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Wind power

isoenergy can help to advise on the feasibility of wind energy projects but does not specialise in the installation of wind turbines.


Windmills were first developed in ancient Persia during the second century BC and only came to Europe in the early middle ages. The first records of windmills in England go back to the 11th or 12th centuries. Early windmills were used for grinding corn and pumping water, normally for land drainage. They are of course a traditional part of the Dutch landscape and their traces can be seen all over Britain. The milling and pumping applications of windmills were superseded by steam power during the nineteenth century.

Electricity-generating wind mills began to be developed at the end of the nineteenth and beginning of the twentieth centuries but it was not until the last ten to fifteen years that both small and large-scale wind generation have become prevalent in the UK. A number of other European countries have deployed significantly greater numbers of wind turbines than we have.

Onshore wind generation in the UK is of course very controversial. On the one hand it is very effective in the UK because the British Isles are very windy, generation is renewable (though there are carbon costs in manufacture and construction), and it is cheap to deploy. Onshore wind is by far the cheapest renewable energy source that can be deployed at significant scale, and according to Government figures, generated enough power in 2011 for 2.4 million homes and save more carbon emissions a year than is emitted by a city the size of Leeds.

On the other hand, to work well wind turbines need to be sited in exposed and windy locations, which of course are often also areas of outstanding beauty and environmental sensitivity, the costs of generation are greater than equivalent fossil fuel sources, and wind is fundamentally an intermittent resource that does not generate continually, but only when the wind is within the right range of speeds.

The installation of wind turbines is controlled by planning legislation and the sale of the electricity generated can be a worthwhile income stream. The calculation of the economic benefit of installing wind generation depends on a detailed analysis of the site and is complicated by the need to budget a significant programme of routine maintenance.

isoenergy can help to advise on the feasibility of wind energy projects but does not specialise in the installation of wind turbines.

How it works

A wind turbine converts the kinetic energy of the wind first into electrical energy that can be fed into the National Grid.

  • The wind turns the blades of the turbine which are connected to a shaft.
  • The shaft rotates and drives a gear box that speeds up the rate of rotation.
  • The output from the gearbox drives an electrical generator that produces electricity.
  • The output from the generator is matched in frequency, phase and voltage to the national grid supply
  • The National Grid transmits the electricity to where it is consumed

Turbines normally start to operate at wind speed of about 4-m/s and reach maximum power at about 15 m/s. When the wind is much stronger than this they have to shut down to avoid damage to themselves.

A typical wind turbine consists of a tower, blades, a mechanism for facing the blades into the wind, and a gear box and generator mounted in the unit at the top of the tower. Some turbines operate with a variable speed and some are controlled to operate at a fixed speed.

The maximum theoretical power output from a wind turbine is proportional to the area the blades sweep and the cube of the wind velocity – provided the wind speed is such that the turbine can operate safely. A small turbine is unlikely to provide worthwhile quantities of energy as its performance will be dominated by mechanical losses, and any turbine needs to be sited in the right place. The typical wind velocity varies across the country and depends greatly on local geographic features such as woods and hills. This is why the siting of wind turbines in the UK has tended to be in more exposed areas of the North and West of the country.