Up to now, wind turbines had to be firmly rooted on the seabed with large and costly structures. In developments from Norway and the US, described to the Engineers Ireland conference in Dublin this week, turbines can be moored to the seabed while being kept upright by submerged but buoyant structures that act as counterweights for stability.

The prototype of Statoil's Hywind, designed to work in depths up to 700m, has been anchored in the North Sea off Norway since 2009 and delivering power to the country's grid. Statoil is considering locations for a first small "demo park", among them waters off the Isle of Lewis, in the Hebrides, and also off the coast of Maine, in the US.

An American system, for much shallower depths, will be tested off the coast of Portugal this summer.

Neither system is probably anywhere near ready for the worst of Ireland's Atlantic storms, but turbines built like icebergs could take a lot of offshore wind power even farther out to sea.