Using the Photovoltaic Effect For Electricity

The photovoltaic effect is the basic principle behind solar panels, which are, unsurprisingly, also known as photovoltaic panels or even PV panels.

When you first saw an item with a photovoltaic array or a photovoltaic cell when you were younger (it was probably a solar-powered calculator) it seemed to work like magic.  When the display on the calculator started looking a bit dull after spending ages in a school pencil case, all you had to do was put it in a sunny windowsill and hey presto!  It worked well again.

But if you’re interested in solar energy and solar power, it doesn’t hurt to know a bit more about the photovoltaic effect and how it works.  First of all, a few terms:

• photovoltaic:  an adjective to describe anything that turns the light of the sun (from the Greek word photos meaning light) into electricity (volts).
• photovoltaic cell (also called a solar cell): a small device that uses the photovoltaic effect.  This is the sort that you had in solar powered calculators.
• photovoltaic module: a collection of several individual photovoltaic cells in one device.  This is pretty much a standard solar panel.  Also known as a photovoltaic panel.
• photovoltaic array:  lots of photovoltaic modules all connected in parallel to generate a respectable amount of electricity.

The photovoltaic effect (also known as the photoelectric effect) is the key principle here with all of these things, whether they’re cells, modules, panels or arrays.  While to most people, quantum physics is something in the realms of science fiction and high-tech particle accelerators, quantum physics is what makes the photovoltaic effect work (the other practical application of this field is in CD players).

How the Photovoltaic Effect Works

What happens is this (leaving out all the formulae – we’ll spare you Plank’s Constant and Einstein’s Special Theory of Relativity, which all get involved here):  An incoming photon (or particle of light, or a light wave – but we won’t get into that one, as it involves other dimensions than the normal four) strikes an atom in a suitable conductive material, such as a metal or the semiconductor silicone.  The energy of that photon is transferred to an electron in the outer shell of the atom and is enough energy to let it make a quantum leap and break free.  Normally, the electron can’t do much and is quickly reabsorbed, allowing the excess energy to be released as heat (otherwise everything with silicone or metal would be able to generate a charge).

However, if the free electron can get a current going, it will.  Of course, the photovoltaic cell needs to be wired up so the current can be used.  This current works in pretty much the same way as any current: a free electron moves to the next atom and becomes part of its outer shell, which knocks another electron out of that outer shell and so on around the circuit.  It’s easy to imagine this as being like one of those card games where everyone receives a card from the person on their left then passes a card to the player on their right.

Who Discovered the Photovoltaic Effect?

The photovoltaic effect was first used to turn sunlight into motion via electricity in 1901, which is when electrical pioneer Dr Nikola Tesla patented his “apparatus for the utilization of radiant energy”.  As well as pioneering photovoltaics, Tesla was the brain behind most electrical motors and means of generating electricity.  So whether you use photovoltaic panels as a form of alternative energy or use wind-powered turbines – or switch on any electrical gadget – you have this genius to thank.