Energy Vault: storing electricity in concrete blocks
Swiss start-up ‘Energy Vault’ has developed a 20 MWh electricity storage system capable of ‘feeding’ 2.000 households a whole day long by using concrete blocks and cranes. It’s a low-tech ‘dry’ version of ‘pumped hydro’, using water storage at different levels to generate electricity when needed. The idea was launched last weekend at the KentPresents Idea Festival in Connecticut (US).
Dry version of pumped hydro
Apart from using huge lithium-ion batteries, ‘pumped hydro’ is the most used method to ‘store’ surplus electricity when not needed instantly on the grid. Using water reservoirs on different levels, water is pumped to the upper level when an excess of ‘green’ electricity from windmills or solar panels is available.
When supply is low and extra power is needed, the water flows down through a generator to make electricity again. In Belgium this technology is used at Coo and the lakes of L’Eau d’Heure. Worldwide three-quarters of all pumped hydro storage systems is built in only ten countries today, as an abundance of water is often a scarce commodity.
The Swiss want to do more or less the same by using 35 ton concrete cylinders, partly made of waste material and a 120 metre high crane with six arms… needing a circular space of about 100 metres in diameter.
Lifting and stacking concrete blocks
The Swiss actually developed the software to have a ‘dry system’ that can be applied anywhere. The crane picks up concrete blocks automatically when surplus electricity is available to drive the lifting motors and stacks the blocks in a tower around the crane shaft. When power is needed, the crane lowers the blocks using gravity to drive its generator and produce electricity again.
Quartz.com reporter, Akshat Rathi, traveled from London to Biasca (Switserland), near the Italian border, to see a demonstration plant with a 20 metre ‘miniature’ version of the system with a single-armed crane and barrel-shaped concrete blocks of 500 kg.
Computer controlled trolley
An actual system would be six times taller and have six arms, with a computer controlled crane arm’s trolley that is equipped with a camera to locate and stack the blocks precisely. The trolley is programed to compensate for wind gusts to keep the blocks from swinging.
The Swiss needed only 2 million dollar and nine months to develop this solution and claim they have taken several orders to build the full system already. Details about those orders are not given, so far.
150 dollar per kWh
Energy Vault CEO, Robert Piconi, is convinced that “by the time the company delivers it’s tenth 35 MWh plant”, they can bring costs down to 150 dollar per kWh. He claims the system can be used for 30 years without major maintenance costs.
Today storage in lithium-ion batteries costs about 280 to 350 dollar per kWh, but some experts predict these prices could drop as low as 100 dollar per kWh when they are mass-produced in the years to come.