Introduction: A wind turbine is a machine made up of two or three propeller-like blades called the rotor. The rotor is attached to the top of a tall tower. As the wind blows it spins the rotor. As the rotor spins the energy of the movement of the propellers gives power to a generator. There are some magnets and a lot of copper wire inside the generator that make electricity.
Because winds are stronger higher up off the ground, wind turbine towers are about 30 metres tall to allow the rotor to catch more wind energy. The turbines are built with a device that turns the rotor so that it always faces into the wind.
Just one wind turbine can generate enough electricity for a single house or the electrical energy to pump water or to power a mill which grinds grain. The electrical energy can also be stored in batteries.
- Moving air is called wind.
- Energy recovered from the force of the wind is called wind energy.
- The energy possessed by wind is because of its high speed.
- The wind energy is harnessed by making use of wind mills.
Harvesting of wind energy:
- The strike of blowing wind on the blades of the wind mill makes it rotating continuously.
- The rotational motion of the blade drives a number of machines like water pump, flour mills and electric generators.
Wind farms: Wind farms are places where many wind turbines are clustered together. They are built in places where it is nearly always windy. The electricity that is generated at a wind farm is sold to electricity companies that provide the electricity to people living in cities and towns.
- When a large number of wind mills are installed and joined together in a definite pattern it forms a wind farm.
- The wind farms produce a large amount of electricity.
- The minimum speed required for satisfactory working of a wind generator is 15 km/hr.
- It does not cause any air pollution.
- It is very cheap.
- Wind energy is friendly to the surrounding environment, as no fossil fuels are burnt to generate electricity from wind energy.
- Wind turbines take up less space than the average power station. Windmills only have to occupy a few square meters for the base; this allows the land around the turbine to be used for many purposes, for example agriculture.
- Newer technologies are making the extraction of wind energy much more efficient. The wind is free, and we are able to cash in on this free source of energy.
Disadvantages: The main disadvantage regarding wind power is down to the winds unreliability factor. In many areas, the winds strength is too low to support a wind turbine or wind farm, and this is where the use of solar power or geothermal power could be great alternatives.
Distribution of wind speed: Distribution of wind speed (red) and energy (blue) for all of 2002 at the Lee Ranch facility in Colorado. The histogram shows measured data, while the curve is the Rayleigh model distribution for the same average wind speed.
The strength of wind varies, and an average value for a given location does not alone indicate the amount of energy a wind turbine could produce there. To assess the frequency of wind speeds at a particular location, a probability distribution function is often fit to the observed data. Different locations will have different wind speed distributions. The Weibull model closely mirrors the actual distribution of hourly wind speeds at many locations. The Weibull factor is often close to 2 and therefore a Rayleigh distribution can be used as a less accurate, but simpler model.
High altitude winds: Power generation from winds usually comes from winds very close to the surface of the earth. Winds at higher altitudes are stronger and more consistent. Recent years have seen significant advances in technologies meant to generate electricity from high altitude winds.
Feeding into grid:
Induction generators, often used for wind power, require reactive power for excitation so substations used in wind-power collection systems include substantial capacitor banks for power factor correction. Different types of wind turbine generators behave differently during transmission grid disturbances, so extensive modelling of the dynamic electromechanical characteristics of a new wind farm is required by transmission system operators to ensure predictable stable behaviour during system faults (see: Low voltage ride through). In particular, induction generators cannot support the system voltage during faults, unlike steam or hydro turbine-driven synchronous generators. Doubly fed machines generally have more desirable properties for grid interconnection. Transmission systems operators will supply a wind farm developer with a grid code to specify the requirements for interconnection to the transmission grid. This will include power factor, constancy of frequency and dynamic behavior of the wind farm turbines during a system fault.