low-cost method of storing coastal wave energy

"There are 2-forms of pumped storage capable of grid scale energy storage, one technology involving storage reservoirs located at high elevation and the other involving underground storage chambers such as abandoned mines near the coast. Coastal mountains and coastal plateaus occur at many locations internationally, with prospects for development involving pumped storage between upper and lower reservoirs. Many years ago along the coast of Cornwall UK, mines were excavated along the coast that went below sea level and into the earth under the sea. That precedent proves the possibility of underground chambers near or next to the coast."

http://www.renewablesbiz.com/article/15/09/potentially-low-cost-method-storing-coastal-wave-energy

This article caught my attention because I have for a long time believed that pumped storage, abandoned coastal mine shafts and wave/wind energy could all come together sometime in the future to provide energy and freshwater solutions.

This article mentions abandoned mines in the Cornwall region which is likely where CWE will be building their first commercial wave energy array.  

This location seems to have almost identical attributes to an Australian location that I have written about in the past, the coast between Sydney and Wollongong is that region.

The Illawarra escarpment stretches all the way from Stanwell Park to Bulli.  The plateau above the coast line varies from 200 metres to over 700 metres.  Located on the plateau are three reservoirs that feed into the Sydney and Wollongong water supply systems.

Coal has been mined in the region for well over a hundred years and the mine shafts are adjacent to the sea, some actually below the sea floor.  These mine shafts are ready made reservoirs that could be utilised in a pumped storage scheme.  The upper reservoirs are the dams on the plateau.

The wave and wind resources are right there as well.

Sydney, Wollongong and Newcastle are well on the way to becoming a megalopolis and will need all the energy and water it can get.