2.1. How Wind Is Created?

2.1 How Wind is Created.
Wind is defined as air in motion. (1) When wind is being describe you first give the strength of the wind followed by the direction the wind is coming from e.g. extremely windy for a time, with strong to gale force and blustery west to northwest winds. (2)
Wind is powered by the sun and by the rotation of the planet. Wind from the sun is caused by the uneven heating of the earth by the sun. The equator is heated much more by the sun than the poles. The hotter air expands and rises creating a flow of air. Wind from the rotation of the earth is caused by the Coriolis effect.
“As air moves from high to low pressure in the northern hemisphere, it is deflected to the right by the Coriolis force. In the southern hemisphere,
The first wind mill to produce electrical power was designed and built in Scotland in July 1887 by James Blyth. This wind mill used storage cells to power a light. Blyth then went on to wright a paper describing his wind mill. The paper was presented to Philosophical Society of Glasgow on 2 May 1888. In May 1895 Blyth had an improved design built and it produced 10hp to storage cells, the wind mill ran for 27 years. (5)
The 20th century brought with it the large scale production of electricity through wind farms. This is where wind mills become wind turbines. There was also use of smaller type turbines where the electrical grid could not reach. This was capitalised by Joe Jacobs and Marcellus Jacobs who set up a factory in Minneapolis that produce turbines to create electricity off the grid.(6)
This brings us up to now where there is an emphasis on renewable energy and an active effort to reduce the world’s reliability on fossil fuels. The largest wind farm in Ireland is Meentycat in Co. Donegal its capacity is 88.5MW. This wind farm can supply electricity to approximately 45,000 homes. (7)
2.3 Converting Wind Energy into Electrical
This is another important aspect to look at when designing a turbine. This is important because if the blades are moving slowly most of the air will pass through the gaps and no energy will be extracted from it. On the other side if the blades are moving too quickly they will be trying to extract energy from each other’s dirty turbulent air this is less efficient. The optimal tip speed ratio depends on the number of blades the optimal ratios are shown in figure 2 below. (14) Figure 2 - Optimal Tip-Speed Ratio for different number of blades (15)
Vertical axis wind turbines have different tip-speed ratio’s the darrieus type can have quite high ratios, while the savonius type will be less than 1 because it can’t move faster than the wind speed.

2.5 Horizontal Axis Wind Turbines (HAWT).
Horizontal axis wind turbines are the most common type you see today. They generally have three blades witch rotate around the horizontal axis. They must face into the wind at all times. This is archived by using a yawing. The blades are connected to the main shaft witch is connected to a gear box. The gear box is used to increase the speed of rotation from the blades to a more suitable speed for the generator to produce electrical