OK, so you have been doing a bit of research and have decided that you want a wind turbine of your own. Here are a few simple guidelines to help you get started and, hopefully, fill in some of the grey areas that I have found are not well covered elsewhere. These are all applicable to UK setups only and please note that some of the details (especially regarding ROC registration) vary for Scotland and Northern Ireland too. If you are outside the UK then these notes won't be of much direct use to you I'm afraid.
If you want to delve deeper into the physics and technology behind wind power then a really good guide is available from the Danish Wind Industry Association.
The first question is - do you really have enough wind to make a turbine a feasible proposition?
Spending a lot of hard earned cash to install a turbine only to find it produces a small fraction of the energy you expected is going to be a big disappointment. Ideally you would do what wind farm companies do and erect a mast (the same height as you plan for the turbine) put an anemometer (wind gauge) on it and record your actual wind speed on site for at least 12 months. Obviously that's going to be costly and time consuming so luckily there is a short-cut but with some trade-off in accuracy. The DTI have a database that details the average annual windspeed at 3 different heights above ground level, at 10, 25 and 45 meters, for each 1 kilometer square area across the UK.
To use it you need to know the Ordnance Survey 6-figure map reference for the particular 1 km square where you plan to site your turbine. See the instructions here. Please note that these figures are calculated based upon known factors such as wind measurements at a few locations and the topology of the land. Factors such as turbulence from trees and buildings are not taken into account. Check the reference you need on an OS map - don't rely on the Post Code lookup. It could give you a neighbouring grid square and not the one you want.
Also be aware that the Annual Average Windspeed doesn't tell the whole story - averages can hide information just as much as reveal it. For example, if your average is 5 m/s then this could mean that your site has 5 m/s winds for all 365 days a year (a low speed for a medium size turbine and unlikely) or it could mean than you have 10 m/s winds for half the year and no winds at all for the other half (a much better wind profile for a turbine and also the more likely situation in the UK at least). The missing piece of information, that is not provided by the DTI database figures, is the 'standard deviation' - in the first example this would be zero and in the second it would be 5.
To compensate for this lack of information it is possible to get a better idea of the overall wind pattern across a year by using a statistical tool called a Weibull distribution and to understand this a little better than I can explain here take a look at the Danish Wind Industry Association website although I have to admit that the Weibull figures are themselves an averaged approach and may not accurately depict the wind speed pattern at any one particular location. Nevertheless, in the absence of any anemometer readings, it is the best we can do.
Having discovered what the notional average annual wind speed is for your planned turbine location you can re-read the turbine manufacturers datasheets with fresh eyes. Most manufacturers base their claimed generation figures on a wind speed of 12.5 meters/second. Was your figure this high? I would guess not as pretty much nowhere in the UK has an average wind speed anything like that. Probably between 5.0 and 7.0 meters/second is much more likely. So if you had thought that a 1 kiloWatt turbine was going to do then you may have to think about a slightly bigger size instead. As the energy available from the wind varies in proportion to the cube of wind speed the amount you can generate from a 6 meters/second wind is only a little more than 10% of what you would get from a 12.5 meters/second wind. So your 1 kiloWatt turbine is only going to generate approximately 110 Watts at 6 meters/second wind speeds.
If you are trying to calculate what percentage of your annual electricity consumption you will be able to offset by installing a wind turbine do remember that the wind does not blow all the time. Most figures suggest that in the UK the wind is in fact only blowing about 30% of the time on average. So if this applies to your location then 70% of the time you'll be using just as much grid electricity as you are now, assuming you're going for a simple grid-tied system and not one using batteries. The remaining 30% of the time you'll be generating and consuming at the same time. Whatever is left over will be fed back to the grid.
Once you have determined the average annual wind speed for your site and calculated the total number of kWh you wish to generate each year you can use this calculator to roughly estimate the diameter of the turbine blades that you will need.
If you are planning to have a turbine mounted on a mast then you will want to install as tall a mast as possible so as to minimise the effect of ground turbulence on the turbine.
How far will the mast be from the house? The distance will affect the size (and therefore cost) of cables and the voltage of turbine you should select (greater distance = higher voltage) in order to minimise power loss in the cables.
Alternatively you may be planning to have a turbine bolted to your house. If so then you need to be aware of any turbulence caused by nearby structures (other houses, trees, etc) that may cause a lower amount of wind energy to be available. You will also want to be certain that your building is structurally sound and capable of holding the mast. Be aware that there are many people who hold the view that building-mounted turbines are a waste of time and money due to lower than predicted generation caused by turbulence.
At the time of writing this (August 2006) the UK government have announced plans to introduce a new Statutory Instrument to simplify the planning process for small scale renewable generation schemes. This should remove the need for full planning approval for some installations by extending the scope of Generally Permitted Development. It is, however, not expected to become law until September 2007.
