Most solar panels used in homes and businesses can be classified into three types: polycrystalline, monocrystalline, or thin film. There are many ways to manufacture solar panels, and this determines their final appearance.
The different types of solar panels are easily identified based on their appearance, and each type has advantages and disadvantages. Silicon is the most common material used for solar panels, and it is used for both monocrystalline and polycrystalline cells. There are more materials available to produce thin film solar panels, but many are manufactured from silicon as well.
In terms of physical appearance, the main difference between monocrystalline and polycrystalline solar panels is the color and shape of the solar cell. While monocrystalline panels have black cells with rounded or notched corners, the polycrystalline ones have blue cells with square corners.
Monocrystalline Solar Panels
Mono stands for single, which indicates that monocrystalline solar cells are produced from a single crystal of silicon. During their manufacturing process, silicon crystals are grown into large ingots which are then cut into individual solar cells. These cells are then assembled into solar panels.
Thanks to their uniform crystal structure, monocrystalline solar panels have the highest efficiency among the types commercially available, which is above 20%. Monocrystalline panels are also characterized by their color, which is black or a very deep blue.
Compared with other solar panel types, monocrystalline panels are the most efficient option but also the most expensive. They are normally recommended when there is little space available, since their high efficiency maximizes the amount of electricity obtained. Monocrystalline panels were the first type to be invented, and as a result they are the most developed.
Polycrystalline Solar Panels
Also known as multicrystalline solar panels, these are the most common type. As their name suggests, polycrystalline cells consist of several small crystals of silicon in an irregular arrangement. The crystal fragments produce when monocrystalline cells are cut can be recycled to produce polycrystalline cells.
These panels are manufactured by melting multiple silicon fragments and pouring them into a mold, instead of using a single crystal. This process has a lower cost, but it results in a slightly lower efficiency of 15% to 20%. As a result, a larger area must be covered with polycrystalline panels to convert a given amount of sunlight into electricity. However, thanks to their lower price per watt of capacity, polycrystalline panels command the largest market share.
Polycrystalline panels can be considered the intermediate option in terms of cost and efficiency. They are less expensive than monocrystalline panels, while offering a higher efficiency than the thin film. These panels are recommended for most projects, since they offer decent efficiency for a reasonable cost.
Thin Film Solar Panels
As their name implies, this type of solar panels does not use silicon cells. Instead, the semiconductor material is simply applied as a thin layer on a substrate. This manufacturing process is very cheap, but it results in a much lower efficiency compared with monocrystalline and polycrystalline panels. This doesn’t mean they aren’t useful.
Most thin film panels only have an efficiency slightly above 10%. The most efficient models reach an efficiency close to 15%, which is comparable to the lower end of efficiency for polycrystalline panels. Unlike the other solar panel types, these can be manufactured from materials other than silicon, including cadmium telluride (CdTe) and copper indium gallium selenide (CIGS).
Many portable solar panels are of the thin film type to achieve a lower weight. The thin film manufacturing method can also be used to produce flexible solar panels or roll up solar panels. Thin film panels are also common in mobile applications where low weight is an advantage, such as RV solar kits.
How to Categorize the Different Types of Solar Panels
Once you know the appearance of each type of solar panel, telling them apart is very simple. You must simply observe the physical features and color of the panel:
- If the solar panels have a uniform surface that is not divided into individual cells, they are thin film panels, regardless of the color.
- If the solar panels have blue cells with straight edges, they are polycrystalline. As mentioned above, this is the most common type.
- If the panels have black or dark blue cells with rounded edges or an octagonal shape, they are monocrystalline.
In spite of their differences, the three solar panel types are based on the same physical principle. When sunlight reaches their surface, photons (light particles) cause the movement of electrons, producing an electric current. In fact, this happens when solar panels are exposed to any source of light, but sunlight happens to be abundant and free.
Monocrystalline and polycrystalline panels can also be described by the number of solar cells they have. 60-cell and 72-cell panels are the most common, and 96-cell panels are also available. Some solar panels have their cells cut in half with laser, which provides a slight improvement in service life and efficiency.
The following table summarizes the advantages and disadvantages of the three main types of solar panels. The best choice depends on the application, and neither of the types can be considered better than the rest:
|Solar Panel Type||Benefits||Disadvantages|
|Polycrystalline||Good efficiency. Intermediate price.||Less efficient than monocrystalline panels.|
|Monocrystalline||Highest efficiency.||Highest price.|
|Thin film||Lowest price. Lightweight.||Lowest efficiency.|
The appearance of solar panels is a subjective factor, but it can also influence the purchasing decision. Assuming a client has the budget and site conditions for any type, the solar panel choice may be based on how it looks. For example, while some building owners may prefer the uniform surface of thin film panels, others may prefer the conventional blue color of polycrystalline panels.
Another important factor that clients must consider is the life and quality of the solar panel type. Monocrystalline panels are more expensive because of their efficiency. Oftentimes, higher efficiency leads to a longer life and faster charging times. They also power almost four times the electricity of thin film solar panels, and they’re much more space-efficient. If a consumer was looking to buy panels for a fast-paced environment requiring consistently large amounts of electricity, the consideration of monocrystalline panels would be wise.
With that same logic, thin film panels are ideal if you’re looking at carbon offset. They’re also very good when you have a large space that needs covering (without the need for the highest-efficiency) because of their ability to easily cover massive spaces and rooftops.
Other Types and Styles of Solar Panels
The three solar panel types described above are the most common, but other options have been developed for specific applications. This section will describe other ways to harness sunlight.
Thermal Solar Panels
Thermal solar panels are different from the other types, since they are designed to heat water instead of producing electricity. Instead of having solar cells, these panels have tubes that are designed to circulate a combination of water and antifreeze. The tubes are painted black or covered with a dark surface to maximize the amount of sunlight absorbed.
Bifacial Solar Panels
Bifacial solar panels are characterized by their ability to gather sunlight from both sides, by exposing both the front and the backside of solar cells. This increases electricity generation: all the sunlight reflected from the surface below the panels reaches the solar cells as well. Bifacial panels can be monocrystalline or polycrystalline, and they are available in framed and frameless versions.
Transparent Solar Panels
Transparent solar panels are still an emerging concept. Since they are transparent, a large portion of the sunlight received is allowed through. While this reduces efficiency, it also increases the possible applications of transparent solar panels. They can be used as windows in homes or vehicles, and as covers for the screens of mobile devices, among other applications. The more panels used, the higher the efficiency will be.
Heliostats are not solar panels strictly speaking, but they are used for large-scale power generation with sunlight. Heliostats are mirrors that track the sun, reflecting light and focusing it on a specific target. Arrays of heliostats can be used to gather sunlight from a large area, focusing it to create an intense heating effect. The concentrated heat is enough to drive a steam turbine and generator. This concept is called concentrating solar power, or CSP.
Concentrator Photovoltaics (CPV)
Concentrator Photovoltaics is an emerging technology that uses lenses or mirrors to focus sunlight into a highly efficient solar panel. CPV technology achieves a higher efficiency than even monocrystalline panels, but the potential applications are limited by a high cost. CPV systems are often combined with solar trackers and cooling systems to increase efficiency further, but this also makes maintenance more complex – adding to the overall cost. Maintenance costs add up, and this is an important factor to consider when purchasing.