As part of Belgium's phase-out of nuclear energy and move toward renewables, the country plans to build an island from scratch to store excess energy generated from offshore wind farms.
"We have a lot of energy from the wind mills and sometimes it just gets lost because there isn't enough demand for the electricity," a government spokeswoman told Reuters. "This is a great solution."
Over the next five years, a doughnut-shaped island will be built out of sand about four kilometers off the coast. Just three kilometers in diameter, it will mostly be a huge seawater reservoir in the middle that's used to store and recover energy.
The system works by combining wind energy and hydroelectric power to pump seawater in and out of the reservoir. When demand is low, the pumps rely on excess wind energy to pump out the water. As demand increases, the water is let back in, which regenerates the electricity - like with a hydroelectric dam.
The island would also house an offshore substation to convert the voltage of offshore wind for the electric grid.
The project hasn't gotten the go-ahead yet and at least partially relies on strengthening transmission lines that would carry the energy to land.
Nuclear power accounted for 57% of Belgium's energy in 2011, but the country is seeking to reduce that dependence with the help of 2,300 megawatts (MW) in wind power generated by its North Sea wind farms.
Belgium hopes to shut down its two nuclear power plants by 2025, each of which produce 3,000 MW of electricity.
As of 2011, only 1,078 MW of wind power connected to Belgium's grid, but that could grow to more than 4,000 MW by 2020, says the European Wind Energy Association.