Solar Wind Canada

Technology: Tower & Foundation: Tower Types and Designs

Overview

In order to achieve optimal performance of a wind turbine, it is necessary to position turbine at a height in which laminar wind flow can be accessed. Depending upon the location of the site, the tower may range from 10m to 30m for a typical wind turbine installation. Towers come in a variety of designs, the predominant design being the tilt-guyed tubular tower, followed by guyed-lattice towers, and finally free-standing mono-pole or lattice tower.

Tilt-tubular Tower

A typical 25m tilt-tower (click to view enlarged image)

These popular towers are designed to provide an economical manner of installing wind turbines into laminar wind without the need for heavy equipment such as those required for the larger commercial turbines. The basic components of such towers is a tubular central pole, ranging from 2" to 4" in diameter, guy-sets or clamps that fit onto the tower central tube and to which the guy wires are attached, four sets of guy wires and anchors, guy pole and bases/foundations for the central pole and guy anchors.

This design requires the tower to be guyed in four directions. This enables the raising and lowering of the tower safely, unlike the 3-guyed transmission towers, which require special heavy-equipment such as cranes to raise and lower the towers. The combination of correctly spaced guy-anchors, and the number of guy-wires installed will create a very stable tower structure, offering decades of service with little or no maintenance. The other advantage of tilt-towers is to permit servicing of the turbine without the need to climb towers. The procedure for lowering the tower is the exact reverse of the same procedure raising the tower. This minimizes the cost of maintenance over the life of the turbine, and eliminates risks with respect to climbing the tower. For shorter towers, in the range of 10 - 15m, the tower with turbine can be raised or lowered with a manual winch with the help of three people. Higher towers will also require a winch, preferably a worm-type of winch, one which is secured well to a vehicle such as a pick-up truck.

A typical 30m guyed-lattice tower
(click to view enlarged image)

Tilt-towers are also available in lattice form, sharing the same properties and installation as the tilt-tubular towers, however, these are generally more expensive as compared to the tubular towers, and do not offer any significant advantages over the tilt-tubular towers.

Guyed-lattice Tower

The guyed-lattice tower shares many of the properties with the tilt-lattice tower, except in one aspect, size.

A mono-pole free-standing tower supporting a 10kW Bergey turbine. (click to view enlarged image)

The guyed-lattice towers are designed to support larger turbines with roters ranging in diameter from 3m to 10m. These towers will require heavy equipment to raise and lower the towers, however, the towers do allow servicing through climbing the tower.

The guyed-lattice tower is secured to a base-plate on the tower foundation and bolted in place. Although there are claims to a tilt-lattice tower that can be raised and lowered with a hinge-like apparatus in its base, these are very uncommon, and therefore, the usual design is a fixed-base tower. The guyed-lattice tower is raised and lowered with the turbine attached, similar to the tilt-tubular tower. These towers will require only three guy-wires and anchors sets for the entire tower, unlike its tilt-tubular counterpart.

Free-standing Mono-pole / Lattice Tower

The free-standing tower, whether mono-pole or lattice tower is the strongest tower but also the heaviest. It is usually installed using a crane. Although it is possible to have hinges installed on this type of tower, the crane or other heavy equipment is still necessary for tower raising and lowering. This tower has the advantage of no guy wires so that it may be the best option for places where ground space is limited, and is generally, less visually obtrusive as compared to the guyed-tower designs. SOLAR WIND Canada is working with sources to make available free-standing mono-pole towers as an alternative to guyed-lattice towers for the larger turbines, and is working with a similar design for the smaller turbines of 1kW rating.