If for example you needed a 1000MWh plant you could have a plant with 5 x 300MWh turbines, two spinning @< 50% capacity so there is a reserve in case of sudden increase in load or you could have one shut for maintenance and one spinning reserve.
If your wind stops that's gone, the solar is only good for perhaps eight hours/day, batteries are good for smoothing flow and how much hydro would you need?
