Battery energy storage is merely one of the thousands of energy storage methods. Scottish start-up Gravitricity has recently commenced the construction for its 250KW pilot program of “gravity-based energy storage”, which will initiate testing in 2021. The program uses weight potential energy to generate power, which paves a new path for the development of energy storage from renewable energy.
Gravitricity aims to establish the program at abandoned drilling platforms and pits. The energy storage technology is somewhat similar to pumped-storage hydroelectricity, where the gravity media for water storage power stations is “water”, whereas the gravity media for Gravitricity is “weights” between 500 and 5,000 ton, which puts abandoned drilling platforms and pits to good use by repeatedly hoisting and releasing a 16m long rig within a 150-1,500m drilling well, for which the rig is first pulled to the top of the abandoned drilling well using the electric winch, and is released straight down when power is needed that would further “release” the stored electricity. The concept is identical to that of pumped-storage hydroelectricity plants, as both methods are able to stabilize and adjust power grids.
The company will first build a 16m long rig at Leith, which is expected to be completed by the end of the year, with testing commencing next year. Gravitricity claims that the rig is able to respond rapidly and provide electricity within one second, and possesses the same speed as lithium ion battery, as well as maintains stability for the frequency of the power grid. As commented by the company, the capacity of each unit is between 1-20MW, with a lifespan of 50 years that will not experience a reduction in both capacity and performance. The rig is able to expeditiously release effective load within merely 15 minutes, or release gradually within 8 hours.
Gravitricity states that the efficiency of the particular system is between 80 and 90%, thus requiring less cost than that of general lithium battery plants.
The technology is similar to another gravity-based energy storage Energy Vault, though the latter “develops from the surface” by employing a piece of equipment that is roughly 35 floors high and contains a large six-arms crane at the top, which resembles a building that is in the midst of construction from afar. Energy Vault first compiles concrete blocks weighing 35 tons each into a high tower, and relocates the cement block to the ground using the crane on the top of the tower whenever power is required, where the generator is operated through potential energy.
(Cover photo source: Gravitricity)