Frequently Asked Questions

Q. What happens when the wind doesn't blow?
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.

Q. How strong does the wind have to blow for the wind turbines to work?
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).

Q. Do I have to stop the wind turbine or take it down in very windy weather?
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.

Q. How long do wind turbines last?
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.

Q. Do wind turbines produce electricity all of the time?
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%.

Q. How does a wind turbine work?
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.

Q. Where can I site a wind 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.

Q. Are wind turbines noisy?
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.

Q. Do wind turbines affect livestock?
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.

Q. What does Mean Annual Wind Speed represent?
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.

Q. What is the lowest annual mean wind speed where it makes economic sense to install a turbine?
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.

Q What is the best tower height for me?
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.

Q. How much space do I need for a turbine?
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.

Q. I dont have room on my site for guy ropes; can I have a freestanding 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.

Q. I want to mount my turbine on the roof of one of my buildings. Is this possible?
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 (<2.5 kW) turbines currently being marketed for mounting on buildings, as the performance of these have yet to be verified. Wind speeds at rooftop height are generally much lower than the NOABL database would suggest, especially in urban or semi urban areas. The turbulence created by the building itself, as well as other possible obstructions, such as trees and neighbouring buildings, will greatly reduce the power output of the turbine, and make the whole financial viability questionable.

For further information, we suggest you read some of the information on Hugh Piggot of Scoraig Wind's webpage.

Q. Can the turbine be re-sited if I move?
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.

Q. How do I work out what generating capacity I need?
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.

Q. Is a bird strike a likely problem?
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'

Q. Is lightening strike likely to be a problem?
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.

Q. I live on the side of a hill or a valley will I still get the wind?
Yes, in some cases wind speeds are actually stronger than that at the top of the hill. However, this is very dependant on the topography, and the higher up the turbine is, the more it will generally produce.

Q. Will a wind turbine supply all of my needs?
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

Q. Can I use a turbine to heat my 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.

Q. Will my computer still work on a wind system?
Yes, modern inverters are pure sine wave output. In general better quality power than the grid.

Q. Do I need to change any of my house wiring?
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

Q. Can I have three phase?
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.

Q. Do I need planning permission for a wind turbine?
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.

Q. What does CCL mean on my energy bill mean?
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

Q. Who do I contact first?
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 wisit their website at www.est.org.uk/

If you find that your questions are not fully answered by the content within this web site please do not hesitate to contact us for further information.

Q. How much do turbines cost? Click here to go to our financial examples page

Q. What is the payback time? Click here to go to our financial examples page

Q. What are Renewable Obligation Certificates? Click here to go to our financial examples page

Q. What are stand-alone / off grid turbines?
Designed to operate where there is no mains supply. Together with a battery / inverter system it is possible to have a continuous, reliable source of power at 230 volts AC. Excess power can be used to provide heating through storage heaters or hot water radiators.

Q. Can I connect my wind turbine direct to the electricity grid network?
Yes, installing an inverter allows you to connect direct to the grid.

You have to get

a) a connection agreement with your local Distribution Network Operator

b) a power purchase agreement set up with your supply company.

(note, the DNO and the Supply Company may not be the same - Your DNO may be one company, for example Scottish Power, whilst your Supply Company may be another, i.e. British Gas)

We would normally handle a) for you as part of the install and commission tasks. b) is for you to shop around and choose the best deal available. We can however recommend an independent consultant who can assist you (for a small additional fee) to search the market for the best deal.

Grid connect systems are cheaper and require less space and a bit less maintenance than battery systems. Power generated by this sort of turbine can be fed back into the grid when not needed and therefore is never wasted.

Systems up to 16 amps per phase can be connected to the grid without any charge from your electricity company. Systems over 16 amps may be subject to a charge by the electricity company (typically GBP300) and must be approved by them before the connection is made. Some locations may be unsuitable for grid connection if the electricity company decides it will have an adverse effect on their network. This is more likely to be the case if your electricity supply is at the end of a long low voltage line (the transformer that feeds your house is more than a few poles away) and / or you share that line with a few neighbouring properties.

Q. How does a Grid Connect Inverter System Work?
You can connect your wind turbine inverter directly into the consumer unit! No batteries are needed!

A grid connect inverter package converts raw power output by the wind turbine into electricity that is synchronised to the grid and is fed directly into the house or business fuse board.

A connection agreement is required with the electricity company.

During periods of windy weather you might produce more power than you are using - in this case power will be exported to the grid. On the other hand if you are using more than the turbine is producing at any particular instant, the extra is drawn from the grid as normal.

For sites that have a high baseload (continuous usage of electricity), the turbine may never export to the grid and all the power will be used on site. In this case a simple connection agreement is all that is needed.

For installations that will export a significant proportion of the electricity produced by the turbine to be exported then it is best to enter into an agreement with an electricity supplier so you can get paid for the exported units.

Q. Do I need to have an energy storage system?
Yes, wind is a fluctuating resource and some form of storage medium is usually required. It could be electrical storage in a large battery, heat as hot water or in storage heaters or as water in a water tank for a water pumping system. It could also be exporting power to the grid which is a kind of storage (depending on the rate you get for buying it back later!).

Q. What type of batteries do I use? How long will they last?
They are usually lead-acid deep-cycle cells quite different from automotive batteries. Lifetime is dependent on plate design but typically 6-15 years.

Q. How does a Direct Heating System Work?
Wind is a fluctuating resource. In order to get a smooth and useful output of heat we direct turbine output straight into electrical storage (or direct) heaters, which then feed your house as heat is needed. The wind turbine controller includes an automatic switch-over which can be used to direct heat to two different outlets with a thermostat trigger. In a domestic situation these are often connected up to water heating with a temperature switchover to space heating.

In a UK climate, most of the wind is available during winter when heating is also a priority. Of course, most buildings lose (need) more heat when it is windy. There are always periods when heating is required but there is no wind - another source of heating is needed for these periods.

This page was last updated on 17/11/2007