As their name suggests their blades rotate around a vertical axis. This is quite different to the horizontal turbines which look more like an airplane propeller.

One of the advantages of a vertical turbine is that it works with wind from any direction. This means that the design can be a bit simpler and have less mechanical parts than the horizontal type. Horizontal turbines usually have a tail fin to help them orientate into the wind correctly.

Vertical axis turbines come in two different types. There are lift turbines and drag turbines. Both have their advantages and disadvantages.

The lift turbines are sometimes known as Darrius Turbines after their inventor George Darrius. The rotating blades are aerofoil in design much like an airplane wing. The leads to more efficient operation, so that for a given power output the span of the blades can be smaller. While this might seem an attractive property for the urban environment, greater blade speed leads to greater noise.

Another issue with the lift style of blade is they are not actually self starting, they need a small push to get them going. This initial push can be supplied by a power supply or by incorporating a drag blade in the turbine

The drag turbine as we have discussed is not as efficient as the lift turbine, but it does have a number of advantages. It is self starting. This means that the design can be simpler. It also runs more slowly. This means it is less noisy. Overall drag turbines have been available for longer than the lift turbine and have a good track record of operation in the real world.

Wind power has been the poor relation of alternative power generation for the domestic market, which has tended to focus on solar power. The irony is that wind power can be more cost effective than solar providing the conditions are right. In order to consider wind power you will need an average speed of at least 5 meters per second or 11 miles per hour. The other important factor is turbulence. As the wind strikes building and trees turbulence is created. For efficient operation turbines need a nice clean wind.

Before you go to the expense of buying a wind turbine, which can cost around $10,000 to $15,000 for a 1 KW unit, it is essential that you test out the micro environment around the proposed site of installation this can be done with a measuring device called an anemometer