Although current efficiency ratings are between 15 and 18 percent, the future looks bright, with recorded ratings in some test labs almost as high as 50 percent. In fact, researchers at the National Renewable Energy Laboratory (NREL) have reported test results exceeding 100 percent for quantum efficiency. Below are stated how efficient solar panels are for better use.
As solar panel efficiency increases, energy output increases. For homeowners, this means greater savings. As solar panel manufacturers improve construction models, the initial upfront cost of installing a solar energy system will decrease. As renewable energy becomes more efficient, the dependence on fossil fuels to produce usable electricity will disappear.
Efficiency Ratings for Solar Panels
When determining solar panel efficiency, scientists measure the ability of solar cells to convert solar irradiance into energy. A more efficient panel will naturally produce more energy. Efficiency ratings are stated as a percentage, so a 15 percent rating means 15 percent of the sunlight hitting the panel is available to generate electricity.
Although the current efficiency ratings for solar panels used for residential applications are low, improvements are horizon. Leading manufacturers are on the verge of streamlining the process of working with multi-junction cells. This will ultimately create high-efficiency solar cells with lower manufacturing costs.
Higher efficiency solar panels and lower costs will invigorate the solar industry. In areas with limited roof space, the increased efficiency power output will increase the use of residential solar power.
How to Determine Efficiency Ratings
Determining the efficiency rating of a solar panel requires a bit of math. The equation begins with the amount of sunlight that reaches the surface of the earth in your location. This base figure is also known as “incident light” or “incident radiation flux.”
First, multiply the incident light by the total square meter area of your solar panel. Second, divide the maximum wattage of your panel by the answer from step one. Multiply the resulting figure by 100 percent to learn the efficiency rating.
For Instance, if your sunlight measures 1,000 watts and your panel size are two square meters, your first figure is 2,000 watts. If the peak power of your panel is 400 watts, the panel efficiency equals 20 percent.
400 divided by 2000 equals 0.2; 0.2 times 100 percent equals 20 percent
The first efficiency rating you will see on your data sheet is dependent on perfect conditions. Your actual efficiency will be lower due to cell temperature, the amount of sunlight shining on the panel, and weather conditions.
Why is Solar Panel Efficiency Important?
With current trends toward downsizing, solar panel efficiency is critical. Smaller homes mean less roof space. To create a net-zero home using solar photovoltaics, efficient panels must be a consideration.
Low-efficiency solar cells may not produce adequate solar energy in warmer climates to power air conditioners. Using the most efficient solar cells can produce an adequate power output with a smaller roof space. This is optimum when the desire is to remain completely off-grid.
Even if you aren’t striving for a net-zero footprint, high-efficiency panels mean installation cost savings by requiring fewer panels.
Reading a Data Sheet
Solar efficiency can be found on the specification sheet for most solar panels. Although you don’t need to understand everything on datasheets completely, it is good to know what the various ratings mean will help.
Datasheets normally contain several sections, which include ratings within a testing environment under strict controls. Additional sections contain information about operation under real-world conditions. Although solar panel manufacturers format their sheets slightly differently, they all contain similar information.
Terms you may see on a datasheet:
Standard Test Conditions (STC)
This is a set of standard criteria in use throughout the industry to create baseline testing.
Normal Operating Cell Temperature (NOCT)
This represents testing conducted in a realistic environment, usually using regional temperatures.
Open Circuit Voltage (Voc)
This represents the voltage production of a solar panel with no load. This number is useful when determining how many panels you will need in a solar system.
Short Circuit Current (Isc)
This represents the highest current production under standard test conditions.
Maximum Power Point (Pmax)
Sometimes known as “the sweet spot.” This measures the combination of volts and amps that produce the highest wattage.
Maximum Power Point Voltage (Vmpp)
Represents the voltage at the highest power output.
Maximum Power Point Current (Impp)
Represents current at the highest output point.
Understanding Peak Power vs. Efficiency
Peak power is the maximum performance your solar panels can produce. Efficiency is the rate at which your panels can convert sunlight into useable electricity. Although knowing the peak power rating for your panels is important, you will probably never achieve that level of energy production.
Peak power ratings are measured under strict lab conditions. The Standard Test Conditions (STD) are:
- Cell temperature is 77℉ (25℃).
