Image courtesy © Lester Lefkowitz/Stone/Getty

It's about 3:30 p.m. as you walk out of the library into the bright, open parking lot. It's been a hot day, 98 F. As you and your mom climb into the car, you're immediately aware of the sun's power. It feels like you're climbing into an oven. And in a way, you are. The car, which is essentially a big metal and glass box (yep, that sounds like an oven), has been soaking up the sun's rays so it is filled with thermal (heat) energy. As you sit there, desperate for the air conditioning to cool things down, it's easy to understand why people want to utilize the sun as an energy source.

On a clear, sunny day, the sun shines approximately 1,000 watts of energy per square meter of the planet's surface. If we could collect all of that energy, we could use it to power our homes and offices. Solar energy can be harnessed and converted into two types of energy: thermal energy and electricity. Thermal energy can be used to dry clothes outside and heat water for cooking and bathing. It also can heat living and work spaces. When people talk about thermal energy, they usually group it into two types -- passive and active. Simply building your house so that it takes advantage of direct sunlight, is an example of passive thermal energy. If you go a step further by placing solar panels on your roof, which will absorb and store solar energy, that's considered an active system.

Image courtesy University of Michigan Solar Car Team, photo by Tim Allan University of Michigan solar car team with their car Continuum

When you think about solar-powered gadgets, probably the first thing that pops into your head is a solar-powered calculator. Small solar cells inside the calculator convert solar energy into electricity. Solar yard lights, emergency road signs, parking lot lights and more use solar cells to generate electricity. The solar cells on calculators and satellites are photovoltaic cells or modules (modules are simply a group of cells electrically connected and packaged in one frame). Photovoltaic cells, as the word implies (photo = light, voltaic = electricity), convert sunlight directly into electricity. But how, exactly, do these devices work?

Solar Power Saves Lives Imagine walking 10 or more miles every morning to find firewood, which you need to boil water and cook. What if these walks are not safe? You know that each day people are attacked while foraging for wood. But no matter how dangerous it is or how frightened you are, you have to go – every morning. This was the reality for thousands of Sudanese refugees. Now, thanks to the Solar Cooker Project, feeding a family is a lot less dangerous. By using solar cookers, the need for wood-based fuel has been reduced by two thirds. A $30 donation to the project pays for an entire cooking kit, which includes two solar cookers per family, two pots, two pot holders, a one-year supply of plastic bags and training on how to use the kit.