Power storage is a critical challenge for adoption of intermittent renewable power sources and also for being able to help shift base load to peak load requirements. There are many approaches being pursued, but the Energy Island, conceived for off the coast of the Netherlands, is an extremely innovative concept.
The Energy Island
incorporates a new concept in pumped hydro storage — an inverse offshore pump accumulation station (IOPAC).
On the Energy Island when there is a surplus of wind energy, the excess energy is used to pump seawater out of the interior "subsurface-lake" into the surrounding sea. When there is a shortage of wind power, seawater is allowed to flow back into the interior "lake" through commercially available generators to produce energy.
Ahh, pumped hydro storage. Something which we know well and that has been around since the late 19th century. Pumped storage works well as a partner to wind power, storing at roughly an 80-90% efficiency. Pumped hydro storage thus enables reliable power supplies with wind power.
Well, there is something new and innovative here. KEMA, Lievense and the Das brothers have designed an artificial island that would, in essence, be somewhat like a Pacific atoll, but the inner water surrounded by the outer ring would be sealed off from the larger ocean. The interior reservoir would be 50 meters deep, enabled by the mud of the seas off the Netherlands. And the island (the dikes/outer ring) would be made from the materials dredged to create the reservoir.
On that outer ring would be a long line of wind turbines for sending power ashore. When producing excess power, sea water would be pumped out of the enclosed lake into the surrounding sea. When there is greater demand, sea water flows back into the "lake," driving generators. The analysis to date suggests a 12-hour power delivery at 1.5 gigawatts (roughly equal to three coal-fired plants). The KEMA analysis suggests a total annual storage capacity of 20 GWh or "enough energy to offset 500 to 840 kilotons of CO2 emissions."
Note that the Energy Island truly does seem to be an island of energy. Not only the wind mills and electrical generators from sea water, but as well a chemical plant (better far from an urban area) and a liquid natural gas (LNG) terminal.