ADVERC Explains Solar Panels.
Updated Friday 07/08/2009 10:53am
What does a solar panel do?
Simply, a solar panel is made from cells, these solar cells (or photovoltaic cells) will convert light into electrical energy.
So how does a solar panel work?
There are more than one type of solar panel, but nearly all work by the same fundamental physics, and the very large majority of commercially available panels are made from silicon (Si). When silicon absorbs sunlight of a certain wavelength an electron is excited into a state which is delocalized. In other words, this electron is now free to move around the entire panel. however, in a piece of plain old Si, there is no reason for it to go one direction rather than another (and electricity is the net movement of electrons in a single direction). In fact, the electron will move around in the Si randomly, and then eventually this electron will simply return to the ground, or return to its unexcited state and release heat. However, in the solar panel, there is something called a junction, where two slightly different materials meet. The two materials are actually both made of Si, but each one has a tiny percentage of other atoms mixed in with a different element. When an electron reaches this junction, it is either accelerated across it, or repelled by it, depending on which direction it is coming from (imagine water and a hill... water accelerates down the hill, but can't go up it). Now there is directionality to the system. You then attach a wire to each side of this junction, and when sunlight is absorbed, the free electrons now only flow in one direction, from one side of the junction to the other, driving a current through the external circuit. Electricity is just that -- electrons having a net flow in a single direction along a wire.
The two types of solar panel (Monocrystalline and Polycrystalline)
Monocrystalline solar panels are made from single (mono) crystal (crystalline) cells. These cells tend to be expensive but more efficient than polycrystalline.
Polycrystalline solar panels are composed of many crystallites of varying size and orientation. These are less efficient but are cheaper to manufacture than monocrystalline.
Should i buy Monocrystalline or Polycrystalline solar panel?
Both mono and polycrystalline will do the same job of turning light energy into electrical energy. What you should look for is the wattage of the solar panel, this is the power output. A 12v 10W monocrystalline solar panel will produce the same as a 12v 10W polycrystalline solar panel.
So what wattage should i go for?
In the uk we suggest a minimum ratio of 10W of solar panel to every 100Ah capacity of battery to replace the natural discharge typically experienced over the winter time. In the summer time that 10W solar panels performance increases to a potential 3 ampere hours (Ah) per day.
Is there anything else i need to know?
Yes, remember to budget for a solar panel regulator. A regulator is needed on all systems using solar panels to prevent overcharging which can lead to batteries being damaged.
