renewable Energy Laboratory (NREL) sought to determine the global warming potentials (GWPs) of different storage technologies.

The analysis examined the GWP attributed to 1 kWh of stored electricity delivered to the nearest grid substation connection point for pumped storage hydropower (PSH), compressed-air energy storage (CAES), utility-scale lithium-ion batteries (LIBs), utility-scale lead-acid (PbAc) batteries and vanadium redox flow batteries (VRFBs). Closed-loop PSH and CAES are designed for long-duration storage, while batteries are intended to be used for a shorter time frame.

The researchers calculated the GWP attributed to 1 kWh of stored electricity delivered to the nearest grid substation connection point. They estimated the GWP for closed-loop PSH was estimated to range from the equivalent of 58 g to 502 g of carbon dioxide/kWh. This storage option offered the lowest GWP on a functional unit basis, followed by LIBs, VRFB, CAES and PbAc.

Closed-loop PSH appears to be a promising energy storage option in terms of its life cycle greenhouse gas emissions and can play a key role toward meeting national climate goals. The study published in Environmental Science & Technology assumed the average PSH facility to have storage capacity of 835 MW and an average estimated 2,060 GWh of stored energy delivered annually from a renewable resource-based electricity mix.