Wind in the UK

Wind power is now a mature technology, boasting an installed worldwide capacity in excess of 10 000 MW. Turbines have been around long enough to demonstrate their economic life and reliability. They typically last 20-25 years and are available for generation 97-99% of the time.

Turbines come in two main generic forms, classified by their axis of rotation. The first, and most common form of turbine, has a horizontal axis. This has the advantage of being efficient and can be self-starting. Such turbines are already being mass-produced.

The second turbine type – which rotates on a vertical axis – is generally less efficient and must normally be mounted very close to ground level where wind speeds are lower. These tend to be built as one-off devices. Machines used in new wind farms in Europe are generally of the first type and rated at around 500-1500 kW, where a 500 kW turbine might have 40 m diameter blades mounted on a 40 m high mast.

The UK has around 340 MW of installed commercial wind turbines – much less than Germany, Denmark, Holland or Spain. Germany, for instance, has six times the installed capacity of the UK.

ETSU says that wind energy is fundamental if the UK is to meet a significant proportion of its energy needs from renewables. Surprisingly, though, most of the projects awarded contracts under the latest round of nffo were for landfill gas: 141 of the 261 projects were for electricity generated from landfill gas, while there were just 39 wind projects. Admittedly, part of this is due to planning constraints. Whereas in 1993 around 70% of wind energy proposals were accepted by UK planners, the figure is now only 20% – despite support by prominent environmental organisations like Friends of the Earth.

Much current development in the wind energy industry is therefore directed towards using huge offshore turbines. However, there may be an alternative.

Wind energy in buildings

Full-scale wind turbines are not used in urban areas mainly because:

• wind speeds near the ground are lower in urban areas due to the surface roughness produced by buildings;

• turbines are generally located at least 500 m away from inhabited buildings, roads and power lines due to their visual intrusiveness, noise and electromagnetic interference.

However, the visual and noise impact of turbines is likely to be much smaller in towns – where they are surrounded by other buildings and cars. This means planning consent may come easier than in rural areas.

Siting turbines near buildings brings the additional advantage of avoiding the need for high voltage, long distance power line infrastructure. If wind turbines are incorporated in a building scheme from the outset, the whole development cost may only rise marginally.

Buildings may even be used to accelerate local wind flow through the swept area of a turbine. This enables an integrated turbine to capture more of the available wind energy – especially important given the wind regimes at most urban sites.

A prototype building for the EC-funded Project ZED used this strategy. This project proposed a hypothetical accelerator building for London. The concentration effect has been proven in lab tests using concentrators for stand-alone turbines.

For successful integration of wind turbines in buildings the turbines must be safe, reliable and capable of producing a significant proportion of the annual electricity demand of the building – say 20% as a minimum. If not, the turbines risk being seen as a gimmick.