As they look for better wind conditions, wind developers have recently been exploring deeper water projects using floating rather than bottom-fixed turbines. Although still in their infancy, floating turbines potentially allow wind farms to be built far out to sea, with less disruption to shipping, fishing, and people living on the coastline, and less damage to the seabed.
But that doesn’t mean they are much easier to put in place. The ocean isn’t a friendly place. Although floating turbines don’t need to be driven into the ground, they still have to be transported long distances, and attached using mooring cables. It’s dangerous and difficult work, which is often delayed by bad weather, and a lack of specialized equipment and manpower.
A startup in Norway thinks it might have a solution, though. Called WindFlip, the idea is to use a lightweight barge to float the turbine horizontally to the site, and then erect it by letting in water at one end, allowing the turbine to rise into the air, with the device still attached. Once securely tethered, the WindFlip is then filled with air, releasing it again to the water, ready for the next installation.
Ane Christophersen, WindFlip’s general manager, says the current method for transporting and installing floating turbines is costly and time-consuming, and unsuited for some places. Because turbines are transported vertically, the water is sometimes too shallow near the shore, she says.
Although still at the prototype stage, WindFlip potentially allows developers to reach sites more quickly, and to install turbines without needing crane equipment. Christophersen says the WindFlip can travel at about eight knots, compared with a vertically driven barge which goes only at one knot, because of the drag in the water.
The concept grew out of a student project, which was later backed by a government research fund, and Statoil, Norway’s oil and gas company. In 2010, WindFlip built a 1:45 scale model. It is now looking for an turbine installer firm to take on the concept, before it offers a fully fledged product back to Statoil, which is commericalizing its Hywind floating turbine.
Christophersen hopes the WindFlip will be used in countries like Spain, Portugal, and Japan, where the ocean is either too deep for bottom-fixed turbines, or where geological conditions make floating structures more attractive.
"Where you have waters 10 to 50 meters deep, they are going to build bottom-fixed. But there are large markets where they won’t be doing that, because they don’t have the shallow waters, or they have earthquakes," she says.