Key Energy has installed a three-phase flywheel energy storage system at a residence east of Perth, Western Australia. The 8 kW/32 kWh system was installed over two days in an above-ground enclosure, dramatically cutting the time needed to install the flywheel system.
The website notes (In diagrams and pictures, not the movie) that these can be buried below grade to mitigate flying big spinny objects. The big spinny thing also lives in a vacuum and rests on magnetic bearings to reduce friction. The enclosure they put it in seems to have pretty thick walls, but can’t tell if they are thick enough if the big spinny thing decides to explosively disassociate. It would have been nice to hear what the thing sounds like during initial spin up and in normal operation.