Learn How Wind Energy Works

It’s not necessary to be a nerd to understand how wind power works

Wind is caused by the uneven heating of the Earth by the sun and the fact that temperatures are invariably attempting to reach an equilibrium (heat is obviously moving to a cooler area). With the rising expense of energy and the destruction of the environment from non-renewable fuels, it is more and more equitable to harvest this renewable resource.

The benefits of wind energy are that it is virtually free (after you buy the equipment) and there’s no pollution. The disadvantages include the fact it’s not a continuing source (the velocity varies and many times it is insufficient to make electricity) and it typically requires about one acre of land.

How Wind Energy Works

The volume of power that’s available varies by wind speed. The amount available is called it’s power density and it is measured in watts per square meter. Due to this, the U.S. Department of Energy has separated wind energy into classes from 1 to 7. The common wind speed for class 1 is 9.8 mph or less while the average for a class 7 is 21.1 or more. For effective power production, class 2 winds (11.5 mph average speed) are often required.

Normally, wind speeds increase as you get higher above the Earth. This is why, the typical wind mill is installed on a tower at least 30 feet above obstructions. There are 2 basic kinds of towers useful 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 set them up. 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 may be easily raised and lowered for maintenance.

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

That there are two basic types 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 vertical or horizontal 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 around the globe. 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 required to maintain the unit pointed into the wind. A downwind turbine doesn’t need 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 allowed to turn at excessive speeds. Therefore, units should have automatic over-speed governing systems. Some systems use electrical braking systems although some use mechanical type brakes.

The output electricity from the alternator is sent to a controller which conditions it for use in the home. The usage of residential wind power systems requires the home to either remain tied to the utility grid or store electricity in a battery for use when the wind doesn’t blow sufficiently.

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

The price 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 less expensive with increasing system size. At the 50 watt size level, for instance, a small residential power windmill would cost about $8.00/watt compared to approximately $6.00/watt for a PV module.

That’s why, 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.

The author

Mary Jones writes for the residential wind energy systems website, her personal hobby blog centered on suggestions to reduce CO2 and lower energy costs using alternative power sources. My complete Bio