Solar Energy

If you just go outside during a sunny day, you can feel it. You can feel your body warming up as a result of the interaction with the light from the sun. In fact, at our location in the solar system, the sun gives us about 1,000 watts per square meter of power. Of course, the trick is to get this energy into something more useful like electrical energy. One way to do this is with a solar panel (photovoltaic cell). This is essentially a solid-state device (with no moving parts) for which light can cause an electron energy transition to produce electric current. Yes, that’s an over simplification—but you get the idea. It turns light energy into electrical energy.

But wait! There’s another way to use solar power. It’s called a concentrated solar power plant. The idea is to arrange a bunch of mirrors to all reflect sunlight to a central point. The object at this solar focal point will then get extremely hot, and you can use that hot thing to heat up water to produce steam and then turn an electric turbine. Oh, usually the extremely hot thing will be a liquid—maybe like molten salt. That way you can heat up some stuff and then move it to make some steam while still heating up other parts of the liquid.

OK, but is solar power also renewable? It’s fine if you say that it’s a renewable energy source, but technically it’s not. The solar energy comes from the sun (that’s probably obvious). But the sun produces energy mostly due to nuclear fusion reactions in the core. Guess what? In 5 billion years, the sun is going to run out of energy. So it’s not technically renewable, but in the time span of the life of the sun, it’s practically unlimited.