Solar Photovoltaic Cell Basics
When light shines on a photovoltaic (PV) cell – also called a solar cell – that light may be reflected, absorbed, or pass right through the cell. The PV cell is composed of semiconductor material; the “semi” means that it can conduct electricity better than an insulator but not as well as a good conductor like a metal. There are several different semiconductor materials used in PV cells.
When the semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the material called electrons. This extra energy allows the electrons to flow through the material as an electrical current. This current is extracted through conductive metal contacts – the grid-like lines on a solar cells – and can then be used to power your home and the rest of the electric grid.
The efficiency of a PV cell is simply the amount of electrical power coming out of the cell compared to the energy from the light shining on it, which indicates how effective the cell is at converting energy from one form to the other. The amount of electricity produced from PV cells depends on the characteristics (such as intensity and wavelengths) of the light available and multiple performance attributes of the cell.
An important property of PV semiconductors is the bandgap, which indicates what wavelengths of light the material can absorb and convert to electrical energy. If the semiconductor’s bandgap matches the wavelengths of light shining on the PV cell, then that cell can efficiently make use of all the available energy.
Learn more below about the most commonly-used semiconductor materials for PV cells.
Silicon is, by far, the most common semiconductor material used in solar cells, representing approximately 95% of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and the most common semiconductor used in computer chips. Crystalline silicon cells are made of silicon atoms connected to one another to form a crystal lattice. This lattice provides an organized structure that makes conversion of light into electricity more efficient.
Solar cells made out of silicon currently provide a combination of high efficiency, low cost, and long lifetime. Modules are expected to last for 25 years or more, still producing more than 80% of their original power after this time.
A thin-film solar cell is made by depositing one or more thin layers of PV material on a supporting material such as glass, plastic, or metal. There are two main types of thin-film PV semiconductors on the market today: cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). Both materials can be deposited directly onto either the front or back of the module surface.
CdTe is the second-most common PV material after silicon, and CdTe cells can be made using low-cost manufacturing processes. While this makes them a cost-effective alternative, their efficiencies still aren’t quite as high as silicon. CIGS cells have optimal properties for a PV material and high efficiencies in the lab, but the complexity involved in combining four elements makes the transition from lab to manufacturing more challenging. Both CdTe and CIGS require more protection than silicon to enable long-lasting operation outdoors.
Perovskite solar cells are a type of thin-film cell and are named after their characteristic crystal structure. Perovskite cells are built with layers of materials that are printed, coated, or vacuum-deposited onto an underlying support layer, known as the substrate. They are typically easy to assemble and can reach efficiencies similar to crystalline silicon. In the lab, perovskite solar cell efficiencies have improved faster than any other PV material, from 3% in 2009 to over 25% in 2020. To be commercially viable, perovskite PV cells have to become stable enough to survive 20 years outdoors, so researchers are working on making them more durable and developing large-scale, low-cost manufacturing techniques.
Organic PV, or OPV, cells are composed of carbon-rich (organic) compounds and can be tailored to enhance a specific function of the PV cell, such as bandgap, transparency, or color. OPV cells are currently only about half as efficient as crystalline silicon cells and have shorter operating lifetimes, but could be less expensive to manufacture in high volumes. They can also be applied to a variety of supporting materials, such as flexible plastic, making OPV able to serve a wide variety of uses.PV
Quantum dot solar cells conduct electricity through tiny particles of different semiconductor materials just a few nanometers wide, called quantum dots. Quantum dots provide a new way to process semiconductor materials, but it is difficult to create an electrical connection between them, so they’re currently not very efficient. However, they are easy to make into solar cells. They can be deposited onto a substrate using a spin-coat method, a spray, or roll-to-roll printers like the ones used to print newspapers.
Quantum dots come in various sizes and their bandgap is customizable, enabling them to collect light that’s difficult to capture and to be paired with other semiconductors, like perovskites, to optimize the performance of a multijunction solar cell (more on those below).
Another strategy to improve PV cell efficiency is layering multiple semiconductors to make multijunction solar cells. These cells are essentially stacks of different semiconductor materials, as opposed to single-junction cells, which have only one semiconductor. Each layer has a different bandgap, so they each absorb a different part of the solar spectrum, making greater use of sunlight than single-junction cells. Multijunction solar cells can reach record efficiency levels because the light that doesn’t get absorbed by the first semiconductor layer is captured by a layer beneath it.
