Basics

N.B. The information herein provided is a synthesis and integration of the ELREN Training Manual content as prepared by the Tipperary Institute, Ireland on behalf of CARLOW LEADER core partner.

How Wind is Created

Wind is caused by the movement of air masses around the earthglobe.
Wind force and direction is influenced by:
1. the earth's temperature (which is in turn affected by earth's curvature) -> [The earth is heated by the sun. The curvature of the earth means that the tropics (i.e. areas closer to the equator) are considerably warmer than those regions at higher latitudes. This causes air movements and, depending on the position on the earth, results in trade/global winds and in regions of higher and lower atmospheric pressure.]
2. the earth's rotation -> [The rotation of the earth has an additional affect which is termed the "Coriolis Effect". This causes the winds direction to change depending on location e.g. in the Northern Hemisphere north-bound winds are caused to veer to the right/west creating what are called "westerlies".]

A key latitude which affects the direction of wind globally is 30 degrees (North and South). At this latitude the Coriolis rotational effect prevents the hot air, which has risen from the equator and is moving northwards or southwards, from progressing further. This results in high pressure areas in this region and low pressure areas at the equator.
In practice, the presence of wind can be assessed by measuring the atmospheric pressure (measured in 'bar' or 'pascals') in a particular area by a barometer. In general, areas of high pressure indicate little wind and fine weather while areas of low pressure tend to indicate windy weather and rain.

Source: http://www.ecmwf.int/samples/d/banner/page.html

In general, the direction of the prevailing wind can be determined, based on latitude, as shown here.

In addition to the above effects at a global level, there are local conditions which also affect wind direction and force. These include: altitude, proximity to the sea (sea breezes), topography (valley winds) etc.

Understanding Energy and Power in the Wind

Concepts and calculation details involved in estimating the kineting energy associated to wind characteristics are provided in the ELREN Training Manual.

Wind Energy and Electricity Generation

With the developments in the production of electricity and the electricity network in the late 19th century and early 20th century experimentation into the production of electricity using wind mills started.
The major developments in this regard occurred in Denmark and were lead initially by Poul La Cour. A driver behind the development was the need to supply electricity to rural areas within Denmark. His first machine, built in 1891, powered a dynamo. Further experimentation lead to the designs being commercially developed.
Research and development in Germany and the USA up until the mid 1970s met with varying levels of success. This was primarily due to the low energy prices at the time restricting the interest, at a strategic level, in developing wind energy.

Installed Wind Power Generation Facilities

According to EWEA estimates issued on 01.02.2007 the Total EU-25 Wind Power Generation Capacity at the end of the year 2006 amounted to 48.027 MW. For details by country and comparison with the year 2005 see EWEA website (link).

Wind Farm Typologies

(table)

Small Scale Wind Turbines

Small Scale Wind Turbines (SSWT) can generally be classified as being <250kW. The use of SSWT is primarily focused on scenarios where electricity will be used on site and not exported to the electricity grid.
There is a wide range of designs and systems available. An important design consideration for SSWT is to match the size of the turbine with the electrical load profile at the final utilisation site.
In situations where net-metering or smart metering is available, the viability of SSWT can be considerably advanced. This is due to the fact that excess power from the turbine can be exported to displace imported electricity and batteries, invertors etc are not required. The situation with net-metering varies considerably across the EU.
A particularly good resource to review small scale wind is the Home Power Magazine (link).