Wind energy has been in use for quite a long time now, with windmills being used effectively to do mechanical work. With the growing need for alternative sources of energy, man is reusing an old method of tapping wind energy to produce electricity.
Wind turbines are being constructed, and wind farms are being developed to harvest energy all over the globe. The cost of construction of such machines varies according to their types and the scale on which they are being built. These devices have two basic designs, each with its own pros and cons.
The first and the commonly used type is the horizontal axis wind turbine, which has a tower and blades that turn to generate electricity. The second and lesser known design is the vertical axis wind turbine or VAWT, where the rotor is arranged in a vertical direction, and is not pointed towards the direction of the wind. Cost varies according the designs.
Efficiency of Wind Turbines
A turbine can convert a maximum of about 59% of the wind energy to electrical energy. This was determined by a German physicist, Albert Betz, in 1919, and is known as Betz's law. Though it does seem like an insufficient percentage of energy production, wind turbines can give decent energy returns. Some factors that affect the efficiency of such devices are:
These machines are usually designed to run at a specific wind speed, and any variation in wind velocity can lower their efficiency.
Extreme change in temperatures can affect the running of a wind turbine. Although, this issue is being addressed with improved designs, alterations in temperature still cause changes in energy conversion efficiency in windmills.
Loss of Energy
There is a loss of energy due to friction and resistance. Though work is being done to improve designs to reduce and limit this loss, it still does persist. Even the best designs of such machines can harness only up to 70 - 80% of kinetic energy.
Cost of Building Wind Turbines
The expense varies according to the type and size of the turbine that is being built. It could be a large, medium, or a small one. Installing a wind generator at home can cost you up to $4,000 to $9,000. However, making a simple homemade wind generator will cost you much lesser, and if you can afford it, you can then try to scale it up to a bigger size.
For commercial purposes, the scale of the machines has to be larger to be productive. The common ones used are about 2 MW in size. The cost of installing a 2 MW machine could range anywhere between $3 million-$4 million. The expenses are high because it includes cost of construction, transportation, setting up transformers, location costs, and maintenance.
Cost efficiency can greatly depend on the type of turbine, its location, and design. Also, an extensive study on the feasibility of the project has to be carried out at the building site, to measure the wind power and its variation in speed. The turbine design can greatly affect its efficiency.
HAWT or horizontal axis wind turbines give better energy returns only at areas with high and fairly constant wind speeds, and are very expensive to build and transport. VAWTs are cheaper to construct, and do not need unidirectional or constant wind speed, but may not give good energy returns on a large-scale basis.
Although wind turbines cost a lot of money to construct, they can be used as a part of alternative energy harnessing strategies, especially in pragmatic areas feasible for the functioning of these machines.