Comprehensive Guide to Solar Panel Types
The push for renewable energy sources has led to a surge in solar energy use. In the past decade alone, the solar industry grew by almost 50%, buoyed by federal support such as the Solar Investment Tax Credit and strong commercial and industrial demand for clean energy.
As the solar sector continues to rise, it’s worth studying the backbone of the solar industry: solar panels.
This guide will illustrate the different types of solar panels available on the market today, their strengths and weaknesses, and which is best suited for specific use cases.
What is a Solar Panel?
Solar panels are used to collect solar energy from the sun and convert it into electricity.
The typical solar panel is composed of individual solar cells, each of which is made from layers of silicon, boron and phosphorus. The boron layer provides the positive charge, the phosphorus layer provides the negative charge, and the silicon wafer acts as the semiconductor.
When the sun’s photons strike the surface of the panel, it knocks out electrons from the silicon “sandwich” and into the electric field generated by the solar cells. This results in a directional current, which is then harnessed into usable power.
The entire process is called the photovoltaic effect, which is why solar panels are also known as photovoltaic panels or PV panels. A typical solar panel contains 60, 72 or 90 individual solar cells.
The 4 Main Types of Solar Panels
There are 4 major types of solar panels available on the market today: monocrystalline, polycrystalline, PERC, and thin-film panels.
Monocrystalline solar panels
Also known as single-crystal panels, these are made from a single pure silicon crystal that is cut into several wafers. Since they are made from pure silicon, they can be readily identified by their dark black color. The use of pure silicon also makes monocrystalline panels the most space-efficient and longest-lasting among all three solar panel types.
However, this comes at a cost — a lot of silicon is wasted to produce one monocrystalline cell, sometimes reaching over 50%. This results in a hefty price tag.
Polycrystalline solar panels
As the name implies, these come from different silicon crystals instead of one. The silicon fragments are melted and poured into a square mold. This makes polycrystalline cells much more affordable since there is hardly any wastage, and gives them that characteristic square shape.
However, this also makes them less efficient in terms of energy conversion and space, since their silicon purity and construction are lower than monocrystalline panels. They also have lower heat tolerance, which means they are less efficient in high-temperature environments.
Passivated Emitter and Rear Cell (PERC) panels
PERC solar panels are an improvement of the traditional monocrystalline cell. This relatively new technology adds a passivation layer in the rear surface of the cell that enhances efficiency in several ways:
- It reflects light back into the cell, increasing the amount of solar radiation that gets absorbed.
- It reduces the natural tendency of electrons to recombine and inhibit the flow of electrons in the system.
- It allows greater wavelengths of light to be reflected. Light waves over 1,180nm can’t be absorbed by silicon wafers and simply pass through, so they end up heating the cell’s metal back sheet and reduce its efficiency. The passivation layer reflects these higher wavelengths and stops them from heating up the back sheet.
PERC panels allow greater solar energy collection in a smaller physical footprint, which makes them ideal for limited spaces. They are only slightly more expensive to produce than traditional panels, due to the added materials needed, but they can be manufactured on the same equipment, and can end up having a lower average cost per watt due to their efficiency.
To get a better feel for the benefits of PERC panels, check out our blog 5 Important Benefits of PERC Solar Panels You Need to Know.
Thin-film solar panels
Thin-film panels are characterized by very fine layers that are thin enough to be flexible. Each panel does not require a frame backing, making them lighter and easier to install. Unlike crystalline silicon panels that come in standardized sizes of 60, 72, and 96-cell counts, thin-film panels can come in different sizes to suit specific needs. However, they are less efficient than typical silicon solar panels.
Thin-Film Solar Panel Variations
Unlike crystalline panels that use silicon, thin-film solar panels are made from different materials. These are:
- Cadmium telluride (CdTe)
- Amorphous silicon (a-Si)
- Copper indium gallium selenide (CIGS)
Cadmium telluride (CdTe)
CdTe has the same low-cost advantage as polycrystalline cells while possessing the lowest carbon footprint, water requirement, and energy payback time of all solar panels types. However, the toxic nature of cadmium makes recycling more expensive than other materials.
Amorphous silicon (a-Si)
Amorphous silicon panels (A-Si) derive their name from their shapeless nature. Unlike mono-and polycrystalline solar cells, the silicon is not structured on the molecular level.
