According to proposals made last week by the DCLG (Department for Communities and Local Government), each house would be allowed to install one wind turbine without planning permission.
The Consultation Paper mentions striking a balance between energy production and potential impact and they suggest a max rotor diameter of 2m, and a max height of 11m.
What does this mean from a design point of view?
It's complicated, because a proliferation of smaller turbines (in different colours, at different heights, some fixed to the roof, some on free-standing poles) could create a huge amount of clutter on a residential street and potentially be more damaging than a single well-designed, taller and larger installation shared by several houses.
The example below is a simplistic one, but I hope it illustrates the point. A small 2m turbine, if the wind blows, might generate around 1500-2000 kWh per year - which might be roughly half the requirement of a house.
However, a larger turbine (set a short distance away from the houses) with a 7m diameter might generate 24,000kWh per year - approx half the requirement of 12 houses - and leave the houses themselves uncluttered.
To make things more complex, we know that the amount of electricity generated rises sharply with wind speed, which makes it very difficult to judge the relative costs and benefits of different heights.
In some situations an extra 3m of height might lead to a massive increase in the amount of energy generated. In some situations a higher post may be perfectly acceptable from a design point of view, but the need to apply for planning permission would deter this, even though it would be much more sensible.
Having said all this, there's no easy answer to the impossible 'balance between energy production and potential impact'. Anything larger than 2m or higher than 11m would begin to have a wider impact on surrounding houses, and it's right that they should be subject to judgement on a case-by-case basis through the planning system.
For this reason, the 2m/11m compromise would seem as good as any - but it would still be a compromise. Decisions would be taken on the basis of these numbers and not on the basis of urban design quality or renewable energy efficiency.
Hmm. Don't wind turbines need to be located something like 10m above any object within 100m to be at all effective?
Sounds like this could potentially lead to a lot of clutter and bad will between neighbours for a very low (and only occasional) wattage.
Posted by: David | April 17, 2007 at 05:39 PM