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Large Wind Turbines

December 17, 2012
Paul Gipe

Henning Holst's Short History of the Danish Wind Industry

Henning Holst is one of Germany's pioneering community wind developers. Located in the center of the wind energy universe in Husum (the gray city by the sea) in northwestern Germany, he was there at the creation.

Holst spoke briefly at the Husum wind energy exhibition this past September about the early history of wind. When he speaks, I've learned from past experience, it's time to whip out my notebook and get to work. Here are a few notes from that presentation.

Tvind's Role

There were two wind turbines installed at Tvind, the radical community on the Jutland coast in the 1970s. The "Tvind" turbine is well known worldwide. Installed in 1978, the 2 MW machine is still operating.

But there was another turbine, not so well known, not so glamorous, because it was much, much smaller. While Tvind was 54 meters in diameter, this other turbine, the ugly duckling of the two, was only 9 meters in diameter. It preceded its big brother and was the first wind turbine in Denmark that used cantilevered, that is unstayed, blades. It was this turbine and the blades for it that led to the birth of the Danish wind industry.

The blades on the smaller Tvind turbine were developed by Tvind and because of its political philosophy, the technology was made publicly available - the first "open-source" blade design decades before the word was invented. Anyone could take the design, the mould, and build their own blades.

One of those doing so was Erik Grove Nielsen. He used the design to build 4.5 meter long blades under the nom-de-guerre of ?KAER-Vinge (Vinge being the Danish for "blade"). It was 1977, the blades used a crude Hütter flange for attaching the blade to the hub. Significantly, they would find out later, the blades had no tip brake for overspeed protection.

Folkecenter's Role

Now my notes are a little fuzzy here, so the exact sequence may not be historically accurate. Look for future articles on this topic.

Then Nielsen and Preben Maegaard at the Folkecenter for Renewable Energy began development of a 5-meter long blade in 1981.

Maegaard, a forceful personality, insisted that critical components of the wind turbine, including blades, should be readily available to all potential manufacturers. This was a key development as it enabled a flowering of wind turbine manufacturers, all using basically the same components. The story of HVK illustrates this.

HVK's Role with Vestas & Bonus

HERBORG Vind Kraft or HVK began building wind turbines in the late 1970s with a young inventor fresh out of college, Henrik Stiesdal.

In 1979 HVK built a 10-meter diameter turbine with OKAER blades and mounted the rotor directly on the Hansen gearbox.

Subsequently there was a fierce wind storm on the west coast of Denmark and a number of turbines lost their blades. HVK and OKAER realized they needed overspeed protection, mechanical brakes were not enough. This led to the adoption of pitchable blade tips like those that had been used decades before on the Gedser machine.

Vestas stepped into the picture. It's development of Darrieus turbines convinced Birger Madsen, another famous Danish pioneer, that they needed to take another approach.

HVK was teetering on the edge, leading Vestas to license the design. This resulted in Vestas' V10.

A short time later, Vestas designed its derivative the 55 kW V15 which included a separate main shaft with mechanical brakes on the main shaft. This was Vestas first truly commercial wind turbine.

Henrik Stiesdal, meanwhile, went on to Bonus, now Siemans where he is still the head of technology development.

Ground Up vs Top Down

As Holst notes, it was only five years from the time that inventors were relying on scrap parts to the development of true commercial wind turbines.

Summarizing this now world famous "ground up" development model, Holst says it was "NIVE, not Nibe". NIVE is a reference to the group founded at the Folkecenter for Renewable Energy. Nibe is a reference to the official, top-down, government funded development of large wind turbines. The Danish government through Risø National Laboratory developed two turbines at Nibe: Nibe A, a classic stayed-rotor design made famous by Gedser, and Nibe B, with a modern cantilevered rotor. These turbines became a technological dead-end, while the grassroots development of wind turbines ultimately prevailed.

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