Solar power – how does it all work?

This short article tries to answer the most common questions I was asked during my years as a renewable energy engineer.

When I first started installing solar power systems I was amazed. It just seemed like magic to me. Now I understand how solar power is used, but I still have to stop and marvel when I see electrical power apparently falling out of the sky.

Years of designing self-contained solar power systems took me all around the world, from the Scottish islands to the Amazon basin. Solar power can be made to work anywhere in the world.

I’m not going to go into great technical detail because there’s no need. Light gets converted to electrical power whether you understand the quantum physics or not.

I’ve just tried to give you all the answers you need in a way that anyone can

understand.

Please feel free to make as many copies of this eBook as you like and give them to your friends and colleagues. All I ask is that you keep it intact, do not delete or modify any of the hyperlinks and do not charge for it.

How does a solar 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 metre is just that, a square 1 metre by 1 metre.

So there’s enough power for 10 light bulbs on every square metre?

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 metre 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.