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How does a solar energy panel work?

That’s a big question, let’s split it into a few smaller ones.

How is light turned into electricity?
It’s just another form of energy conversion. Really it’s no different to burning wood; energy from the sun is turned into chemical energy in the wood. Burning the wood converts chemical energy to heat energy.

When the sun shines on a solar panel, the photovoltaic effect converts the light energy to electrical energy. The power from the solar panel is proportional to the amount of light shining on it that is if the light gets twice as bright, you get twice as much power.

How much power?
Well, in direct sunshine at midday, the power reaching the surface of the earth from the sun is a bit more than 1000 Watts per square metre.

Hang on, a thousand what’s per who?
I suppose it’s bound to get a bit technical. A Watt is a measure of power.
It’s used for light bulbs. A 100 Watt light bulb uses 100 Watts of power.
A square meter is just that, a square 1 meter by 1 meter.

So there’s enough power for 10 light bulbs on every square meter?
No. Well, yes but only when it’s really sunny and even then you can’t get at it all. Remember that the light has to be converted into electricity.

Quite a lot of it is lost in this process; some is reflected away and some
makes the solar panel hot. Very hot. So all in all between 10% and 15%
of the light is converted to electricity, that is 100 or 150 Watts per square
meter in full sunlight.

But what if it’s not sunny?
Good question. It doesn’t really have to be sunny, there’s always some
sunlight during the daytime, that’s how come solar power can work in
Britain. If you mean “what about when it’s dark”, then that takes us onto
the next question.

What can I do with the power?
Well, before you ask that question, you really need to know the answer to
this one:

What sort of power is it?
In case you didn’t know, solar panels don’t generate what we consider traditional power. Traditional power is 230 Volts AC (117 Volts in the USA), while solar panels generate about 12 Volts DC.

AC stands for Alternating Current and DC stands for Direct Current. The important differences are that the voltage of an AC source can be changed by using a transformer, whilst DC can’t. On the other hand DC can charge a battery whilst AC can’t. That’s why traditional power is always AC and car electrical systems are always DC.

So I can’t make solar power into traditional power with a transformer?
No, you need something called an “inverter”. But you can charge a battery.