Energy Vault says its China-based gravity battery system will be complete in Jube. (Image Credit: Energy Vault)
Gravity batteries are a potential solution for renewable energy sources, including wind and solar power. Energy Vault, a Switzerland-based startup, is almost finished with the construction of two gravity batteries in Texas, United States, and Shanghai, China.
Generally speaking, gravity batteries draw in energy from a power source and use a pulley to lift a heavy object like a large mass of weight or concrete. The object falls whenever power is needed, turning the potential energy into electricity. Energy Vault says its gravity batteries "can be built almost anywhere, either co-located with solar or wind plants or simply connected to support dispatchability and grid stability."
Instead of using water in a hydropower unit for energy production, Energy Vault relies on "proprietary cement/polymer-based composite bricks that can be made of ultra-low-cost materials: soil, mine tailings, coal ash, incinerated city waste, and other remediation materials."
An individual brick weighs 24 metric tons, has double the density of water, and has sufficient compressive agility. They consist of 99% compressed dirt along with a polymer and water mixture for stabilization. The startup's technique stores renewable energy and "utilizes material that would otherwise be destined for landfills at a very financial and environmental cost."
Before lifting or lowering a brick, the pulley hauls it and places it inside the elevator. These bricks are then hauled 35 stories up, where they remain in place until power is needed. They're then lowered down, producing power in the process. Lowering each brick at 1.9m/s generates one megawatt. After reaching the bottom, the brick is moved toward the middle of the building. Energy Vault also says these bricks will have 80MWh and discharge 4-8MW for 8-16 hours.
According to the startup, the hoisting machinery is better than turbines or hydro plant pumps. As a result, it produces a round-trip efficiency of over 80% compared to chemical batteries. In addition, it achieves energy savings of 70% compared to current technologies.
The 400-foot-tall gravity battery building in China is for a waste management and recycling company called China Tianying. This is engineered to have 100MWh that can provide power to 3,4000 homes for a day. Meanwhile, the 460-foot-tall structure in Texas is for Enel, an energy firm, and will have 36MWh.
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