| | | Wind Energy

From WikiVerde

Since ancient times, the power of the wind has been harnessed for various purposes. It was the Egyptians who used the wind to sail ships on the River Nile and later on, windmills were used extensively to grind grain. It’s said that the earliest wind mills came into existence in Persia, modern-day Iran. The basic design of the windmill was improved considerably by the Dutch.

Wind and the Environment

It was in the 1970s that severe oil shortages, propelled experts to think about alternative energy sources. However, it was not until the 90s that experts really pushed for a solution to curtail the increasing deterioration of the environment. Over a period of time, wind energy has emerged as an economical power resource in various parts of the world. It’s a clean fuel, and wind farms, do not produce air or water pollution. This is because no fuel is essentially burnt. Many countries have systematically built their capacity to generate electricity through wind energy, as they are a wonderfully renewable alternative to conventional power plants. It really seems to be the best solution in terms of alternative power generation, and the increasing use of wind turbines, illustrates this fact with aplomb.

How Wind Turbines Work

The design of the wind turbines helps them exploit the wind and the energy of the wind. This is done using the wind energy that exists at a certain location. The optimum tower height is decided upon by the method aerodynamic modeling, which also chooses the number of blades to be used, shape of the blades; the various control systems that need to be put in place, etc. The job of almost all, modern day wind turbines, is the conversion of wind energy into electricity for the purposes of energy distribution. The wind turbine is composed of three integral parts that all come together to help in the process of electricity generation through wind power:

Rotor Component – It accounts for around 20% of the cost of the turbine. The job of this component is to convert the wind energy into a low speed rotational energy of the intermediate variety.

Generator Component – Almost 34% of wind turbine cost is taken up by the generator component as it consists of various integral facets like control systems, gearbox component, electrical generator etc. The purpose of this component is to convert the low speed rotational energy into electrical energy.

Structural Support Component – Around 15% of the cost of the wind turbine is taken up by the structure which constitutes the tower.

The Different Types of Wind Turbines

An axis enables the rotation of the wind turbine. There are two types of wind turbines and these are differentiated by the axis in which the turbine rotates. Turbines that use a horizontal axis are more popular then vertical-axis turbines.

Horizontal Axis Turbines

Horizontal axis wind turbines, commonly known as HAWT, are widely used and include an electrical generator and a main rotor shaft that is placed at the top of a tower. A wind sensor generally helps a large turbine to point itself, and in this they are also helped by a servo motor. In the case of small turbines, this is not necessary as a simple wind vane can do the needful. The purpose of the tower is to produce turbulence behind it and hence the horizontal axis turbine points upwind. However, there are downwind varieties also, but if you are looking for reliability and efficacy then upwind machines are the way to go.

The Various Advantages of Horizontal Axis Wind Turbines:

• Stability, as the blades are away from the center of the gravity of the turbines.

• Best of angles of attacking the wind, the wings can be warped. Thus the maximum amount of wind energy can be collected throughout the day.

• Minimal damage in storms, as the rotor blades can be pitched during a raging storm.

• The tall tower means that, one can get access to the strongest of winds. Wind speed is of paramount importance when it comes to power generation.

Vertical Axis Wind Turbines

As the name suggest, the rotor shaft runs vertically in these types of turbines. The best part about such turbines is that the placement of gearbox and generator can take place near the ground. This defeats the need for a tower. Moreover, the turbine need not be pointed towards the wind.

Subtypes of Vertical Axis Turbines:

Eggbeater Turbines – The innate efficacy of such turbines is pretty good, but they create large ripples of torque and cyclic stress that are liable to harm the tower. This essentially means that such turbines are not reliable. Moreover, as a general rule they do require an external power source.

The Gorlov Helical turbine – As the name suggests, it has a helical configuration. It was patented in 2001 and is a self-starting, low-vibration, lower torque ripple and low cyclic stress machine. It is more reliable and quite effective compared to the earlier models of the vertical axis turbines.

Giromill - It’s like a Darrieus turbine, but without the associated curved blades. The blades of this turbine are straight in nature. It also comes with a variable pitch, meaning that it will have a relatively flat torque curve and will offer effective and superior performance, even in turbulent winds.

The Various Advantages of Vertical Axis Wind Turbines:

• Easy on maintenance, as almost all the parts of the vertical axis wind turbines are near the ground.

• Vertical rotor blades, means there is no need for a yaw device, thus reducing costs to a great extent.

• A higher airfoil pitch angle means superior aerodynamics, and a marked decrease of drag both at high and low pressures.

• These can be installed on hilltops, ridge lines, passes, and mesas. This is because in such landforms the wind speed is higher at the ground level, as the winds are either moving upwards on a slope or are being funneled through a pass.

• No need for a free standing towers, hence, minimizing associated expenses.

Sources

http://en.wikipedia.org/wiki/Wind_turbine

http://www.eia.doe.gov/kids/energyfacts/sources/renewable/wind.html

http://www.esru.strath.ac.uk/EandE/Web_sites/02-03/zero_emission_bldgs/descripwindturbines.htm