How do solar panels work?
Quick answer
Solar panels are made of photovoltaic cells, usually silicon, that release electrons when sunlight hits them. That flow of electrons is direct current (DC) electricity, which an inverter converts into the alternating current (AC) used in homes.
From sunlight to electricity
- Sunlight hits the cellLight is made of tiny packets of energy called photons. When they strike a silicon solar cell, they transfer their energy to electrons in the silicon.
- Electrons break freeThe energized electrons are knocked loose from their atoms and can move around freely.
- An electric field pushes themEach cell has two layers of silicon treated with different elements, creating a built-in electric field that pushes the loose electrons in one direction. That directed flow is an electric current.
- Wires collect the currentThin metal lines on the cell gather the electrons and send them out of the panel as direct current (DC).
- The inverter converts itAn inverter changes DC into alternating current (AC), the type of electricity that home outlets and the power grid use.
No moving parts, no fuel, no noise. A solar panel turns light into electricity using an effect first spotted by the French physicist Edmond Becquerel in 1839, when he was just 19.
The photovoltaic effect
“Photovoltaic” combines photo (light) and volt (electricity). Most panels use silicon, the same material in computer chips. The two silicon layers in each cell are “doped” with small amounts of other elements: one layer ends up with spare electrons, the other with gaps where electrons are missing. Where the layers meet, an electric field forms. When light knocks electrons loose, that field sweeps them toward one side, and connecting the two sides with a wire lets them flow as current.
A single cell produces only about half a volt, so a panel links 60 to 72 cells together to get useful power.
How efficient are solar panels?
Most panels sold for homes today turn roughly 18 to 23% of the sunlight that hits them into electricity. The rest becomes heat or reflects away. That might sound low, but sunlight is free and abundant, so even a modest rooftop system can cover a large share of a household’s needs.
The first practical silicon solar cell, built at Bell Labs in 1954, managed about 6%.
Do solar panels work on cloudy days?
Yes, but less well. Panels respond to light, not heat, so they still produce power under clouds, typically somewhere between 10 and 25% of their full output depending on how thick the cover is. They don’t work at night, which is why many systems pair with batteries or stay connected to the grid.
In fact, very hot weather slightly lowers efficiency. Panels perform best on bright, cool days.
How long do solar panels last?
Most manufacturers guarantee panels for 25 years, and many keep working longer. Output slowly drops with age, usually by around half a percent a year.
The light they capture comes from the sun’s surface at about 5,500°C. Here’s how hot the rest of the sun is.
Sources
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