Wind is the result of the uneven heating of the Earth by the sun and the fact that temperatures will always be trying to reach an equilibrium (heat is always moving to a cooler area). With the rising price of energy and the damage to the environment from fossil fuels, it is more and more equitable to harvest this renewable resource.
The benefits of wind energy are that it is virtually free (once you purchase the equipment) and there’s no pollution. The disadvantages include the fact that it isn’t a consistent source (the speed 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 can be found varies by wind speed. The total amount available is termed it’s power density and it’s measured in watts per square meter. That is why, 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 even more. For effective power production, class 2 winds (11.5 mph average speed) are frequently required.
Usually, wind speeds increase as you get higher above the Earth. For that reason, the typical wind generator is installed on a tower no less than 30 feet above obstructions. There are 2 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 place 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 known as the 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 a good 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 built 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 a better option for the more urban areas worldwide. An upwind turbine is created for the wind to impact the airfoils before it does the tower.
Residential Wind Turbine
These units normally have a tail on the turbine which is required to maintain 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 allowed to turn at excessive speeds. Therefore, units should have automatic over-speed governing systems. Some systems use electrical braking systems while 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 will not blow sufficiently.
When the home is linked with the grid, the excess electricity that is created by the residential wind power system can be sold to the utility company to reduce and sometimes even eliminate your utility bill. During times with not enough wind, the home is supplied power from the utility company.
Wind Scheme Grid Tied
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 stop 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 wind mill would cost about $8.00/watt when compared with approximately $6.00/watt for a Photo voltaic module.
That is why, everything being equal, PV is more affordable 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 cost of a wind generator (excluding electronics) is down to $1.50/watt.
Mary Jones
To the readers of the Way to Go Green org Blog; this is a quest post by Mary Jones, who we thank very much for offering to guest post for us and we invite you all to visit her nice blog.
Who am I ? – Mary Jones writes for the residential wind power systems weblog, her personal hobby blog centered on tips to reduce Carbon dioxide and lower power costs using alternative power sources.
If you wish to read my complete Bio: http://www.residentialwindturbines.org/about