While all solar cells with more than one bandgap are multijunction solar cells, a solar cell with exactly two bandgaps is called a tandem solar cell. Multijunction solar cells that combine semiconductors from columns III and V in the periodic table are called multijunction III-V solar cells.
Multijunction solar cells have demonstrated efficiencies higher than 45%, but they’re costly and difficult to manufacture, so they’re reserved for space exploration. The military is using III-V solar cells in drones, and researchers are exploring other uses for them where high efficiency is key.
Concentration PV, also known as CPV, focuses sunlight onto a solar cell by using a mirror or lens. By focusing sunlight onto a small area, less PV material is required. PV materials become more efficient as the light becomes more concentrated, so the highest overall efficiencies are obtained with CPV cells and modules. However, more expensive materials, manufacturing techniques, and ability to track the movement of the sun are required, so demonstrating the necessary cost advantage over today’s high-volume silicon modules has become challenging.
Learn more about photovoltaics research in the Solar Energy Technologies Office, check out these solar energy information resources, and find out more about how solar works.
Sunny superpower: solar cells close in on 50% efficiency
For solar cells, efficiency really matters. This crucial metric determines how much energy can be harvested from rooftops and solar farms, with commercial solar panels made of silicon typically achieving an efficiency of 20%. For satellites, meanwhile, the efficiency defines the size and weight of the solar panels needed to power the spacecraft, which directly affects manufacturing and launch costs.
To make a really efficient device, it is tempting to pick a material that absorbs all the Sun’s radiation – from the high-energy rays in the ultraviolet, through to the visible, and out to the really long wavelengths in the infrared. That approach might lead you to build a cell out of a material like mercury telluride, which converts nearly all of the Sun’s incoming photons into current-generating electrons. But there is an enormous price to pay: each photon absorbed by this material only produces a tiny amount of energy, which means that the power generated by the device would be pitiful.
Hitting the sweet spot
A better tactic is to pick a semiconductor with an absorption profile that optimizes the trade-off between the energy generated by each captured photon and the fraction of sunlight absorbed by the cell. A material at this sweet spot is gallium arsenide (GaAs). Also used in smartphones to amplify radio-frequency signals and create laser-light for facial recognition, GaAs has long been one of the go-to materials for engineering high-efficiency solar cells. These cells are not perfect, however – even after minimizing material defects that degrade performance, the best solar cells made from GaAs still struggle to reach efficiencies beyond 25%.
Further gains come from stacking different semiconductors on top of one another, and carefully selecting a combination that efficiently harvests the Sun’s output. This well-trodden path has seen solar-cell efficiencies climb over several decades, along with the number of light-absorbing layers. Both hit a new high last year when a team from the National Renewable Energy Laboratory (NREL) in Golden, Colorado, unveiled a device with a record-breaking efficiency of 47.1% – tantalizingly close to the 50% milestone (Nature Energy 5 326). Until then, bragging rights had been held by structures with four absorbing layers, but the US researchers found that six is a “natural sweet spot”, according to team leader John Geisz.
Getting this far has not been easy, because it is far from trivial to create layered structures from different materials. High-efficiency solar cells are formed by epitaxy, a process in which material is grown on a crystalline substrate, one atomic layer at a time. Such epitaxial growth can produce the high-quality crystal structures needed for an efficient solar cell, but only if the atomic spacing of each material within the stack is very similar. This condition, known as lattice matching, restricts the palette of suitable materials: silicon cannot be used, for example, because it is not blessed with a family of alloys with similar atomic spacing.
Devices with multiple materials – referred to as multi-junction cells – have traditionally been based on GaAs, the record-breaking material for a single-junction device. A common architecture is a triple-junction cell comprising three compound semiconductors: a low-energy indium gallium arsenide (InGaAs) sub-cell, a medium-energy sub-cell of GaAs and a high-energy sub-cell of indium gallium phosphide (InGaP). In these multi-junction cells, current flows perpendicularly through all the absorbing layers, which are joined in series. With this electrical configuration, the thickness of every sub-cell must be chosen so that all generate exactly the same current – otherwise any excess flow of electrons would be wasted, reducing the overall efficiency.
Bending the rules
Key to the success of NREL’s device are three InGaAs sub-cells that excel at absorbing light in the infrared, which contains a significant proportion of the Sun’s radiation. Achieving strong absorption at these long wavelengths requires InGaAs compositions with a significantly different atomic spacing to that of the substrate. Additionally, their device has been designed with intermediate transparent layers made from InGaP or AlGaInAs to keep material imperfections in check. Grading the composition of these buffer layers enables a steady increase in lattice constant, thereby providing a strong foundation for local lattice-matched growth of sub-cells that are not riddled with strain-induced defects.
The NREL team, which has pioneered this approach, advocates the so-called “inverted variant” structure. With this architecture, the highest energy cell is grown first, followed by those of decreasing energy, so that the cells lattice-matched to the substrate precede the growth of graded layers. This approach improves the quality of the device, while the fabrication process also results in the removal of the substrate – a step that could trim costs by enabling the substrate to be reused.
One other technique that can further boost solar-cell efficiency is to FOCUS sunlight on the cells, either with mirrors or lenses. The intensity of light on a solar cell is usually measured in “suns”, where one sun is roughly equivalent to 1 kW/m 2. Concentrated sunlight increases the ratio of the current produced when the device is illuminated compared to when it is in the dark, thereby boosting the output voltage and increasing the efficiency. The gain is considerable: the NREL device achieves a maximum efficiency of just 39.2% when tweaked to optimize efficiency without any concentration, a long way short of the 47.1% record.
When Geisz and colleagues assessed how the performance of their six-junction cell varies with concentration, they found that peak efficiency occurs at 143 suns. Nevertheless, the device still produces a very impressive 44.9% efficiency at 1116 suns, which would generate a large amount of power from a very small device. As a comparison, a record-breaking cell operating at 500 suns could deliver the same power as a commercial solar panel from just one-thousandth of the chip area. At such high concentrations, however, steps must be taken to prevent the cell from overheating and diminishing performance.
Just over a decade ago, this approach to generating power from high-efficiency cells spawned a concentrating photovoltaic (CPV) industry, with a clutch of start-up firms producing systems that tracked the position of the Sun to maximize the energy that could be harvested from focusing sunlight on triple-junction cells. Unfortunately, this fledgling industry came up against the unforeseeable double whammy of a global financial crisis and a flooding of the market with incredibly cheap silicon panels produced by Chinese suppliers. The result was that so few CPV systems were deployed that even on a sunny day when all operate at their peak, their global output totals less than one-tenth of the power of a typical UK nuclear power station.
Far greater commercial success for makers of multi-junction cells has come from powering satellites, most recently buoyed by the rollout of satellite broadband by companies such as OneWeb and Starlink. The key advantage here is that high-efficiency cells can drive down the costs of making and launching each satellite. As well as reducing the number of cells needed to power the spacecraft, higher efficiencies shrink both the size and weight of the solar panels that form the “wings” of the satellite. While launch costs have plummeted over the last few decades, satellite operators can still expect to pay almost 3000 per kilogram to get their spacecraft into orbit – and thousands of satellites are due to be deployed over the next few years.
For a solar cell in space, the crucial metric is the value at the end of its lifetime – after the device has been bombarded by radiation
However, for a solar cell in space, the crucial metric is not the initial efficiency but the value at the end of its intended lifetime after the device has been bombarded by radiation. Compound semiconductors hold up to this battering far better than those made from silicon. Early studies showed that the difference in efficiency of compound semiconductors rises with age from 25% to 40–60%, which ensured the dominance of triple-junction cells for space applications. Even so, the efficiencies of the best commercial cells for satellites remain limited to around 30–33%. This is partly because the solar spectrum beyond our atmosphere has a stronger contribution in the ultraviolet, where it is much harder to make an efficient cell, and partly because there are no concentrating optics to FOCUS sunlight onto the cell.
To drive down the watts-per-kilogram of solar power in space, a US team working on a project known as MOSAIC (micro-scale optimized solar-cell arrays with integrated concentration) has been making a compelling case for CPV in space. The team points out that it should be relatively easy to orientate the solar panels on a satellite to maximize power generation with lenses in front of the cells shielding them from radiation. Concentrations must be limited to no more than around 100 suns, however, because cells in space cannot be cooled by convection, only by heat dissipation through radiation and conduction.
For CPV to have a chance of succeeding in space, the large and heavy solar modules used in early terrestrial systems must be replaced with a significantly slimmed-down successor. Technology pioneered by project partner Semprius, a now defunct CPV system maker, excels in this regard. The firm developed a process that uses a rubber stamp to parallel-print vast arrays of tiny cells, each one subsequently capped by a small lens.
