Swiss startup Energy Vault is working on a gravity-based energy storage system that could revolutionize the renewable energy industry.
The system involves lifting a heavy object on a pulley and converting potential energy back into electricity when needed. The firm is completing two such units near Shanghai, China, and Texas, USA.
The gravity battery system developed by Energy Vault is a reliable solution to the unpredictable nature of renewable energy sources like solar and wind power. Unlike traditional battery systems, it does not rely on land topography or geology, which makes it an ideal choice for installation almost anywhere. The system uses “proprietary cement/polymer-based composite bricks” that can be made from ultra-low-cost materials to lift and store energy. Each brick weighs 35 metric tons, has a specific gravity twice that of water, and enough compressive strength to lift and store the energy.
The system uses a mechanical crane powered by a surplus of power from sunlight or wind to lift the bricks 35 stories into the air, where they stay suspended until power is needed. In times of need, the bricks are lowered, pulling on cables that spin turbines, producing electricity. The blocks can store up to 80 megawatt-hours of energy and continuously discharge 4 to 8 megawatts for 8 to 16 hours. The system claims a round trip efficiency of more than 80 percent, which is more efficient than hydro plant pumps or turbines.
The company has partnered with China Tianying and Enel to build the system in China and Texas, respectively, with the former set to have an energy storage capacity of 100 megawatt-hours and the latter 36MWh. The system promises energy savings of up to 70 percent compared to current competing technologies and has minimal degradation in storage capacity over time.
With its custom-designed 6-armed crane operated with “proprietary algorithms and machine vision,” the whole system is fully automated.
The system’s reliability and cost-effectiveness make it a promising solution to support dispatchability and grid stability for renewable energy sources.