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Renewable Energy Series: 2. Wind Power

Following on from our first renewable energy blog on Solar Power, we now focus on wind power looking at its pros and cons, the technology behind it and examples of where it is used. Wind power is a renewable energy source that harnesses the earth’s winds which are driven by the sun’s heat. Over Europe and especially the UK the winds are high and regular with average wind speeds typically ranging from 5-11ms^-1. With the current rate of development of wind farms, it is looking like they may soon produce more power than nuclear plants within the next few years.


The maximum wind power (P) measured in Watts can be calculated using the following equation:

Where ρ is the air density (kgm^-3), v^3is wind speed, A is rotor swept area (m^3) modelled as an actuated disk and Cp is the maximum power coefficient, less than or equal to 16/27. This coefficient was first derived by German physicist Albert Betz from the principles of conservation of mass and momentum based on an actuated disk. The diagram below shows the control volume around a disk where T is the torque (Nm) acting on the disk equal to A multiplied by the difference in pressure (P2 - P1) measured in Pa.

Source: MIT


The wind turbine extracts power from the wind in the form of this torque and the remaining power in the wind is the sum of the axial and angular kinetic energies. The angular momentum is proportional to the torque of the wind turbine and so efficiency increases at higher rotational speed. Gearboxes are used to allow the rotor speed to match the winds.

Source: Eco Tech Institute


Our blog details why exactly wind turbines have only 3 blades as many other designs have been trialled including the Savonius VOWT (Vertical Axis Wind Turbine) and the Giromill/Darrieus VAWT. The efficiency and cost of designs always need to be considered and so many alternative designs have not been developed.

Source: Hopefulenergy.com


In the UK, wind power makes up for more than 11% of total electricity generation and a rapid expansion in the industry is expected. This could result in an increase in the number of high skilled jobs available and looks like an exciting area of engineering to be in. Glocal projects such as Lake Turkana in Kenya provide unique travel opportunities for engineers working in this sector. Lake Turkana has 365 turbines, benefiting from strong, steady and predictable winds making it an ideal location to use them. There are also other uses of wind power such as battery charging and water pumping.

Source: Lake Turkana Wind Power

As previously mentioned, wind speeds are not constant and thus wind power is not completely reliable and the supply of energy cannot always meet its demand. Therefore wind power alone will not be a renewable energy solution. Instead it needs to be used in conjunction with other renewable forms such as solar and hydro power. To some wind turbines can also be unsightly and generate noise. However wind turbines are renewable, causing no pollution or emissions and the wind is a sustainable energy source.


Wind farms are becoming increasingly common off-shore where wind speeds are higher as there is less turbulence which can be created by trees, buildings and topography. Adapted ships are used to drive a tube up to 30m long down into the seabed and designs are still being adapted to improve reliability and reduce maintenance to the turbines.          

                     

Interested in offshore engineering? Check out our Types of Engineering page which looks at what a career in this sector involves, example jobs, the skills required and professional institutions you can join to keep up to date with news and events in this area.        

Once again, thank you to Nia Hughes for her contribution towards this blog series.

Luke T Seal Engineering