The best results have come from stacking a dual-junction GaAs-based cell on top of an InP-based triple-junction cell separated by a very thin dielectric polymer. Current cannot pass through this polymer film, so separate electrical connections are made to extract the current from each cell independently. While this doubles the number of electrical connections, it eliminates the need for current matching between the two devices. Lifting this restriction gives greater freedom to the design, potentially enabling this approach to challenge the efficiency of NREL’s record-breaking device under high concentrations. Operating at 92 suns under illumination which mimics that in space, the team’s latest device, still to be fully optimized, has an efficiency of 35.5%.
The NREL researchers know what they need to do to break the 50% barrier. The goal they are chasing is to cut the resistance in their device by a factor of 10 to a value similar to that found in their three- and four-junction cousins. They are also well aware of the need to bring down the cost of producing such complex multi-junction cells.
Also chasing the 50% efficiency milestone is a team led by Mircea Guina from Tampere University of Technology in Finland. Guina and colleagues are pursuing lattice-matched designs with up to eight junctions, including as many as four from an exotic material system known as dilute nitrides – a combination of the traditional mix of indium, gallium, arsenic and antimonide, plus a few per cent of nitrogen.
Dilute nitrides are notoriously difficult to grow. Back in the 1990s, German electronics powerhouse Infineon developed lasers based on this material, but they were never a commercial success. recently, Stanford University spin-off Solar Junction showcased the potential of this material in solar cells. Although the start-up went to the wall when CPV flopped, devices produced by the company grabbed the record for solar efficiency in 2011 and raised it again in 2012 with triple-junction designs. Guina and co-workers are well positioned to take their technology further. They have made progress in producing all four of the dilute nitride sub-cells needed to produce record-breaking devices, and their efforts are now focused on optimizing the high-energy junction. The team’s work has been delayed due to the COVID-19 pandemic, but Guina believes that the approach could break the 50% barrier, possibly raising the bar as high as 54%.
There is still a question of impetus, however. The lack of commercial interest in terrestrial CPV may well encourage Guina to change direction and FOCUS on chasing the record for space cells with no concentration. Much of today’s multi-junction solar-cell research is not focusing on power generation here on Earth, so while that 50% milestone is tantalizingly close, it might not be broken anytime soon.
Richard Stevenson is editor of Compound Semiconductor magazine, e-mail firstname.lastname@example.org
Solar Panel Efficiency in 2023
Solar panel efficiency measures how well solar panels are able to convert sunlight into usable electricity.
Thanks to advances in technology, solar panel efficiency has steadily improved over time. As a result of this increase in the current solar panel efficiency, you can get the same amount of power with fewer panels on your roof, or more power with the same number of solar panels.
This article will explain what solar panel efficiency means, how the average efficiency of solar panels affects power production, the role high-efficiency solar panels play in the clean energy transformation, and more.
What Determines Solar Panel Efficiency?
Your solar panel’s ability to produce energy by converting the sunlight it receives to usable electricity depends upon five crucial factors: materials, wiring, reflection, age, and temperature.
Impact of Materials on Solar Panel Efficiency
Solar panel manufacturers use different substances to create different types of solar panels, including:
- Polycrystalline silicon
- Monocrystalline silicon
- Cadmium telluride
- Multi-junction solar cells
Each solar panel material helps determine how much sunlight will be converted to electricity. Most manufacturers today use monocrystalline silicon solar cell technology for their panels because of their superior efficiency. Monocrystalline photovoltaic (PV) cells are more efficient than other panel types because they are made from a single crystal of silicon, which means electrons can move more easily through the cell.
In addition to existing solar panel materials like silicon, solar companies are exploring other materials that could deliver even more efficient panel technology, including both organic and more recyclable options. (We have a deeper discussion of these developments below.)
Impact of Wiring on Solar Panel Efficiency
Solar panels can be wired in series and in parallel, and the different wiring configurations have an impact on how your solar panel system will function and how much power it can produce. There are advantages and disadvantages to each option, so it’s one of the decisions a solar panel company will make when designing the ideal solar power system for your home.
Wiring also helps determine the right inverter for your solar arrays, whether it’s a string inverter, power optimizer, microinverter, hybrid inverter, or something else entirely. The type of inverter that is used–especially in terms of how power is collected from the panels and sent to your house, battery storage, and electricity grid–can impact your solar panel system’s overall efficiency.
