Switzerland-based Energy Vault says it has built a large gravity storage installation in China which will help balance the electrical output of a wind farm, and it is now being "commissioned" before connection to the grid.

The EVx gravity storage system works by raising and lowering concrete blocks to store and release potential energy, and will store 100MWh of energy, which it can deliver at 25MW. Built in Jiangsu Province, it is the world's first commercial gravity energy storage system, apart from the pumped hydroelectric storage systems which provide the majority of all energy storage in the world, according to Energy Vault.

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– Energy Vault

Gravity storage has been proposed by a number of players, as a way to store solar and wind energy that has been generated at times when demand is low. On a sunny day, for instance, a solar farm's output could be stored as potential energy by raising concrete blocks. In the evening, the blocks can be lowered, powering dynamos that deliver the electricity when it is needed.

Commentators have cast doubt on the practicality of gravity storage, arguing that the system stores comparatively small amounts of energy compared with the embodied energy and emissions of the concrete and steel used in its construction. Clean energy site CleanTechnica has described the concept as “terribly silly in obvious ways," pointing to the fragility of crane systems, and the immense embodied emissions in the concrete blocks used in Energy Vault's EV1 prototype, which was built in Switzerland in 2020, with a 5MW/35MWh specification.

Energy Vault says it has addressed these systems with its newer EVx design, which encloses the lifts in a building, and plans to use reclaimed ash and other waste material in the blocks, instead of concrete. The company also claims to have improved on the EV1's 75 percent round-trip efficiency (which would mean the system returned 75 percent of the electrical energy stored), reaching a promised 80 percent.

The company began its installation in Rudong, Jiangsu Province, with partners Atlas Renewable and China Tianying (CNTY), in March 2022, according to an Energy Vault release, and the system has now "entered the first phases of commissioning," according to a statement this week.

“Happy to share our continued progress and a critical milestone achieved with our partners Atlas Renewable and China Tianying related to commencement of commissioning activities of the world’s first EVx gravity energy storage system,” said Robert Piconi, chairman and chief executive officer of Energy Vault. “Look forward to sharing more on this first EVx deployment and our planned future gravity technology deployments globally as we see increasing demand for longer duration energy storage.”

Piconi said the construction faced two Covid-related stoppages in its first year, but the company is now positioned to deliver larger storage projects with partner China Tianying announcing a further 100MWh gravity storage project in Huailai County, Hebei Province. The project, to be located in Cunrui Town, will provide stable and eco-friendly green electricity to data centers in the region, says Energy Vault.

Eric Fang, chief executive Officer at Atlas Renewable, said: “This first deployment of Energy Vault’s EVx technology will serve as a model for global decarbonization technology partnerships, and as we have previously announced, are already working on multi-GWh deployments of Energy Vault’s gravity technology in China to support and ideally accelerate China’s current 30-60 net carbon neutral plans.”

Highlighting the market adoption of Energy Vault’s gravity technology, China Tianying's subsidiary, Jiangsu Nengying New Energy Technology Development Co., Ltd., announced last week that it has entered into an agreement with the People's Government of Huailai County to build an additional 100MWh gravity energy storage project in Huailai County, Hebei Province, China. The EVx system is also reportedly featured in a roster of projects scheduled by the National Energy Administration of China.