So, in the meantime, you are going to need Full Planning Approval in order to erect a turbine of any useful size. (You may be able to persuade a planning officer that your structure is 'temporary' and so does not require Planning Approval - good luck!) Some Planning Authorities have decided not to charge a fee for applications to site building-mounted wind turbines. Check with your local office to see if this applies in your area.
The planning process will add to the cost and also possibly delay your project. Generally speaking planning departments are supportive of small scale renewable generation schemes. However if you live in a Conservation Area or a National Park then you may find otherwise and may even find that the planning officers require you to produce an Environmental Statement based upon an Environmental Impact Assessment. You will need to do some background research into the details of your areas Local Plan, which should be available on the internet, to see if it has anything specific to say about small scale wind turbines. Here are a couple of examples that I have seen recently.
"Consequently, only small scale wind energy developments will be allowed where they can be accommodated in the landscape and all other impacts on the environment, such as noise, can be reduced to acceptable levels."
(North York Moors National Park Local Plan - Section 11.11)
"Schemes consisting of a single wind turbine, and other small energy generation schemes to serve one or a small group of properties, will be permitted if the proposal conforms to the other policies in this Local Plan."
(Brecon Beacons National Park Local Plan - Section 10.11)
The priority for selecting the exact spot (if you have the luxury of a choice!) for your turbine must be to select a spot with the minimum of turbulence so that as 'clean' a windflow as possible gets to the blades. However this may conflict with what the planners may allow as that site may also cause visual intrusion for any neighbours or affect the view from nearby roads or public footpaths. If possible you should try to take steps to mitigate any such visual intrusion by careful selection of the exact location of your turbine. As an example our turbine is located at pretty much the highest point on our land. There are no tall trees or buildings nearby at all. But the turbine might have been quite visible from the nearest road which, at one spot, anyone travelling along it would have been looking directly at the turbine, and with the blades just breaking the horizon. Luckily there are a few small trees growing in the hedge at the bottom of the field with the turbine in and one of them is just in the right spot to 'mask' the view of the turbine from the road. Making sure that the turbine was located in just the right location was then an easy choice to make. Here's a photo to help you see what the result was. This photo was actually taken in November when there were few leaves on the trees which further hide the turbine from view during most of the year.
Below is the same photo which has been edited to show where the turbine is 'hiding'.
Small details like this could make the difference between a successful Planning Application and a refusal.
Allow at upto 3 months to get Full Planning Approval. You normally must already have obtained this before you submit an application for a grant. You must also submit your grant application, and obtain approval, before commencing any work or ordering equipment.
As the wind is only an intermittent source of energy you'll normally want a method of providing power even when the wind isn't blowing. There are three basic options.
You basically use the grid as a "big battery". Whenever you are not generating enough to meet your consumption needs you will import electricity from the grid - just as you do now. If you are generating more than you are using then the excess will be exported to the grid (and, in practice, will be used by your neighbours).
Anyone with a grid-tied generator of any description (wind, PV, hydro, CHP, etc) can only connect with the full agreement of their local Distribution Network Operator (DNO). All equipment/wiring used will need to be approved by them and be certified to meet the G83/1 (for upto 16 Amps per phase) or G59 (over 16 Amps) regulations. The DNO have some discretion on this matter and can accept generators over the 16A limit under G83/1 if they wish. The paperwork required for G59 is more complicated than G83/1 and is really aimed at small power stations. You'll most definitely want to stay with G83/1 if at all possible and your plans need to be discussed with the appointed person who handles small scale generation in your local DNO at an early point in the project.
Part of the regulatory compliance is that any inverter you use has to be capable of monitoring the grid voltage and closing down automatically whenever the grid goes down. The relevant programmable parameters in the inverter have to be agreed with the DNO.
You also need an On/Off switch (clearly labelled) that can be padlocked in the Off position so that if someone needs to work on the line nearby they will be able to come and lock your generator off of the grid if they wish to. Your site will be plotted on their mapping system so they know where you are. They will also want a schematic of your installation and a copy of the electrical engineers commissioning certificate before you go 'live'.
So with a simple grid-tied system whenever the grid is down then your own generator is effectively down as well.
Most off-grid systems currently utilise a series of lead-acid batteries as a store. These are similar to car batteries but are more specifically like "leisure" batteries used in caravans and boats. These are designed to cope with deep discharge situations. Sizing the right batteries will be a major part of the design stage of your project. Time spent in correctly maintaining your batteries is time well spent and will prolong their life - which is finite so you'll need to budget longer term for their eventual replacement.
If, like me, you know virtually nothing about batteries then here is a useful basic guide.