- The light intensity of 1,000 watts per square meter.
- An atmospheric density of 1.5 air mass.
- The angle of sunlight is directed on cells at a 90-degree angle.
All solar panels receive testing under the same testing conditions that are equivalent to real-world circumstances. This means that testing conditions are based on the sun reaching a solar panel at 41.81° above the horizon. Panels are at a 37° angle, and the light intensity equates to the noonday sun on the equinoxes in spring and fall.
Solar panel efficiency testing occurs under both STC and NOCT. Although the peak efficiency rating is great, it is more realistic to expect efficiency nearer the NOCT rating.
Below is a video explaining how efficient solar panels are.
How Construction Affects Solar Panel Efficiency
The construction of your solar panels affects their efficiency. Currently, monocrystalline solar panels are the most efficient. They are also the most expensive. In the future, it will be interesting to watch the development of thin-film solar cells.
It is important to understand the basics of solar panel construction and how that affects efficiency.
Monocrystalline Solar Cells
Monocrystalline solar panels include a single block of unbroken silicon. Because the process requires high-quality silicon, the manufacturing process is more difficult. The components and manufacturing process adds expense to these panels. In exchange, customers receive reliability and durability.
The average efficiency of a monocrystalline solar panel ranges between 15 and 20 percent.
The appearance of monocrystalline silicon solar cells is shiny and black, which is offers a better look for rooftop solar systems. They perform very well in lower light circumstances and work well even in areas where full sun is unavailable.
Polycrystalline Solar Cells
The construction of polycrystalline cells consists of grains of silicon. Their appearance is sometimes bluish and may appear flakey. The manufacturing is an easier process, which makes these panels less expensive.
Polycrystalline silicon cells average an efficiency rating of 13 to 16 percent.
The trade-off with lower efficiency requires more polycrystalline cells to produce ample electricity to power a home.
Thin-film solar technology has been in development for more than 20 years. While they currently have efficiency ratings on the lower end, the future for thin-film cells looks bright. It takes more solar panels to produce the same electricity as more efficient solar panels with lower efficiency.
Thin-film solar panels use films of semiconductors fused onto plastic, glass, or metal. These semi-flexible film solar panels offer the ability to create non-traditional mounting on curved surfaces.
There are currently three types of thin-film panels:
- Cadmium telluride (CdTe)
- Amorphous silicon (a-Si)
- Copper indium gallium selenide (CIGS)
Research and development of this technology will see increased usage as efficiency continues to increase.
Other Factors That Affect Solar Panel Efficiency
The one factor in solar panel efficiency that cannot be controlled is the weather. Even with the most efficient solar panel, the lack of incoming sunlight lowers the overall efficiency of any solar system.
The amount of sunlight reaching your solar panels isn’t all that affects the efficiency. While the peak solar cell efficiency rating can tell you the maximum, the minimum value can be much lower.
Although material plays a factor, there are additional factors that also affect efficiency. Wiring organization and distribution of busbars that capture and transfer electrical power can also affect efficiency. Reflection of light can reduce efficiency.
Some of the most efficient solar panels use bifacial and multijunction features. Bifacial solar panels can absorb light on both sides of the panel. Multijunction solar panels can absorb light with varying wavelengths. This technology is being employed on both traditional-style panels and thin films.
With continuing advancements, solar panel efficiency may double in the coming years.
Efficiency Ratings Affect Solar Panel Cost
Another great benefit of increased solar efficiency is lower costs. Because the solar panel market is so competitive, some industry experts are predicting continuing cost reductions.
With increased efficiency, more electricity will enter the municipal grids via net metering programs. For the environment, this means decreasing dependence on fossil fuels. Additionally, as solar cell technology continues to advance, photovoltaic panels will positively impact climate change.
Using Mounting Angle to Increase Solar Panel Efficiency
Ideally, your local installers will place solar panels on a south-facing roof angled between 30 and 45 degrees. With flush-mount solar panels, this angle is determined by the pitch, or slant, of the roof. The direction the roof is facing has more impact on cell efficiency than the slant of the roof.
The direction of your roof, also called the azimuth angle, can greatly affect the operating efficiency of your solar panels. Even with high-efficiency solar panels, a west- or east-facing roof will decrease power output by as much as 20 percent.
