The following points constitute a simple guide to installing a small scale domestic wind turbine:

1. Get a reliable estimate of the wind speed at the proposed site
2. Mount the turbine as high as possible and ensure that it is well clear of obstructions (ensure that the turbine can be easily reached for inspection and maintenance).
3. Try to have a clear, smooth fetch to the prevailing wind, e.g. over open water, smooth ground or on a smooth hill.
4. Use the correct cable with adequate current carrying capacity (particularly important for low voltage machines).
5. Check the need for planning permission and try to minimise the environmental impact of the turbine.

• Planning issues

Nearly all small wind energy installations require planning permission and their erection should be carried out in consultation with other local stakeholders, i.e. such as neighbours. Deciding factors influencing the granting of permission include environmental considerations, access to the site, noise and visual effect. Overall, national planning policies support the development of small scale wind energy and Planning Policy Statement 22 (PPS22) sets out a clear national policy framework on renewable energy for planning authorities in England.

• Connection issues

Despite efforts by the electricity distribution companies to streamline their procedures, the process of obtaining an electrical connection to the public electricity network can be complex.

A wind turbine can feed electricity into the national grid, so long as the grid connection complies with technical and safety requirements. The national grid carries electricity at very high voltages, with a network of transformers to ‘step down’ the voltage until it reaches 230-240 Volts for domestic supply. Exporting power to the grid will involve making a connection at an appropriate voltage.

The power from a variable source, such as the wind, will tend to fluctuate. These fluctuations need to be moderated electronically so that the exported electricity matches the grid. Both the voltage and the frequency of the current needs to conform, for the very good reason that many electrical appliances would be damaged otherwise (230/240 Volts at a frequency of 50 Hertz is the UK standard for domestic supply).

The technical issues around grid connection need to be discussed with the appropriate network operator. Compliance with the relevant Engineering Recommendation is a legal requirement and is a job for a qualified engineer.

• Structural issues

It is important when mounting a domestic wind turbine on the side of a house or roof that the structure itself is robust enough to support the installation.

• Assessing the site

The most important aspect of any potential site for a wind turbine is, obviously, the strength of the wind. Wind speed can be measured by using an onsite anemometer which can be hired or contracted out to consultants. The more data that is collected the better the estimates for potential electricity generation will be.

In general, small scale wind turbines start to generate electricity in wind speeds of approximately 2.5-4 m/s with their rated optimum wind speed being 10-12 m/s. For instance, a 6 kW turbine at a wind speed of 5 m/s will generate an average of 11,000 units of electricity a year.

Small variations in wind speed can produce large changes in energy output. An 8m/s wind will produce 80% more energy than a 6m/s wind. Wind speed increases with height and it is essential that the knowledge of the local wind resource is comprehensive to maximise the potential of any give turbine.

Due to the relative immature of the technology and market there is not much data currently available on whether the siting of a turbine on a roof reduces yield due to turbulence or increases it due to a “wind flow enhancement” process.