Offshore wind farms sparked by HVDC
A unit of E.ON, Germany’s largest utility, is working on a project to link the world’s largest offshore wind farm to the German power grid at minimal impact to the environment.
The 400-megawatt (MW) wind farm, located 130 kilometers from the coast in the North Sea, is expected to save carbon dioxide emissions of 1.5 million tons per year by avoiding the need for additional fossil-fuel generation.
ABB is connecting the park —the most remote wind farm in the world—using high-voltage direct current (HVDC) transmission technology. Although HVDC has been available for more than 50 years, ABB’s development of the technology to produce the related HVDC Light about 10 years ago provided the technological means to build wind parks far from the coast, according to the company.
Germany aims to generate 20% of its power from renewable sources by 2020, compared with about 14% in 2007. Wind power accounted for about 40% of Germany’s electricity from renewable sources last year, but with the best onshore locations already developed, the country’s utilities are turning to offshore sites.
The main attraction of going offshore is the enormous wind resource available. Average wind speeds can be 20% higher than on land, and the resulting energy yield from wind farms as much as 70% higher.
While three-phase alternating current (AC) links are a cost-effective way to connect small offshore wind farms near the coast to the electricity network, HVDC Light is emerging as the potential technology of choice for more distant offshore parks.
According to ABB, power can be fully controlled using HVDC Light, so that the intermittent electricity supply from a wind farm cannot disrupt the grid. An HVDC Light transmission system can also be started from a powerless state, such as could be the case if the wind hasn’t been blowing at all. The company also notes that with HVDC, very little electricity is lost during transmission, even over long distances.
The use of oil-free cables running underwater to the coast, then underground to a substation 75 kilometers inland, is another way in which the transmission technology minimizes the environmental impact of the NORD E.ON project. The 80-turbine farm is scheduled to enter service in 2009.