Learning About Solar Energy From the Dept of Energy: It’s a bit cloudy
Interest in solar energy as an energy source rises and sets along with the tax credits that fuel its growth. Because I am essentially a kid at heart, I visited the Energy Kid’s Page of the Energy Information Administration to learn more.
The Energy Information Administration (EIA), created by Congress in 1977, is a statistical agency of the U.S. Department of Energy. “Our mission is to provide policy-neutral data, forecasts, and analyses to promote sound policy making, efficient markets, and public understanding regarding energy and its interaction with the economy and the environment.”
The Energy Kid’s Page starts off in a friendly manner in a way that even I could understand:
The sun has produced energy for billions of years. Solar energy is the sun’s rays (solar radiation) that reach the earth.
Some of this solar energy is converted to heat, which is used to heat water and building interiors.
So far, so good.
Solar energy can be converted to electricity in two ways:
- Photovoltaic (PV devices) or “solar cells” – change sunlight directly into electricity. PV systems are often used in remote locations that are not connected to the electric grid. They are also used to power watches, calculators, and lighted road signs.
- Solar Power Plants – indirectly generate electricity when the heat from solar thermal collectors is used to heat a fluid which produces steam that is used to power generator. Out of the 15 known solar electric generating units operating in the United States at the end of 2006, 10 of these are in California, and 5 in Arizona. No statistics are being collected on solar plants that produce less than 1 megawatt of electricity, so there may be smaller solar plants in a number of other states.
With childlike wonder, I pressed further, wanting to learn how energy-efficient, renewable solar energy can help reduce fossil-fuel-generated electricity (half of which comes from burning coal, which in turn creates the 104 tons of mercury annually we have the pleasure of breathing, drinking, and eating).
So I dug into the Photovoltaic Section. Without warning or proper disclosure, The Energy Kid’s Page sent me back to college for my PhD in electronics. (Guys: Seriously, do you really think your Kid Page is kid-friendly?!)
With quick googling, I found an online university and enrolled, studied night and day for four entire weeks, got my PhD, and now am delighted to give you this kid-friendly solar systems wauchope explanation of solar energy.
We’ll shine a light on photovoltaic energy and the three types of solar power plants.
Photovoltaic energy is the conversion of sunlight into electricity. A photovoltaic cell, commonly called a solar cell or PV, is the technology used to convert solar energy directly into electrical power. The solar cell is a nonmechanical device usually made from silicon alloys.
Sunlight has photons. Photons have energy. The solar cell gets slammed by photons and absorbs some of them. Others bounce right off like basketballs or pass through like ghosts.The absorbed photons knock electrons out of place. Electrons are the stuff that electricity is made of. The electrons bubble up to the surface of the solar cell.This movement to the surface creates an imbalance. When you hook up a wire from the solar cell to an outside battery, you create a path that the electrons will follow.That flow into the battery is electricity.
A single photovoltaic cell will power your calculator and your curiosity, but not much more. At 1 or 2 watts, you need hook up a bunch together to get some real juice flowing. This is called an array, and can include as many cells as you can afford. Definitely a case of the more you spend, the more you save.
Don’t Stick It Where The Sun Don’t Shine
Sunlight is constant – the clouds and fog are not. Climate conditions significantly effect the amount of solar energy received by a photovoltaic array and, in turn, its performance. Most current technology photovoltaic modules are about 10 percent efficient in converting sunlight. Further research is being conducted to raise this efficiency to 20 percent.
The battery collects direct current (DC). You need alternate current (AC) flowing through your light fixtures. Solid state devices called inverters convert DC power to AC. Problem solved.
Photovoltaic Energy Recap: photovoltaic or solar cells absorb the slings and arrows of outrageous photons from the Sun, which shove electrons to the surface of the cells, where you store them by having them flow through a wire into a battery. You break out your inverter to make that battery energy usable. But at 10% efficiency, they suck big time in consistently poorly lit areas, such as Sweden during November to January when they’re nearly blacked out and lighting their way with seal blubber candles and Ikea accent lamps.