As a solution to the unreliable nature of renewable energy sources such as solar and wind power, a Swiss startup called Energy Vault is nearing the completion of two gravity battery units that are located in China and Texas. The idea behind a gravity battery system is to lift a heavy object (like a large mass of concrete or a weight) using energy from a power source, and when energy is needed, the object can fall, and the potential energy is converted back into electricity.
The gravity-based storage system does not rely on land topography or geology and can be built almost anywhere; the system utilizes low-cost bricks made of ultra-low-cost materials like soil, mine tailings, coal ash, incinerated city waste, and other remediation materials. Each brick weighs 35 metric tons and is designed to have a specific gravity at least twice that of water and enough compressive agility. The company’s system has a storage capacity of up to 80 megawatt-hours and can continuously discharge 4 to 8 megawatts for 8 to 16 hours.
The Energy Vault system being constructed in China
The firm claims its conventional hoist machinery is more efficient than hydro plant pumps or turbines, resulting in a round-trip efficiency of more than 80%, and energy savings of 70% are being claimed when compared to current competing technologies, with no degradation in storage capacity over time.
Energy Vault is also building its 400-foot-tall project in China for a waste management and recycling company named China Tianying; according to CNET, the project is designed to have an energy storage capacity of 100 megawatt-hours, which can power 3,400 homes for a day and the system is expected to be completed in June.
Regarding the system in Texas, it is set up for the energy firm Enel and will feature a 460-foot-tall structure with a total capacity of 36MWh. Energy Vault assures the automation of the entire system using their specially designed 6-armed crane, which is controlled by unique algorithms and machine vision that facilitate the arrangement and positioning of the bricks in a specific sequence.