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Using a crane and concrete blocks to store energy for later retrieval

posted by Jason Kottke   Aug 21, 2018

A Swiss company has designed a system for storing energy in concrete blocks. The blocks are lifted by a crane when surplus energy is available (say, when the Sun is shining or the wind blowing) and then, when energy is needed later, allowed to fall, turning turbines to generate electricity.

The innovation in Energy Vault’s plant is not the hardware. Cranes and motors have been around for decades, and companies like ABB and Siemens have optimized them for maximum efficiency. The round-trip efficiency of the system, which is the amount of energy recovered for every unit of energy used to lift the blocks, is about 85% — comparable to lithium-ion batteries which offer up to 90%.

Pedretti’s main work as the chief technology officer has been figuring out how to design software to automate contextually relevant operations, like hooking and unhooking concrete blocks, and to counteract pendulum-like movements during the lifting and lowering of those blocks.

The storage of energy in this way isn’t new…the ARES project uses hills and heavy trains to accomplish the same thing.

It’s a wonderfully simple idea, a 19th century solution for a 21st century problem, with some help from the abundant natural resource that is gravity. When the local utility’s got surplus electricity, it powers up the electric motors that drag 9,600 tons of rock- and concrete-filled railcars up a 2,000-foot hill. When it’s got a deficit, 9,600 tons of railcar rumble down, and those motors generate electricity via regenerative braking — the same way your Prius does. Effectively, all the energy used to move the train up the hill is stored, and recouped when it comes back down.

There’s something really interesting about big kinetic machines operating as though they were computers, autonomous black boxes where data flows in and out that can operate anywhere with a bit of flat ground.