FAQ – Wind
Q. What happens when the wind doesn’t blow
Q. How strong does the wind have to blow for the wind turbines to
Q. Do I have to stop the wind turbine or take it down in very windy weather?
Q. How long do wind turbines last?
Q. Do wind turbines produce electricity all of the time?
Q. How Does a wind turbine work?
Q. Where can I site a wind turbine?
Q. Are wind turbines noisy?
Q. Do wind turbines affect livestock?
Q. What does Mean Annual Wind Speed represent ?
Q. What is the lowest annual mean wind speed where it makes economic sense to install a turbine?
Q What is the best tower height for me?
Q. How much space do I need for a turbine?
Q. I dont have room on my site for guy ropes; can I have a freestanding tower?
Q. I want to mount my turbine on the roof of one of my buildings. Is this possible?
Q. Can the turbine be re-sited if I move?
Q. How do I work out what generating capacity I need?
Q. Is a bird strike a likely problem?
Q. Is lightning strike likely to be a problem?
Q. I live on the side of a hill or a valley will I still get the wind?
Q. Will a wind turbine supply all of my needs?
Q. Can I use a turbine to heat my home?
Q. Will my computer still work on a wind system?
Q. Do I need to change any of my house wiring?
Q. Can I have three phase?
Q. Do I need planning permission for a wind turbine?
Q. What does CCL on my energy bill mean?
Q. How much do turbines cost?
Q. What is the payback time?
Q. What are Renewable Obligation Certificates?
Q. What are stand-alone / off-grid turbines?
Q. Can I connect my wind turbine direct to the electricity grid network?
Q. How does a Grid Connect Inverter System Work?
Q. Do I need to have an energy storage system?
Q. What type of batteries do I use? How long will they last?
Q. How does a Direct Heating System Work?
If the wind isn’t blowing, wind turbines do not produce energy. Most wind turbines have a ‘cut-in’ wind speed of around 3 metres per second (m/s) which is approximately 6mph. During the times when the wind is not strong enough for the turbine to generate electricity a back up from the National Grid or a diesel generator may be required.
Wind turbines start turning and producing electricity in just over a 5 mph wind. The energy available in the wind rises dramatically with wind speed – most of your power will come from periods when the wind is over 10 mph. (a “gentle breeze”) and reach maximum power output at around 12 m/s (around 28 mph).
No, the wind turbines that we supply have a patented blade mechanism that means that they never exceed their design rotation speed. This means that they can run through the most severe weather without damage, and, they go on producing full power output.
A wind turbine typically lasts around 20-25 years. If serviced and maintained regularly. During this time, as with a car, some of the moving parts may get worn and need replacing.
A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs dependent on wind speed. Over the course of a year, it will generate about 30% of the theoretical maximum output. This is known as its load factor. How high the load factor will be on your particular site depends on the Mean Annual Wind Speed. Load factors can be as high as 50% in places like Orkney. The load factor of conventional power stations is on average 50%.
The basic design of electricity generating turbines remains the same whatever their size and output.
The wind turbine is comprised of a tower, topped by an enclosure called a nacelle, and the rotor, which is a 2 or 3 bladed propeller-like structure connected to the nacelle. The nacelle houses all of the electrical components such as an electrical generator, power control equipment and other mechanical equipment, which is connected to the rotor.
The rotor blades are made out of light composite materials such as fibreglass. They are well researched and shaped to maximise the energy harnessed. The wind strikes these blades, and due to their shape, causes the rotor to spin. When the wind is strong enough, the rotational energy in the rotor is converted to electrical energy within the generator. Some turbines use a gearbox to speed up the rotation, whilst others use a gearbox-less design, where the rotor drives the generator directly.
For small scale wind turbines that are grid connected a special inverter and controller are required to convert the direct current (DC) to alternating current (AC is mains electricity) so that the electricity can be used to power household appliance and lighting. Any unused or excess electricity can then be exported to the grid and sold to your electricity supply company.
Domestic wind generators are usually sized in the range of 1kW up to 6kW but in some instances they could include a 15kW or 25kW turbine.
Serious consideration much be given to positioning of the turbine to get the best performance and reliability from it.
The output from a wind turbine is highly sensitive to wind speed. It is essential that turbines should be sited away from obstructions, with a clear exposure or fetch for the prevailing wind. Wind speed also increases with height so it is best to have the turbine high up, and most small turbines have towers much higher relative to their diameter than large ones.
In practice, turbines need to be located near to the user, as far as possible though, keep away from local obstructions such as large trees and houses, or use a taller tower to ensure that the turbine is well above the obstructions.
note: It is likely that the installation of any wind turbine will require planning permission and you would need to contact the planning department at your local council for clarification.
The economics of installing a small wind turbine are always dependent upon adequate wind resource. A good average wind speed is needed and this should be looked into before investing in a wind power system. The DTI UK Wind Speed Database is available from the Department of Trade and Industry website and contains estimates of the annual mean wind speed throughout the UK. This can be used as a guide for assessing wind speeds in your general location
We can get a reasonable estimate of the wind resource of a site from its location. There is a database, which gives an estimate of mean annual wind speeds (MAWS) at 1km intervals all over the British Isles for heights of 10, 25 and 45 m.
Please note: the UK wind speed data base provides an approximate method. The actual wind speed at your site may also be influenced by the local topography and any nearby obstructions such as trees, buildings etc. However, it will provide you with a useful indication of the likely energy capture from the wind turbine.
Apart from a gentle swishing it is possible to stand underneath a turbine and hold a conversation without having to raise your voice.
