KEMA, in partnership with the 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 concept design is the initial result of an on-going feasibility study being conducted for Dutch energy companies.

The Energy Island designed by KEMA, Lievense and the Das brothers 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.

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 megawatts, depending on the water level. It also would have an annual storage capacity of more than 20 gigawatts — enough energy to offset 500 to 840 kilotons of CO2 emissions.

The Energy Island concept is an important step forward in demonstrating the role of large-scale energy storage in enhancing the reliability of the power supply, stabilizing the cost of electricity, and reducing CO2 emissions.