The photo is sourced from advancedsciencenews.com
The system’s operational principle will resemble that of pumped storage power plants (PSPPs), which use excess electricity to pump water from the lower reservoir to the upper one and then discharge water into the lower reservoir when energy demand goes up, thus setting off power generators. Energy Vault’s project envisages the construction of several ground shafts, which will resemble similar tower crane designs on the outside. Each shaft will contain composite blocks that will be lifted up during the hours of low energy demand by an electric motor that will be powered by a nearby wind farm. During increases in energy demand, the blocks will descend under the action of gravity. As a result, kinetic energy will be converted into electricity.
The absolute weight of each of the blocks will be 35 tons, and their specific weight (in terms of the occupied area) will be twice that of water. Energy Vault estimates that the ratio of stored and back-generated electricity will be 75%. Unlike with lithium-ion batteries, the efficiency of the system will not depend on the number of charge-discharge cycles. While the system’s energy storage duration will total 4 hours, Energy Vault plans to increase that figure to more than 12 hours in its new installations. The system is intended to have the advantage of low cost: the installation does not require expensive metals (such as cobalt, lithium or nickel), and composite blocks can be created from industrial waste, such as mine tailings (waste from rock processing), excavated soil from construction sites or coal ash.
Energy Vault’s project will facilitate the commercialisation of the gravity-based energy storage technology, which will soon also find application in the hydrogen energy industry. Scotland’s Gravitricity jointly with VSL Systems UK is planning to build the first British underground hydrogen storage, which will be set up in a 5-metre-wide and 365-metre-deep underground shaft lined with steel. The shaft will be able to store 100 tons of hydrogen at a time under a pressure of 220 bar. This volume will be sufficient to power more than 1,000 freight trucks.
