About Solar Ovens

How Solar Ovens Work

Solar Alchemy: From sunlight to cooking fuel

Until the last century, sunlight was still largely a mystery.

“Some regard [sunlight] as the same element as fire, but in the state of its greatest purity,” wrote French-Swiss scientist Horace-Bénédict de Saussure in the late 1700s.

Light to heat

De Saussure had a different take. He believed sunlight isn’t hot like fire but somehow passes heat onto other objects.

Light from the sun, we now know, is packed with energy—about 1,000 watts for every square meter. By drawing on a simple but profound principle, solar ovens convert this light energy to heat energy.

All things—bricks, car hoods, food in a solar oven—are made of atoms. The atoms are constantly vibrating and crashing into one another. The higher the temperature of an object, the faster its atoms shake.

Sunlight is electromagnetic radiation. When sunlight strikes a brick wall—or car hood or food in a cooker—the radiation excites the atoms, causing them to vibrate faster and get hotter.

The secret of glass

De Saussure’s sunlight fascination led him to conduct the first scientific experiments to understand why “a room, a carriage, or any other place is hotter,” as he wrote, “when the rays of the sun pass through glass.”

He built a set of five glass nesting boxes and set them, one inside the next, outside on a black table. The table absorbed the sun’s rays and converted the light into heat. The outermost box was coolest, de Saussure observed. Temperatures inside the other boxes became hotter in succession--so hot that fruits placed in the smallest box, “were cooked and became juicy.”

He was on to something. Clear glass, scientists later determined, lets short visible light waves pass through but blocks longer heat waves.

“Someday some usefulness might be drawn from this device,” wrote de Saussure, for it “is actually quite small, inexpensive, [and] easy to make.”

Now that you have a better understanding of how solar ovens work...it's time to meet the Solavore Sport!.