Solar panels sort of look the same, don’t they? They’re these black rectangular things that make electricity out of sunlight. That’s all there is to it, right? The truth is that just because two solar panels look similar, that doesn’t mean they work in exactly the same way.
There’s a constant drive in the industry to refine and improve the way that basic solar cell technology works. If we look at the sorts of solar cells that you can go and buy with your own money today, there are three main types that matter. These are monocrystalline, polycrystalline, and thin film solar cells. Confronted with a choice between these three technologies, which is right for you? The good news is that the relative merits of each technology are very easy to understand.
Monocrystalline solar cell technology is the oldest and most mature form of solar cell. This means that these panels are best understood compared to newer methods of making solar cells.
It’s called a monocrystalline panel because the entire panel is made from the same crystal substructure. If you look at the panel with the naked eye, you’ll see it’s all one uniform color. Remember how you made sugar crystals in school by using a crystal “seed”? Monocrystalline cells are made in pretty much the same way. A silicon seed crystal is put into hot, molten silicon. The crystal is grown this way, and from there it’s processed into the thin wafers needed to make solar panels, among other things.
Monocrystalline cells are the most efficient, with numbers over 20% becoming commonplace among new panels. These panels are also compact, which makes them a great choice for portable camping chargers and the like. It also means that, watt for watt, you’ll use less space on your roof compared to other panel technologies.
The main downside is that these panels are more expensive than other choices, but they also have the longest lifespan. You can expect more than the 25 years that these types of panels are warrantied for when you buy a well-known brand. To top it all off, they also show the least drop in performance with higher temperatures. Higher temperatures generally mean less efficient power conversion.
Polycrystalline panels have taken over the market share from monocrystalline panels in a big way. Apparently, they are now the dominant type of panel installed in American homes. These cells are made in a similar way to monocrystalline cells, but the seed crystal is not pulled to create the monolithic crystals of the older technology.
The main advantage of this alternative approach to making silicon crystals for solar applications is price. Polycrystalline cells are less efficient than monocrystalline panels in general, but they’ve improved so much that they come pretty close to the older technology’s efficiency numbers. Couple that with their lower price and it is no wonder they are the more popular choice. They do, however, suffer more losses in warm weather, and the panels most people will get only produce 14-16% power conversion efficiency. This means you need more panels and more roof space. On balance, however, this is the more cost-effective choice.
The Third Choice: Thin Film
While both silicon crystal technologies are well established, there is now a third choice. Thin film solar panels do not use solid silicon crystals. Instead, the makers take a material such as glass and then coat it in a thin film of PV material. Different designers use different materials layered in different ways, but that’s the basic concept.
These panels are significantly less efficient than the competition, at somewhere between 7% and 13%. However, they are so much cheaper that, as long as you have the space, you can make up for it by just having a lot of them.
These panels aren’t that much affected by high temperatures and are easy to mass produce. As engineers and scientists figure out how to make them more efficient, they stand a good chance of becoming the default consumer choice. Since the film is sprayed into a glass or similar surface, it also means these panels can come in many different shapes and sizes. This means putting solar panels in places where they have not been possible before.
For now however, they are not a great choice for home installations, since most people just don’t have the space. To make matters worse, they don’t last nearly as long as the solid crystal technologies. You can, however, bet on thin-film technology improving rapidly over the next few years, as scientists figure out the optimal combinations of PV materials to coat them with. In the long run, thin film panels might become the norm.