You can also have a system that uses both grid-tie and batteries with an intelligent switch that can swap over to the batteries if the grid is down. This gives you the best of both systems but obviously will be more expensive. SMA make an "Island" unit that is specifically designed for the purpose.
With any of these options you'll need to ensure that you have enough space to install the required equipment and, with batteries, you'll need to provide adequate ventilation as well. Here's a photo of our rectifier/inverter set-up. 
It occupies a space of approximately 1.5m high x 1m wide x 0.5m deep.
For domestic installations the UK government replaced the Clear Skies scheme with the Low Carbon Building Programme (LCBP) in April 2006. If you live in Scotland then you will need to apply to SCHRI instead of the LCBP scheme or if you are in Northern Ireland then there is the EREF. To qualify for grant funding under the LCBP your property must first be insulated to the highest standards if this has not already been done. You can find more information here. Funds are currently made available on a "first come, first served" basis. So you will need to get in early with your application.
The LCBP scheme will only grant fund a system that uses equipment that is on their approved list and that is installed by an approved company. You cannot get grant funding for a DIY project. Existing Clear Skies products and installers will be listed up until 1st December 2007.
For wind turbines the grant is £1,000 per kW upto a maximum of £2,500 (reduced from 5,000) or 30% of the total cost, whichever is the lower. For example: a 1kW turbine costing £1,500 would get 30% = £450; a 2kW turbine costing £10,000 would get £1,000 per kW = £2,000; and a 6kW turbine costing £20,000 would get the maximum allowable = £2,500.
Please note that once issued an LCBP grant approval is time-limited and, for wind turbines, will expire in four months. If you need a time extension, due to delays caused by the supplier, to allow you to complete your project then you must ask for one - don't just assume that you'll get the grant money anyway. You can get upto a 2 month extension. When the project is finished you'll need to submit the final bill and a copy of the commissioning certificate for your turbine in order to get the grant cheque released to you. Be prepared for this to take some time as well.
The minimum you need to have is a meter wired from the inverter that records the kWh that you generate. You can get Renewable Obligation Certificates (ROCs) for this. The OFGEM document entitled 'Renewables Obligation: Guidance for small generators (50kW and under)' describes the registration process in more detail. The value of ROCs changes over time based on a few variables but you can use this calculator to roughly estimate their likely value.
You may also want to install an 'export meter' which records how much you physically send out to the grid. (You may not want to do this as you have to pay for the meter and it may cost more than the value of your exports - so you could be out of pocket). Also OFGEM decide on the threshold that determines whether a system falls below what is called the Small Scale Third Party Generating Plant (SSTPGP) Limit. Since November 2004 this has been set at 30kW. Any generating system above this limit will need to be fitted with an Half Hourly Meter for export. These are extremely costly to install and read (in the region of £500 per annum) so the economics need to be checked carefully. In some circumstances your DNO may decide that you will need a Half Hourly Meter even if your system is less than the 30kW limit - another reason why you should discuss your plans with your DNO at an early stage.
The price you pay for your imports and what you get back for your exports varies from one provider to another, and also varies depending upon what part of the country you're in. There is a good summary of the options available on the West Wales ECO Centre site but be aware that suppliers are coming up with new ideas and the tariffs on offer are changing all the time.
It seems that some electricity suppliers are proving quite reluctant to offer contracts to their customers to purchase the electricity that is exported. This is despite the fact that they were asked to setup voluntary schemes as part of the Climate Change and Sustainable Energy Act which came into force in August 2006. If they fail to implement such schemes then the Secretary of State (Hilary Benn, MP) is required to implement changes to their licences that will force them to comply. The Act defines a microgeneration system as being one comprising biomass, biofuel, fuel cells, PV, water, wind, solar, geothermal and combined heat and power systems - all upto 50kW in size.
I have signed up with NPower who offer a payment for exports equal to their import price - or what is sometimes called a "net metering" arrangement.
In the 2007 Budget the Chancellor announced that income from the sale of surplus renewable electricity back to the grid and income from ROCs will be free of income tax.
Here are some photos showing the installation process for our 6kW Proven. Installing a turbine of this size (on a 9 meter mast) is a major undertaking requiring detailed preparation and planning. If you are using an approved installer then you should be confident in their ability to carry out the project.
If you have decided that a wind turbine is for you then - Good Luck! If you have any comments, suggestions or questions about any of this information then I will be pleased to hear from you.
You can check out the ongoing discussions about wind power (and other renewable energy systems) at these sites:
The Energy Saving Trust have produced a very informative downloadable Best Practice Guide called Installing small wind-powered electricity generating systems - Guidance for installers and specifiers. (1.6 Mb) This covers all the basic building and electrical requirements in some detail.
There are also a couple of books which I highly recommend:
