Generation Solar Renewable Energy Systems



	Servicing a 3kW turbine on a lowered tower.

The turbine

A wind turbine is a device that converts wind energy into electricity. This electricity can be generated as either DC (direct current) or AC (alternating current). Larger systems typically generate AC. Wind turbines are rugged beasts and are designed to last more than 25 years.

System components

There are two types of stand-alone (i.e. non grid-connected) wind systems. Hybrid systems combine wind with another energy source - such as diesel or PV power - whereas autonomous systems are entirely self-sufficient. Non grid-connected wind turbines are typically small (500W-10kW) Larger wind turbines (3kW and up) are typically grid-connected. This enables them to use the grid as a large reserve which, is capable of accepting excess power and available when extra power is required. In addition to standard electrical equipment such as fuse boxes, cable, circuit breakers, voltmeters, and ammeters, a wind system might contain any of the following items:

1. Batteries

If you need power when the wind isn't blowing, you will need a back-up power supply (i.e. a fossil fuelled generator or the grid) and/or a battery system.

Most small wind systems use lead-acid batteries, such as deep-discharge lead-calcium or lead-antimony batteries.

Battery storage is generally rated in amp hours (Ah). This denotes the amount of current which the battery is able to deliver over a given number of hours at its normal voltage and at a temperature of 25 degrees Celsius. Capacity decreases with lower temperatures, and increases when discharged more slowly.



	No sun? No problem!

2. Charge regulators

These regulate the amount of current entering the battery and protect it from overcharging or completely discharging. Some small turbines have built-in regulators and do not require an additional regulator.

3. Inverters

An inverter changes electricity from DC (such as that produced by small wind turbines) into alternating current (AC) - which is used by most household appliances. This conversion is about 75-95 per cent efficient.

Larger turbines use the inverter as their interface between the turbine, the loads, and the grid.

Inverters are rated in watts (W) according to the continuous power that they invert/convert. However, inverters can also deliver much larger amounts of current for short periods of time - this is called surge capacity.

Most inverters produce a modified sine wave, which can run 98 per cent of typical household loads although stereo equipment and TV's may hum slightly. Inverters that produce a pure sine wave, which works perfectly even with computers and sound systems, are also available but are more expensive.

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