NOVA

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Narrator

Sand is silicon and oxygen. Celo can free the silicon by putting it in combat with the element magnesium that wants oxygen even more. He then adds heat. And after a few seconds the magnesium becomes hot enough to react and the reaction begins to spread all the way through mixture. (dramatic orchestral music) Here goes. What we've done is we freed the silicon of the oxygen. Once the test tube is cooled, what we're left with is no longer the sand, instead a dark and rather shiny reflective material. This is the silicon itself. -

Narrator

In its pure crystalline form silicon looks more like a treasure, but its real value comes when you shine light on it. Now, silicon is what we call a semiconductor and semiconductors don't conduct electricity all that well until you shine light on them, and suddenly the electrons can move. And that opens up a whole universe of possibilities. -

Narrator

These possibilities are now being mined around the world. And one of the best places to see this new treasure in action is in China. At one of the leading manufacturers of silicon-based solar panels. Trina Solar. (machine whirring) The challenge with solar energy is bringing down costs which is done in part by increasing the efficiency of each silicon cell. Technical innovation here are focused on increasing the amount of energy we get out of the light that hits a photovoltaic cell. -

Narrator

The basic science of photovoltaic technology is straightforward. It's been around since the 1950s. Photo means light. And so when a photon of light hits a silicon atom its energy knocks an electron loose, which is then directed through the silicon to the thin wires on the cell. That stream of electrons is electricity that can power anything from your toaster to your TV. (suspenseful music)