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Renewable resources. It’s a problem that we face every day whether we realize it or not. With every pump of a gas handle, with every press of a car’s accelerator, with every plug of our smartphone chargers, we’re consuming fuel. And one day, that fuel’s going to run out. So why don’t we use the one energy source that won’t run out – the sun?
The sun is a magnificent entity. It provides the world with enough energy to power all of civilization. The only problem is how do we capture and harness that energy? What good is a bunch of free energy if we can’t convert it into a useful medium? Therein lies the issue, and it’s much more difficult to solve than you might imagine.
“Wait a minute” you say, “we’ve had commercial solar electricity since the 1980’s!” And you would be right in saying that. However, the trouble isn’t in how to convert the sun’s energy into electricity. We already know how to do that – just not on a level that can be mass-consumed. To understand the limits of solar energy, we need to know how solar panels work.
So join me as I dig into the inner workings of solar power. Let’s take a closer look at the process involved in transforming sunlight into a viable fuel source.
Solar energy begins, as you would expect, with the sun. That giant ball of fire that hangs in the sky is the perfect source of energy. Unlike coal, the sun doesn’t clog up our atmosphere with carbon dioxide. It’s easily accessible so we don’t have to go drilling around the world. Working with solar energy presents no threat to humans (except maybe for the occasional sunburn).
And most of all, solar energy is free. Apart from building the actual receptors and maintaining the equipment, solar energy has no cost associated with it.
So how does it all work?
Energy is all around us in different forms. Light is energy. Heat is energy. Movement is energy. Stillness is (potential) energy. The sun gives off a massive amount of light and our goal is to convert that light energy into something we can use, namely electrical energy.
In most cases, when light hits an object, it’s converted into heat energy. Think back to your last beach visit. As you sat out in the sun, your skin grew hot. It’s a simple fact of life that we’ve all experienced. But there exist certain materials that convert light into energies other than heat. Silicon is one of those materials.
When light hits silicon, it doesn’t dissipate as heat. Instead, the electrons in the silicon molecule jump around move, producing an electrical current. In order to utilize silicon in this way, however, you need large silicon crystals that are big enough to produce noticeable amounts of electricity.
Older versions of solar technology used silicon crystals. As it turned out, this method of solar light conversion wasn’t very feasible because large silicon crystals are difficult to grow. When something is difficult, the price of it remains high. If the price stays high, widespread use becomes unlikely.
Nowadays, solar technology uses a different material. This new material is composed of copper, indium, gallium, and selenium and is aptly named copper-indium-gallium-selenide, or CIGS. Unlike silicon, the crystals made from CIGS are smaller and cheaper, but they are much more inefficient than silicon in converting solar light.
And that’s where we are today. Solar electricity accounts for very little of the world’s energy production, and it will stay that way until scientists either find a new material that works as well as silicon or discover a method of cheaply producing large silicon crystals.
As inefficient as solar panels are right now, there are a few methods that are used to improve the capture and storage of solar electricity. One way is to use a battery that stores the energy, allowing consumption when there is no sun–at night and during cloudy days. Another way is to use a heliostat.
What is a heliostat? You can think of it as a large mirror (or many mirrors) attached to a rotating pole or platform (or many poles and platforms). Unlike solar panels, heliostats don’t directly absorb the sun; instead, they use mirrors to redirect the sun’s light and aim it at stationary solar panels for absorption.
Heliostats are mostly controlled by computers. These computers are fed certain pieces of data (the location of the heliostat, the location of the solar panel, the time and date) and the data is crunched until the computer can calculate the sun’s position in the sky. Once that’s done, the computer adjusts the mirror’s angle so that the sun’s light will bounce off of it and hit the target solar panel.
The greatest benefit of the heliostat is that a multitude of them can be arranged to be aimed at a single solar receptor. Whereas normally a solar panel might only receive some coverage of sunlight, an arrangement of heliostats can drastically amplify the amount of light being converted.
But even with heliostats, solar energy still has a long way to go before it can be used on a widespread scale. If it weren’t for the problem of converting the actual sunlight, solar energy would be the most renewable, most affordable, and most healthy-for-the-environment fuel for our civilization. That is, until the sun explodes.