Green Electric Solar Electricity Guide
“Electricity is really just organized lightning” ~ George Carlin
A guide like this would normally be quite technical, filled with circuit diagrams and an expectation that you know a lot about electricity. Well, not this blog! I have purposely attempted to make it easy to understand, so that even the home handyperson can successfully build this system.
You will be learning the basics as you progress, with an explanation of why certain design decisions are made, enabling you to make an informed choice if you want to make any changes.
However, we still need to understand some basic electrical terminology so that we can design, construct and test our small solar power system to ensure success.
Let us explore some basic electrical terminology that we will be using throughout this article.
Battery: a source of energy storage that has two metal surfaces separated by a combination of chemicals in order to store electricity. Switch: a device that opens or closes a circuit. When it is on it allows the current to flow. When off it breaks the circuit and prevents the current flow.
Electron: is a fundamental part of an atom that carries a small negative electrical charge. Electrons can move via a conductive material like wire carrying the charge with them. This movement is what we refer to as electricity.
Current: the flow of electricity (sometimes called Amperage). Current is measured in amperes or amps.
Voltage: is the force at which the energy is delivered. This electrical pressure drives the electrical current around the circuit. Voltage is expressed in volts. In our case, we will be making a 12-volt system.
Power: is the rate at which energy is delivered to, or from the system. Power is measured in Watts.
Energy: is the ability to do work or perform a task like run a motor or light a light globe. Energy can be measured in many ways.
The fundamental unit of energy is a Joule but it is more convenient, when dealing with electricity, to use Watt-Hours (Wh) or kilowatt-hours (kWh).
Open Circuit Voltage: A condition when two terminals are not connected to anything (an “open circuit”), so no current can flow into or out of either terminal. The voltage (voc) between the terminals is the open-circuit voltage of the device.
Direct Current and Extra Low Voltage
During this guide, we will be using extra low voltage — between 10.5 to 14.5 volts, which is the nominal range for a solar photovoltaic system.
This voltage is perfectly safe when handled with basic respect and you do not require a licensed electrician to do the wiring. We will also be using direct current (DC) as opposed to alternating current (AC) which is connected to households and supplies household appliances. Direct current utilises a positive (+ve) and a negative (-ve) wire and the electrons flow along from negative to positive, powering whatever device you connect to the circuit.
Just to confuse things, even though it is the electrons moving, for historical reasons, most electrical textbooks and diagrams show what is known as, “conventional” current, which flows from positive to negative. It does not change our understanding about what is happening but we need to be aware and check our information to make sure of our connections.
12V DC is also used in cars, small trucks, caravans, and motorhomes (RVs) so the range of appliances that you can connect to your system is vast. From powering fans to small fridges, pumps to iPods, the application for this type of system is endless. To store these electrons, you will need some batteries.
To charge the batteries you will need a generator of some sort. You could hook them up to a battery charger via the mains supply, but this does not provide you with a continuous supply should you experience a blackout or forced grid shutdown. What is required is a source of renewable energy, which has a low capital cost, is essentially free to run, and easy to maintain.
Solar modules are probably the best choice in sunny climates and for most applications because there is essentially little maintenance, and no ongoing fuel costs.
There are several kinds of solar modules but the most popular types are crystalline panels. If you look at a solar module, you can see that it is made up of many single thin blue black wafers which are the solar cells, all protected by a glass cover.
This two-layered wafer is made from purified silicon. The top layer usually has a tiny amount of phosphorus added to it, which makes this layer release electrons freely (negative type layer). The bottom layer usually has boron added to it, which tends to trap electrons (positive type layer). When a photon of light hits the silicon at or near the junction, it excites an electron to freedom and leaves a hole behind in the silicon atom in the wafer.
Electrons move across the silicon in one direction. Because the single solar cell is connected to all the other cells in a circuit loop, the electrical current (caused by the free electrons) flows in the loop, generating electricity.
The other main type of panel is an amorphous panel. It works in much the same way but is constructed differently and has a solid dark or black surface with no easily visible cells
Other Renewable Sources
Wind turbines are suited for cloudier and windier climates. However you could use both solar and wind turbines and install what is known as a hybrid system. Wind turbines are relatively inexpensive to purchase these days and have relatively low maintenance requirements, but they do need reasonably stiff winds to generate useful power. The subject of wind power will not be covered in this article.
If you are fortunate to have an ample supply of free flowing water in a creek or stream on your property, you could even use micro-hydro, which would be the best solution by far in this situation. A micro-hydro installation would be subject to possible planning or council restrictions. The flow of the water moves a wheel that is connected to a generator.