Hydro would essentially be used as a battery, not to produce most of the power. You can generate hydro power when there's a lull in the wind or on a cloudy day.

Hydro would essentially be used as a battery, not to produce most of the power. You can generate hydro power when there's a lull in the wind or on a cloudy day. I'm really talking about biomass, and I mention it because it's more dispatchable, meaning that it can be used to smooth some of the fluctuations in wind and solar. There are better technologies than lead-acid batteries. Thermal salt storage and flow batteries are two interesting options. Thermal salt storage has already been used in conjunction with solar thermal energy, but it could be used with any generation source. There are some ongoing large flow battery demonstration projects, such as an 800 MWh / 200 MW battery being built in Dalian, China. 5% of the surface of the country isn't so bad. But wind is stronger and steadier offshore, so it's better to line the coastline with wind farms.