Within the panels themselves, wiring and “busbars” (the metal connecting solar cells in the solar panel that actually captures and transfers electricity) have an effect on efficiency, with more efficient panels using different configurations and different technologies to improve this process.
Impact of Reflection on Solar Panel Efficiency
The amount of light reflected away from a solar cell’s surface impacts solar panel efficiency. Solar panel efficiency depends on the amount of light they can absorb and convert into electricity.
If light reflects off the surface of the panel, it can’t become electricity, which lowers the efficiency of that panel. Solar power panels with textured surfaces and anti-reflection coatings can help minimize the amount of light that gets reflected away.
Impact of Age on Solar Panel Efficiency
The average lifespan of solar panels is about 25 to 30 years. Throughout this period, your solar system should generate all the electricity you need to power your home, unless the panels get blocked by too much shade, dirt, or other debris.
However, during that 25- to 30-year timeframe, your panel efficiency will slowly decrease over time, until they eventually reach a point where the solar panels don’t create enough electricity for all of your home’s needs. This degradation rate is factored into the initial design of a solar power system, but it still impacts your solar panel’s efficiency.
Impact of Temperature on Solar Panel Efficiency
The climate of your area impacts solar panel efficiency, as the energy levels of electrons are determined by their level of excitement. Contrary to what you might think, solar panels are more efficient at lower temperatures. Because the electrons on the thin layer of silicon are calmer and less excited, they can move with greater ease and increased numbers through the transmission lines to generate solar power.
When it is hot, the electrons are more excited and moving in different directions. This makes it more challenging for them to move effectively through the transmission lines, leading to lower solar energy production levels during a hot day.
In other words, you will experience higher voltage and enhanced generation efficiency during a cold sunny day compared to a hot sunny day.
How To Calculate Solar Panel Efficiency
The easiest way to calculate the efficiency of your solar panels is with this formula:
Efficiency (%) = (Pmax ÷ Area) ÷ (1000) x 100%
- Pmax = max solar panel power (in Watts)
- Area = length x width of the solar panel (in m2)
- 1000 = Standard Test Condition (STC) irradiance
Let’s break it down a bit for deeper comprehension.
Find your panel’s max power capacity
You can find this information labeled as Pmax or maximum power on the spec sheet for your solar panels.
Get your panel’s physical dimensions
The standard panel dimensions are 65 inches by 39 inches, but you can also find and verify this information for your own panels–specifically, length and width–on the specification sheet.
Calculate the power unit area of your panel
To get the power unit area of your module, divide its Pmax into its area.
Factor in the STC
Standard Test Condition (STC) represents the ideal environment used by solar manufacturers when testing average solar panel output. These conditions include a cell temperature of 25 °C and air mass of 1.5, and solar irradiance of 1000 W/m2. That value of 1000 W/m2 is what’s used in the efficiency equation.
Calculate solar panel efficiency
Using some sample numbers, we can walk through the math. Assuming your solar panels are 2 m2 in area, produce 400 watts, and receive 1,000 W/m2 of sunlight, the efficiency of your solar panels is 20%.
Efficiency (%) = (400 ÷ 2) ÷ (1000) x 100%
Solar Panel Efficiency in 2023
The average solar panel efficiency in 2023 ranges from 15% to 20%. At the high end, the most efficient solar panels available for public use achieve 22% efficiency.
While the majority of solar panels available in the United States today are below 20% efficiency, we can anticipate that the efficiency of solar energy systems will continue to improve as the solar industry pursues advanced photovoltaic technology.
History of Solar Panel Efficiency
The first major breakthrough in solar power was made by Alexandre-Edmond Becquerel in 1839. He discovered the photovoltaic effect, the root of the modern solar cell. Since then, solar innovation and improvement have remained a FOCUS for the scientific community and the solar industry as they look to improve solar panel efficiency and increase energy output over time.
Below is a brief synopsis of major advances in solar energy efficiency over the last three decades, courtesy of new solar panel technology.
