Literature Review History The harnessing of wind energy started around 200 B.C in Persia. Early wind mills were used for small domestic applications, such as grinding grain or drawing up water. In 1887, James Blyth, a Scottish academic came up with the first known electricity producing wind turbine.
With the discoveries of large reservoirs of fossil fuels in the early 70’s, wind turbines were almost entirely eliminated from the energy energ y generation market. Later on, with growing information and awareness with regards to global warming and climate change, renewable sources of energies, and their related relat ed machinery such as wind turbines saw a steady rise in manufacturing as well as the research and development sector.
Classification Wind turbines are generally divided into two main types based on the orientation of the axis on which they are supported. 1- Horizontal Axis Wind Turbines (HAWT): This is the most common and the more conventional wind turbine. Advantages: Being the more conventional type, horizontal axis wind turbines are much cheaper than their vertical counterparts. One reason for this could be the fact that they use much lesser material per square inch to be manufactured than vertical axis wind turbines. In addition, the specifications of the horizontal axis wind turbine require it to be mounted atop a high rising tower/mast. This allows for better power yield as the wind speed is higher and more even at greater heights. Disadvantages: The three main components of the wind turbine, namely the gearbox, generator and the main rotor shaft, are all placed near the top of the wind turbine. This type of setting makes the horizontal axis wind turbines somewhat unstable. Furthermore, the wind turbine needs to be always pointed in the direction of the incoming wind in order to extract maximum power. This poses a problem in places where the wind flows in an uneven manner. Furthermore, horizontal axis wind turbines are infamously known for their notoriously loud nature. In addition, the extreme amount of blade span, with a nominal value of 15 m, make HAWTs impractical for small applications as well as in installation in urban areas. Finally, due to the high placement of all the mechanical and electrical components of the turbine, the maintenance costs of are usually very high.
Some typical HAWT applications
Some typical VAWT applications:
2- Vertical Axis Wind Turbines (VAWT): These are the modern type of wind turbines that use vertically mounted flat plates as blades. Advantages: Vertical axis wind turbines are perfectly suited for small power applications. The orientation of the blades of the VAWT allow it to harness wind energy through all directions. Hence it is perfect for small niche applications such as on top of buildings. Furthermore, all the three main components of the wind turbine, namely the gearbox, generator and the main rotor shaft, need not be placed at the top. Hence the y can either be grounded near the base of the turbine or can be separately located in a power room. This property of the VAWT makes it not only more stable, but also less costly in terms of maintenance costs. Furthermore, being much less noisy and much more compact in terms of blade size, VAWTs provide are perfectly suited for small power urban applications. Disadvantages: Due to their low height and close proximity to the ground, VAWTs can never be as efficie nt and as high power yielding as HAWTs. Furthermore, the 360 degree rotation of the blades cause high dynamic loading to occur in the structure. Also, the costs incurred in additional material required for the flat plates as well as the low yield have not yet been balanced out justifiably by the low maintenance costs.
References http://en.wikipedia.org/wiki/File:Wind_turbine_1888_Charles_Brush.jpg http://www.victordanilochkin.org/research/turbine/papers/HAWT%20versus.pdf
