Small wind systems

A small wind system is made up of the following parts:

Wind turbines: The rotors of the wind turbines consist of two or three blades that are aerodynamically designed to capture the maximum energy from the wind. The wind turns the blades, which spin a shaft connected to a generator that makes electricity. There are two basic categories of turbines i) smaller DC based permanent magnet turbines (mainly used for rural electrification) and large induction turbines, often used in conjunction with an existing grid. Small wind turbines use permanent magnet alternators to produce wild AC power that is in turn rectified to DC and used together with a battery bank (see below). Small turbines are usually made with few moving parts and are designed for rural applications where frequent maintenance is difficult
Commercial wind turbines range from a few hundred watts to 20 kw to over one megawatt with a life time estimation of 20 years.

Tower: Turbines are mounted on towers – typically 80-120 feet high – a mainframe that supports the rotor, generator, and tail which keeps the blades facing the wind. For small home systems, smaller towers around 4 to 6 meters can be used to assist in maintenance and transportability. For larger power systems, such as for schools on rural communities, the minimum tower height should be around 18m. Towers may be self-supporting, but more commonly use guy wires.

Charge controller: The charge controller controls the charging of the battery by the wind turbine and usually serves the following functions:

• Battery over-charge control to prevent the wind turbine from charging the battery too heavily
• Malfunction protection from inverter and other system components
• Lightning protection
• Protection from inverse direction current flow, where the battery may discharge through the wind turbine
• An easy disconnection point to separate the wind turbine from the power system

In addition to the tower and turbine, small wind energy systems require a foundation usually made of reinforced concrete; a wire run, to conduct electricity from the generator to the electronics; a disconnect (or safety) switch, which allows the electrical output to be isolated from the electronics; a power processing (or conditioning) unit, which makes the turbine power compatible with the utility power and a system energy meter, which records energy production.

Battery bank

• Low voltage disconnect to disconnect the battery when it reaches a low state of charge
• Fast acting fuses to protect the user and battery bank from short circuiting in the DC loads
• Polarity protection so that devices cannot be connected improperly
• Manual disconnection to allow the user to disconnect all of the DC loads safely

Inverter

• A wide DC input range and stable AC output
• High conversion efficiency and very low idle power consumption
• Able to sustain the surge power when starting lare loads
• Over current and over voltage protection
• Low voltage protection to keep battery from being heavily discharged
• Wire shortage, fast acting fuses and wrong connection(polarity) protection

<//strong>: Most household appliances use AC. Therefore, inverters are usually added to the system to convert DC into AC.

Features of a common inverter:<//strong>: When the electricity produced by the wind turbine exceeds the system load, the extra power can be stored in a battery bank. Due to speed variations, wind systems do not provide a constant level of power supply, thus the battery system also stores surplus power for use in times of calm or low wind. Electricity is stored in the battery in DC form. Power system battery banks are made up of multiple units of stationary deep-cycle batteries linked together in series. The size is determined by the load capacity, the wind pattern and desired storage time.

Load controller: As explained above, electricity from these systems is produced in DC form and can be used directly for any DC loads, such as light bulbs, radios, TVs and many industrial appliances. If DC loads are used, a DC load controller must be implemented to serve the following purposes: