Swiss startup Energy Vault wants to lift concrete weights (density 2.4 ton/m3) to store renewable energy when there is no pumped hydro as alternative, currently 96% of the world’s energy storage capacity, with 75% of it in 10 suitable countries only.
The idea: 120 m crane lifting 35 ton of concrete blocks and pile them up neatly. Storage capacity 20 MWh, sufficient for 2,000 household-days. Round-trip efficiency 85%. The lifting and positioning is done automatically, no human intervention necessary, thanks to camera’s and software. The system is relatively insensitive to wind, software compensates for it. The idea is to use building waste, municipalities otherwise pay money for to get rid off.
Currently a demo site with 20 m crane and 500 kg blocks is in operation.
Concrete battery: $150/kWh
First commercial projects are said to be realized early 2019.