On average, an a-Si cell requires only a fraction of the silicon needed to produce typical silicon cells. This allows them to have the lowest production cost, at the expense of efficiency. This is why a-Si panels are suited for applications that require very little power, such as calculators.
Copper indium gallium selenide (CIGS)
CIGS panels use a thin layer of copper, indium, gallium, and selenium deposited on a glass or plastic backing. The combination of these elements results in the highest efficiency among thin-panel types, though still not as efficient as crystalline silicon panels.
Solar Panel Types by Efficiency
Among all panel types, crystalline solar panels have the highest efficiency.
- Monocrystalline panels have an efficiency rating over 20%.
- PERC panels add an extra 5% efficiency thanks to their passivation layer.
- Polycrystalline panels hover somewhere between 15-17%.
In contrast, thin-film panels are usually 2-3% less efficient than crystalline silicon. On average:
- CIGS panels have an efficiency range of 13-15%.
- CdTe ranges between 9-11%.
- a-Si have the lowest efficiency at 6-8%.
Solar Panel Types by Power Capacity
Monocrystalline cells have the highest power capacity, thanks to their single-crystal construction that allows a higher output rating in a smaller package. Most monocrystalline panels can generate up to 300w of power capacity.
Recent advances in solar technology have allowed polycrystalline panels to bridge the gap. A standard 60-cell polycrystalline panel is now capable of producing between 240-300w. However, monocrystalline panels still beat polycrystalline in terms of power capacity per cell.
Because thin-film panels don’t come in uniform sizes, there is no standard measure of power capacity, and the capacity of one thin-film panel will differ from another based on its physical size. In general, given the same physical footprint, conventional crystalline panels output more power than a thin-film panel of the same size.
Solar Panel Types by Cost
Monocrystalline panels (or modules as they are technically known) carry a hefty price tag, due to its energy-intensive and inefficient manufacturing process with only a 50% yield for every silicon crystal.
Polycrystalline modules are cheaper because they make use of the crystal fragments leftover from monocrystalline production, which results in a simpler manufacturing process and lower production costs.
Among thin-film solar panels, CIGS is the most expensive, followed by CdTe and amorphous silicon. Apart from the lower acquisition cost, thin-film modules can be easier to install thanks to their lighter weight and flexibility, which lowers the cost of labor.
While the total cost of residential systems has declined by more than 65% over the last decade, the soft cost of a system has actually risen from 58% of total system cost in 2014 to 65% in 2020.
For more information about soft costs, check out our article on the soft costs in the solar industry. and what’s being done to reduce them.
|Panel (Module) type
|Average Cost per Watt
|1 – 1.50
|0.70 – 1
|Copper indium gallium selenide (CIGS)
|0.60 – 0.70
|Cadmium telluride (CdTe)
|0.50 – 0.60
|Amorphous silicon (a-Si)
|0.43 – 0.50
Note that these figures don’t include the cost of installation and labor. With labor and other overhead factors, the total can rise to 2.50 to 3.50 per watt.
Other Factors to Consider
The temperature of a solar panel can affect its ability to generate energy. This loss of output is reflected through the temperature coefficient, which is a measure of the panel’s decrease in power output for every 1°C rise over 25°C (77°F).
Monocrystalline and polycrystalline panels have a temperature coefficient between.0.3% / °C to.0.5% / °C, while thin-film panels are closer to.0.2% / °C. This means that thin-film panels can be a good option for hotter environments or places that experience more sunlight throughout the year.
The updated International Building Code of 2012 requires solar panels to match the fire rating of the roof where they are installed. This is to ensure that the modules do not accelerate the spread of flames in the event of a fire. (California goes one step further by requiring the whole PV system, which includes the racking system, to have the same fire rating).
As such, solar panels now carry the same classification rating as roofs:
- effective against severe fire test exposure
- flame spread should not exceed 6 feet
- required for wildland-urban interface areas, or areas with high fire severity and wildfire risk
UL 1703 and UL 61703 standards address hail storms, by dropping 2-inch solid steel spheres on solar panels from a height of 51 inches, and by firing 1-inch ice balls on PV panels with a pneumatic cannon to simulate hail impacts.
Because of their thicker construction, crystalline panels can withstand hail hitting at speeds of up to 50mph, while thin-film solar panels carry a lower rating due to their thin and flexible nature.
