Some History

Back in 1600 and something a bloke named Benjamin Franklin thought it would be a good idea to fly a kite in a thunderstorm. I wasn't around at the time but the story goes that the kite had a metal string leading down to a wooden handle and attached to the metal string was a key. When young Ben touched the key he got the jolt of his life and in doing so became the first person in recorded history to deliberately give himself an electric shock. So ushered in the dawn of the electrical age.

Ben was followed by some well remembered folk like Watt, Edison, Tesla, Marconi, Ohm, Voltaire, Ampère and the like, as well as a heap of men and women history has forgotten.

Some of the forgotten men and women ...

These folk did the hard yards and came up with all the stuff on how electricity behaves and how to generate and store it. Lets have a bit of a look at what they came up with.

What is Electricity?

Sorry, I don't really know!
I would describe it as an invisible substance that came out of wires and made things like lights and the stereo and TV and stuff work and that it could be a bit shocking if you touched it (sorry). Basically it can be described as a bunch of things called electrons that flow through wires. These things can do a bit of work for us.

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 small solar system voltage
24 volts - A common small house or large motorhome voltage
48 volts - A more serious voltage for medium - 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 or 220 - 250 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 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 blender in a desirable manner.

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 must 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.

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. The voltage will remain the same.

An example of parallel connection (above), voltage will be unchanged, power output can be taken from any terminal.

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), voltage will be doubled; power output can only be taken from remaining terminals on both devices.

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 nave bar to the left of this page or click here to proceed with your learning

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