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small wind
Anyone interested in installing and maintaining a small wind generator on a tower of any height faces a daunting task: assembling and erecting a 100-foot tall, 4,000-pound steel tower is a formidable job for even a trained crew, let alone the do-it-yourself homeowner. Once the tower is installed, another challenge arises since the tower must be climbed to install or service the wind turbine. One small wind turbine owner told me that if he were meant to be 100 feet in the air, he would have been born with 95-foot legs! Enter the tilt-up tower. Tilt-up towers are guyed lattice or pipe towers that are assembled on the ground with the wind generator perched on top and raised to a standing position from ground level with a winch, truck, or tractor. When you need to work on the wind turbine, the operation is reversed and the tower with turbine is lowered back to the ground. This technology eliminates the need for climbing, so even those who are absolutely terrified of heights can install and service their own wind turbines. Tilt-up towers are similar to guyed towers, but instead of being guyed in the minimum three directions like the familiar radio transmission towers, they are guyed in four directions. This is because it is not possible to safely raise or lower a three-guyed tower. When a three-guyed tower is lowered to about a 45° angle, "down" to the tower is no longer straight below the tower, but off to the side. As a result, the tower, with its now slack side cables, begins its descent in a new direction. A 100-foot tower with a 500-pound wind turbine mounted on it means that the equivalent of 50,000 foot pounds of force are being exerted on the slack guy cables as they become taut when the tower inevitably falls. The likely result is a seriously damaged tower and wind generator. The addition of a fourth guy direction eliminates this problem for tilt-up towers. In order to transfer loads to safely raise or lower a tilt-up tower, a structure known as a "gin pole" is added at the tower’s base, making the tower look "L" shaped at the bottom. Additionally, the base of the tower is hinged, and there is some sort of pulley system incorporated between the gin pole and one of the tower anchors to raise and lower the tower. All of this makes the installation of a tilt-up tower slightly more complex than a standard three-guyed wind generator tower. The added hardware, cable, and concrete also raises the cost slightly over the three-guyed tower, but most non-climbers are more than happy with the fact that climbing is no longer required. Bergey Windpower sells a climbable lattice tilt-up tower for their 7-meter turbines. While it’s designed specifically for the 10-kW BWC EXCEL, any wind turbine up to 7 meters could be mounted on this tower with an appropriate stub tower. In addition, Bergey sells the NRG Systems TallTower for its smaller turbine, the BWC 850. Both of these towers are complete with all components provided except the holes in the ground, concrete, and rebar. Lake Michigan Wind & Sun sells two different tower kits for different sizes of wind generators. The 4-inch tube kit will support a wind turbine with up to a 2.7-meter rotor, and the 5-inch pipe kit will hold a wind generator with up to a 4.5-meter rotor. Both kits include the necessary couplings, anchors, pivot assembly, guy cables, turnbuckles, and hardware. Twenty-foot lengths of tube or pipe should be purchased locally to eliminate expensive shipping costs. Holes, concrete, and rebar are also extra costs. The towers from both companies were engineered to hold the turbines they were designed for, thereby eliminating all guesswork on the part of the homeowner when applying for the required building or zoning permit. For information on tilt-up towers, contact Bergey Windpower Co., Inc., by phone, (405) 364-4212, or fax, (405) 364-2078, or Lake Michigan Wind & Sun, Inc., by phone, (920) 743-0456, or fax, (920)-743-0466. -- Mick Sagrillo, Sagrillo Power & Light Co.
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