Wind turbines generate electricity by harnessing the power of the wind – the UK has 40% of Europe’s wind energy blowing over it, making it a travesty that successive governments have neglected our turbine industry and allowed other countries to become world-leaders in the technology.
In 2012 commercial windpower (produced by turbines rated at between 1 – 2.5 MW) accounted for around 5 GW onshore and 2.5 GW offshore power generation. The Sustainable Development Commission estimates that the UK could theoretically produce a ‘practical’ maximum of 150,000 gigawatt hours (gWh) - approximately half of the UK’s electricity requirements.
The UK is an ideal country for wind power generally, and specifically domestic turbines (known as 'microwind' or 'small-wind' turbines). A typical micro system on a good site could easily generate more power than you currently use.
Costs & savings
The cost of a wind turbine will depend on the size and the mounting method: building-mounted turbines cost less to install than pole-mounted ones, but are only up to about 2kW in size.
The average size of a micro-wind turbine is 6kW, which can cost up to £10,000 for equipment and installation – however so much depends upon the site. A well-sited 6kW turbine will generate around 10,000kWh per year.
Much like sunlight, wind is free, and so once you've paid for the initial installation your electricity costs will be greatly reduced, or even wiped out completely!
Micro wind turbines are covered by FITs and the Green Deal, which could earn you on average £2,000 per year. Like PV, the FIT means that you get paid for the electricity you generate even if you use it – if you don’t use it, you can export to the local grid (as long as you're connected to this!) and get paid for that too. Unfortunately, if your home is completely independent of the grid, then the turbine must be connected to batteries, which are very expensive and need replacing regularly.
Since so much depends upon how windy the site is, you are advised to check Encraft Tools in the first instance, and then run an anemometer at the requisite height for a year to check.
Wind turbine output is determined by a number of factors:
· Quantity of wind at hub height, measured in meters per second (m/s)
· Quality of wind – obstacles such as hills, trees, buildings, cause turbulence. Turbines do not like turbulence.
· Yaw – gusts of wind can move a turbine erratically around its axis (yaw) but do little to generate power and can seriously contribute to mechanical failure.
· Swept area of the rota – the size of the blades determines the energy capture, as the generator cannot generate more power than the rotor can capture.
· Blade design effects efficiency
· Generator’s resistance to the rotor means that the rotor will only start spinning at a certain speed, the ‘cut in’ speed, which is usually much lower than the optimal speed.
· Cabling losses - energy is always lost through transmission and cabling should be carefully specified and designed to minimise losses over distance. There is a difference between cabling designed to deliver power to a battery and cabling designed to link in with the grid.
· Conversion and conditioning losses - turbines connected to batteries require a voltage regulator to prevent overcharging, and energy is lost both in this process and that of inverting the DC supply for domestic AC use; those who are off-grid might like to avoid such losses by running DC lighting and appliances. Grid connected turbines require a grid controller, an isolator and a synchronous inverter – all leading to losses.
All turbines have a ‘Power Curve’ - this illustrates the power output at a given wind speed for that particular model of Wind Turbine, and should be calculated by an independent third-party. Once you know exactly how windy your site is, this helps to choose the right turbine for you.
If used on appropriate sites, domestic wind turbines will generate useful electricity that would otherwise be drawn from the grid - thus reducing the carbon footprint. However, the sad fact is that for many their first experience of ‘micro generation’ has been anything but happy, with actual performances often dramatically undershooting expectations due to poor citing and specifying. For the majority of people living in urban areas, installing wind turbines on or close to buildings with overall windspeeds of less than 5m/s is not a realistic viable proposition.
Since they are mechanical devices, regular maintenance checks are necessary, and will generally cost around £200 depending on turbine size. A well-maintained turbine should last more than 20 years, but you may need to replace the inverter at some stage during this time, at a cost of £1,000 or up to £2,000 for a large system. Of course, other components may also need replacing over time.
In England and Scotland a domestic wind turbine may be classified as Permitted Development, in which case planning permission will not be needed. However, the criteria are complex, and very different in England and Scotland and it is recommended that you contact your local planning office at an early stage to check whether planning is required - you may even have to have planning permission to erect an anemometer. Planning permission is always required in Wales or Northern Ireland.
Note: Windmills (as opposed to Wind Turbines) produce direct mechanical energy which is not generally required in modern life. Although they are no longer used to mill flour generally, they are still used as water pumps (windpumps actually) most famously in the American mid-west, Australia, and parts of Africa. Historically they also drained the Fens and much of Holland, hence the windmill being synonymous with the Netherlands!