The basic science of photovoltaic technology to harvest solar energy has been around since the 1950s. Find out how shining light on the natural semi-conductor silicon—collected from sand––can generate electrical power.
Harvesting Electricity from Sand
Published August 15, 2018
Andrea Sella: Sand is an extremely unassuming material, after all, we played with it as children, and yet, within it is a substance, which has changed all our lives: silicon.
Narrator: Sand is silicon and oxygen. Sella can free the silicon by putting it in combat with the element magnesium that wants oxygen even more. He then adds heat.
Sella: And after a few seconds, the magnesium becomes hot enough to react, and the reaction begins to spread all the way through the mixture. Here it goes. What we’ve done is we’ve freed the silicon of the oxygen. Once the test tube is cooled, what we’re left with is no longer the sand, but 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.
Sella: 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 manufactures of silicon-based solar panels, Trina Solar. The challenge with solar energy is bringing down costs, which is done, in part, by increasing the efficiency of each silicon cell.
Zhiqiang Feng: The technical innovations 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 T.V.
- Digital Producer
- Arlo Perez
- Editorial Review
- Julia Cort, Ari Daniel
- © WGBH Educational Foundation 2018