The next generation of the Energy Vault stores several gigawatt hours
A prototype with exactly these specifications has been standing in the municipality of Arbedo-Castione in the Bellinzona district since August 2020. Mathematically, the capacity of this Energy Vault is around 57 megawatt hours (MWh) – in practice, the effective value is 35 MWh, while the output power is four megawatts. With these key data, the gravity storage system qualifies as an intermediate buffer to bridge lulls during the day or to feed energy into the power grid at night. However, this system does not work entirely without high-tech. After all, the interaction of lifting and lowering the composite blocks made from alternative cement and waste materials must be perfectly orchestrated. An AI-based software platform that also integrates technologies such as machine vision is responsible for automatic control. The tower’s efficiency is around 90 percent, according to Energy Vault. Meanwhile, the Lugano-based company is developing the next generation of the gravity storage system, which will take the overall performance up a notch. The facility’s designs are reminiscent of a giant high-bay warehouse, with algorithmically controlled blocks in constant motion within the building. The modular plant is designed to be expandable in ten megawatt hour increments up to a capacity of several gigawatt hours. The first contracts for the new plant are a done deal – for example, DG Fuels, a company from Washington, D.C., that specializes in the production of sustainable aviation fuel, has ordered capacities of around 1.6 gigawatt hours (GWh).
The cryogenic energy storage system from Great Britain is a high-tech solution
British inventiveness is also making a tangible contribution to the storage of electricity from renewable energies. The London-based company Highview Power is currently building the world’s largest liquid air energy storage facility in Carrington near Manchester, which will supply around 50,000 households with electricity for five hours, starting in 2023. This plant will also serve as a classic intermediate buffer. From a technical point of view, the solution appears more complex than the Swiss gravity storage system – the British rely on cryogenic liquids as a storage medium. In this so-called cryogenic energy storage, ambient air is compressed using surplus electricity from wind or solar power plants and liquefied by cooling it to minus 196 degrees Celsius. This liquid air can be temporarily stored in insulated low pressure tanks. When this energy is needed in the grid, the plant switches to the discharge cycle: It releases the liquid air from the tanks, which then expands and drives a turbine to generate electricity through evaporation. Incidentally, the plant incorporates a great deal of technology from MAN Energy Solutions. The Augsburg-based company is contributing the entire turbomachinery train – including various compressors, air expanders, and cryogenic components. The cryogenic battery is expected to provide 50 megawatts of power and at least 250 megawatt hours of electric energy. According to Highview Power, the technology can be scaled to provide several gigawatt hours of storage. However, its efficiency is still relatively low. The British company cites a ballpark figure of 60 percent, which can be increased to 70 percent by using waste heat and cooling to generate energy. Here, too, the first contracts have already been signed. In Spain, the regions of Asturias, Cantabria, Castilla y Leon, and the Canary Islands have already ordered their liquid air storage systems. A plant with a capacity of 400 MWh is planned for Vermont in North America.