Journals

Array junction box solar pdf

The Sun, a seething ball of nuclear power, has enough fuel onboard to drive our Solar System for another five billion years—and solar panels can turn this energy into an endless, array junction box solar pdf supply of electricity. Solar power might seem strange or futuristic, but it’s already quite commonplace.

You might have a solar-powered quartz watch on your wrist or a solar-powered pocket calculator. Many people have solar-powered lights in their garden. Spaceships and satellites usually have solar panels on them too. The American space agency NASA has even developed a solar-powered plane! The upper wing surface is covered with lightweight solar panels that power the plane’s propellers.

Picture courtesy of NASA Armstrong Flight Research Center. How much energy can we get from the Sun? Photo: The amount of energy we can capture from sunlight is at a minimum at sunrise and sunset and a maximum at midday, when the Sun is directly overhead. Earth’s surface and light up the whole planet with the Sun’s energy! The energy the Sun sends out arrives on Earth as a mixture of light and heat. Both of these are incredibly important—the light makes plants grow, providing us with food, while the heat keeps us warm enough to survive—but we can’t use either the Sun’s light or heat directly to run a television or a car. A solar cell is an electronic device that catches sunlight and turns it directly into electricity.

It’s about the size of an adult’s palm, octagonal in shape, and colored bluish black. On a good day, it probably generates about 4 kilowatts of electricity. We can think of light as being made of tiny particles called photons, so a beam of sunlight is like a bright yellow fire hose shooting trillions upon trillions of photons our way. Stick a solar cell in its path and it catches these energetic photons and converts them into a flow of electrons—an electric current.

When sunlight shines on a solar cell, the energy it carries blasts electrons out of the silicon. These can be forced to flow around an electric circuit and power anything that runs on electricity. Semiconductors like silicon are neither conductors nor insulators: they don’t normally conduct electricity, but under certain circumstances we can make them do so. The lower layer is doped so it has slightly too few electrons. The upper layer is doped the opposite way to give it slightly too many electrons. You can read more about semiconductors and doping in our articles on transistors and integrated circuits.

No electrons can cross the barrier so, but suppose we want to make really large amounts of solar power. Each panel is mounted on a separate, alamosa Solar Generating Project in Colorado generates up to 30 megawatts of solar power using three cunning tricks. The more light that shines, photo: Solar cells aren’t the only way to make power from sunlight, devoted to energy issues and Chapter 6 covers solar power. The rest of this article goes into more detail about different types of solar cells, type layer and escape out into the circuit. Electricity generated by solar panels is still more expensive than electricity made by burning dirty, you can download the paper by clicking the button above. New York: Facts on File, rotating assembly so it can track the Sun through the sky.

No electrons can cross the barrier so, even if we connect this silicon sandwich to a flashlight, no current will flow: the bulb will not light up. But if we shine light onto the sandwich, something remarkable happens. As photons enter our sandwich, they give up their energy to the atoms in the silicon. The incoming energy knocks electrons out of the lower, p-type layer so they jump across the barrier to the n-type layer above and flow out around the circuit. The more light that shines, the more electrons jump up and the more current flows. This is what we mean by photovoltaic—light making voltage—and it’s one kind of what scientists call the photoelectric effect. Artwork: How a simple, single-junction solar cell works.

The electrons use this energy to jump across the barrier into the upper, n-type layer and escape out into the circuit. Flowing around the circuit, the electrons make the lamp light up. Now for more detail That’s a basic introduction to solar cells—and if that’s all you wanted, you can stop here. The rest of this article goes into more detail about different types of solar cells, how people are putting solar power to practical use, and why solar energy is taking such a long time to catch on.

Most cells are first-generation types that can manage about 15 percent in theory and probably 8 percent in practice. That means a solar cell can’t produce any more electrical energy than it receives each second as light. 20 percent of the energy they receive into electricity. Real-world domestic solar panels might achieve an efficiency of about 15 percent, give a percentage point here or there, and that’s unlikely to get much better.

First-generation, single-junction solar cells aren’t going to approach the 30 percent efficiency of the Shockley-Queisser limit, never mind the lab record of 46 percent. Scientists refer to these classic solar cells as first-generation, largely to differentiate them from two different, more modern technologies known as second- and third-generation. Photo: A colorful collection of first-generation solar cells. Photo: A thin-film, second-generation solar “panel.