While there is no formal solar classification rating for hurricanes, the Department of Energy recently expanded its recommended design specifications for solar panels to safeguard against severe weather.
The new recommendations include:
- Modules with the highest ASTM E1830-15 rating for snow and wind loading in both the front and back.
- Fasteners with true locking capability based on DIN 65151 standard
- The use of through-bolting modules with locking fasteners instead of clamping fasteners
- The use of 3-frame rail systems for improved rigidity and support against twisting
- Tubular frames over open-shaped C channels
- Perimeter fencing around PV systems to slow down wind forces
Light-Induced Degradation (LID)
LID is a performance loss commonly seen in crystalline panels during the first few hours of sun exposure. This happens when sunlight reacts with oxygen traces left over from the manufacturing process, which affects the silicon lattice structure.
The LID loss is directly tied to the manufacturing quality and can range from 1-3%.
Summary: Solar Panel Types Compared
|Highest to lowest:
So, Which Solar Panel Type Should You Use?
As crystalline and thin-film panels have their own pros and cons, the choice of solar panel ultimately comes down to your specific property and condition settings.
Those living in a dense area with limited space should opt for highly efficient monocrystalline modules to make the most of the physical space and maximize utility savings. If budget permits, going for PERC panels can lower energy generation costs even more in the long run.
Those with a sufficiently larger property can save on upfront costs by using polycrystalline solar panels, where a bigger panel footprint can offset the lower panel efficiency. However, a larger footprint could also mean added labor costs, so it’s not necessarily cheaper to get a higher quantity of less expensive panels. While the initial cost may be low, it may eventually be offset by reduced efficiency and higher operating expenses in the long term.
As for thin-film solar panels, these are best suited for locations where the heavy and labor-intensive installation of crystalline silicon is not feasible. Such locations can include commercial buildings with tight spaces or thin roofs; compact spaces such as recreational vehicles and watercraft; and areas that require flexible installation instead of rigid paneling.
Keep in mind that solar panels are designed for long-term installation, which can be as long as 25 years. So whatever type you choose to go with, make sure to do your homework to ensure that it’s the best option for your needs.
How do solar panels work?
What makes these alternative energy sources function?
Solar panels crown rooftops and roadside signs, and help keep spacecraft powered. But how do solar panels work?
Simply put, a solar panel works by allowing photons, or particles of light, to knock electrons free from atoms, generating a flow of electricity, according to the University of Minnesota Duluth. Solar panels actually comprise many, smaller units called photovoltaic cells — this means they convert sunlight into electricity. Many cells linked together make up a solar panel.
Each photovoltaic cell is basically a sandwich made up of two slices of semi-conducting material. According to the Proceedings National Graduate Conference 2012, photovoltaic cells are usually made of silicon — the same stuff used in microelectronics.
To work, photovoltaic cells need to establish an electric field. Much like a magnetic field, which occurs due to opposite poles, an electric field occurs when opposite charges are separated. To get this field, manufacturers dope silicon with other materials, giving each slice of the sandwich a positive or negative electrical charge.
Specifically, they seed phosphorous into the top layer of silicon, according to the American Chemical Society, which adds extra electrons, with a negative charge, to that layer. Meanwhile, the bottom layer gets a dose of boron, which results in fewer electrons, or a positive charge. This all adds up to an electric field at the junction between the silicon layers. Then, when a photon of sunlight knocks an electron free, the electric field will push that electron out of the silicon junction.
A couple of other components of the cell turn these electrons into usable power. Metal conductive plates on the sides of the cell collect the electrons and transfer them to wires, according to the Office of Energy Efficiency and Renewable Energy (EERE). At that point, the electrons can flow like any other source of electricity.
Researchers have produced ultrathin, flexible solar cells that are only 1.3 microns thick — about 1/100th the width of a human hair — and are 20 times lighter than a sheet of office paper. In fact, the cells are so light that they can sit on top of a soap bubble, and yet they produce energy with about as much efficiency as glass-based solar cells, scientists reported in a study published in 2016 in the journal Organic Electronics. Lighter, more flexible solar cells such as these could be integrated into architecture, aerospace technology, or even wearable electronics.
There are other types of solar power technology — including solar thermal and concentrated solar power (CSP) — that operate in a different fashion than photovoltaic solar panels, but all harness the power of sunlight to either create electricity or to heat water or air.
