small wind efficiency depends a lot on the height of the turbine tower

Consider a proper height for your wind turbine. Wind turbulence and physical obstructions close to the ground reduce the wind speed and consequently the system output and its energy-efficiency.

That's a direct result of the cube rule: the power output of a wind powered system varies as the cube of the wind speed. In other words: if the wind speed doubles (or decreases by half) the power of the wind system will increase (or decrease) eight times.

Obstacles & wind speed

Wind turbines should be sited upwind of any obstacle, and that's the function of the turbine tower.

Use a tower to raise the turbine above fences, trees, buildings and other possible obstructions near the ground; that's very important for the success of your wind electric system. Obstructions create wind turbulence and decrease the wind speed dramatically.

This is particularly apparent with urban systems; they have very small towers - often just a small pipe - and that, and the obstructions affecting the wind flow and speed, make them typically ineffective... Towers are typically supplied together with the other parts of the wind power system; manufacturers require their turbines to be installed on their towers and within certain height limits.

Wind Lattice TurbineHow tall should a turbine tower be?

A general rule of thumb states that the bottom of the turbine blades should be at least 30 feet/9 meters above the top of any obstacle within 300 feet/90 meters of the tower.

Height and capacity of a wind turbine
The height of small wind turbines doesn't depend on the capacity of the turbine. Size and tower height are are not directly related. A 5-kWh turbine can have a tower from, say, 30 to 140 feet in height…
See also: Small Wind Systems Location

Local and state rules about Wind Turbine Systems height

Covenants may impose height restrictions to small wind turbine towers, in some areas: say, maximums of 30-40 feet/9-12 meters, which can have a very negative impact on the performance the turbines. Pay attention to it.

Types of small wind turbine towers

There are two main types of small wind turbine towers: the self-supporting or free-standing type, and the guyed type.Tilt-down towers are a good choice for small wind turbine systems. They provide an easy way of performing routine maintenance….

Guyed towers are the least expensive; they are common and easy to install, and come with different designs and materials (avoid aluminum towers: they are prone to cracking); they aren't easy to climb - an important feature for maintenance and repairs - and require more land than self-supporting towers.

Non-guyed tilt-up/cylindrical towers use pipe or tubing and a self-supporting design. They do not use guy wires and have a smaller footprint. These towers can include climbing pegs and are a little more expensive than guyed towers.

Mega-turbine towers
Mega turbines towers are made of tubular steel and their height varies with site conditions. In the Texan Snyder Wind project, in Scurry County, the 21 Vestas V90 3.0 megawatt turbines are mounted on 345 feet (104 m) towers.

Wind Guyed Pole TurbineLattice configuration

Lattice towers use welded steel profiles and are a cheap and tested option.

Most lattice towers aren't guyed, though there are guyed configurations: three-legged lattice structures suspended on all three sides by guy wires. Typically, they are climbable.

 

 

 

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