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With our residential wind power guide, we look at the practical use of wind energy to power your home. Wind is caused by the uneven heating of the Earth by the sun and the fact that temperatures are always trying to reach an equilibrium (heat is always moving to a cooler area). With the rising cost of energy and the damage to the environment from fossil fuels, it is becoming more equitable to harvest this renewable resource.
The advantages of wind energy are that it is virtually free (after you purchase the equipment) and there is no pollution.
The disadvantages include the fact that it is not a constant source (the speed varies and many times it is insufficient to produce electricity) and it typically requires about one acre of land.
If you live in the USA, you can receive a 30% tax credit (up to $4000) for the installation of a residential wind turbine.
The amount of power that is available varies by wind speed. The amount available is called it's power density and it is measured in watts per square meter. For this reason, the U.S. Department of Energy 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 more. For effective power production, class 2 winds (11.5 mph average speed) are usually required.
In general, wind speeds increase as you get higher above the Earth. For this reason, the typical wind turbine is installed on a tower at least 30 feet above obstructions.
There are two basic types of towers used 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 can be easily raised and lowered for maintenance.
The kinetic (moving energy) from the winds is harnessed by a device called a 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). 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 instead of flat and resemble the propellor of a small airplane.
A turbine is classified as to whether it is designed to be installed with the rotor in a horozontal or vertical positon and whether the wind strikes the blades or the tower first. A vertical turbine typically requires less land for it's installation and is a better option for the more urban areas of the world. 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 keep the unit pointed into the wind. A downwind turbine does not require a tail as the wind acting on the blades tends to keep it oriented properly.
These turbine systems would be damaged if they were to be allowed to turn at excessive speeds. Therefore, units must have automatic overspeed governing systems. Some systems use mechanical type brake system where the blades fold back against the turbine body at a predetermined wind speed. This is commonly called "furling". Other systems use electrical systems for breaking where torque is produced to counteract a part of the wind's force. The latest innovation is called variable pitch technology. This is where the angle of the blades relative to the wind striking them is changed to lower the speed.
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 tied to the utility grid or store electricity in a battery for use when the wind does not blow sufficiently.
When the home is tied to the grid, the excess electricity that is produced by the residential wind power system can be sold to the utility company to lower and sometimes even eliminate your electric bill. During times with not enough wind, the home is supplied power from the utility company.
If you are considering a residential wind power system, you can check out our wind system ratings page to compare the brands. You could spend hour upon hour sorting through the different brands and the various claims of the manufacturers. But, we have already done the research and put the results in a format that is easy to understand.