Flywheel energy storage is neat: https://en.wikipedia.org/wiki/Flywheel_energy_storage https://en.wikipedia.org/wiki/Flywheel_energy_storage Add energy (speed)

Flywheel energy storage is neat: https://en.wikipedia.org/wiki/Flywheel_energy_storage https://en.wikipedia.org/wiki/Flywheel_energy_storage Add energy (speed) when available, use it to power things when not.