The first ever solar photovoltaic cell was invented around 1940, and had a paltry 1% efficiency. To power a single home using solar panels of such sort, you would need the roof space of more than ten homes.
Fast forward eighty years, and the market is flush with a plethora of solar panel options with high efficiencies and innovative tech. Today, customers can choose from several types of solar modules - from P and N-type panels to mono and bi-facial ones, from half-cell and full cell panels to DC vs AC ones.
But as we have learnt in this modern world of ours, too much choice can be a difficult thing. Customers purchasing solar are often confused about which type of solar panels suits them best. And that’s why we decided to create this article, which discusses all the types of solar panels and how to choose what’s right for you. Let’s dive in.
Monocrystalline Vs. Polycrystalline Solar Panels
Until about 10 years ago, before all the new innovations jumped into the market, there were essentially just two types of solar panels - monocrystalline and polycrystalline. These are the two major types of crystalline solar panels, i.e. panels made from crystalline silicon.
Monocrystalline, as the name suggests, includes solar cells built from a single crystal of silicon. Poly, on the other hand, is constructed from many smaller silicon crystals bound together. The key difference between both is efficiency.
At the molecular level, mono-Si panels have a much more uniform structure, allowing more power to flow, resulting in higher efficiencies, often crossing the coveted 20% mark. Poly-Si panels suffer from an irregular structure, resulting in lower efficiencies, usually less than 17%. Until a few years ago, polycrystalline modules ruled the market, thanks to their low cost.
But as the overall costs of solar equipment have fallen, mono-Si panels are clearly overtaking their poly counterparts. They offer much higher power in a smaller space, without much added cost. There is another type - the thin film modules. However, thin film panels are still in their infancy and not commercially viable.
Which One Should You Choose: The choice here is simple - always choose monocrystalline modules over polycrystalline ones.
Monofacial Vs. Bifacial Solar Panels
On the quest to maximizing solar panel efficiency, someone decided to utilise a huge area on a solar panel that was so far unutilised - the rear side of a panel. Bifacial solar panels have solar cells on both sides of the panel.
Although the rear side does not receive direct sunlight, PV cells can work on indirect, diffused sunlight too. The rear side generates less power, of course, but the increased cost is often proportional to the increased power generation.
Bifacial Solar Cell Diagram
Bifacial panels use a transparent back sheet and transparent central lamination layers so that light can pass between the cells to the other side.
However, bifacial modules work best when the light falling on the rear side of the panel is significant. For example, if your panels are laid flat on the roof, their rear side is going to be mostly dark, so bifacial panels won’t make a good choice.
Which One Should You Choose: If your panels will be some distance away from the ground, and you have limited space, such as on a patio roof, then bifacial panels are a good choice.
P-type Vs. N-type Solar Panels
Solar cells are made of different layers - a positively charged (p-type) and a negatively charged (n-type) layer. Traditional solar panels have been designed to have p-type as the more dominant layer, covering most of the thickness, and also located on the base.
This structure is good for space-based solar, from where the technology evolved. However, the boron in the p-type base layer is known to react with oxygen impurities and decrease efficiencies. This is why n-type solar made its entry. N-type cells have the n-type layer as the dominant and base layer. This eliminates the above-mentioned effect (also known as LID), and improves panel efficiency.
N-type vs p-type base layer (source: Luxor Solar)
Currently, n-type panels are a bit more expensive than p-type panels, but they also promise notably higher power output.
Which One Should You Choose: If you lack space or don’t mind spending a little extra for having state-of-the-art equipment for many years to come, go for n-type solar panels. If you just need a simple solar power setup and have ample space for maybe an extra panel, go for p-type.
AC Vs. DC Solar Panels (With or Without Microinverters)
We know, we know! There is no such thing as AC solar panels, but hear us out. It is true that solar panels always generate DC current. This is why we need an inverter, because most household appliances work with AC input. Traditionally, power from all solar panels is sent into an inverter, which churns out AC power, which then goes to the appliances.
Microinverters are a new technology, or a smart makeover of the existing technology, where each solar module gets its own small inverter. The power coming out of each solar panel is converted to AC right away. And hence, some manufacturers like to use the term AC solar panels.
The terminology aside, microinverters are an excellent step in the evolution of solar power. They can be more efficient than string inverters, reduce power losses from shading or improper orientation, and they even come with far better warranties and lifespans.
A Microinverter by AP Systems
Which One Should You Choose: Microinverters are still significantly more expensive than string inverters. They make sense only in cases where frequent shading or soiling of the array is an issue. They are also a good choice for roofs with complex, imperfect layouts. Other than that, you don’t necessarily need to go for microinverters, unless you don’t mind spending a little extra to get the best possible tech on the market.
Other Types of Solar Panels
Following are some other types of solar panels that we haven’t covered in the list above. The main reason for not including these above are that these panels either have a very small market share or cater to a very specific application(s). Let’s take a look.
1. Flexible Solar Panels
Flexible solar panels are, as the name suggests, panels that can be bent or rolled to fit on odd-shaped surfaces. These panels come without a glass or aluminum frame, and are usually employed in applications like pasting on boat decks or RV roofs. These panels are more expensive and can be less efficient, making them unsuitable for rooftop applications.
2. Portable Solar Panels
Portable solar panels are used for mobile or applications where durability is an important criterion. These panels come with rugged build, sometimes foldable design, and often have a plug-and-play design which allows connecting them to a portable battery within a few seconds and without tools. These panels are more expensive and are not needed in regular arrays.
3. Concentrated PV
Concentrated solar has always been limited to solar thermal applications, but newer innovations are bringing it to solar photovoltaics. It uses a gigantic reflector to concentrate sunlight on a narrow tube containing solar cells. This concentrated sunlight can produce electricity at a much higher efficiency than regular solar modules. However, this technology is still in its infancy, and requires complex equipment and high cost.
4. Building Integrated PV (BIPV)
Building Integrated Photovoltaics have been around for quite some time now, and are a great solution for buildings which either don’t have the roof space for traditional systems or do not wish to have traditional systems on them.
BIPV integrates regular building elements like windows and roof shingles with solar cells, making them generate power. BIPV is often less efficient than traditional solar panels, and naturally more expensive.
Summing It Up
Solar panels have come a long way in terms of technological development, and buyers today are faced with a myriad of options. This can sometimes be confusing.
Many of the newer technologies promise higher efficiencies and smaller footprints, but almost always, they come with higher costs. The good news is that the most widely installed type of solar panels are often the correct options for the majority of us.
There are very specific and unlikely scenarios wherein the newer, unconventional technology is your only option left. However, those who are happy shelling out a little more money to have the latest and the hottest tech can always choose among one of the above-mentioned, more innovative options. For the rest of us, a standard system with monocrystalline solar panels and a string inverter works wonders!