- 1992: The University of South Florida manufactures a 15.89% efficient thin-film cell
- 2012: Solar Frontier achieves 17.8% efficiency
- 2015: First Solar CdTe thin film technology reaches 18.6% efficiency
- 2015: SolarCity hits 22.04% efficiency
- 2015: Panasonic’s 72-cell prototype achieves 22.5% efficiency
- 2015: SunPower attains 22.8% efficiency with its X22 panel
- 2016: The Swiss Center for Electronics and Microtechnology and the National Renewable Energy Laboratory achieve 29.8% efficiency
- 2016: The University of South Wales researchers attain 34.5% efficiency
- 2017: George Washington University and Naval Research attain a 44.5% solar cell efficiency
- 2018: Research into perovskite reveals a theoretical upper limit of 66% efficiency
To be clear, a majority of these high efficiency ratings of the most efficient solar panels are achieved in a laboratory setting, and aren’t yet possible at a commercial scale due to high production costs.
The National Renewable Energy Laboratory has been tracking the increase in research-cell efficiencies for a variety of solar panel technologies, and it shows the continued stair-step of improvements over time:
Solar panel efficiency over time has come a long way, thanks to the relentless efforts of solar panel manufacturers and scientists. These continual improvements in solar panel efficiency are great for the environment because they reduce our reliance on electricity created from fossil fuels and send even more energy to the grid. The clean energy they produce helps reduce our reliance on fossil fuels and also helps us combat greenhouse gas emissions.
Why are Modern Solar Panels Efficient?
There are two main reasons why modern solar panels are more efficient: advances in research and the materials used.
Solar Power Research
The desire to improve solar power efficiency drives the development of new solar panel technology, as these significant breakthroughs to improve solar energy systems continue in solar research centers across the globe.
Leading research facilities like the National Renewable Energy Laboratory and The Swiss Center for Electronics and Microtechnology use their resources, technologies, and expertise to conduct experimental studies that help develop the high-output solar panels of the future.
Improvements To Materials
Silicon has been the preferred semiconductor material for generating solar energy, and manufacturers have used silicon for decades because solar cells fabricated from it are low-cost, high-efficiency, and long-living.
Solar panel researchers continue to find new ways to increase the effectiveness of silicon, including the creation of ultra-thin crystalline layers, enhanced production processes that remove silicone dust from solar cells, and next-generation growth methods. These modern techniques have resulted in the dramatic solar efficiency improvements we discussed earlier in the article.
Beyond silicone, ongoing experimentation with more efficient materials like perovskite, and the incorporation of various solar technologies in the design process have combined to create the potential for even more highly efficient panels in the future.
Comparing Cost and Value to Rate Efficient Solar Panels
The average current solar panel efficiency ranges from 15% to 20%, but if you wish to install more efficient panels, you should be ready to pay more.
When designing a solar power system, consider the cost-benefit tradeoff between the higher price of more efficient panels and the amount of additional energy they create before you make that investment. It might be more economical to just install a few more lower-efficiency panels, compared to upgrading all panels to a higher efficiency to produce the same amount of power.
Because most customers buy panels that are 15% to 20% efficient, most manufacturers still produce a majority of their panels in that normal efficiency range. However, some circumstances may warrant the installation of high-efficiency solar panels, such as limited roof space or a complicated roof layout.
The space on your roof can impact the number of panels that can be installed. If that space can’t fit the number of lower-efficiency panels required to generate enough power for your needs, solar installers may use more efficient panels at an extra cost.
The design of your roof also determines the number of residential solar panels your home needs, and how they can be positioned. For example, if the area of your roof with more space isn’t angled to receive much sunlight, the area with less space will be considered. This could result in a custom layout for your solar panels which could increase your budget.
If you have a complex roof layout, Palmetto can work with you to determine the solar panel system design that will generate the electricity you need.
The Future of Solar Panel Efficiency
Various research centers are working to increase solar panel efficiency by experimenting with new materials such as organic photovoltaics, concentration photovoltaics, and quantum dots. Manufacturers are also incorporating exciting new technologies that drive the industry forward, including:
- Building-integrated PV panels
- Perovskite solar cells
- Floating solar farms (floatovoltaics)
- Solar skins
- Solar fabric
Floating solar farms are being deployed worldwide, and studies show that in utility-scale settings they can produce more electricity compared to ground-mounted or rooftop installations, thanks to the cooling effects of the water that boost their efficiency. The application of building-integrated PV and solar skins also demonstrates that the future of solar power efficiency is looking bright.
How To Improve the Efficiency of Your Solar Panels
Solar panels are designed to run efficiently without the homeowner needing to do anything. However, you can help ensure your panels are reaching their maximum efficiency by engaging in two simple chores:
- Keep shade off your solar panels
- Clean your panels regularly (Learn more about Solar Panel Cleaning)
You can also help detect possible issues with the efficiency of your solar panel system by tracking its performance through a mobile app like the Palmetto App and enrolling in a routine maintenance service like Palmetto Protect. If the performance of your panels has deteriorated, Palmetto can advise you on steps you can take to generate the electricity your home needs.
