Sustainability

Wind farms have gradually become an accepted, if occasionally resented, element of Britain's hills and coasts. Although their domestic counterparts have proved popular with the leaders of certain political parties, they have yet to find favour beyond self-consciously ecological households. And large turbines integrated into big urban schemes are about as common as hen's teeth.

This might be about to change, and the bellwether of that change may be the £100m, 42-storey Castle House development in Elephant & Castle, south London, which has been granted planning permission and is topped by three integrated 9 m high wind turbines.

Castle House is likely to prove influential because it is one of the first experiments in finding technological solutions to the problem posed by planning policy statement 22, which allows councils to demand that a percentage of a development's energy needs be supplied from on-site renewable sources. In London, the drive is to have developments produce 10% of their own power. Peter Sharratt, director of sustainability at consultant WSP Environmental UK, points out that the industry is moving towards wind power because there are subsidies available for it, it speeds up planning applications and helps with a development's public image. And, of course, London is a fairly windy city.

The risk implicit in Sharratt's list is that the turbines could appear gratuitous: an aesthetic flourish or an exercise in ecological propaganda. For a scheme to be credible, it must prove that it is genuinely energy efficient. The developer behind Castle House, for example, says the scheme will exceed the limits on energy use set out in Part L of the Building Regulations by 13% and that the turbines will produce enough electricity to light the entire development.

Away from the dense urban topology of inner London, the Bahrain World Trade Centre, which was designed by Atkins and will be completed this summer, contains the world's first large-scale integrated wind turbines. The centre's two 50-storey sail-shaped towers will support three 29 m diameter horizontal turbines. The 240 m scheme overlooks the Arabian Gulf, which will provide offshore breezes. These turbines are expected to provide up to 15% of the building's annual energy requirement.

The extent to which the design of a building is affected by the integration of turbines depends on where it is. The Bahrain towers flaunted, but turbines in cities with have to deal with the kind of "blot on the landscape" objections raised against rural windfarms, so they have to be less obtrusive.

Atkins’ World Trade Centre development in Bahrain includes the world’s first large-scale integration of wind turbines into a building’s design

Meanwhile, there are a number of technical challenges specifiers will have to deal with if they want to integrate this form of turbine into their design. Neil Campbell, an associate at BDSP Partnership, a building services engineering consultancy, points out that there are some significant technical differences between putting a turbine on

top of a building and integrating it within the fabric. He says: "It's complex to identify all the issues in parallel. We'll need advice on acoustic, absorbent material, vibration, insulation and energy all at the same time."

The most important issues to be resolved are the amount of noise produced by the rotating machine at night and the means for preventing vibrations from being transferred into the building.

Neville Rye, director of WSP Buildings UK, points out that not every new building will be able to have an integrated wind turbine. First of all, it is not suitable for low-rise buildings that are sheltered by their neighbours. There might also be some problems with technical interface in the electromagnetic field. Rye explains that although it hasn't been proven yet, some mobile phone companies are opposing integrated turbines on the grounds that they may interfere with their microwave traffic.

Some studies predicted that the integration of a turbine would disproportionately increase the building's cost. Sharratt says that, on the contrary, it has been proven that wind energy has a relatively short payback period compared with other energy efficient applications, which makes the adoption of this kind of energy commercially viable. According to Atkins, the premium on turbines on its Bahrain towers was less than 3% of the project value.

Designers might like to look at the turbines as the main feature of their building and plan their budget around this. The typical cost of a 6 kW integrated turbine is estimated at between £35,000 and £45,000, depending on the complexity of the work needed.

Finally if the use of integrated wind turbines in an urban environment takes off, some planning adjustment might be required. For example, right of wind may replace right of light when determining whether to grant a planning application. Sharratt says: "Future high-rise buildings may affect your existing building. We have to consider the right to use the wind and find out how you safeguard your investment to be sure other developments do not undermine the energy efficiency of your building."

Castle House will be the first high-rise scheme in the UK to include integrated wind turbines