The rotor designs and the direct drive system (no gearbox) of the types of turbines we can supply, all ensure quiet operation. It is generally accepted that there will not nuisance to neighbours if the wind turbine noise is less than 10dbA above background noise levels. On a typical site in the countryside, it is expected that this condition can be met at distances greater than about 10 rotor diameters from the wind turbine base. Therefore, as a general rule, the nearest residents to the wind turbine should be more than 10 rotor diameters away.
The noises from the wind turbine are gentle, and it would be quite reasonable to locate the wind turbine less than 10 rotor diameters from your home.
www.npl.co.uk/acoustics/techguides/wtnm is a wind turbine noise model that lets you calculate noise levels in dbA.
Wind farming is popular with farmers, because their land can continue to be used for growing crops or grazing livestock. Wind turbines do not disturb sheep, cows or horses.
Wind speed obviously varies with time, from nothing on calm days to occasional violent gusts. If the wind speed at a site is recorded over a year, it will be seen to vary about a mean wind speed value. This is the annual mean wind speed (AMWS) and is an indication of how much wind energy is available. In the UK, MAWS could be as low as 4 m/s (9.0 mph) for an inland site to around 8 m/s (13 mph) or higher on the most exposed sites
The NOABL Wind Speed Model is an industry recognised tool for calculating the annual average wind-speed at a site in the UK. Accurate to within 1km2.
We consider that a site with an annual mean wind speed above 5m/s is a reasonable one. Compared to this, the energy capture will be roughly half as much on a 4m/s site, or twice as much on a very windy, 9m/s site.
In general, the higher the tower, the higher the average wind speed that the turbine will experience. Our initial site survey will give you estimates of the expected energy output from the ranges of turbines we supply at various tower heights. Tall towers are needed to get the turbine above the turbulence created by nearby trees or buildings. However, taller towers are more expensive as they require more steel and a larger foundation on higher wind speed sites. Shorter towers are generally adequate.
Ideally, the turbine should be sited as far away as possible from obstructions like buildings or trees, which may block the wind and cause turbulence. As a guide, the wind turbine should be about twice the height of obstructions around it (for at least the prevailing wind direction).
Space is needed to set out the anchorage points for the guy ropes or to lower the tower for maintenance. The ground area required depends on the height of the tower.
Yes however the cost of the freestanding tower will be more than a guyed design. The freestanding tower base will require concrete in deep foundations. More work and expense will therefore be required to install the foundations for this type of tower. Freestanding towers are favoured in areas accessible to livestock which tend to use guys as scratching posts.
There are a number of turbines in the market designed for mounting on buildings, and some which can be either building mounted, or freestanding on a tower remote from your house. Turbines more than a couple of kW cannot be fitted to building, except perhaps large industrial buildings.
We do not recommend any of the small (
For further information, we suggest you read some of the information on Hugh Piggot of Scoraig Wind’s webpage.
Yes, provided the new site is suitable. Costs will be incurred to dismantle the turbine, transport it to the new site and re-install it. An estimate of these costs can only be prepared after a survey of the old and new sites.
A typical home requires around 5,000 kWh of power per annum for normal domestic use, and around 15,000 kWh of heating per annum. An assessment of the power requirements of your particular application will need to be made in order to determine which turbine will meet your needs best. We do this by looking at how many kWh you require, and seeing which size of turbine will produce that amount of energy in the windspeed you have on your site.
Bird-strike is not likely to be a problem. More information about this can be found on the following pages:
* Royal Society for the Protection of Birds: Policy – Wind farms
* Danish Wind Industry Association: Birds and Wind Turbines
* American Wind Energy Association: Putting Wind Power’s Effect on Birds in Perspective, an article by Mick Sagrillo with a special section on ‘Home-sized wind systems’
Lightning strikes do occur however the turbine is earthed and any potential strike would dissipate safely into the ground.
Insuring the turbine may be a wise precaution, and it may be possible to include it on your existing policy, consult your insurance broker, as many will accept wind turbines onto a house insurance policy.
Yes, in some cases wind speeds are actually stronger than that at the top of the hill. However, this is very dependent on the topography, and the higher up the turbine is, the more it will generally produce.
This will depend on the size of wind turbine and the on site wind speed. Generally, in a good wind speed site, a 2.5 kW turbine can supply all the electricity for an average home that is not heated with electricity, whilst a 6 kW turbine can supply all the energy (including heating) for an average home
Yes, there are dedicated systems for heating. You can also use a larger machine to supply heat and power. Combining a wind turbine with a ground source heat pump can be especially successful. We generally recommend that turbines always be grid connected as it is easier to claim ROCs on grid connected turbines than it is on non grid connected installations.
Yes, modern inverters are pure sine wave output. In general, better quality power than the grid.
No, the output from the inverters is 230V 50Hz. All we need is a spare way on the main consumer unit to fit a new circuit breaker for the turbine. In some cases, we can connect the turbine in a sub consumer unit (for example in a garage or an outbuilding), providing the cabling to it is heavy enough
Yes, there are three phase inverters available. Larger turbines, i.e those above about 6 kW generally need to be connected on more than a single phase in most domestic installations.
At the moment yes, although this may change in the future if wind turbines are afforded “Permitted Development Status”. We would always advise that planning permission is sought, before getting too excited! A few words with your local planning officer may indicate if any potential problems are foreseen. Quite a few of the sites we survey are not suitable for wind turbines, due to neighbour proximity or other restrictions.
Climate Change Levy. This is a Tax on the energy you use and is currently 0.43p per kWh, applied to all non domestic supplies
It is likely that the installation of any wind power system will require planning permission and you would need to contact the planning department at your local council for further information. We would suggest that you try to gauge the informal opinion of the local planners before committing to making a full planning application, as this will cost upwards of GBP120
The Energy Saving Trust are on hand to provide you with information regarding possible grant you may be eligible for and comprehensive information on all types of renewable energy call them on Tel 0800 915 7722 or visit their website at www.est.org.uk/
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