Increasing the average efficiency of solar panels remains a key driver of developments in the solar panel industry. Improvements to efficiency is good news for everyone involved in the New Utility Revolution, as it means we can power our homes and businesses with more of the sun’s rays and fewer fossil fuels.
Since solar panel efficiency depends upon materials, wiring, reflectivity, age, and temperature, researchers pursue every possible lead to enhance those factors so that more electricity can be generated more effectively.
At Palmetto, we use some of the most efficient solar panels in the market to maximize your solar production. We know that saving money on your utility bills and helping to save the planet is important to you, which means we’ll help you create the best possible solar panel system for your home.
Interested in adding efficient solar panels to your roof? Learn how much you could be saving with our Estimate Savings Tool today!
Solar Panel Efficiency: What Does It Really Mean?
When you review the technical specifications of solar panels, their efficiency values may give a negative first impression. As of 2021, monocrystalline solar panels are in the range of 20-23%, while polycrystalline panels are below 20%. However, conversion efficiency is not a critical factor when using sunlight. a free and virtually limitless resource.
Save on electricity bills and cut building emissions with solar power.
On the other hand, when the energy inputs for power generation are fossil fuels, efficiency becomes much more important. Coal power plants are typically 30-40% efficient, while combined cycle gas plants are around 50-60% efficient.
- These generation systems have a higher efficiency than solar panels, but looking only at this metric can be misleading.
- Solar panels are less efficient in terms of energy conversion, but their input is free and they operate with zero emissions.
Solar panel efficiency is only an issue when space is limited, since you may not reach the planned capacity in kilowatts. The solar panels used in commercial and industrial roofs have typical dimensions of around 80” x 40”, and the most efficient models exceed 400W. If you want to install 400 kW, you need 1000. this represents more than 22,000 sq.ft. for the solar panels alone, plus the spacing required for maintenance purposes.
What Determines Solar Panel Efficiency?
The top solar manufacturers are constantly investing millions in research and development, with the goal of improving their photovoltaic cells. However, this has paid off over time:
- Back in 1990, solar panels could only convert around 10% of sunlight into electricity.
- As of 2021, the most efficient solar panels in the market are approaching 23% efficiency.
- In other words, solar panels can now produce 2.3 times more energy with a given space, compared with how they performed 30 years ago.
The efficiency of solar cells is determined by the photovoltaic material, and also how the module is wired and designed overall. Monocrystalline cells are more efficient, since they’re made of single silicon crystals of high purity. On the other hand, polycrystalline cells are made of multiple crystals, and this impacts their efficiency.
This does not mean that polycrystalline solar panels have a lower quality. They have a lower conversion efficiency due to their material properties, but there are high-quality solar modules of both types.
What Are PERC Solar Cells?
Many of the top-performing panels that are currently available use PERC technology, which increases productivity by up to 12%. PERC stands for Passivated Emitter and Rear Contact, and these cells have many design features that boost their efficiency.
- PERC cells have a reflective layer below them. sunlight that goes through is reflected back into the photovoltaic material, generating more power.
- They also have anti-reflective coatings and surface textures that maximize the sunlight captured and converted into electricity.
PERC cells are often cut in half to reduce their electrical resistance losses, further increasing their power output. You will notice that many solar panels are now using 120 or 144 half-cells, instead of the traditional 60-cell and 72-cell designs. Since solar cells are cut in half, their total space requirements are almost the same and panel dimensions are not affected significantly.
How High-Efficiency Solar Panels Save Space
As the efficiency of photovoltaic cells continues to increase, solar panels will be capable of generating more watts per square foot.
- A 400W solar panel that measures 80” x 40” is producing 18W per sf.
- With an efficiency increase of 33%, it would be possible to generate 24W per sf.
Generally, having space for solar panels is not an issue in buildings like shopping malls and distribution centers. However, multi-story buildings have a large floor area relative to their roof area. and plenty of the available space is already used by HVAC equipment. In these cases, high-efficiency solar panels will maximize the kWh output per square foot covered.
