Wind technology that can bob about on the waves will open up vast amounts of opportunity, but does it work?
What’s afloat? Wind turbines, as it turns out. The world’s first floating wind farm is nearing completion 15km off the coast of Aberdeen, Scotland – a 50MW plant consisting of six turbines. Swimming not far behind it, Royal Dutch Shell and Scottish Power have proposed a gigawatt-scale plant elsewhere off Scotland’s coast.
Offshore wind farms where turbines are fixed to the seabed can be built in water shallower than about 60 metres, which leaves about four-fifths of windy ocean locations around the world off developers’ maps. The International Energy Agency estimates there is enough wind resource in gusty, deep-water regions to satisfy the world’s 2040 energy needs by more than 10 times.
Fixing a fan to the top of a tower and bolting it to the ground is technology a child can understand, but what if there’s no ground? Wind turbines are tall and top-heavy, and they produce gyroscopic forces that, on land, can be transferred to deep concrete foundations. Adapting the technology to a shifting, liquid surface has been no trivial task. Engineers who started with prototypes in university wave pools have since scaled up their devices into demonstration units tested off the coasts of Portugal, Norway and Japan.
So far, the propellerheads at wind technology companies have settled on four methods of floating wind machines at sea.
American company Principle Power offers a semisubmersible solution. In one version of this a buoyant steel triangle is formed by two water-filled ballast tanks that balance a turbine, which makes the third leg of the device. Once deployed, water is pumped around the hollow triangle structure to keep it stable.
Norwegian firm Equinor has taken a simpler approach, creating an enormous, 80-metre-tall bottle with a fan on top – almost like the proverbial message in a bottle. The entire thing is counterweighted by its heavy bottom, filled with rocks, water or anything that’s cheap and weighty.
Two other designs include Glosten, from the US, which in partnership with GE has developed a star-shaped structure with a turbine at its centre that can be tethered to the ocean floor, and Norwegian firm BW Ideol, with an empty square barge that is stabilised by water that gurgles around inside its frame. A prototype off the coast of Japan has made it through three typhoons, the company says.
Off the beach
Onshore wind energy has proven itself about a thousand times over in Australia but offshore generation is still somewhere over the horizon, although there are 12 proposals in the works for capacity totalling about 25GW.
Many of those offshore wind proposals are located near ports and some are expected to power onshore hydrogen facilities. Only one of the developers so far is thinking of using floating turbines, a 1.5GW proposal off the coast of Victoria near Gippsland. None of the proposals has reached construction phase.
Offshore wind has also arrived on the radar at the Australian Energy Market Operator, which sees about 40GW of capacity at four wind zones off the coast of NSW, Victoria and Tasmania.
Investors and engineers will be attracted to a new source of uncorrelated resources in offshore wind, as they fret over the slow withdrawal of dispatchable coal and gas. People who live within the many renewable energy zones in Queensland, NSW, Victoria and South Australia where new wind and solar projects are expected to take root will also be interested in offshore wind. If it’s out of sight, it’s out of mind.