I don't much like messing with the coast line as opposed to building reservoirs inland.  Every time we mess with the coast lines we seem to foul up some major habitat.
There are enough mountains in most locales to be able to use water storage.  

If we switch to plug in electric vehicles we should be able to use them to store excess nighttime production as well.  IE, design the plug in points to only function after the local peak or if in an emergency at a much higher price.  Our current electrical systems are sized for the peak + a safety factor.  On our little island that means we have 135 MW of capacity to handle the daily peak of about 75 with an average of 50-55 MW for example.

We also need to shift the location of high energy industry to areas with lots of wind power much as we used to local Al smelters near hydro sources.  Server racks can sit pretty much anywhere.