An Introduction To Wind Power

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TYPES OF SYSTEMS
Three basic wind energy systems are available. The first is a grid connected system with battery back up. The second is a grid connected system without battery backup. The third is a stand-alone system that is not connected to the grid.

A grid connected wind turbine can reduce your consumption of utility power. If the turbine cannot deliver the amount of energy you need the utility makes up the difference. When the turbine produces more electricity then your house needs, the excess power can be sold back to the utility company.

IS YOUR SITE RIGHT FOR WIND
The US Department of Energy (DOE) has regional information that shows whether wind speeds in your area are generally strong enough to justify investing in a wind system.

In order for a wind energy system to be effective you must have at least 10 mile per hour (4.5 meters per second) average wind speeds.
Read the FAQ titled "What is the average wind speed for my area?" You will find a wind speed map. If your site is located in the white areas of this map the regional wind average speed is less then 9.8 mph and wind may not be a good choice for you.

If your site has wind speeds greater then 10mph you have to also consider the geography of your site. Consider existing structures and future ones that my block the wind. Look at trees, buildings, and hills. These could all effect the performance of your wind energy system. Ideally you want to be the well above any air turbulence caused by obstructions.

If your site is flat this is great. If your site is hilly you have to be careful in selecting your location. The best location for a wind turbine in this case is on top or on the side of a hill that is hit by the prevailing winds. If you are in a gully or on the leeward (sheltered) side of a hill you will not receive any wind at all. If you have a complex terrain you may have to purchase a recording anemometer. This will measure the wind speeds at you site with the intent of finding the best mounting height and location.

RESEARCH POTENTIAL LEGAL OBSTACLES
Before you invest any time and money, you should research the potential legal obstacles to installing a wind system. Some jurisdictions, for example, restrict the height of structures permitted in residentially zoned areas.

WIND SYSTEM BASICS
All wind systems consist of a wind turbine, a tower, wiring and the balance of system components: controllers, inverters and/or batteries.

Wind turbines consist of a blades on a rotor, a generator mounted on a frame and a tail. The spinning blades turn the rotor capturing the kinetic energy of the wind. This is converted to rotary motion to drive the generator. The best indication of how much energy a turbine will produce is the diameter of the rotor. This determines the amount of wind that will intercept the turbine.

Wind speeds increase with height in flat terrain. This is why towers are used to mount the wind turbine. Generally speaking, the higher the tower the more power the wind system can produce. A general rule of thumb is to mount the wind turbine 30 feet above any obstacle that is within 300 feet of the tower.

Experiments have shown that relatively small investments in increased tower height can yield high rates of return in power production. For instance, to raise a 10kW generator from a 60 foot tower height to a 100 foot tower height involves a 10% increase in overall cost but it can produce 25% more power.

CONNECTING A WIND TURBINE TO THE GRID
There are two ways to tie into the grid, with and without batteries. If you are looking for a wind system without batteries there is a limited selection of equipment to choose from. Bergey Windpower offers a 10kW wind turbine with a grid connected inverter that does not require batteries. If you don't have the proper site for a 10kw generator you are locked into having a system with batteries.

For example, if you want a 400 watt wind turbine from Southwest Windpower. The turbine is connected directly to the batteries.

This turbine has a charge controller built into it so it will not over charge the batteries. Not all turbines have controllers built into them. A load diversion controller is typically used to prevent the wind turbine from damaging the batteries. A load diversion controller is a fancy way of saying that when the batteries are full a load is turned on to consume the extra power from the wind generator. Most times heating elements are used because they can draw a constant high amount of power.

Once your batteries are protected you will need a way to connect to the utility grid. A Trace SW inverter is the best way to make this connection. This inverter runs off of batteries. When the batteries are charged the inverter acts similar to the load diversion controller. It will take the extra power the wind is producing and will divert or sell this power to the grid. The SW inverter will also provide you with a way to backup critical loads in you home when the utility grid fails. This is a design side note, you will still need a controller to prevent the batteries from overcharging. This inverter is design to disconnect from the utility grid when the utility grid fails. You must have a means to offset the full power output of the wind generator to prevent battery overcharge.