One of the downsides (or maybe double-edged swords) of kinetic energy storage is that it's relatively easy to accidentally get all of the energy out at once. A

One of the downsides (or maybe double-edged swords) of kinetic energy storage is that it's relatively easy to accidentally get all of the energy out at once. A stick of butter and an 2-tonne truck at 216 km/h both "contain" about 1 kilowatt-hour of energy. The butter could maybe burn your house down but the truck could easily kill a couple of dozen unprotected humans in a fraction of a second.