Theoretically, the average wind speed throughout the year over Ireland is about 12 metres per second, or a little over 25 miles per hour. I say theoretically, as this is the "geostrophic" wind - in a sense the speed at which the air ought to move over the surface of our island, as propelled by the pressure forces in the atmosphere.
In practice, however, the actual wind is rather less; the free movement of the air near the ground is retarded by the local topography and by a myriad of natural and man-made obstacles in its way.
But the geostrophic wind is a useful measure for comparison. Ireland's average wind of 12 m/s, for example, compares with an average of about 11 m/s over most of the UK, 10 over northern France and 9 m/s over central Germany. This tells you something you have more than likely realised already - Ireland is a rather windy place.
Now, this wind is potentially useful as a source of energy. Wind machines have been used for centuries to grind grain and to pump water, but nowadays the most common way of tapping the energy is by means of turbines.
These have two or three rotor blades facing into the wind, which are forced to rotate at anything from 15 to 50 revolutions per minute; the revolving blades spin a shaft inside the turbine, and this in turn forms part of a generator which produces electricity. Wind turbines are often grouped together in a "wind farm".
The potential of wind farms was largely ignored worldwide until comparatively recently. The 1970s oil crisis, however, spawned a desire in many countries to reduce dependency on imported oil, and more recently interest in wind energy has been enhanced by concerns about global climate change related to the use of fossil fuels. When they were first introduced, wind farms were very expensive, but over the years the installation costs have dropped, and consequently the economics of obtaining electricity from the wind have become significantly more attractive.
The first wind farm in this country was installed at Bellacorick, Co Mayo, in 1992. It comprised 21 wind turbines and had a rated capacity of a little over six megawatts, capable of generating enough electricity to supply about 3,000 homes. There are more than 20 wind farms in operation on the island now, and the number is increasing steadily.
Enthusiasts envisage wind farms producing up to 20 per ent of the State's electricity needs by 2010, but most people would see the figure as overly optimistic.