Wind energy is a form of solar energy produced by uneven heating of the Earth's surface. Wind resources are best along coastlines, on hills, and in the northern states, but usable wind resources can be found in most areas. As a power source wind energy is less predictable than solar energy, but it is also typically available for more hours in a given day. Wind resources are influenced by terrain and other factors that make it much more site specific than solar energy. In hilly terrain, for example, you and your neighbor are likely to have the exact same solar resource. But you could have a much better wind resource than your neighbor because your property is on top of the hill or it has a better exposure to the prevailing wind direction. Conversely, if your property is in a gully or on the leeward side of the hill, your wind resource could be substantially lower. In this regard, wind energy must be considered more carefully than solar energy. Wind energy follows seasonal patterns that provide the best performance in the winter months and the lowest performance in the summer months. This is just the opposite of solar energy. For this reason wind and solar systems work well together in hybrid systems. These hybrid systems provide a more consistent year-round output than either wind-only or PV-only systems. One of the most active market segments for small wind powered electric generators manufacturers is PV-only system owners who are expanding their system with wind energy.

Most wind powered electric generators are horizontal-axis propeller type systems. Vertical-axis systems, such as the the egg-beater like Darrieus and S-rotor type Savonius systems, have proven to be more expensive. A horizontal-axis wind powered electric generator consists of a rotor, a generator, a mainframe, and, usually, a tail. The rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator.

The rotor usually consists of two or three blades. A three blade unit can be a little more efficient and will run smoother than a two blade rotor, but will cost more. The blades are usually made from either wood or fiberglass because these materials have the needed combination of strength and flexibility and don't interfere with television signals.
The generator is usually specifically designed for the wind turbine. Permanent magnet alternators are popular because they eliminate the need for field windings.

A low speed direct drive generator is an important feature because systems that use gearboxes or belts have generally not been reliable. The mainframe is the structural backbone of the wind turbine and it includes the slip-rings that connect the rotating (as it points itself into changing wind directions) wind powered electric generators and the fixed tower wiring. The tail aligns the rotor into the wind and can be a part of the overspeed protection.

Wind powered electric generators were quite a deceptively difficult product to develop and many of the early units were not very reliable. A PV module is inherently reliable because it has no moving parts and, in general, one PV module is as reliable as the next. Wind powered electric generators, on the other hand, must have moving parts and the reliability of a specific machine is determined by the level of skill used in its engineering and design. In other words, there can be a big difference in reliability, ruggedness, and life expectancy from one brand to the next.

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A wind powered electric generators perform more efficiently when positioned where the wind can get to it. Turbulence, which both reduces performance and works the turbine harder than smooth air, is highest close to the ground and diminishes with height. Also, wind speed increases with height above the ground. A tower at least 30 ft. is recommended. Smaller turbines typically go on shorter towers than larger turbines. A 250 watt turbine is often, for example, installed on a 30-50 ft tower, while a 10 kW turbine will usually need a tower of 80-120 ft.Ý We do not recommend mounting wind powered electric generators to small buildings that people live in because of the inherent problems of turbulence, noise, and vibration. The least expensive tower type is the ham radio antenna guyed-lattice tower. Smaller guyed towers are sometimes constructed with tubular sections or pipe. Self-supporting towers, either lattice or tubular in construction, take up less room and are more attractive but they are also more expensive. Telephone poles can be used for smaller wind powered electric generators. Towers, particularly guyed towers, can be hinged at their base and suitably equipped to allow them to be tilted up or down using a winch or vehicle. This allows all work to be done at ground level. Some towers and turbines can be easily erected by the purchaser, while others are best left to trained professionals. Anti-fall devices, consisting of a wire with a latching runner, are available and are highly recommended for any tower that will be climbed. Aluminum towers should be avoided because they are prone to developing cracks.

Towers are usually offered by wind powered electric generators manufacturers and purchasing one from them is the best way to ensure proper compatibility. Remote Systems Equipment The balance-of-systems equipment used with a small wind powered electric generators in a remote application is essentially the same as used with a PV system. Most wind powered electric generators designed for battery charging come with a regulator to prevent overcharge. The regulator is specifically designed to work with that particular turbine. PV regulators are generally not suitable for use with a small wind powered electric generators because they are not designed to handle the voltage and current variations found with turbines. The output from the regulator is typically tied into a DC source center, which also serves as the connection point for other DC sources, loads and the batteries. For a hybrid system the PV and wind systems are connected to the DC source center through separate regulators, but no special controls are generally required. For small wind powered electric generators a general rule-of-thumb is that the AH capacity of the battery bank should be at least six times the maximum renewable's charging current, including any PV elements. The wind industry has had good experience using battery banks that are smaller than those typically recommended for PV applications.