Solar power is DC, so there is no 'rotational mass' of any sort. Solar is run through inverters to make it AC. Since this is an electronic process, synchronization occurs thousands of times a second.<br><br>Wind power turbines may be AC, but they are variable speed so they also get synced to the grid via electronics. Power is stored on a cycle by cycle basis in banks of supercapacitors. The incoming charge controller and outgoing load controller operate independently of each other.<br><br>Battery storage is best organized as a '3-tier' system: storage at the generator farm, storage at switchgear stations, and storage at end-user-consumers, such as cars and appliances. Farm storage should be focused on leveling 'surges' - huge gusts or temporary lulls, making it possible for the rest of the grid to compensate with a 'bit of play'. Switchgear storage is basically the 'tank farm' of long term battery storage - these should be able to maintain six month reserves. These are designed to even out the longest swings, the variation between winter troughs, summer peaks, fall and spring wind surges, etc. Homes and businesses should design their storage systems to handle two week grid outages, as might happen during ice storms or hurricanes.<br><br>When entirely renewable storage grids settle out, this is most likely how they will be configured.