How do wind turbines work?
Put very simply, the blades of the turbine catch the wind. The wind blows the blades, and this movement spins the turbine, generating electricity. The stronger the wind that is blowing, the more electricity is produced.
Technical information made simple
There are two types of domestic-sized wind turbine:
Mast mounted: these are free standing and can be put up in exposed positions such as in a large garden or nearby field, but you need to have the space. They have a capacity of around 2.5kW to 6kW.
Roof mounted: these have a smaller capacity than most mast mounted systems, typically around 1kW to 2kW. They are usually installed on the roof of a home if it is sufficiently exposed to the wind.
The capacity of a micro-wind turbine is described in kW, though this isn’t as accurate as it could be because different turbines reach their described capacity at different wind speeds. Because of this, the BWEA (British Wind Energy Association) Reference Annual Energy is also used to provide a measure of the energy performance of a turbine. There is also the BWEA Reference Sound Level describes the level of noise the turbine produces as heard from 25 and 60m away, rounded to the nearest decibel.
- When the wind blows over a micro wind turbine it turns the turbine’s blades. This motion turns the rotating shaft the blades are connected to. This shaft, in turn, sits inside a generator. The part of the shaft inside the generator is surrounded by a magnetic field, meaning that when the shaft turns it generates electricity. Smaller turbines’ blades can be attached directly to a generator.
- The turbine produces DC electricity. This electricity flows through an inverter, which sits between the turbine and your home’s electrical wiring. The inverter converts your DC electricity into AC electricity, and this electricity can then be used to power the lighting and appliances in your home.
- You have a choice as to whether you connect your turbine to the Grid. If you do, you can qualify to receive FIT payments for the electricity you generate and the surplus electricity you export to the grid. However, if you live in a rural location remaining off the Grid may be useful as you can then store your surplus electricity in batteries to use when the supply from your turbine is low, allowing you to be less reliant on electricity from the Grid.
- If you connect your turbine to the grid, any electricity that you generate but don’t use is automatically exported back to the grid. Similarly, any electricity you need to use from the grid is automatically supplied, for which you will be charged, though you will make a saving on your electricity bill overall.
The FIT scheme is a government backed scheme designed to reduce the payback time for renewable technology installations. If you qualify, it pays you per unit of electricity generated, regardless of whether you use it, and for every unit generated and then exported. These payments are made according to tariff rates which are set when you sign up, and the rates are linked to the RPI too. Under current rules, you will receive these payments for 20 years. Current tariff rates for a standard (1.5-15kW) installation are 21.65p/kWh, and the export rate is 4.64p/kWh. A typical, well sited mast mounted turbine could make £160 a year from the Export Tariff and £2,700 a year from the Generation Tariff. For more information visit our FIT page.
You can get the cost of the installation paid for you using a loan from the Green Deal scheme. Another government-backed initiative, it collects your loan repayments through the savings your system makes on your energy bill, making the installation in effect free to you. Visit our Green Deal page for more information on the scheme.
If you are planning to install a domestic wind turbine it is recommended that your location is exposed to an average wind speed of 5 meters per second to make the turbine a worthwhile investment. You can test the wind speed of your location (or even test multiple locations) using an anemometer, which should be placed in your location for at least 3 months but ideally 12 months.
- Do I need to own a field to have a wind turbine?
- It depends on whether you're considering a roof mounted or pole-mounted (freestanding) system. Pole-mounted turbines do tend to work best in exposed locations such as fields, as they tend to experience less turbulence caused by obstacles such as buildings and trees. The ideal location for a freestanding wind turbine is at the top of a gentle slope.
- What is the best wind turbine type and height for me?
- Factors such as whether you want a roof mounted or freestanding system, planning permission and any limitations to foundations may dictate the type and maximum tower height to be considered, but in general, the higher the tower, the higher the average wind speed that the turbine will experience. A taller tower should generate sufficient extra energy to justify any additional cost, especially if there is turbulence created by nearby trees or buildings that can be avoided with extra height.
- How much do wind turbines cost?
- A typical 1kW roof-mounted wind turbine will cost around £2,000, with larger 2.5kW and 6kW freestanding (pole-mounted) systems costing around £15,000 and £22,500 respectively.
- What maintenance or servicing is required for a wind turbine?
- You should get your turbine checked by your installer or another accredited technician every year, which should cost between £100 and £200. Your inverter may need to be replaced once during the turbine's 20 year lifetime - this costs between £1000-£2000 for a large freestanding system. Turbines with batteries (off-grid systems) will need their batteries replaced every 6-10 years.
- How much of the time do wind turbines produce electricity?
- Wind turbines produce electricity 70-85% of the time, but they generate different outputs dependent on the local wind speed. Over the course of a year, a small wind turbine in the UK will generate about 7.5% (for roof mounted turbines) to 30% (for larger turbines) of the amount it would generate in a constant strong wind. This is known as its 'load factor' (or 'capacity factor').
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