This article is only concerned with wind turbines that can be sensibly added to a residential home. Unlike other forms of renewable energy, wind power requires very little explanation. Most of us will understand that the wind rotates a wind turbine generating electricity. The question addressed here is how effective are they and are they worth the investment. To work out how much energy you may generate you need to know how windy it is in your area, and there are several resource on the internet to do this, just do a Google search, or have a look the site by the Department for Business, Enterprise & Regulatory Reform (BERR) it has a good resource for this, please follow the following link.
| For those interested, wind turbines come in two main types; horizontal axis (HAWT) and vertical axis (VAWT) (see diagram ). Horizontal axis turbines are the more familiar ‘windmill’ type where the blades rotate in a vertical plane about a horizontal axis and the turbine is dynamically rotated on its tower to face the wind. Vertical axis turbines do not need orientation into the wind. Vertical axis turbines are particularly suited to small wind power applications because they have a small environmental impact and no noise, the technology is less mature than HAWT. |
| Wind Strength... |
It gives wind speeds at 45m, 25m and 10m above ground level. Wind speed 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, AMWS 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.
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The general consensus is that you will need at least 5m/s to make it worthwhile and this seems to be the number most suppliers use when they quote the generating capacity of their systems. It is also apparently the average wind speed in the UK. The table below shows a few systems with a range of typical manufacturer quoted generating capacity and estimates a payback periods. The total cost of the installations is about £ 15,000, +/- £ 5000. Accuracy is very tricky here because it depends on the foundations required, the battery storage system used (or grid connection) and the windmill chosen.
| System 1 | System 2 | System 3 | |
| Annual energy generation | 2500 kWh | 3750 kWh | 5000 kWh |
| Equivalent standard rate mains electric price of this energy | £ 295 | £ 443 | £ 590 |
| Payback period with and installation cost of £ 10000 | 33.9 years | 22.6 years | 16.9 years |
| Payback period with and installation cost of £ 15000 | 50.8 years | 33.9 years | 25.4 years |
| Payback period with and installation cost of £ 20000 | 67.8 years | 45.2 years | 33.9 years |
System 3 is probably at the high end of what is possible with a 5m/s wind speed and the numbers in the table for this system probably reflects what would happen with an average annual wind speed closer to 7m/s, So to get a payback period for your investment below twenty years you probably need to be in a very windy area and have paid as little as possible for your system.
