Introduction to wind power
The pros and cons of wind power regularly fill the pages of newspapers, yet it’s still quite difficult to pin down the facts about it. Two things there’s no dispute about are that:
- the UK is the windiest country in Europe, and
- the wind blows most in winter, which is when we use most electricity.
There’s considerable agreement that wind has huge potential for affordable, large-scale generation through onshore and off shore wind farms.
At a domestic level, things are less clear. Whether wind is right for you will depend on your location and circumstances. If you have a clear site for the turbine, away from obstructions, with high average wind speeds, it’s worth investigating.
Is wind power suitable for my home?
The success of wind power depends totally on the suitability of your site. The key factors are:
- An average wind speed of at least 5 or 6 m/s (metres per second).
- No obstacles nearby which might reduce the wind speed or create turbulence. These include buildings, trees or hills. An ideal site is a smooth hill top with a clear, open stretch to the prevailing wind.
- You are able to connect the turbine to your property and to the national grid.
Wind Speed: You can get an indication of wind speed in your area from the UK windspeed database. Speed is given in meters per second at 10m high. However, this should be viewed as a starting point only, as the figure is an average for the square kilometer that you live in.
Actual wind speeds for your site can vary
enormously from the average. Field trials by the Energy Saving Trust and Encraft both
found that average wind speeds at many sites in the trial are significantly lower than indicated by the DTI database.
RenewableUK provides an excellent free guide to installing a small wind system.
Site: The research cited above found that building-mounted wind turbines in urban and suburban areas are unlikely to perform well, and where building mounted turbines did perform well, a much better return would have been achieved by installing a mast-mounted wind turbine.
In terms of connection - both to the grid and to your property - this is likely to be by underground cable. The more cable you need, the more expensive it's likely to be.
Noise: data on noise is generally available from the manufacturer. It is measured in decibels per wind speed. For example, the Proven 6kW wind turbine creates a noise of 45dB at a windspeed of 5m/s and 65 dB at 20m/s. This compares with whispering, or leaves rustling (30dB) or the noise of city centre traffic 95dB. Click the link for more on wind turbine noise.
Wind speed lookup
Please note this is based on an average wind speed in your postcode area, and is only an indication. If you have trees, buildings etc between you and the prevailing wind the speed may well be lower than shown.
What size / cost for wind turbines?
Micro turbines, which are generally in the range of 500 watts to 2.5 kW, will cost around £2,000 upwards installed according to the Energy Savings Trust.
Small turbines, ranging in size from 2.5kW to 8kW, are a much heftier investment. Prices are likely to be anything from £11,000 upwards.
- A mast-based grid connected 6kWp Proven Engineering costs c. £25,000 plus groundworks to install.
The size you choose will depend on your site, the amount of power you want to generate and how much you want to spend. Connecting to the grid is expensive, and probably won’t be worth it for less than a 2kW turbine. A 5kW system is likely to generate around 15,000kWh of electricity in a year – which means it would cover its cost in 10 years.
The cheapest way to install a wind turbine is to make your own. The Centre for Alternative Technology publishes a book Windpower Workshop which describes how to build your own from second hand and scrap materials.
The Feed-in tariff guarantees an income for electricity generated. For the period 1 October 2014 - 31 March 2015, the tariffs for new installations are below.
1.5kW or less: 16.00 p / kWh
>1.5kW - 15kW: 16.00 p / kWh
>15kW - 100kW: 16.00p / kWh
>100kW - 500kW: 13.34p / kWh
>500kW - 1.5MW: 7.24p / kWh
>1.5MW: 3.07p / kWh
The export tariff is: 4.77 p/kWh
Click here to download the full feed-in tariff rate table for all (non-solar) installations
The feed-in tariff payments are tax-free (for domestic customers), index-linked, and will continue for a 20 year period. To qualify you will need to use an MCS accredited installer and product.
Do I need planning permission for wind turbines?
There are permitted development rights for (a very small number of) small wind turbines. However, none of the turbines currently accredited by MCS meets the criteria for permitted development, so if you want to get the feed-in tariff you will need to apply for planning permission.
Your local authority will be looking at the visual impact, noise, vibration, electrical interference (with TV aerials) and safety, in making a decision. More information can be found on the planning portal.
If you want to install a building mounted turbine building regulations will normally apply around size, weight and force exerted on the mounting points. They also apply to the electrical installation work.
How do wind turbines work?
Wind turbines are mounted either on a building or, preferably, on a mast.
- The wind rotates the blades of the turbine
- which turns a rotor shaft
- which generates low voltage DC (direct current) electricity.
- An inverter converts it to AC (alternating current or mains type) electricity.
What happens next depends on whether or not the system is connected to the grid.
In off-grid systems the power generated charges a bank of batteries. To get the most from the system, you can programme it to divert electricity to other uses such as water or space heating if the batteries are full.
If you are connected to the mains grid, then when you generate more electricity than you use, you can sell the excess to your supplier. When you are not generating enough to cover your needs, you can buy electricity from your supplier.
Micro turbines, mounted on the roof of your house, are designed to supplement the mains electricity supply, reducing the amount you need to buy. They can plug into a standard 13amp socket.
Turbine life is up to 22 years. They need servicing every few years to ensure they are efficient. Battery life is shorter – about six to 10 years.
What’s the best mounting for wind turbines?
Turbines can either be mounted on a free standing tower (mast) or micro turbines can be fixed to the roof of a building.
Wind speeds increase with height, so it is generally considered best to put your turbine on a mast. A small increase in the wind speed will lead to a proportionally much larger increase in the amount of electricity generated (the change is cubed – so twice the wind speed will lead to eight times as much power; half the wind speed will generate an eighth as much). A tower also helps avoid turbulence caused by trees or buildings.
Research by Warwick Wind Trial
and the Energy Savings Trust field trials both found that no building-mounted turbine performed as well as expected, and where micro turbines are viable,
people would be better off going for larger systems. Wind turbines are generally not suitable in urban or suburban settings.
Calculate wind power potential
How do I choose a wind turbine?
There are two measures of performance for wind turbines: a power rating and the energy output for the turbine. The latter, which is measured in kWh (kilowatt hours, the unit that electricity is measured in), is the most significant. It’s no good having a high power rating if the turbine needs hurricane strength winds to turn it and it stands idle a good deal of the time.You can find a list of the performance data provided by manufacturers on a variety of micro and small turbines at RenewableUK. Reviews of micro and small turbines are available at Better Generation.
While these figures can indicate comparative performance of turbines, the actual performance depends entirely on the conditions at your site. The Warwick Wind Trials found that variation in the performance of the same wind turbine can be as much as 28 times when comparing two sites less than a mile apart.
If you wish to claim the feed-in tariff you must use a MCS accredited installer and product.
More information on wind power
From the blog:
Your questions answered
Choosing an installer
GeneralWind power: accessible yet frustrating