lobal rooftop solar energy is growing at a stunning rate. According to the U.S. Department of Energy, more than 3 million American homeowners have already switched to solar, and this number is expected to reach 5 million by 2025. And it's hardly surprising: solar power opens immense saving opportunities and helps effortlessly reduce individual carbon footprint.
If you too would like to get on board with solar power and enjoy the benefits it offers, you will have to go through the tedious but necessary process of choosing solar panels. Deciding on the right panel type is usually the first obstacle on this path. A great number of homeowners opt for polycrystalline solar panels as the most affordable solution. But let’s dig a little deeper and see how exactly they are different from monocrystalline panels, and what are their strengths and weaknesses.
What distinguishes a polycrystalline solar panel?
A solar panel comprises several smaller units called solar cells, or photovoltaic (PV) cells. These devices capture solar energy and directly convert it into electricity using the photovoltaic effect. The overwhelming majority of PV cells are manufactured from crystalline silicon – a semiconductor material valued for its optimal efficiency, reasonable cost, and long lifespan.
The primary difference between polycrystalline and monocrystalline solar cells lies in manufacturing technology. Monocrystalline cells are made from a single silicon ingot which is sliced into thin wafers. These wafers are later processed into solar cells and assembled into a PV module. Polycrystalline solar cells, also called multicrystalline or poly-Si cells, are manufactured from several different fragments of silicon instead of a single ingot. These fragments are melted and poured into a mold, where they align together into a cubic or rectangular model which is cooled and cut into wafers.
A polycrystalline solar panel can be easily recognized just by its appearance. First of all, you can distinguish it from its monocrystalline counterpart by color. Poly-Si cells are blue because of the way small crystals in their structure interact with sunlight: the grain boundaries create a speckled, shimmering appearance which is perceived by the human eye as a blueish hue. Monocrystalline solar panels, on the other hand, are black due to how the light is reflected off the single crystal.
Another distinctive feature is the edges of the cell. Polycrystalline solar cells have straight edges because they are cut from rectangular silicon blocks, while monocrystalline cells have rounded corners as they are cut from cylindrical silicon ingots.
The advantages of poly-Si solar modules
Now that we've explored what a polycrystalline solar panel actually is, let's focus on its pros and cons. So, what are the advantages that make those blue modules attractive to homeowners?
The main benefit of multicrystalline solar panels is that they won't hit your wallet too hard. The high initial cost is causing a major hindrance for homeowners who would like to get into solar. Monocrystalline options may be too pricey, and poly-Si panels offer a lower-cost alternative that still enables them to take advantage of solar energy. The average price for a polycrystalline solar panel is between $0.90 and $1 per watt, which means a typical 6kW system would cost from $5,400 to $6,000. For comparison, the price of the same-sized monocrystalline system ranges from $6,000 to $9,000.
Another advantage multicrystalline panels have over monocrystalline options is better environmental outcomes. They are considered more environmentally friendly because they don’t require individual forming and produce less waste as all of the silicon is utilized in the manufacturing process.
Lifetime comparable with that of monocrystalline
Poly-Si panels enjoy quite a long lifespan for their price. Even though they are usually covered by shorter warranties, they generally last as long as monocrystalline modules, that is 25-35 years.
The disadvantages of poly-Si solar modules
Multicrystalline solar panels come with their own set of disadvantages. We will consider the most substantial of them.
The most serious weakness of these modules is lower efficiency. PV cell efficiency is the amount of sunlight falling on its surface that is converted into electricity. A polycrystalline solar panel typically has an efficiency rate of 13-16% range, while an average monocrystalline system is 15-20% efficient. This is due to the cell structure: the boundaries of multiple crystals inside a poly-Si cell limit the movement of electrons leading to lower performance.
Even though the efficiency difference may seem not so critical, it will noticeably affect your electricity bills in the long run.
This drawback follows from the previous one. Since a polycrystalline solar panel produces less energy in watts per one square meter, it occupies more space to achieve the desired efficiency.
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Longer ROI period
If your panels are installed under a Power Purchase Agreement (PPA), you pay for each kilowatt hour (kWh) of energy your PV system generates, which means the panel type does not matter. But if you choose to invest in your own solar modules, the more energy you produce the shorter your return on investment (ROI) period is. This means with a poly-Si system it will take you longer to break even on your investment.
Lower heat tolerance
Poly-Si modules are characterized by a lower temperature coefficient – the indicator that shows how solar cells perform at high temperatures. Most multicrystalline panels have a temperature coefficient of around -0.5%, which means they lose half a percent of their efficiency for every degree Celsius the temperature rises above the optimal levels. This coefficient is between 0.3% and -0.45% for monocrystalline modules.
The choice of color depends on personal preferences. However, some people find blue panels slightly less aesthetically pleasing and don’t like how they stand out against the background of black roof shingles.
Bottom line: a polycrystalline solar panel can be a good compromise
To sum it all up, polycrystalline panels can be an optimal compromise if you would like to go solar without wrecking your budget. They offer all the necessary features for harnessing the power of the sun and help reduce your energy bills as well as your carbon footprint.
But negative aspects also have to be taken into account. Poly-Si modules are less efficient, less heat tolerant and do not look as sleek as monocrystalline alternatives. So, if you do decide to settle on polycrystalline panels, make sure they come from a reliable manufacturer and are backed by a comprehensive warranty.