Wind turbines (UK domestic)
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Wind turbines have been on the UK domestic market many years, but their popularity and public awareness is now increasing substantially.
Claims about their efficiency and productivity are under some debate due to the disparity of manufacturer's forecasts with case study results. The prime problem is that they are routinely being installed in areas with wind speeds much too low to realise a useful level of energy return. Wind generation requires wind speeds above those found in the great majority of inhabited areas.
Article: Can a home wind turbine make money?[1]
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[edit] Planning permission
In England planning permission has been granted to only 50% of applications while in Scotland more than 90% are being approved.[2]
The regulations are expected to change in 2007 with wind turbines coming under the same planning guidance as satellite dishes.
[edit] Wind-speed
Many of the manufacturer's examples rely on assumptions about average wind speed which, in practice, is very variable. This is particularly important because power input to a wind turbine is proportional to the cube of the wind-speed. Consequently halving the wind speed reduces input power by a factor of eight, not by a half.
The change in output power is greater than this factor of 8, since wind generators only begin to generate at a point well above zero wind speed. Thus wind speed in the locality is a critical factor.
It is therefore important that local average wind-speed is determined, and that buildings or other natural features that may disrupt the smooth flow of the wind are taken into account before purchasing. Most built up areas in Britain do not have sufficient windspeed for productive generation. The presence of other buildings in built-up areas make wind speeds even lower. Only some of the more exposed rural locations may have promise.
In unsuitable areas, one alternative suggested may be to form a cooperative, such as the Baywind Energy Co-operative, to provide a larger-scale turbine to serve the local community. While there are few of these in the UK, they are common in other countries, notably Denmark, where around 5% of the population are involved in such schemes [1]. However it is generally better to place turbines in more suitable high wind speed areas, which are not generally centres of population.
[edit] Example costs
The following example costs are taken from manufacturer's literature. See the section above regarding the importance of wind-speed in these examples.
Refer to bettergeneration.co.uk for an index of domestic turbines.
- Windsave turbine WS1000 (1 kW)
- Claimed average output: 500 kwH per year
- Note: 2 years warranty, expected working life of 10 years
- Materials: £1,600
- Installation: Included
- Tax: Included
- 30% Clear Skies Grant: £500
- Total Costs: £1,100
- Swift turbine (1.5 kW)
- Claimed average output: 2000 kwH per year
- Materials: £3,500
- Installation: £1,950
- Tax: £272
- 30% Clear Skies Grant: £1,700
- Total Costs: £4,022
- Stealthgen by Eclectic Energy (0.4 kW)
- Claimed output: 660 kwH per year
- Materials: £875
- Installation: not included, estimate £800
- Tax: Included
- Grant: not currently available
- Total costs: £1,675
[edit] Return on investment
Using the lower end estimates of power generation where possible, if we ignore interest rates, the calculation of how long the turbines take to pay off comes out to be at least 20 years. Taking interest into account, there is no real likelihood of ever recovering the equipment cost.
Unfortunately for the domestic wind turbines currently on the market there is little case study data to support the manufacturers' claims of power generation and their marketing relies on calculations making assumptions about average wind speed.[3]
- Assumptions
- Life of the turbine is at least 20 years with no maintenance costs (for some models the bearings have a forecast life of 10 years)
- Placed in a windy position with no near fences, trees or buildings
- Exclude costs of planning permission
- Exclude potential cash-back benefits of renewables obligation certificates
- Assume 1 kwH is worth 10p
- Number of years running before costs are paid off
- Windsave Turbine generates 500 kwH per year being equivalent to £50 of electricity per year. Calculation is Investment divided by Returns per Year = £1,100/£50 = 22 years. This is 12 years longer than the manufacturer’s stated working life of 10 years.
- The Swift Turbines higher estimate of 2000 kwH per year is worth approximately £200. This gives £4,022/£200 = 20.1 years.
- Stealthgen quoted at 660 kwH per year (quoted by StealthGen but unsupported by case studies) equivalent to £66. This gives £1,675/£66 = 25.3 years.
Unfortunately even these figures assume zero interest, no chance of needing to pay for repairs, and lifetimes exceeding even the manufacturer's claims. The reality is therefore significantly worse, and payback of costs is not likely.
[edit] Footnotes
- ^ "Can a home wind turbine make money?", BBC News, 2006-10-25. Retrieved on 2006-12-03.
- ^ Small Wind and planning. The British Wind Energy Association (2006). Retrieved on 2006-12-03.
- ^ "Lower bills may not be blowing in the wind", The Guardian, 2006-06-25. Retrieved on 2006-12-03.
[edit] See also
- Wind turbine
- Wind power in the United Kingdom
- Energy policy of the United Kingdom
- Energy use and conservation in the United Kingdom
[edit] References
- BWEA small wind website, has links to the Low Carbon Building Programme for grant information and to the DTI to calculate wind speeds.
- The Energy Saving Trust for information about grants, manufacturers and installers
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