You are thinking about buying solar panels, but got confused about which type to go for? You’re at the right place. There’s a myriad of variables that you should take into account when you are buying a solar photovoltaic (PV) system – our job here at Energy Informative is to help you sort through them!
In this article, you will learn everything you need to know about the different types of solar panels for home use (mono-, polycrystalline and thin film).
Let’s start with the different types of solar panels currently on the market, list their benefits and downsides, and then look at a few typical scenarios where certain types would be the better than others (hopefully one of them resonates with you).
Almost 90% of the World’s photovoltaics today are based on some variation of silicon. In 2011, about 95% of all shipments by U.S. manufacturers to the residential sector were crystalline silicon solar panels.
The silicon used in PV takes many forms. The main difference is the purity of the silicon.
But what does silicon purity really mean? The more perfectly aligned the silicon molecules are, the better the solar cell will be at converting solar energy (sunlight) into electricity (the photoelectric effect).
The efficiency of solar panels goes hand in hand with purity, but the processes used to enhance the purity of silicon are expensive. Efficiency should not be your primary concern. As you will later discover, cost-and space-efficiency are the determining factors for most people.
Crystalline silicon forms the basis of mono- and polycrystalline silicon solar cells:
Solar cells made of monocrystalline silicon (mono-Si), also called single-crystalline silicon (single-crystal-Si), are quite easily recognizable by an external even coloring and uniform look, indicating high-purity silicon, as you can see on the picture below:
Monocrystalline solar cells are made out of silicon ingots, which are cylindrical in shape. To optimize performance and lower costs of a single monocrystalline solar cell, four sides are cut out of the cylindrical ingots to make silicon wafers, which is what gives monocrystalline solar panels their characteristic look.
A good way to separate mono- and polycrystalline solar panels is that polycrystalline solar cells look perfectly rectangular with no rounded edges.
The first solar panels based on polycrystalline silicon, which also is known as polysilicon (p-Si) and multi-crystalline silicon (mc-Si), were introduced to the market in 1981. Unlike monocrystalline-based solar panels, polycrystalline solar panels do not require the Czochralski process. Raw silicon is melted and poured into a square mold, which is cooled and cut into perfectly square wafers.
String Ribbon solar panels are also made out of polycrystalline silicon. String Ribbon is the name of a manufacturing technology that produces a form of polycrystalline silicon.
Temperature-resistant wires are pulled through molten silicon, which results in very thin silicon ribbons. Solar panels made with this technology looks similar to traditional polycrystalline solar panels.
Evergreen Solar was the main manufacturer of solar panels using the String Ribbon technology. The company is now bankrupt, rendering the future for String Ribbon solar panels unclear.
Depositing one or several thin layers of photovoltaic material onto a substrate is the basic gist of how thin-film solar cells are manufactured. They are also known as thin-film photovoltaic cells (TFPV). The different types of thin-film solar cells can be categorized by which photovoltaic material is deposited onto the substrate:
Depending on the technology, thin-film module prototypes have reached efficiencies between 7–13% and production modules operate at about 9%. Future module efficiencies are expected to climb close to the about 10–16%.
The market for thin-film PV grew at a 60% annual rate from 2002 to 2007. In 2011, close to 5% of U.S. photovoltaic module shipments to the residential sector were based on thin-film.
Solar panels based on amorphous silicon, cadmium telluride and copper indium gallium selenide are currently the only thin-film technologies that are commercially available on the market:
Because the output of electrical power is low, solar cells based on amorphous silicon have traditionally only been used for small-scale applications such as in pocket calculators. However, recent innovations have made them more attractive for some large-scale applications too.
With a manufacturing technique called “stacking”, several layers of amorphous silicon solar cells can be combined, which results in higher efficiency rates (typically around 6-8%).
Only 1% of the silicon used in crystalline silicon solar cells is required in amorphous silicon solar cells. On the other hand, stacking is expensive.
Cadmium telluride is the only thin-film solar panel technology that has surpassed the cost-efficiency of crystalline silicon solar panels in a significant portion of the market (multi-kilowatt systems).
The efficiency of solar panels based on cadmium telluride usually operates in the range 9-11%.
First Solar has installed over 5 gigawatts (GW) of cadmium telluride thin-film solar panels worldwide. The same company holds the world record for CdTe PV module efficiency of 14.4%.
Compared to the other thin-film technologies above, CIGS solar cells have showed the most potential in terms of efficiency. These solar cells contain less amounts of the toxic material cadmium that is found in CdTe solar cells. Commercial production of flexible CIGS solar panels was started in Germany in 2011.
The efficiency rates for CIGS solar panels typically operate in the range 10-12 %.
Many thin-film solar cell types are still early in the research and testing stages. Some of them have enormous potential, and we will likely see more of them in the future.
Lastly, we`ll briefly touch on the subject of building integrated photovoltaics. Rather than an individual type of solar cell technology, building integrated photovoltaics have several subtypes (or different methods of integration), which can be based on both crystalline-based and thin-film solar cells.
Building integrated photovoltaics can be facades, roofs, windows, walls and many other things that is combined with photovoltaic material. If you have the extra money and want to seemlessly integrate photovoltaics with the rest of your home, you should look up building integrated photovoltaics. For most homeowners it`s simply way too expensive.
Having your particular situation evaluated by an expert would be the best way to find out what solar panel type would be best for your household. Here are some of the typical scenarios we see:
For those who don’t have enough space for thin-film solar panels (the majority of us), or if you want to limit the amount of space their PV-system takes up, crystalline-based solar panels are your best choice (and they would likely be the your best choice even if you had the extra space). There are not a whole lot of solar installers and providers that offer thin-film solar panels for homeowners at this point.
You will have a choice of different solar panel sizes. The 180, 200 and 220-watt rated solar panels are usually physically the same size. They are manufactured exactly the same way, but under- or overperform when tested, hence ending up in different categories for power output.
If size is important, you should go for the highest rated power output for a particular physical size.
Both mono- and polycrystalline solar panels are good choices and offer similar advantages.
Even though polycrystalline solar panels tend to be less space-efficient and monocrystalline solar panels tend to produce more electrical power, this is not always the case.
It would be nearly impossible to recommend one or the other by not examining the solar panels and your situation closer.
Monocrystalline solar panels are slightly more expensive, but also slightly more space-efficient. If you had one polycrystalline and one monocrystalline solar panel, both rated 220-watt, they would generate the same amount of electricity, but the one made of monocrystalline silicon would take up less space.
If you want the lowest costs per rated power, or in other words, pay as little as possible for a certain amount of electricity, you should investigate if thin-film solar panels could in fact be a better choice than mono- or polycrystalline solar panels.