The world's first floating windfarm has taken to the seas in a sign that a technology once confined to research and development drawing boards is finally ready to unlock expanses of ocean for generating renewable power.

After two turbines were floated, five now bob gently in the deep waters of a fjord on the western coast of Norway ready to be tugged across the North Sea to their final destination off north-east Scotland.

The  £200m Hywind project is unusual not just because of the pioneering technology involved, which uses a 78-metre-tall underwater ballast and three mooring lines that will be attached to the seabed to keep the turbines upright. It is also notable because the developer is not a renewable energy firm but Norway's Statoil, which is looking to diversify away from carbon-based fuels.

Irene Rummelhoff, head of the oil firm's low-carbon division, said the technology opened up an enormous new resource of wind power. 

"It's almost unlimited. Currently we are saying [floating windfarms will work in] water depths of between 100 and 700 metres, but I think we can go deeper than that. It opens up ocean that was unavailable," she said.

Offshore windfarms are springing up across the North Sea for a reason - its waters are uniquely shallow enough to allow turbines to be mounted atop steel poles fixed to the seabed. 

However, such fixed-bottom turbines can only be installed at water depths down to 40 metres, making them little use for the steeply shelved coastlines of the US west coast or Japan.

"If you look at coastlines around the world, there's few that have sufficient area at depths down to 40 metres so if they want to deploy offshore wind, they need to introduce floating wind," said Rummelhoff.

As well as opening up new frontiers such as the Atlantic and the Mediterranean, floating windfarms could be placed farther out to sea to avoid the sort of aesthetic objections that scuppered a  £3.5b windfarm off the Dorset coast. 

While Hywind is a minnow among modern offshore wind projects - it will power just 20,000 homes compared with the 800,000 by one being built off the Yorkshire coast - proponents say floating turbines could eclipse fixed-bottom ones in the long run.

"Looking to the next decades, there might be a point where floating is bigger than fixed based," said Stephan Barth of IEA Wind, an intergovernmental wind power body covering 21 countries.

Bruno Geschier, chief marketing officer at Ideol, a French company hoping to build floating windfarms in Japan, France and elsewhere, said he expected floating farms to begin to take off in the next decade, "reaching cruising altitude in the mid-2020s and a big boom in 2030-35".

The commercialisation also means a chance for new countries to emerge as renewable energy leaders. The UK has the most offshore wind capacity in the world, with Germany not far behind, but France, which has none, wants to become a market leader.

"Floating wind is an opportunity for France to step on to the podium," said Geschier.

The Guardian | www.theguardian.com