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How Does Wind Energy Work?

July 1st, 2010 · 1 Comment

This article explains how does wind energy works and the expense of Wind energy.

Wind is a result from the uneven heating of the Earth by the sun and the fact that temperatures will always be attempting to reach an equilibrium (heat is definitely moving to a cooler area). With the rising price of energy and the destruction of the environment from standard fuels, it is increasingly equitable to harvest this renewable resource.

The benefits of wind energy are that it’s virtually free (once you buy the equipment) and there is no pollution. The disadvantages include the fact it isn’t a consistent source (the speed varies and many times it is insufficient to generate electricity) and it typically requires about one acre of land.

How Wind Energy Works

The quantity of power that can be found varies by wind speed. The total amount available is known as it’s power density and it’s measured in watts per square meter. For this reason, the U.S. Doe has separated wind energy into classes from 1 to 7. The average wind speed for class 1 is 9.8 mph or less while the average for a class 7 is 21.1 or even more. For effective power production, class 2 winds (11.5 mph average speed) are usually required.

Usually, wind speeds increase as you get higher above the Earth. Due to this, the conventional windmill is installed on a tower no less than 30 feet above obstructions. There are two basic types of towers employed for residential wind power systems (free standing and guyed). Free standing towers are self supporting and are usually heavier which means they take special equipment (cranes) to erect them. Guyed towers are supported on a concrete base and anchored by wires for support. They typically are not as heavy and most manufacturer’s produce tilt down models which is often easily raised and lowered for maintenance.

The kinetic (moving energy) from the winds is harnessed by a device termed as turbine. This turbine includes airfoils (blades) that capture the power of the wind and use it to turn the shaft of an alternator (like you have on a car only bigger).

There are 2 basic kinds of blades (drag style and lifting style). We all have seen pictures of old fashioned windmills with the large flat blades which are an example of the drag style of airfoil. Lifting style blades are twisted rather than flat and resemble the propellor of a small airplane.

A turbine is classified as to whether it is made to be installed with the rotor in a horizontal or vertical position and whether the wind strikes the blades or the tower first. A vertical turbine typically requires less land for it’s installation and is an improved option for the more urban areas worldwide. An upwind turbine is designed for the wind to impact the airfoils before it does the tower.

These units normally have a tail on the turbine which is needed to keep the unit pointed into the wind. A downwind turbine does not require a tail as the wind acting on the blades tends to maintain it oriented properly.

These turbine systems would be damaged if they were to be permitted to turn at excessive speeds. Therefore, units will need to have automatic over-speed governing systems. Some systems use electrical braking systems while others use mechanical type brakes.

The output electricity from the alternator is sent to a controller which conditions it for use in the home. The use of residential wind power systems requires the home to either remain linked with the utility grid or store electricity in a battery for use when the wind will not blow sufficiently.

When the home is linked with the grid, the surplus electricity that is produced by the residential wind power system can be sold to the utility company in order to reduce or even eliminate your power company bill. During periods with not enough wind, the home is supplied power from the utility company.

The expense of Wind Energy

Small residential wind power turbines can be an attractive alternative, or addition, to those people needing more than 100-200 watts of power for their home, business, or remote facility. Unlike PV’s, which remain at basically a similar cost per watt independent of array size, wind generators get cheaper with increasing system size. At the 50 watt size level, for instance, a small residential power wind generator would cost about $8.00/watt compared to approximately $6.00/watt for a Photo voltaic module.

For this reason, all things being equal, Photovoltaic is cheaper for very small loads. As the system size gets larger, however, this “rule-of-thumb” reverses itself.

At 300 watts the wind mill costs are down to $2.50/watt, while the PV costs are still at $6.00/watt. For a 1,500 watt wind system the cost is down to $2.00/watt and at 10,000 watts the price of a wind generator (excluding electronics) is down to $1.50/watt.

About the Author – Mary Jones writes for the residential wind energy weblog, her personal hobby blog centered on guidelines to reduce CO2 and lower energy costs using alternative power sources.

If you want to read my complete Bio: http://www.residentialwindturbines.org/

Tags: Renewable Energy

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