A photovoltaic cell is made up of several layers of materials, each with its own function. The specifically treated semiconductor layer is the most crucial layer in a solar cell. It is divided into two layers (p-type and n-type). see Figure 3), and is responsible for converting the Sun’s energy into usable power via a process known as the photovoltaic effect (see below). A layer of conducting material is present on both sides of the semiconductor, which “collects” the electricity generated. Note that the backside of the cell, which is shaded, can afford to have the conductor totally covered, whereas the front, which is lighted, must use the conductors sparingly to prevent blocking too much of the Sun’s energy from reaching the semiconductor. The anti-reflection coating is the final layer, which is only applied to the lit side of the cell. Reflection loss can be severe because all semiconductors are naturally reflective. To limit the quantity of solar radiation reflected off the cell’s surface, one or more layers of an anti-reflection coating (similar to those used on eyeglasses and cameras) can be utilized.
What are the three different kinds of solar panels?
The efficiency of all PV panels varies. That is, certain types and even brands of solar panels are more effective than others at converting sunlight into power. This is due to the fact that the amount and type of silicon cells in a panel might vary. A Solar Panel’s cost, size, and weight are often determined by the number of cells it contains. Although it is commonly assumed that the more silicon cells in a panel, the higher the wattage and power output, this is not necessarily the case. The quality and efficiency of the solar cells themselves determine the panel’s power output.
We’ll look at the three primary varieties of solar panel cells in this blog: polycrystalline, monocrystalline, and thin-film. The first step in choosing the right panel for your home, business, or community is to understand the differences between the three.
What are the layers that make up a solar panel?
Tempered top glass, framing, anti-reflective coating, and texturization are commonly found in the top layers of a solar cell. Some solar cells may contain more layers (such as multi-layered cells) than others, depending on the technique and function. The following layers in this section provide a broad description of their purpose, layout, and how light interacts with them when flowing through them.
A solar panel has how many parts?
A typical solar panel consists of a silicon cell layer, a metal frame, a glass casing, and various wiring to allow current to flow from the silicon cells. Silicon is a conductive nonmetal that can absorb and transform sunlight into electricity.
What is the material that a solar panel’s top layer is made of?
Solar panel technology is fast improving in terms of efficiency and cost, resulting in a surge in demand. Despite enormous technological developments, basic solar panel manufacturing hasn’t altered much over the years. The majority of solar panels are still made up of silicon crystalline cells sandwiched between a front glass plate and a back polymer plastic back-sheet held together by an aluminum frame.
Solar panels are subjected to harsh environments for the duration of their 25+ year lifespan once installed. Extreme changes in temperature, humidity, wind, and UV radiation can put a solar panel under a lot of strain. Fortunately, most panels are well-engineered to endure harsh weather conditions. Water ingress, cell microfractures, and potential induced degradation, or PID, are all possible causes of failure for some panels. This is why it’s critical that solar panels are made with just the best components. In our other post, top solar panels, we highlight the leading manufacturers who use the finest quality materials and test to the industry’s strictest requirements.
What are the components of solar panels?
Despite the enormous supply of energy beaming in the sky, denialists continue to debate and belittle the benefits of solar power and other renewable sources, repeatedly raising the same questions: What is the efficiency of solar energy? Isn’t it more costly? What happens when the sun sets or the sky darkens?
We’ve debunked those falsehoods previously, but one question we constantly get is, “OK, but what are solar panels made of, and do they harm the environment?”
First, there’s the panel itself.
The big black solar panels you see on homes and businesses are made up of a collection of silicon semiconductor-based solar cells (or photovoltaic cells) that absorb sunlight and generate an electric current. To build a solar panel, these individual cells are linked together.
You can look at the structure of each individual solar cells if you want to get even more technical. They’re made up of two sorts of semiconductors: p-type (positive) and n-type (negative) silicon layers.
The n-type silicon layer has additional electrons that can move around freely, whereas the p-type silicon layer has electron vacancies known as holes. When the layers are brought together, electrons begin to migrate from the n-type to the p-type, forming a unique junction that generates electric potential in the material. When a photon from the sun strikes this junction, it can knock an electron loose, leaving a hole behind. The free electrons begin to congregate near the pole as more electrons fill the newly formed holes. The electrons are subsequently collected and pass via a conductor, resulting in an electric current.
Russell Ohl, a Bell Labs researcher, discovered the P-N junction’s functionality in the 1940s, and that silicon, which is found in sand and is the second most prevalent element in the Earth’s crust after oxygen, has qualities that were conducive to the junction’s development.
