How Does A Solar Panel Work?

A solar panel is essentially a device for converting the energy from the sunlight which falls on it, into another form of energy: either heat or electricity. A typical solar panel consists of a flat rectangular frame, approximately 6 feet by 3 feet.

Normally, a number of such solar panels will be placed on a south facing roof, angled to the sun. They produce their peak output when there is no cloud cover, and the sun is shining directly on all of them.

There are at least three distinct types of panel and they all operate in quite different ways.

Water Heating Panels

A water-heating panel usually consists of a very shallow box, with glass on one side (the side which is to be exposed to the sun) some sort of insulation on the other side (the bottom), and a pipe-arrangement to take water through the box between these two.

How do they work? Well, a solar panel of this kind relies, mostly, on the peculiar properties of glass. Glass is a material which, as we all know, lets light through easily; what isn’t so well known is that it doesn’t let heat through very easily at all, it is in fact an excellent thermal insulator.

So, in a water-heating solar panel, the sunlight enters thorough the glass, and then hits the pipes or container which holds the water. This latter is usually painted black, so that it absorbs the sun’s rays and turns them into heat very readily.

Once the sunlight has been converted into heat in this way, it cannot easily ‘escape’ through the insulation at the back, and, critically, it cannot escape through the glass at the front either. 

This situation results in the contents of the panel, in particular the water, becoming much hotter than the ambient temperature outside, typically, 130-150 degrees Fahrenheit on a warm day (80 degrees).

The heated water is then fed into a hot water tank, it’s often just as simple as that. Learn about how you can make your own solar water heater here.

Air (or space) Heating Panels

These are generally even less complex than the water-heating kind. They simply have some material inside at the back of the box (panel) which is colored black and easily absorbs sunlight. This material is selected to be one which has the property of heating up quickly when exposed to sunlight, metal painted black, and black slate are examples.

The air in the box becomes hot through contact with this material, and, as before,  heat cannot easily escape out of the panel. When the heated air is required, a vent is opened from the back. 

This is one of the most straightforward forms of solar heating imaginable. If you’re interested in the DIY approach, you can learn more by reading our Solar Heater Guides Review.

Electricity Generating Solar Panels

These operate in quite a different way, they convert the sunlight falling onto them, into electricity.

How do they do this? Well, a panel is essentially a surface made up of a  number of ‘phovoltaic’ power cells, which are kept together in a frame, or flat ‘matrix’, so that all the cells are exposed to the sun.

Each panel will have, typically, but certainly not always, around 64 power cells, arranged in a matrix of 8 across, by 8 down. Each power cell is essentially a flat piece of silicon, usually twice as high as it is across, that has some circuitry and connections attached.

The cells are connected together via an electrical circuit within the panel. Each cell receives sunlight onto its surface, and converts this to electrical energy. The electricity generated by the cell is added to the panel’s circuit.

Which still begs the question, of course, how do the individual power cells work, how does a power cell convert the solar energy (sunlight) which falls on it, into electricity?

Well, in order to explain that, we will have to delve into the realms of Physics, but only briefly. Of course it is absolutely not necessary to understand the science of a photovoltaic cell in order to make use of solar panels, or even to build a DIY one,  but for those who are technically curious, here goes…

Basically, any solid, such as the silicon of the power cells,  is made up of atoms, each atom consists of an atomic nucleus, with electrons which surround it. When something very energetic, like a wave of sunlight, hits an atom, what usually happens is that an electron flies off, and escapes. Where there is an atom which is missing an electron in this way, there is a very small, positive, charge on the material in which the atom is found.

If many, many atoms are missing an electron, then a significant positive charge is created, and an electric current is formed.

Solar panels may be very high-tech or low-tech, but either way, they produce energy which is non-harmful to the environment, and affordable.

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