IT HIT THEM LIKE A TON OF BRICKS

The inspiration behind Swiss startup Energy Vault: use stacks of “brick like” composite blocks to store energy—in effect, turning a pile of blocks into a battery.
It’s a simple idea: use solar- and wind-generated electricity the grid doesn’t need at the moment to raise stacks of composite blocks to a height. Leave them there until the grid needs more power, then lower them and release their stored energy.
The company’s old-fashioned technology uses motors fueled by excess renewable energy, such as a desert would produce in the middle of the day or an ocean at tides, to spool cables that raise the blocks up a shaft.
When the grid runs short of electricity, the blocks slowly descend, pulling on the cables that, in turn, spin a generator.
Energy Vault’s proprietary technology raises one 35-ton composite block 100 meters, or more than 325 feet, in less than a minute. 
Normally, the composite blocks descend at about two meters, or a little more than six feet, per second but artificial intelligence can slow or speed the pace, depending on how much power needs to be generated and how quickly.
A “vault” of 10,000 blocks could produce 27 gigawatt-hours of electricity a year with 80- to 85-percent efficiency, according to the company.
The estimated operating cost: about $65 per megawatt-hour, almost half the $128 per mwh cost of using a lithium-ion battery.
In the demonstration project, 35-ton composite blocks were made locally from dirt and other locally sourced materials, even solid waste, and needed no cement to bind the materials into a solid mass.
TRENDPOST: Beyond operating costs lower than lithium-ion batteries and using locally-sourced materials that don’t need cement as a binder, the system doesn’t need water or rare earth minerals, can deliver power when the wind doesn’t blow and the sun doesn’t shine, and won’t degrade over time.
Tests at the California Institute of Technology indicate that the shafts of composite blocks could withstand category 4 hurricanes and magnitude 8 earthquakes.
One drawback: the Swiss demonstration site takes up 14 acres of land.
However, there are thousands of sites in deserts, atop toxic waste dumps, and in other places not useful in other ways where energy vaults could provide renewable power for decades to come.

The workings of an energy vault, showing shafts, composite blocks, and the motors that move them.
Credit: Energy Vault.