In search for cheaper, longer energy storage, mountain gravity could eventually top lithium-ion
Mountain gravity energy storage could be a viable way to store electricity for longer durations and at larger scales than lithium-ion battery storage can, according to a study recently published in the academic journal Energy.
The idea of gravity as a form of storage is an example of ongoing research into additional storage options beyond lithium-ion batteries. Despite large cost reductions over the past several years, some experts still view lithium-ion systems as not economically-efficient enough at scale to fully back up the amount of renewable energy expected to come onto the grid due to states’ long-term clean energy goals.
Using mountains for storage could be combined with hydropower and prove to be economically attractive for microgrids, islands and areas with high electricity costs, the study published by the Austrian scientific group International Institute for Applied Systems Analysis (IIASA) said.
The researchers propose that a motorized system similar to a ski lift could pull containers full of sand to a crane at the top of a mountain. The sand can then be sent back down the mountain propelled only by the force of gravity, generating electricity in the process.
The basic concept is similar to a gravity storage technology proposed by the Swiss company Energy Vault, which recently received a greater than $100 million equity investment from SoftBank’s Vision Fund. That technology generates electricity through gravity by lowering concrete blocks in a tower.
Lithium-ion battery storage is the fastest-growing storage type and utilities across the U.S. have procured battery storage as a way to back up intermittent renewable energy. But the length of time that they can deploy energy — typically four hours or shorter for — may not be long enough for the greater and greater amounts of solar and wind resources needed to come online to meet emissions reductions goals.
“High-renewables grids, as mandated by many states, will require extremely long durations of storage, potentially on the order of 10-20 hours to shift variable solar power to cover nights and cloudy days, and weeks or even months to shift energy from high-wind months to lower-wind periods,” Wood Mackenzie head of energy storage Daniel Finn-Foley told Utility Dive. He noted that lithium-ion batteries “scale up poorly,” with costs effectively doubling every time the duration of a lithium-ion battery system doubles.