Commercial Wind Farms Design And The Challenge For Green Wind Power

November 4th, 2008 by Steve Evans

Wind turbines are designed to reach their rated power at a hub height wind speed of 12-18 m/s (33-40 mph). When you consider the power rule you will understand that it is important that they furl above the maximum speed during high winds.

The capacity factor for wind turbine power projectss is typically about 25-35%. By that we mean that the percentage of continuous output at maximum capacity actually achieved will not exceed these percentages in most locations. However, predictions of approximately 35-40% are thought to be achievable on some offshore sites especially in exposed northern locations of the United Kingdom.

A persistent problem is that many projects on land (onshore) in the UK, known as ‘wind farms’, have difficulty in getting planning permission – especially in England and Wales.

Resistance from local residents can be slightly less in Scotland, and Scottish development has been substantial (17.5% target) ,but is now constrained by the existing national grid export infrastructure which will need substantially extending. This is something which will in itself bring to play a lot of planning objections.

So, the best sites for wind speed often in exposed west and north of most countries but population centres tend to be further south, so windy areas will tend to require the higher spend needed to upgrade grid connections over long distances. It is often forgotten as well though that road access works for turbine delivery can make these locations difficult and potentially un-economic so such factor are bound to increase pressure for development under the UK’s RO for lower wind sites near major population centers.

Environmental considerations, especially visual impact, aviation radar, designated landscapes, etc, also limit the sites which are suitable. However, the UK is particularly well blessed with good offshore sites. Near-sea siting offers a much larger opening for wind power to make a truly substantial contribution to meeting the UK renewable energy targets, but as the distribution systems, including undersea hubs will be expensive and will need fully funding, such sea based wind farm systems will come at a greater cost.

There is still a big question about intermittency which may yet challenge our distribution engineers to combat without it causing power cuts. It is hard to believe that it is really always windy somewhere! The engineers working within the distribution system companies will have to develop their capability further than exists at present to cope with the inherent intermittency of wind power supplies. This is often said to be a drawback for wind and other naturally variable renewable supply sources.

One way to avoid intermittency in other renewables fields, and to some extent here as well is to go really small. This is called microgeneration and here within the green wind power scene there has been publicity for home-based generation including relatively small, roof-mounted micro wind power turbines. Whether these will really by installed by small businesses and individuals to contribute enough power to make a difference remains doubtful.