Over 15 miles from the coast of Scotland, a wind power project could foreshadow a major part of our clean-energy future. Hywind Scotland, situated in Buchan Deep, is the world’s first floating wind farm, with its five six-megawatt turbines now generating electricity. On shore, a one-megawatt-hour lithium battery also helps smooth its potentially erratic supply of electricity to the grid.

The project, which is a collaboration between the Norwegian oil firm Statoil and Masdar Abu Dhabi Future Energy, makes use of turbine towers that are 253 meters tall, with 78 meters of that submerged in the North Sea. Each tower is tethered using three cables that are anchored to the seabed. 

Floating wind farms far out at sea hold a lot of promise for future energy generation. A recent analysis showed that they operate more efficiently than those on land or close to the coast, to the extent that three million square kilometers of floating wind turbines could supply the entire world’s current energy demand. It’s also a concept that’s catching on elsewhere, with a scheme similar to the Scottish project under consideration in California.

The sticking point, for now at least, is cost. Bloomberg reports that the Buchan Deep project cost a total of $263 million to complete. It currently receives $185 per megawatt-hour of subsidies from the British government, on top of the $65 per megawatt-hour it earns for the wholesale price of the electricity it creates. In other words, it’s damned expensive.

Statoil says that it hopes floating wind farms could produce energy for between $50 and $70 per megawatt-hour by 2030. That’s terribly ambitious—but if it manages the feat, expect to see more wind turbines popping up in the middle of the ocean before long.