Those batteries only really hold a days worth of energy for most typical users , so they ' re good for storing daytime solar overnight , or getting through a short power outage , but aren ' t going to be storing energy generated in summer for the winter . That said , they can still help level out the power levels of the grid , such as storing nuclear generated energy overnight when demand is low , and using it during the day when demand is high . <| sep |> This conference paper describes how China does precisely that . tldr the Great Firewall does active probing of addresses passing suspicious traffic , and blocks those it thinks might harbour a circumvention service . It ' s an arms race between the censors and the protocol designers .