Scientists worked to improve on Ohl’s finding, and Bell Labs introduced the first modern solar cell in 1954.
The presentation prompted a 1954 New York Times story to predict that solar cells would eventually lead to the development of new technologies “to the fulfilment of one of humanity’s most treasured dreams: harnessing the sun’s nearly endless energy.”
Photovoltaic (PV) cells are now primarily mass-produced and laser-cut, a long cry from their humble beginnings.
The inverter comes next. Solar cells gather sunlight and convert it to direct current (DC) electricity. However, alternating current is used in most homes and businesses (AC). Solar panels provide DC electricity, which is converted into usable AC electricity via inverters.
Finally, there’s the mounting mechanism, which keeps everything safe and secure on a roof or on the ground. Solar panels should face south and be set at a 30- or 45-degree angle in the northern hemisphere, depending on the distance from the equator. Track mounts hold the panels in place, but fixed mounts maintain them in place “There are additional options that follow the sun throughout the day, however these are usually more expensive.
OK, so how green is all of this?
Yes, the production of solar panels, like the production of other things, emits carbon dioxide. There is also some valid concern concerning the disposal of solar panels.
However, as solar panel production gets more efficient, the carbon footprint of the product has been greatly reduced. According to a 2016 study, overall emissions reduced by 17 to 24% every time installed capacity doubled in the last 40 years.
Solar energy also produces far fewer greenhouse gas emissions than coal or natural gas, which is unsurprising. Solar panels may endure for decades with no maintenance, and because their parts don’t wear out readily, they’re well-known for delivering clean electricity much beyond their often-extensive warranties, albeit at a little lower efficiency as the years pass.
Some manufacturers offer global recycling schemes for their clients when a panel reaches the end of its useful life.
The median solar system lost only 0.5 percent of its power output per year, according to a June 2012 National Renewable Energy Laboratory (NREL) study that looked at the photovoltaic degradation rates of nearly 2,000 solar installations over a 40-year span. As a result, towards the end of a conventional 25-year warranty, your roof’s solar panels may still be producing at around 87 percent of their original capacity.
Furthermore, as solar becomes more popular, recycling programs and businesses are projected to expand and become more robust in the future.
Download our free e-book, Things Are Looking Bright: The Facts About Solar Energy, to learn even more about the benefits of solar energy, or check out Knowledge Is Power, our partnership with HGTV’s Property Brothers co-host and solar energy enthusiast Jonathan Scott.
The e-book discusses the amazing benefits of solar energy as well as the deceitful techniques used by fossil fuel utilities to protect their bottom lines at the expense of everyone on the planet.
What does MPPT mean in terms of solar panels?
The theory and functioning of “Maximum Power Point Tracking” as employed in solar electric charge controllers are covered in this section.
A maximum power point tracker, or MPPT, is an electronic DC to DC converter that optimizes the match between the solar array (PV panels) and the battery bank or utility grid. Simply put, they convert the higher voltage DC output from solar panels (as well as a few wind generators) to the lower voltage required to charge batteries.
(These are sometimes referred to as “power point trackers,” not to be confused with PANEL trackers, which are solar panel mounts that follow or track the sun.)
So what do you mean by “optimize”?
Solar cells are fascinating devices. They are, however, not particularly intelligent. Batteries aren’t either; in fact, they’re downright stupid. The majority of PV panels are designed to produce 12 volts nominally. The catch is the word “nominal.” In reality, nearly all “12-volt” solar panels are designed to produce between 16 and 18 volts. The issue is that a nominal 12-volt battery is near to an actual 12-volt battery – 10.5 to 12.7 volts, depending on charge condition. Most batteries require between 13.2 and 14.4 volts to completely charge, which is very different from what most panels are designed to produce.
So, now we’ve got this cool 130-watt solar panel. The first snag is that it’s only rated for 130 watts at a specific voltage and current. 7.39 amps at 17.6 volts are rated for the Kyocera KC-130. 7.39 amps multiplied by 17.6 volts equals 130 watts.
Now the Catch 22
So, what happens if you use a conventional charge controller to connect this 130-watt panel to your battery?
Your panel is capable of delivering 7.4 amps. Your battery is charged to 12 volts: 7.4 amps multiplied by 12 volts equals 88.8 watts. You saved over 41 watts, but you had to pay for 130. That 41 watts isn’t going anywhere; it’s just not being created because the panel and battery aren’t a good match. It’s even worse if you have a really low battery, like 10.5 volts, because you may be losing up to 35 percent of your power (11 volts x 7.4 amps = 81.4 watts). You lost approximately 48 watts.
