Are current day rechargeables the restriction for future power-
grids?  Several countries have been researching future
development to convert their fossil fuel based power grids to a
more environmentally friendly solution.  However, the greatest
obstacle to overcome is not how to make the power – but how to
store the excess power for use during times when the winds slow
down and the sun goes down.  Currently we can’t control the
weather, (well not yet, at least) so we are reliant upon Mother
Nature’s random cycles for energy.  Therefore the requirement of
how to store this excess and off-hour power for when it’s really
needed comes into play.    As noted from Wired UK:  ” That power
needs to be stored somewhere so that it can be used, otherwise
renewable energy can’t ever replace coal, oil, nuclear or
similar plants that can output a reliable level of power
whenever needed.  For that reliability, there are three main
options: pumped hydroelectric storage (PHS), where water is
pumped upwards into a reservoir wh