Gravity Energy Storage System
Energy Vault suspends a weight on a rotating machine (motor, generator), lowers the weight to drive the generator when generating power, and raises the weight by the motor to store and discharge the power when consuming it. Unlike ordinary batteries, this method of storing electricity does not undergo a chemical reaction, and therefore does not require the use of rare metals such as lithium. It is even possible to consider solidifying garbage to be used as weights. The cost is therefore low.
After conducting empirical tests of this system at various locations, the company reached an agreement with PG&E (electric power and natural gas business) in California, U.S.A., in November 2022 for the installation of batteries for the system with a capacity of 293MWh (expected to be discharged for up to 48 hours in the event of a power outage), and applied to the state in which it is located to expand the capacity to 700MWh, which has not yet been approved. If approved, construction will begin in the fourth quarter of this year and is expected to last at least 10 years.
In June 2000, the CPUC (California Public Utilities Unified Commission) required the state's private electric utilities to implement microgrids, and PG&E plans to convert its existing transmission and distribution network to a microgrid using an energy storage system developed by Energy Vault.
Western Europe, where wind power is becoming increasingly popular, was expected to be the next country to install an Energy Vault energy storage system after the U.S., but in August this year it was reported that a utility system would be installed in a suburb of Shanghai, which had already completed its energy storage equipment in June and would soon be entering grid-connected power generation. Scaled at 25MW/100MWh (output/storage capacity), it will be the world's first gravity storage battery to be made practical. The Chinese operators are Atlas Renewable and China Tianying (CNTY). They are installed near wind turbines to cope with output fluctuations.
About half of China's power mix consists of coal-fired power generation, which is difficult to control flexibly, while wind and solar power, which have recently experienced high output fluctuations, are increasing rapidly. Pumped storage power generation, which has previously helped to moderate output fluctuations, is no longer sufficient to meet demand, and there is a need to rapidly introduce storage systems that are highly effective at curbing output fluctuations. Although the number of lithium-ion battery installations is increasing, the use of lithium, a rare metal, is also bound to increase.
In this case, gravity storage batteries, which do not use chemicals, do not cost money, and do not require construction time, will become valuable. The number of Energy Vault gravity batteries installed in China may increase dramatically as the country expands its energy storage system for grid systems.
Japan should also consider introducing this system. As installed solar power capacity increases, large power companies other than TEPCO are currently cutting back on solar power output, which is clearly not the ideal way to achieve decarbonization goals.
Japan has a scarcity of domestic lithium resources and therefore has to import lithium metal or lithium-ion batteries, and while alternatives such as NAS batteries (sodium and sulfur) and redox flow batteries (vanadium, etc.) exist, consideration should be given to the introduction of Energy Vault gravity batteries, which do not use chemicals.