One alternative you might consider is to design panels that output 14 volts or less to match the battery.
The panel is rated at 130 watts in full sunshine at a specific temperature, which is catch #22a (STC – or standard test conditions). You won’t receive 17.4 volts if the solar panel’s temperature is too high. You might get under 16 volts at the temperatures encountered in many hot climate places. You’re in danger if you started with a 15-volt panel (like some of the so-called “self-regulating” panels), because there won’t be enough voltage to charge the battery. Solar panels must be designed with enough wiggle room to work in the most adverse conditions. The panel will just sit there looking silly, and your batteries will become even more stupid.
What is Maximum Power Point Tracking?
The term “tracking” is a bit of a misnomer:
Panel tracking occurs when the panels are mounted on a mount that moves with the sun. The Zomeworks are the most common. These maximize output by following the sun as it moves across the sky. These normally provide a 15% increase in the winter and up to a 35% increase in the summer.
For MPPT controllers, this is the polar opposite of seasonal variation. Because the temperature of the panels is lower in the winter, they produce more power. Due to the shorter days, winter is usually when you require the most power from your solar panels.
Maximum Power Point Tracking is a type of electronic tracking that is commonly done with a computer. The charge controller compares the output of the panels to the voltage of the battery. It then determines what the best power output from the panel is for charging the battery. It converts this to the best voltage possible in order to get the most AMPS into the battery. (Keep in mind that the number of Amps into the battery is what matters.) The conversion efficiency of most current MPPTs is around 93-97 percent. In the winter, you can expect a 20 to 45 percent increase in power, whereas in the summer, you can expect a 10-15 percent increase. The amount of gain varies greatly based on the weather, temperature, battery state of charge, and other variables.
As the cost of solar reduces and utility prices rise, grid connection solutions are becoming increasingly popular. There are a variety of grid-tie only (no battery) inverter brands available. MPPT is incorporated into each of these. The MPPT conversion efficiency on those is from 94 percent to 97 percent.
How Maximum Power Point Tracking works
This is where optimization, also known as maximum power point tracking, comes into play. Assume your battery is at 12 volts and is low. An MPPT converts 17.6 volts at 7.4 amps to 10.8 amps at 12 volts, which is what the battery now receives. Everyone is thrilled since you still have almost 130 watts.
At 11.5 volts, you should receive roughly 11.3 amps for 100 percent power conversion, but you’ll need to give the battery a higher voltage to force the amps in. And this is a simplified description; in reality, the MPPT charge controller’s output may vary continuously to ensure that the maximum amps are delivered to the battery.
A screenshot from the Maui Solar Software “PV-Design Pro” computer program is seen on the left (click on the picture for full-size image). When you look at the green line, you’ll notice a dramatic peak in the upper right corner, which symbolizes the maximum power point. An MPPT controller “looks” for that precise point, then performs the voltage/current conversion to match the battery’s requirements. In real life, that peak shifts with the changing light and weather.
In almost all cases, an MPPT tracks the maximum power point, which will differ from the STC (Standard Test Conditions) rating. Because the power output increases higher as the panel temperature goes down, a 120-watt panel can actually put out over 130+ watts in very cold conditions – but if you don’t have some way of measuring that power point, you’ll lose it. In extreme heat, on the other hand, the power lowers – you lose power as the temperature rises. As a result, you gain less in the summer.
Under the following circumstances, MPPTs are most effective:
- Cold weather solar panels perform better in cold weather, but without an MPPT, you’ll lose the majority of the benefits. Cold weather is most likely in the winter, when daylight hours are at their lowest and you need the greatest power to recharge your batteries.
- Low battery charge – the lower the level of charge in your battery, the more current it receives from an MPPT – another time when the extra power is most needed. Both of these situations can exist at the same moment.
- Long wire runs – If your panels are 100 feet apart and you’re charging a 12-volt battery, the voltage drop and power loss can be significant unless you utilize extremely wide wire. This can be quite costly. The power loss is substantially lower if four 12 volt panels are put in series for 48 volts, and the controller will convert the high voltage to 12 volts at the battery. This also means that if the controller is fed by a high-voltage panel, you can use much smaller cable.
