Nib asked
How does a solar panel make electricity?
A solar panel runs on light, not heat: sunlight knocks electrons loose inside silicon, and a built-in one-way push sends them around a wire.
8 steps, drawn by Nib. Read it here, or watch him draw it. Updated .
1light, not heat
Many people think solar panels turn the sun's heat into power. They don't. They run on light itself, and heat actually weakens them.
a common mix-upSolar panels do not turn heat into electricity. They convert light, and extra heat lowers their output.
2heat hurts
Heat is the enemy. A panel rated at half a percent per degree loses a fifth of its power on a sixty-five degree Celsius roof.
Panels are tested at 25 degrees Celsius; a rating of -0.5 percent per degree means 40 degrees hotter gives 20 percent less power.
3two layers
So how does light make power? A rooftop panel is sixty silicon cells. Cut one open: a top layer packed with spare electrons, a bottom layer short of them.
4the border
Where the layers touch, some electrons spill across and set up a fixed, one-way electric push that points up toward the top layer.
5light knocks
Now a photon of sunlight arrives and knocks an electron loose. The push sweeps it upward, and it can't slip back.
6the whole cell
Let's rebuild it whole. A panel is cells, and each cell is two layers of silicon with a one-way push at the border.
7the loop
Light frees electrons, the push sends them up, and a wire carries them through the lamp and home again. No heat needed.
8sixty cells
Stack sixty cells at about half a volt each and you get roughly thirty volts.
Next time you see a roof of panels, remember: they are catching light, and keeping cool helps them.