How Does a Solar Panel Turn Light into Electricity?太陽能板怎麼把光變成電？

🔊Look across the rooftops of Changhua, and you will see rows of dark blue panels on homes, schools, and factories. They sit perfectly still. There is no turbine, no fuel, and no smoke, yet electricity flows out of them all day long. In the last lesson, almost every power plant needed something to spin. How can a solar panel make electricity without moving at all?

🔊In 1839, a 19-year-old French scientist named Edmond Becquerel noticed that shining light on certain materials made a small electric current. This is called the photovoltaic effect: photo means light, and volt is a unit of electricity. More than a century later, in 1954, scientists at Bell Labs in the United States built the first practical solar cell from silicon, the same element found in sand. It turned about 6% of the sunlight that hit it into electricity.

🔊Light travels in tiny packets of energy called photons. A solar cell is a thin slice of silicon, thinner than four human hairs. When a photon hits the silicon, it can give one electron enough energy to break free. Blue photons carry more energy than red ones, but each photon can free only one electron, and the extra energy becomes heat. Some infrared photons carry too little energy, so they pass straight through without freeing anything.

🔊Freeing an electron is not enough, because it would soon fall back into place. So the cell is made of two layers. The top layer has a few extra electrons, and the bottom layer has a few missing ones, called holes. Where the two layers meet, an electric field forms, like a one-way slope. It pushes freed electrons up toward the top and holes down toward the bottom. The electrons can only get back by going around through the wire, and that flow is electricity.

🔊One cell gives less than one volt, so a panel joins many cells in a row. Most panels on roofs today turn about one-fifth of the sunlight that hits them into electricity. Where does the rest go? Some light bounces off, some passes through, and much of it becomes heat. Heat is a problem, too. On a hot summer roof, a panel makes less power: about 0.4% less for every degree Celsius above 25.

🔊In 2024, Taiwan's solar panels made about 15 billion kilowatt-hours, more than any other renewable source. Changhua has more renewable power connected to the grid than any other county. But the sun sets every evening and hides behind clouds, so solar power must be shared with other sources, or saved in batteries and in places like Sun Moon Lake. Still, every one of those panels works the same simple way: light knocks electrons loose, and a built-in slope sends them around the wire.