“Excess power” - they have to have windmills on a different type of regulated connection to the grid so that it does not overload or pump too much power into the system.
“wind doesn’t blow” - when there is not enough wind or it’s calm, backup power plants (usually coal or natural gas) need to come online to keep the windmills moving at a minimum rotation and provide the power not being produced that is needed by customers. There is a lot of energy expended to fire up a coal or natural gas plant (inefficient).
That was my point. When it produces too much energy they can’t currently store it so it’s dumped and when it’s not generating enough they have to have replacement power generation in standby mode to kick in instantly. Can’t just fire up a cold plant.
Until they solve the storage problem wind won’t be a viable source of energy for the power grid. It works well for individual enterprises that also are fed from the grid (coal, nuclear, hydro, gas, etc. All the stuff the enviros hate) to maintain a constant amount of power.