Solar power systems used to provide electricity consist primarily of two components; photovoltaic panels and a battery storage system. The photovoltaic (PV) panels generate electricity, while the battery storage system stores any excess for later, either night-time or overcast days; when there isn't enough sunlight to supply your electrical needs.
Batteries
The battery storage system is usually a large grid of batteries, stored in a well ventilated or vented, safe location, ie basement or specially constructed room. Though batteries are optional, if you intend to be truly “off-the-grid” electricity storage is required, and batteries are almost always the answer.
There are two variants of batteries used in most systems; nickel cadmium and lead acid.
Lead acid batteries are very common, and affordable. They are very similar to lead acid car batteries (differences are discussed below). They have terminals to which wires are attached, and contain metal plates that connect to the terminals. The plates sit in sulfuric acid.
Electricity is made by a chemical reaction between the plates and the sulphuric acid. When they combine, they generate electrons that flow through the terminals and down the attached leads to your power plugs. Photovoltaic solar panel generated electricity does this backwards, recharging the batteries.
The same basic principals apply with nickel cadmium batteries, although there are some practical differences. NiCad batteries cost much more than Lead Acid batteries, but deliver more value. They have higher capacity (can supply longer output than lead acid batteries), and they last much longer.
Both types are known as deep-cycle batteries. This is very different to car batteries.. Car batteries are designed to supply enough power to get your starter motor ticking over, and run your lights and stereo on idle, then the motor takes over in terms of supplying power. Car batteries are shallow cycle batteries.
Solar power batteries on the other hand, have to deliver a smaller current over a far longer time-frame, hence they are designed differently. During the night when the solar panels are not supplying electricity, these batteries do their job.
Charge Controllers
Completely emptying or overcharging a battery can shorten it's lifespan massively.
So, there is an invention that's part of the well-built solar panel system that stops that from happening. That's the Charge Controller.
When discharging, and the battery reaches a certain low level, the controller halts any further drain to prevent the stored charge from going under a designed-in level. It also cuts off while charging, when the battery has reached a set level of capacity stored. Most are designed to allow lead acid batteries to discharge no more than 50% of capacity. This ensures long battery life.
Solar panels will last twenty years, but even good batteries might only last for ten years, often less. Replacing them increases cost, so extending their lifespan is one of the keys to keeping overall costs as low as possible.
To learn more about home solar power systems or the solar power components involved, please visit Solar For Energy – Your Guide To Solar Power.