How a Maximum Power Point Tracker Works:
The Power Point Tracker is a DC to DC converter with a high frequency. To precisely match the panels to the batteries, they take the DC input from the solar panels, convert it to high-frequency AC, and then convert it back to a different DC voltage and current. MPPTs work at very high audio frequencies, usually between 20 and 80 kHz. High-frequency circuits have the advantage of being able to be created using very high-efficiency transformers and compact components. High-frequency circuit design can be difficult due to issues with components of the circuit “broadcasting” like a radio transmitter, producing radio and television interference. Isolation and suppression of noise become critical.
There are a few non-digital (linear) MPPT charge controls on the market. These are far easier and less expensive to construct and design than computerized ones. They do boost efficiency to some extent, but total efficiency varies greatly – and we’ve seen a few lose their “tracking point” and even deteriorate. If a cloud passes over the panel, the linear circuit will look for the next best location, but it will be too far out in the deep end to find it when the sun returns. Thankfully, there aren’t many of these left.
The power point tracker (and all DC to DC converters) work by taking the DC input current, converting it to AC, passing it through a transformer (typically a toroid, which looks like a doughnut), and then rectifying it back to DC before the output regulator. In most DC to DC converters, this is purely an electrical process with no real intelligence involved save for some output voltage management. Solar charge controllers require a lot more intelligence because light and temperature conditions change throughout the day, as well as battery voltage fluctuations.
Smart power trackers
Microprocessor-controlled digital MPPT controllers are available in all modern versions. They recognize when the output to the battery needs to be adjusted, and they shut down for a few microseconds to “look” at the solar panel and battery and make any necessary modifications. Although not exactly new (the Australian company AERL had some as early as 1985), electronic microprocessors have only lately become affordable enough for use in smaller systems (less than 1 KW of the panel). Several firms currently make MPPT charge controls, including Outback Power, Xantrex XW-SCC, Blue Sky Energy, Apollo Solar, Midnite Solar, Morningstar, and a few more.
What is the object in the centre of the solar panel?
A solar cell is a highly complicated and accurate assembly of several components. Solar cells have an anti-reflective coating on the top layer of glass. The anti-reflective coating allows more sunlight reach the semiconductors, while the glass protects the components beneath it. A small grid pattern can be seen while looking at a solar cell. Underneath the glass is a grid of thin metallic strips. The top layer of the cell is made up of glass, anti-reflective coating, and metallic strips.
The most significant part of the solar cell is the intermediate layer. It consists of two layers of semiconductors and is where solar energy is generated through the photovoltaic effect. N-type material makes up the first layer. This is usually silicon that has been combined with a small amount of phosphorous to make it negatively charged. A p-type material is used in the second layer. This positively charged substance is often created by combining silicon with minor amounts of boron.
The solar cell’s bottom layer is divided into two halves. Directly beneath the p-type semiconductor is a rear metallic electrode. To generate an electric current, this rear electrode interacts with the metallic grid in the top layer. The system’s last layer is a reflective coating that reduces sunlight loss. Depending on the intended function and desired cost, different materials may be used in different solar cells. They could potentially have layers on top of the ones already stated. However, all solar cells adopt this basic structure.
How a solar cell works
Let’s have a peek at a solar cell in action. When sunlight strikes a solar cell, it may be reflected, absorbed, or just pass through it. Light absorbed by semiconducting materials is the only source of electricity. The anti-reflection coating causes less light to bounce off, while the reflective backings cause more light that would otherwise pass through to bounce back into the system. Although it is impossible to design a system that absorbs 100% of the light, technological advances are continually improving efficiency.
The semiconductors absorb the light once it reaches the middle layer. The energy within the atoms of semiconductors is then increased by photons, small packets of energy found in all light. The outer rings of the atoms in an n-type material have extra electrons. When it is electrified, those electrons are knocked loose and begin hunting for a place to bind with right away. Because the outer rings of the atoms in the p-type material have holes, it requires additional electrons to be complete. The liberated electrons rush to fill the gaps.
Some electrons will fill holes where the n- and p-layers meet without causing any power to be generated. However, a stumbling block emerges rapidly. This is when the solar cell’s top metallic grid and back metallic electrode become crucial. The free electrons from the n-layer are drawn toward the metallic grid on top. An electric current is created when these electrons are compelled to flow in one direction. These electrons are then transported through an external circuit that captures the electric current using an energy load. After capturing the electricity, the electron travels along the circuit until it reaches the rear electrode, which is close to the p-layer. The holes in the p-type material are then filled by the electrons, and the circuit is complete.