Wind turbines, are they feasible?

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Wind turbine performance benefits from elevation. (Getty Images)

Renewable energy from wind is perceived as one promising solution to the world’s renewable energy and environmental problems, offering the potential of almost pollution free energy. Ali Jadallah of DC Pro Engineering looks at the use of wind turbines in urban areas and wind turbine feasibility.

The interest in wind energy increased rapidly at the beginning of the twenty-first century. Many changes in technology, policy, environmental concerns and the electrical market have occurred that will help wind energy to become a major source of electricity.

In order to use wind turbines efficiently, good site selection and positioning of the turbines is necessary. A good site would have strong, steady wind and low levels of turbulence. According to the UAE Climate, prepared by the ministry of communication, the UAE has an average wind speed of 4.3 knots yearly.

Although wind turbines are usually installed in rural areas -where low population density combines with fewer turbulence inducing obstructions than in urban areas - the installation of wind turbines in urban areas was found to be financially and environmentally recommended.

In urban areas it is unusual to have an open space for wind turbines similar to rural areas, so mounting the wind turbines on the top of high rise buildings would be an optimal solution.

The average wind speed for the mean maximum stations in the table below, which is 4.2 m/s, will be used in this article, since the average mean for all the 20 stations in UAE, which is 2.2 m/s, is below the cut in speed required by the conventional wind turbine.

Wind turbines are usually classified by rated power, but wind turbine energy output also depends on the time the turbine spends producing a certain power.

A rough capacity factor can be obtained from the following graph. This factor depends on the cut-in speed of the wind turbine and the average wind speed on site.

For example, using the graph below, where the cut-in speed is 10 MPH, if the average wind speed in a certain site is 15 MPH, the rough capacity factor will be 20%. This means that the total number of hours in a year is: 8,760 hours x 0.2 = 1,752 hour.

So, having a wind turbine with a rated power of 1.5 MW will give output energy of: 1500 KW x 8760 hr x 0.2 = 2,628,000 KWh (American Wind Energy Association, 1998).

The shape of the idealised power curve graph came from the cubic power, where P = ½ π r ² v³, and this is why the slightest increment in wind speed would yield a substantial increase in power output, since the power is directly proportional to the cube of the wind velocity.

Considering the general electric 1.5 MW wind turbine with cut-in speed = 3.5 m/s and a Rated Speed = 12 m/s, the Rough capacity factor will be 2.2% for the average of the mean maximum stations wind speed in U.A.E (4.2 m/s), as shown in the following graph. (GE Energy, 2008)

From that graph, a table is obtained showing the monthly working hours.

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READERS' COMMENTS

good work
Posted by Mohamed Ibrahim, sharjah on Thursday 12 November 2009 at 18:47 UAE time


very good work ali , people could concentrate on solar energy , we are good in this , thermal energy also fesible

ME
Posted by Ali Jadallah, Sharjah, UAE on Thursday 26 March 2009 at 16:31 UAE time


Thanks Wael, yes it's not feasible at low elevation.

Wind Turbines
Posted by Wael, Sharjah, UAE on Thursday 26 March 2009 at 14:46 UAE time


Good work,finally to end the myth of wind energy in the middle east and conclude that wind turbines are not feasable in the gulf area.

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