US backs advanced offshore wind with $140m
Last updated on 8 May 2014, 1:21 pm
US to test ‘hurricane-resilient’ wind turbines in three projects, supplying extra 67MW of clean energy to grid
By Gerard Wynn
The United States will back three advanced offshore wind farms, including floating and hurricane resistant foundations, with up to $47 million each, the Department of Energy said on Wednesday.
The United States three years ago published a “National Offshore Wind Strategy” which targeted some 54 gigawatts (GW) of offshore wind by 2030, and 10 GW by 2020.
The latest projects, totalling 67 megawatts, are an attempt to drive down costs and so help achieve these targets, and will be installed across the US Atlantic and Pacific coasts by 2017.
“The Energy Department is working with public and private partners to harness this untapped resource in a sustainable and economic manner,” said US energy secretary Ernest Moniz.
“The offshore wind projects announced today further this commitment – bringing more clean, renewable energy to our homes and businesses, diversifying our energy portfolio, and reducing costs through innovation.”
One criticism of offshore wind has been its high cost, especially after taking into account grid connection costs, which make it more expensive than far less physically challenging solar power, British subsidy levels show.
The United States presently has negligible installed offshore wind power, but is in the process of developing some 5 GW of capacity, according to the American Wind Energy Association.
The country is lagging far behind Europe, which already has some 6.6 GW installed, and in particular Britain with some 3.7 GW, show data from the European Wind Energy Association.
The turbine suppliers for the three US projects were all based in Europe, from Siemens (Germany), Alstom (France) and Darwind (the Netherlands).
The US demonstration projects aimed to reduce costs through innovation, the Department said. All three used direct drive technology which eliminates the need for a gearbox, which increases efficiency and reduces complexity thus cutting maintenance downtime.
Two projects will test a so-called twisted jacket foundation, which is fitted to the sea floor using three legs twisted around a central column.
Such a foundation uses less steel than a traditional “radio mast” underwater structure, and was proven in hurricane Katrina to be exceptionally strong.
One of the projects would be piloted far off the coast of Virginia, to test hurricane resistance.
“The Dominion project will install and test a hurricane-resilient design to ensure that offshore wind facilities placed in hurricane-prone US waters are reliable, safe, and cost-effective,” the Department of Energy said.
The third project tests a semi-submersible, floating structure, which is expected to be one of the biggest developments in offshore wind, allowing developers to access deeper water which often also has more wind.
“More than 60% of the offshore wind resources within 50 nautical miles of US coasts are located in deep water, where traditional bottom-fixed foundations cannot be used.”
“In order to maintain their position, these (floating) foundations use a series of mooring lines and anchors attached to the sea floor. Semi-submersible foundations can be assembled on shore and then towed out to sea fully assembled – or taken back to shore for repairs – eliminating the need for expensive specialized vessels and reducing maintenance costs.”
The semi-submersible foundation is shaped like a triangle, with the turbine located on one of the three columns that form the structure. In the same way a ship uses extra weight, or ballast, to remain stable.