It may not seem like it at first glance, but fossil fuels are actually a form of solar energy. Fossil fuels were once organic material, plants, animals and bacteria, that lived millions of years ago. All of these organisms got their power from the sun, often through stages. Plants converted solar energy into chemical power, which then was consumed and converted by herbivores, which in turn fed predators, and so on. Fossil fuel deposits are literally solidified solar power, but to get at the solar energy stored in them they need to be burned. We’ve already covered why that’s not a great idea.
One way to make a process more efficient is to cut out the middleman. Modern solar power attempts to do just that by directly converting the sun’s energy into a form we can use to run our societies. On small scales this relies on photovoltaic solar cells. These are what most people think of when they imagine solar power: those black slates on the roof of a car or the little strips that power calculators. These use a special material that changes the incoming solar radiation into electricity.
On a larger scale, solar furnaces focus light into a blazing inferno which is then used to drive a turbine which generates electricity. This is actually fairly similar to the way that a conventional, fossil fuel driven system works, except that the heat is produced by the sun and not the burning of oil, coal or natural gas. As a result, there’s no emission to speak of beside a little steam.
Solar power has a lot going for it, as even the tiny fraction of the sun’s output that reaches the earth is enough to power the world many times over. It’s also the lowest impact source of power we can come up with given current technology, requiring very little displacement of existing ecosystems. However, solar power is not perfect: it works best in hot and dry places far from existing population centers, which makes it more expensive to construct. It’s also the most diffuse source of green power; while it can potentially supply all of our energy needs, that power is spread across, quite literally, every inch of the planet. And there’s the obvious problem: what do you do at night?