wind towers

A wind turbine tower is not just a support structure. It raises the wind turbine so that its blades safely clear the ground and so it can reach the cleaner, stronger winds at higher elevations. As a general rule it is better to go for as high a tower as makes economic sense. At higher elevations the wind is usually much stronger. Power output from a wind turbine is a function of the cube of the wind speed so even small increases in wind speed from a taller tower can have a huge impact on energy production. The decision of what height tower to use will be based on the cost of taller towers versus the value of the increase in energy production resulting from their use. Usually when you buy a small wind system it comes packaged with a wind tower which is a good match for the size and scale of the turbine.

Another reason for going with a taller wind tower is that the air at higher elevations is generally less turbulent.  At lower elevations, say under 100 feet, the wind can often become quite turbulent due to obstructions from buildings and trees.  The uneven nature of the wind at these elevations puts much more stress on the wind turbine and will cause it to wear out faster. A general rule of thumb is to install a wind turbine on a tower with the bottom of the rotor blades at least 30 feet above any obstacle that is within 300 feet of the tower.

One temptation most homeowners should definitely avoid is attempting to mount a wind turbine on their roof.  First the wind that close to your house will be much more turbulent and not very strong.  Moreover, the turbine generates considerable noise and vibration which not good for the turbine and definitely not very good for you or your house. Always mount a small wind turbine on a tower of some kind.

Types of Wind Towers

There are many types of wind towers on the market today.  They vary in size and structure and are designed to support wind turbines of different size and output.  Here is a quick description of the different types:

• Guyed Tower - A guyed tower is one which is held in place with guy wires. The tower itself is often just a long steel pole which is 30 to 100 feet tall. There are usually three or four guy lines made of steel cable which run from the top of the tower to guy anchors on the ground which hold the tower in place. The anchors are usually set into a concrete base in the ground or held in place with augers that have been drilled into the ground. Guyed towers are often the least expensive type of wind tower and are often an excellent choice for a small residential scale wind turbine.  The one thing you have to consider is that a guyed tower needs considerable space because the guy wires extend well beyond the base of the tower. 

• Guyed Tilt-Up Tower - This is a type of guyed tower which has a pivot joint at the base of the tower so one can easily raise the tower initially or lower it to do maintenance on the turbine later. These type of turbines are one of the best options for residential scale wind turbines.  They can cost slightly more than a traditional guyed tower but can greatly reduce the hassle of setting up the turbine and  maintaining it. As with all guyed towers you need to have plenty of space both for the guy wires and so the tower can be laid down for maintenance.

• Freestanding Lattice Tower - This type of tower is made of wood, steel or aluminum lattice work. The classic wooden windmill used in the old west for pumping water is a good example of a wooden lattice tower. Today most lattice towers are made of steel for strength.  Because this type of  tower cannot be laid down it will usually include a built-in ladder so that someone can climb the tower to do maintenance on the turbine. The latticed frame includes many structural supports and so is usually extremely sturdy and holds up well in high winds.  Latticed towers usually cost more than guyed towers because they use more steel but they have the advantage that they take up less space.  This makes them ideal for more urban locations where there may not be space to put up a guyed tower.  They also work well in areas with very high or uneven wind conditions because of their structural strength.

• Freestanding Tubular Tower - This type of tower is constructed as a large tube often tapered at the  base.   On most of the larger towers of this type there is a ladder in the inside of the tube so that a worker can climb the tower to do repairs and maintenance on the turbine. Most large commercial scale turbines use this design. As the commercial wind industry has grown tubular towers for turbines in the 3 megawatt to 5 megawatt range have become quite large and tall.  Currently the tallest wind turbine in the world is in Lassow, Germany and is 673 feet tall. Typically, commercial wind towers are between 200 feet to 360 feet high and large enough to hold a huge turbine.  Taller towers generally means stronger wind, and because even a slight increase in wind speed can have a large impact on power production it makes economic sense for commercial towers to be quite tall.

• Floating Tower - A floating wind tower is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where bottom-mounted towers are not feasible. In most cases the wind turbines are held in place by wires or chains attached to weights on the ocean floor. One advantage of mounting turbines at sea is that the wind is strong and not disrupted by any terrain features. This makes the wind flow steadier and causes less wear on the turbine. The electricity generated is sent to shore through undersea cables.

  Floating wind turbines are a relatively new invention and are still very much in the development stage. There have been only two operational floating wind turbines used to farm wind energy over deep-water. Blue H deployed the first floating wind turbine 113 kilometers (70 miles) off of the coast of Italy in December, 2007. It was then decommissioned at the end of 2008 after completing a planned test year of gathering operational data. The first large-capacity, 2.3 megawatt floating wind turbine is Hywind, which became operational in the North Sea off of Norway in September, 2009 and is still operational. One reason that floating wind towers are being investigated is that by relocating wind farms into the sea there is less visual pollution as opposed to placing them just offshore. Also, depending upon the location they may be me less likely to obstruct sea traffic than towers near shore locations.