To learn more about solar energy, you can watch this video by NASA. Additionally, you can read the article Top 6 Things You Didn’t Know About Solar Energy by America’s Energy Department.
“Solar Power: A Feasible Future”. Sustainability, University of Minnesota Duluth (2020). https://conservancy.umn.edu/bitstream
“A Review on Comparison between Traditional Silicon Solar Cells and Thin- Film CdTe Solar Cells”. Proceedings National Graduate Conference (2012). https://www.researchgate.net
“How Solar Cells Work”. The American Chemical Society. https://www.acs.org
“Solar Photovoltaic Cell Basics”. Office of Energy Efficiency and Renewable Energy. https://www.energy.gov/eere/solar/solar-photovoltaic-cell-basics
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Solar Panels: 60 vs. 72 Cells
Other than the obvious difference of 12 solar cells, there are pros and cons to using 60 and 72 cells in different solar power systems.
First a little background. Solar panels are made from blocks of silicon ingots that are cut into square cells. Those are the squares that you see that make up the solar panels. Each solar cell produces about a half a volt. Multiple cells are then wired in series, plus to minus, to make a solar panel. Wiring the cells in series increases the solar panel voltage to a usable level. The more cells that are wired in series, the higher the voltage.
For example, if 36 cells are wired in series, you get an output of about 18 volts. The 36 cell solar panel that outputs 18V is perfect for charging a 12V battery bank, since you need a higher voltage to charge a battery. So, a 36 cell solar panel is called a 12V “nominal” panel, as it is designed to charge a 12V battery. Likewise, a solar panel with twice as many cells, 72 cells, outputs about 36 volts, and it is great for charging a 24V battery bank. So it is called? You got it, a 24V nominal solar panel.
All was well and good with figuring out what nominal voltage solar panels to use, just make them match the nominal voltage of the batteries, when along came two different technologies that added an interesting twist to the mix.
Grid-Tie Solar Systems
The first was grid-tie solar. With a grid-tie inverter, you could now convert the DC voltage from the solar panels directly into AC to power your house with no batteries required. So the restriction of 12V, 24V, and 48V went away. This allowed the solar panel manufacturers to use however many cells they wanted to. For solar panels up to about 300W, the industry settled on 60 cells. Using the terminology from the battery world, that’s a 20V nominal panel.
With an Open Circuit Voltage, or Voc, of around 38V, grid-tie solar systems were able to string up to twelve or thirteen 60 cell solar panels in series and stay within the Electrical Code restriction of staying under 600V DC, even when taking temperature into consideration. If they were using 24V 72 cell panels, they would be limited to only 11 in series in cold environments, limiting their system size.
Solar Charge Controllers
The second change was in the battery-based world, with the solar charge controllers, used to manage putting the power from the solar panels into the batteries.
Early on, the shunt or PWM charge controllers (Pulse Width Modulated) had to match the nominal voltage between the solar panels and the battery bank.
MPPT solar charge controllers (Maximum Power Point Tracking) came onto the scene and allowed you to take a higher voltage solar input and reduced the charge controller voltage output to correctly charge a battery bank, while increasing the output current – eliminating any power loss due to forcing solar panels to operate at whatever voltage the battery bank was actually at. This opened up the ability to use any cell count solar panels, as long as the voltage was higher than the battery bank.
60 cell grid-tie solar panels
Since 60 cell grid-tie solar panels are so common now, their price per watt has dropped much lower than the 12V panels, making them an attractive option to charge battery banks. Just remember you have to use a MPPT charge controller to do it. Also note that you cannot use a single 60 cell solar panel to charge a 24V battery bank. You need at least one 72 cell panel or two 60 cell panels in series to have a voltage high enough to charge 24V.
72 cell grid-tie solar panels
So, what about the 72 cell 24V solar panels for grid-tie solar systems? Well, technology and codes move forward, and newer revisions of the electric codes now allow for 1000V strings for grid-tie commercial and utility scale systems.
