Generation Solar Renewable Energy Systems



	A single PV panel on a pole mount

The panels

A photovoltaic (PV) panel contains cells that convert light into direct current (DC) electricity. Most PV cells are made from silicon and last more than 25 years.

A group of panels is called an array.

System components

There are two types of stand-alone (i.e. non grid-connected) PV systems. Hybrid systems combine PV with another energy source - such as diesel or wind power - whereas autonomous systems are entirely self-sufficient.

In addition to standard electrical equipment such as fuse boxes, cable, circuit breakers, voltmeters, and ammeters, a PV system might contain any of the following items:



	Large battery bank in a nicely built battery enclosure.

1. Batteries

If you need power when the sun isn’t shining, you will need a back-up power supply and/or a battery system.

Most PV 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.

2. Charge controllers

These regulate the amount of current entering the battery and protect it from overcharging or completely discharging. Small panels often are manufactured to be self-regulating and do not require controllers.

3. Inverters

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

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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