RD has also reduced the cost of solar panels. You could expect to pay more than 10,000 per kW of capacity 20 years ago, but now home solar systems cost less than 3,000 per kW in many parts of the US. Even lower are possible in the utility sector, where solar arrays are being installed for less than 1,000 per kW.
What is solar panel efficiency and how does it affect your system’s performance?
Solar panels are an amazing technological achievement. They have no moving parts, they are very safe to operate and, if correctly installed, they can provide clean electricity for decades.
For most consumers, a particularly confusing aspect of solar panels is the term efficiency and what it actually means for the success of their solar investment.
Simply put, efficiency is the ratio that measures how much of the incoming sunlight is converted to electrical output by your solar panels. For example, if 100 Watts of sunlight falls on the panels, and 15 Watts of electricity comes out, the efficiency is 15%. Most solar panels in the market have efficiencies in the range of 10-15%.
Why do we lose efficiency when we package solar cells?
Building blocks of a solar array
The building block of any solar panel is a solar cell. The solar cell is a type of semiconductor that generates electrical power when illuminated by sunlight using the photovoltaic (PV) principle. When we package together a whole bunch of solar cells we get a PV module, a fancy industry term that simply means a small solar panel. Joining multiple modules gives us a bigger solar panel. A typical solar installation includes many of these panels strung together in the form of a PV array.
Why is this all important to understand the efficiency of solar panels? Well, because at each step of this packaging and installation process, we lose a bit of efficiency. For example, if you purchase solar panels that are made up of solar cells with 15% efficiency, the panel itself will have a slightly less efficiency (due to the spacing between the solar cells). If these solar panels are installed on your rooftop as a PV array, the resulting efficiency will be even less than the average panel efficiency due to electrical losses, shading and other factors.
What is the most efficient solar panel today?
Since the invention of the photovoltaic principle in the 19th century, the efficiency of solar panels has been increasing dramatically. In the 1950s, researchers at Bell Laboratories produced solar cells with 6% efficiency. In the 1970s and 1980s, researchers experimenting with different types of materials and production techniques gradually increased the level of efficiency. Today, the most efficient solar cells have around 40% efficiency and researchers around the world are working hard to push this level even higher. Unfortunately, most commercially available solar panels are significantly below this record level of efficiency, but there is no doubt that future solar energy systems will be built using higher efficiency solar cells.
Evolution of solar cell efficiencies as of December 2015 (source: NREL). Please click to enlarge.
What is multi-junction technology?
Solar cells are manufactured using different semiconductor materials. Each material can harvest a specific portion of the solar radiation spectrum. By overlaying cells made of different materials, we can increase the total amount of radiation that can be captured. As the sunlight passes through multiple layers of cells, each one optimized to absorb a certain wavelength of light, the overall efficiency can be increased drastically. Today, best performing traditional silicon solar cells have efficiencies around 25% (blue lines in the above chart), while multi-junction cells have surpassed the 40% level (purple lines). This sounds great, but increased efficiency comes at a price: multi-junction cells are much more complex and, as a result, more expensive than traditional solar cells.
Why do solar panels lose efficiency (degrade) over time?
A study performed by NREL revealed that the output of solar panels decreases by 0.5% to 0.8% every year. This is mainly due to the exposure of the panels to the elements, and in very arid climates, intense ultraviolet rays increase the level of degradation. Therefore, over the expected lifetime of a solar panel (20-25 years), it is natural that the efficiency will gradually decrease.
Should I buy the most efficient solar panels on the market?
Increased efficiency means higher output per unit area of solar panels. Thus, if you have two brands of solar panels with the exact same dimensions, the one with the higher efficiency will generate more electricity. Alternatively, the two brands may have the same power rating, but the higher efficiency panel would be smaller, an important consideration for certain solar energy applications.
Although it is tempting to invest in the most efficient solar panels, this may not necessarily be the best investment decision. Some of the more efficient solar panels are billed as premium products with a higher price tag. If you have limited roof space, or you are interested in a specialty application such as solar energy for your boat or your cabin, then a higher efficiency panel may indeed be the best choice. On the other hand, if you have ample roof space, then the reliability of the panels and the price should be the main drivers of your decision.
If you are considering your solar panel options, why not take them for a spin using WhatNextNow Solar GO? Our free tools will help you test drive different solar energy options at your location and give you a much better idea about how much electricity you can generate. And please remember that you are in this for the long-haul. A reliable panel purchased at a good price point can be your best solar investment, even if it’s not the most efficient model on the market.