Read This and Impress Your Friends: Solar Energy 101
Solar energy, at its most basic, is radiant light and heat from the sun. When you feel the warmth of daylight as you walk out from under a shady tree on a summer day, you’re feeling solar energy. But solar energy goes much deeper than that. It is the source of life on earth, the fuel that animates plants to fix carbon dioxide and produce glucose and oxygen, the original source of our food and our lives. As an energy source for human technology, solar energy is renewable, constant and, for all practical purposes, limitless.
As technology has progressed, the uses of solar energy have diversified, generally being classified into two groups, passive solar and active solar. Active solar transforms solar energy into another form of energy to be used in highly diverse ways, whereas passive solar uses heat from solar energy and uses it to heat a building. Active solar encompasses solar water heating, concentrated solar power and photovoltaic (PV) systems, the latter being the focus of our business. Passive solar encompasses efficiently designing buildings to utilize the sun’s heat. If you’re interested in learning more about each of these solar energy technologies, read about them in our further reading section. The focus of our business, however, is solar panel PV systems, those sleek, black, mirror-like sheets you’ve seen lining your most environmentally-oriented friends’ roofs.
PV systems are unique in that they convert solar energy directly into electricity, posing a legitimate solution to energy demands in today’s high-energy world. But let’s start at the beginning of solar power. In 1839, Edmund Bequerel found that certain materials produce electricity when exposed to light. With the help of Einstein in 1905, the characteristics of light and the photoelectric effect were further refined, pathing the way for the design of the first PV system in the 1950s. Although the system made in the ’50s was far too expensive for mainstream use, it used the same properties that solar panels use today. When light is shined on certain materials, they absorb rays of light and release electrons, or really small negatively charged particles. If those electrons are released into an environment that propels them toward a positive charge, you’ve got electricity. There’s obviously a lot of complexity that we’re removing from the picture but at its most basic level, this is how solar panels work.
Now let’s talk about what makes up a PV system. The smallest units of PV systems are called PV cells, which are made of a semiconducting material such as silicon. Semiconducting materials in PV cells release electrons and create an electric field. Electric fields are gradients made from regions of space between positive and negative charges and can be thought of as hills that electrons travel down. Electrons move toward positive charges; therefore, the bottom of the electric field “hill” can be thought of as the positive end of the electric field and the top of the electric field “hill” can be thought of as the negative end of the electric field.
As sunlight strikes the silicon of the PV cell, electrons are freed and released into the electric field where they travel toward the positive charge or the bottom of the metaphorical hill. The amount of electricity that you can generate is proportional to the amount of silicon exposed to light and equal to the number of electrons plummeting down the hill. One or two cells might power a calculator but what if we want to power a house or a city?
Then you simply connect a bunch of PV cells together. Multiple PV cells connected in a circuit make a PV module. Connecting multiple modules creates an array. When you see a solar panel on a roof, you’re looking at an array. A roof covered in solar panels is a PV system, made up of multiple arrays. There’s a lot more to PV systems but this should give you a good start. It all starts with that single PV cell that you powered your calculator in fifth-grade math class with and builds from there. Think of it this way, if we collected every solar-powered calculator in the world, connecting them end-to-end in a circuit and placed that circuit in the Mojave Desert, we could power all of Southern California. It’s time to put your fifth-grade math class to use and get with the program.