Also, grid-tie inverters are getting bigger and bigger, allowing for extremely high wattages getting inverted. Since watts equals volts times amps, a way to increase the wattage of a solar panel is to increase the voltage by adding additional cells. Adding those 12 additional cells generally adds a foot of length to the solar panel. With larger commercial and utility scale projects, larger panel sizes are able to be used. So, 72 cell panels give them a way to regularly make solar panels over 300W. Higher wattage solar panels reduce the number of panels that are needed in the system to reach your target wattage, which can decrease the labor needed to install them. Higher wattage panels may also reduce the amount of balance of system equipment needed, including racking, wire, and in some cases, electronics themselves, if they are using microinverters or DC Optimizers. Note that not all microinverters will support 72 cell solar panels, so 60 cell is still the only option in some cases, mostly for home systems.
Most 72 cell panels still weigh less than the 50 lb restriction set by OSHA, so can be carried by one person, although their size can make it awkward to handle alone. The smaller 60 cell solar panels can be easier to handle.
So…which size solar panel should I use?
What size solar panel you should use for your project depends on a lot of criteria.
- Are you building an off-grid or a grid-tie solar system?
- If it is off-grid, what voltage battery bank are you trying to charge?
- Do you have physical size restrictions that would limit the size of the panel?
- Will the equipment you want to use support the solar panel?
- Will a higher voltage panel restrict the number of panels you can use in a system?
These are all questions you need to ask to determine what size solar panels are right for you.
Split Cell Solar Panels Are The Latest Advancement In Solar Panel Technology
At nearly 65 years old, the humble solar panel has come a long way since its launch by Bell Labs. Since then, numerous innovations have beaten the drum of progress to help solar energy become a viable solution around the globe. The 6% efficiency attained in the early days is a small fraction of the 22% achieved by many of today’s market-leading manufacturers.
Once again, the solar industry had rolled out a significant improvement in design that has increased solar panel performance.
Half cell solar panels are a relative newcomer to the market and are an exciting prospect for homeowners across Australia looking to get the most out of their solar system.
What is a split-cell solar panel?
Split-cell modules contain solar cells that have been split in half using a laser cutter. Rather than having 60 solar cells like a typical panel, half-cells have 120 cells that are half the size.
Each module is effectively two twin panels, which are connected in parallel, while the rows of half cells are joined in series.
The wiring allows the panels to maintain the same overall voltage as a regular panel while increasing output. It is predicted that these will make up 40% of the market by 2028, up from 5% in 2018.
What are the advantages of split cell solar technology?
When cells are cut in half, the amount of current they produce is also halved. However, the halved cells produce just a quarter of the resistance. Less resistance means that the cells can produce power at a more efficient rate, improving their overall performance by around 2-3% when compared to standard panels.
Because the cells are smaller, there is also less wear and tear throughout the panel’s lifetime. Half cell solar panels also tend to crack less, so on average, they are more reliable than traditional modules.
Shade can be the Achilles heel of a solar system, but the design of half cell solar panels negates some of the loss in output. There are six rows joined in series per panel, three more than usual.
A traditional panel can lose up to a third of its power if a cell is covered, however only a sixth of energy production is affected if a half cell is in the shade. Overall, this can make them more effective in patchy shade compared to regular cell modules.
Ordinarily, when one cell within a string is shaded the whole string of panels drops down to the performance of the worst-performing panel. In the long run, this significantly affects the output of your system. This is why nearly all of our customers choose Enphase microinverters over a string inverter.
Half cell solar panels have a lower current in each cell because there are more of them. This reduces the heat concentration and defends against hot spot damage.
Their efficiency, reliability and shade resistance make them great for anyone looking to get extra value out of their installation.
Who manufactures the best half-cell solar panel?
Solaray is currently offering the leading half-cell panels on the market, including:
Founded in Norway in 1996, REC Group is recognised for producing high-quality solar panels with long warranties and excellent reliability.
REC Alpha Pure-R 410W panels feature REC’s innovative design, with high panel efficiency power output thanks to top-quality monocrystalline cells. This enables you to get more out of the space available on your roof – helping to lower your energy bills and shorten the payback time through increased yield and lower costs.
Trina Solar is considered one of the leading manufacturers operating in Australia with an excellent track record of high performance and reliability. Trina Solar has been at the forefront of solar innovations for close to two decades and has multiple efficiency records to its name.
The Trina Solar Vertex has a high power output that combines with exceptional efficiency to squeeze extra value into every panel. Their robust panels can withstand the barrage of harsh weather conditions and are considered one of the best-value solar panels available in Australia.
For more information and pricing, please contact the Solaray Team today.