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Back In Black: At A German Wind Farm, Direct Current From The Company Edison Founded Makes A Comeback

Dorothy Pomerantz
July 19, 2016
The 1893 World’s Fair in Chicago was a high point in American history. The fair boasted the first Ferris wheel, the first moving walkways and the introduction of Pabst Blue Ribbon beer. But for many visitors, the highlight of the six-month-long event was the dazzling lights.
At night, the fair was lit by hundreds of thousands of incandescent bulbs. Although GE founder Thomas Edison had patented the light bulb 14 years earlier, no one had seen a light exhibit on the scale of the Chicago fair.

However, the momentous achievement marked a rare failure for Edison. He had proposed lighting the fair with direct current (DC) power. But his rival, George Westinghouse, came in with a cheaper bid to light the fair with efficient alternating current (AC) technology developed by Nikola Tesla. It was the last salvo in the so-called "war of currents." Westinghouse and Tesla won and AC has been the accepted standard for power transmission ever since.

General Electric engineer Charles Steinmetz works in the laboratory building at his Wendell Avenue home in Schenectady. Thomas Edison invented the light bulb but he lost the "war of currents." Afterwards, the legendary GE engineer  Charles Steinmetz helped electrify America with alternating current, but DC is now coming back. Image credit: Museum of Innovation and Science Schenectady

But DC never disappeared. Direct current still makes more sense when powering devices such as cell phones, PCs, flat screen TVs and even electric cars because a one-way energy flow is all that is needed.

Now, however, DC is ready to roar back. Germany’s massive DolWin3 offshore wind project will be using high-voltage direct current (HVDC) technology to move electricity over 100 miles of subsea cable from turbines spinning in the North Sea to the terrestrial power grid without significant losses. This is the first application of GE's HVDC system. Other HVDC projects have been operating or are planned for Europe, Asia, the Americas and also Africa.

HVDC cables are sometimes called "electrical super highways." New technology breakthrough allowed them to be more stable and lose less power than AC lines over long distances and also when used as underwater cables. HVDC is extra powerful when combined with a renewable energy source like a wind turbine, which often generates power that fluctuates. The technology's inherent stability makes renewable electricity easier to manage.

DolWin3 - Installation of jackets (copyright Nordic Yards) [1] The yellow installation "jacket" in the front of the image will serve as an offshore platform for GE's DC technology. Image credit: Nordic YardsIn Germany, one end of the cable will be connected to an offshore converter platform, which changes the power generated by the turbines from AC to DC. At the other end, it will terminate in the north German town of Dörpen. There, another set of converters will switch the electricity back into AC and feed it into the grid.

This is the first time GE is using high-voltage direct current to bring electricity from the sea to land. The project will generate 900 megawatts at peak output, enough to replace a conventional power plant and supply 1 million homes. GE is supplying the offshore and onshore converter stations, including the power transformers and the underground cables that will carry the electricity.

Efficient, long-distance power transmission is important because offshore wind farms can be twice as productive as onshore installations. "Offshore wind as an energy resource is more stable than onshore," says Cederick Allwardt, technical project director for DolWin3 at GE. "The flow of wind is more streamlined because you don't have buildings or hills to get in the way. "

DolWin3 is part of Germany’s Energiewende transition from nuclear power and conventional power sources such as coal to renewables. Its goal is to generate 80 percent of all electricity from renewable sources by 2050.

20160513_DolWin3 Jacket Sailout (copyright Nordic Yards) The 5,000-ton installation platform for the DolWin 3 project leaves port. Image credit: Nordic Yards