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.
- Will a wind turbine work if I live in a built up area?
- The industry tends not to recommend that a domestic wind turbine is installed in an urban environment for a number of reasons, including: increased turbulence, resulting in higher stresses on the turbine and lower energy capture for any given wind speed; increased margins of safety required when more people are living and working near the turbine; additional measures possibly required to limit the transmission of vibrations into the structure of the building and lower average wind speeds in a city environment reduce the annual energy capture.
- 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.
- What size wind turbine will I need?
- The size of the turbine that's right for your property will depend on a few factors, including whether you want to have a roof mounted or freestanding system, your local wind speeds and the planning restrictions in your area, You should check with the Government's Planning Portal and with your installer when planning your turbine installation.
- 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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