How it began ...

Back in the 19th century a young bloke was frigging around with carbonized bamboo, evacuated glass tubes and inert gasses. After hundreds of prototypes a working example of the first ever electric light globe was made. The young bloke was Thomas Alva Edison and arguably his invention changed forever the world. It was the dawn of the electrical age.

While Edison kick started the electrical age, a heap of lesser known men and women had already pioneered electrical research and come up with some simple formulas on how this stuff called electricity behaves. Curiously no one in the world can tell us exactly what electricity is ... But with the hard yards already done and resting in the knowledge that electricity is pretty simple stuff, let's look at a few basics.For our purposes we need to know that:

Electricity is stuff that flows to appliances through wires.

Electricity has two characteristics called voltage and current. Some examples of voltage are:

12 volts - A common car electrical voltage and a small solar system voltage
24 volts - A common small house or large motor home voltage
48 volts - A more serious voltage for medium to large household solar power systems
96 Volts and above - Serious voltage from a large battery bank for a larger installation.
Mains type voltage - This varies depending on what part of the world you come from, commonly 110 in the USA or 240 volts in Australia, with some countries using 220 volts.

Current - Is the amount of electricity flowing and is proportional to the amount of power being used. A definition would be that an item that uses a large amount of electricity, say a heater or an iron will draw more current than a little electrical appliance like a domestic light globe. Current is measured in amps or more correctly amperes. While voltage could be called the potential of electricity, current is the amount of power that comes out of the wire.

Electricity will be in two forms: AC or DC.

DC Electricity is; "direct current" and is the electricity generated by your solar panels and stored in your batteries.

AC Electricity is; "alternating current" as connected to most houses and buildings in most areas of the world. This is the electricity your inverter will produce to run your appliances like the TV stereo and computer.

Grab a Calculator
Hopefully it will be powered by a solar cell! You are going to have to perform a few simple calculations on a piece of paper called a load sheet. Prior to putting pen to paper however let's take a quick look at what a few of the aforementioned electrical pioneers actually discovered.

Watt and his watts
The watt is named after Mr. Watt. He was a pretty clued up dude and invented (amongst other things) the steam engine. The watt is the unit of energy you should become familiar with. A watt is a measurement of work just like a litre is a measure of liquid. Solar panels are rated in watts.
A simple calculation to remember is: Volts x Amps = Watts. (See "Ohms Law" below). If you refer back above to Volts and Current, the calculation: Volts x Current (in amps) will tell us the amount of work being performed.

The watt as a unit of work is used in other measurements, for example the metric power output of an engine is given in kilowatts (bunches of 1000 watts). 1 horsepower = 746 watts

Enter Georg Ohm
Georg Ohm was a brainy German physicist who loved fooling about with electricity. While doing so he discovered a relationship between voltage, electrical current and work performed (watts) This is called Ohm's law.

Ohms law states (in part) that: Amps (current) x Volts = Watts

Later you will find this calculation very useful. Of course you can reverse this for another common calculation; Watts divided by Volts = Current. Useful stuff indeed! At this stage don't fret about remembering all of this stuff though! Later pages will contain hints as to what to do calculation wise.

Parallel and Series connections
Later on as you ponder connection solar modules or batteries together you will hear the term "connecting in parallel" or the term "connecting in series". It is important to gain an understanding of what this means: Basically speaking a device like a solar panel or a battery will have what is termed as a nominal voltage. The nominal voltage of a solar panel is usually 12 volts. The nominal voltage of a lead acid battery is 2 volts.

A parallel connection between two devices will result in the voltage remaining the same. A parallel connection is connecting the positive and negative terminals of one device to the positive and negative terminals of the other device.

An example of parallel connection is drawn above. This could be 2 x 12 volt solar panels and joined in parallel the output will be 12 volts even though there is two panels together.

A series connection is somewhat different: Opposite polarities are connected. You will take the positive terminal from one device and connect it to the negative terminal of the other. This will double the voltage. See diagrams below.

An example of series connection (above), if this was the same 2 x 12 volt panels then when joined in series the output would be 24 volts. Note how the power is now taken from a terminal on each panel.

The above diagrams could equally apply to batteries. Les't say you have chosen 2 x 12 volt Exide batteries (from our products page on batteries). the top diagram would produce 12 volts. The lower diagram would produce 24 volts.

Perfect Efficiency?
A final part of this rave is on a subject called efficiency. Unfortunately all things won't add up to a perfect power system. You will hear about efficiency in later pages. To summarise what this is is simple:

Your solar system will loose a bit of power as the electrons flow from place to place. A bit is lost in the wires between the panel and the regulator, a touch more is lost in the regulator and still more is lost as the electricity gets stored in the battery. Converting your battery electricity to another form via an inverter will result in still more losses. You will calculate in an efficiency factor using your calculator (with the solar cell). Typically the efficiency factor can be as low as 70% which might sound a tad sad, but there you have it and in reality is is not that grim!

The next lesson is all about calculating what sort of equipment you need in the way of panels and an introduction to a thing called a load chart. Use the navigation bar to the left of this page to progress to the next lesson or use this link: "solar panels"

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