KEMA, in partnership with civil engineering firm Bureau Lievense and technology illustrators Rudolph and Robert Das, has developed an "Energy Island" concept to store power generated from an offshore wind farm.

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 sea water out of the interior ‘subsurface-lake' into the surrounding sea. When there is a shortage of wind power, sea water is allowed to flow back into the interior ‘lake' through commercially available generators to produce energy. The IOPAC is unique from conventional pumped hydro storage systems in that it would be stationed on an artificial island off the Dutch coast in the North Sea and comprised of a ring of dikes surrounding a 50 meter deep reservoir. The island itself would be built from materials dredged to deepen the interior reservoir. KEMA analysis estimates that the proposed Energy Island storage system would have a maximum generation capacity of 1,500 MW, depending on the water level. It also would have an annual storage capacity of more than 20 GWh.