Operation of Ulrich Hütter’s StGW-34 at a test site in the Schwabian Alps

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This 5.5 minute film shows operation of Ulrich Hütter’s StGW-34 research turbine at a test site in the Schwabian Alps (identified as Stötten-Schnittlingen above Geislingen/Steige in the film) from 1957 to 1968. Sepp Armbrust conducted the field tests and made the film as noted in the German text.[1]

The film was mislabeled in NASA’s archives as a film of the Smith-Putnam turbine. I came by the video through Gabriel Altman who is researching the Smith-Putnam turbine.

Note the detail in the film of the yaw drive screw and the yawing of the nacelle. The operator is also shown pitching the blades from the controls shed seen below the tower. Note especially the wobble of the nacelle with the blade passing the tower, a characteristic of two-bladed downwind rotors.

At 40 seconds into the film, the camera reaches the summit and you see two turbines in operation. The larger turbine is the StGW-34 that the film is about. The second, smaller turbine is a derivative of the Allgaier 10, a wind turbine famous in its own right.

Allgaier, now a diversified manufacturer of automotive components, began serial production of the Algaier 10 in the early 1950s. The company built from 150 to 200 of the sleek three-blade, downwind turbine designed by Hütter.[2]

Allgaier 10. Three-blade downwind 11.3-meter (37-foot) rotor with fantail developed by Urich Hütter in the early 1950s. Several museum pieces remain, including this one in Holzhausen, Germany. Note the work platform, integrated 10 kW drive train, blades with full-span pitch control, and characteristic Hütter flange at the blade root near the hub. Though it was a downwind turbine, it used a fan tail (the small rotor) to orient the rotor downwind, a feature overlooked by many later engineers. This unit is one of six that was installed by Klöckner-Moeller, a manufacturer of electrical components. 2005.

Hütter’s Allgaier turbine remains distinctive in the annals of wind energy. It used three slender airfoils that are bolted to the hub with a flange that would become Hütter’s most significant legacy. The rotor incorporated a sophisticated pitch mechanism for closely regulating rotor speed. The integrated drive train creates a compact pleasing nacelle. And unlike many later downwind designs that tried to emulate Hütter, the rotor was mechanically oriented downwind rather than rely on passive yaw. And the whole assembly typically rested atop a tower of three tubular legs with a work platform. Until the rise of the Danish wind industry in the 1980s, this was the world’s most successful commercial-scale wind turbine.

The version in the film has only two blades.

However, Hütter began a commissioned project to design a wind turbine nearly ten times larger. In doing so, he greatly advanced the fledgling field of composite materials, and carried his quest for high tip speeds to the extreme. The result was the StGW-34, a 34-meter diameter wind turbine with a two-blade, teetering rotor. The 100 kW turbine was intentionally designed to have a very high specific area of nearly 10 m²/kW.

The StGW-34 was connected to the grid at the test field in December 1957, and subsequently began testing in 1958. It operated intermittently as a test vehicle until it was scrapped a decade later. As an experimental turbine it suffered extensive outages, eventually throwing a blade in 1961.

It was the design—and the redesign–of these blades in fiberglass that pushed the boundaries of this new technology. The blades were extremely long for the period. This size wouldn’t be seen commercially until three decades later. More importantly to the development of wind energy was how Hütter attached the fiberglass filaments around the bolts—or bolt holes—in a wide diameter flange. This became known as the Hütter flange.

Hütter’s legacy is not high tip-speed ratios, or light-weight downwind, teetered rotors. From his dissertation to the StGW-34, Hütter had proposed a series of high-performance downwind rotors, including a brief foray to a one-blade prototype with an extremely high tip-speed ratio of 12. These design characteristics have all proven commercially unsuccessful.

Instead, Hütter’s legacy is his aesthetic sense that wind turbines must be pleasing to the eye. It is also his insistence on wind turbines designed for high specific area that can be used in areas of low to moderate winds–where most of the world’s people live. It is also his contribution to making blades from composite materials and for a practical and durable method of attaching them to the rotor hub: the Hütter flange.

Hütter gave us the modern wind turbine blade. It was not Hütter that gave us modern wind turbines.

At about 1 min 30 sec you can get a sense of scale as a man climbs the tower. Note that he’s climbing the tower without a helmet or any form of fall protection. This wasn’t good practice then and it certainly isn’t now.

Since the camera is filming the man climbing the tower and then shows the man standing beneath the teetered hub there’s obviously two people on the work platform while the turbine is in operation.

There is also a scene showing the slip rings. It’s not clear if the slip rings were for both power and sensors or just sensors. Today power in a commercial wind turbine is carried down the tower in a continuous cable. There are no slip rings.

[1] Sepp Armbrust. “REGULATING AND CONTROL SYSTEM OF AN EXPERIMENTAL 100-KW WIND ELECTRIC PLANT OPERATING PARALLEL WITH AN AC NETWORK.” In Proceedings of the United Nations Conference on New Sources of Energy: Solar Energy, Wind Power and Geothermal Energy, 7, Wind Power: 201–5. Rome: United Nations, 1961.

[2] Handschuh, Karl. Windkraft gestern und heute: Geschichte der Windenergienutzung in Baden-Württemberg. Staufen bei Freiburg: Ökobuch Verlag, 1991, p. 64.