Most solar panels are on south-facing roofs in the Northern Hemisphere, although people without a south-facing roof can have efficient solar panel energy production on the east- and west-facing roofs.
North-facing roofs will generate some solar energy, but even the most efficient solar panels will have difficulty producing energy without direct sunlight.
Flat-roof solar power is also an option if you have a home or business without facing angles.
What Does the Future Hold?
The future will bring us the most efficient solar panels ever. The best solar panels will be capable of producing more electricity than needed for simple household applications. Production models from leading manufacturers are approaching 50 percent in laboratory testing.
The use of new semiconductor materials and multi-layer construction designs are reaching new heights. Last year a team from the NREL showcased a six-layer solar energy device with an efficiency rating of 47.1 percent!
Although these advancements are still in development, the future looks bright even on a cloudy day. Multi-layer designs and the right combination of semiconductors will utilize more of the sun’s output.
Current Efficiency Ratings
In searching for the most efficient solar panels, scientists consistently produce solar cells that maintain an efficiency rating of just under 25 percent. While even the best solar panels seem to be stuck at this plateau, solar cell technology improves.
Projected Increases Are on the Horizon
As scientists strive to break and maintain an efficiency of over 50 percent, solar energy production continues to gain ground. The NREL has produced a solar cell with a reported external quantum efficiency of over 100 percent. That solar cell is the first Multiple Exciton Generation (MEG) cell.
With MEG technology, extra efficiency is gained by harvesting energy that is normally lost as heat. The theory of MEG has been in development since 2001. Although the process is slow, we could see this solar panel technology available for commercial use soon.
Exploring the Most Efficient Solar Panels
Although solar panel efficiency hovers near 20 to 25 percent, solar power is still a viable option. When consumers look for a solar panel that will provide electricity for their home or business, they want the best currently on the market.
Although we are not recommending the following, we are offering the specifications for comparison.
SunPower Solar Panel Models Offer Choices
SunPower offers four basic solar panel models:
While each offers unique benefits, you will find the greatest efficiency with X-Series. The A-, E-, and P-Series follow close behind. Overall efficiency for SunPower solar panels ranges between 19 and 22.8 percent.
While many manufacturers offer at least a 10-year warranty, SunPower offers a 25-year warranty against defects in its products. In addition, they add a performance warranty that boasts a guaranteed performance of 92 percent after 25 years.
While SunPower is known for efficiency and quality, they are also known for slightly higher pricing.
LG Solar Panels Offer Quality at a Moderate Price
LG offers two basic series, with different features:
- NeON 2 Series
- NeON R Series
Although not as popular, LG panels offer similar reliability when compared to other leading manufacturers. Offering award-winning PV Cell Technology, the NeON 2 Series is among LG’s best-selling models.
However, with efficiency between 18.7 and 19.6 percent, the NeON 2 isn’t quite as efficient as the NeON R Series, which rates between 20.3 and 20.8 percent. However, both series are resilient in rain, wind, snow, and hail, making them a great all-weather choice.
Each LG solar panel carries a 25-year warranty on materials and construction. In addition, the guarantee of 86 percent output efficiency at 25-years and the moderate price range makes LG competitive against its similarly efficient counterparts.
Trina Solar Offers Solar Power Solutions
Among the Trina Solar offerings are the Vertex Series, TALLMAX Series, and DUOMAX TWIN Series. Each series of panels has different efficiency ratings:
- Vertex Series — 21.4 percent
- TALLMAX — 19 to 19.1 percent
- DOUMAX TWIN — 21 percent
Due to their unique PV cell technology, Trina panels have a good temperature coefficient compared with other manufacturers. This produces better operation at higher temperatures.
Meanwhile, Trina Solar uses a high-efficiency N-type i-TopCon cell featuring multi-busbars (MBB) and advanced bifacial technology.
Trina offers less warranty protection with a 10-year warranty against manufacturing defects. Their products are highly rated and suitable for both residential and commercial buildings. Their commercial panels carry a higher power rating than many competitors.
Panasonic Solar Panels Offers Versatility and Performance
Panasonic has devoted 40 years to the development of solar technology. Meanwhile, their entire inventory of panels boasts a solar efficiency of 21.2 percent. Panasonic is so confident about the performance of its panels that they guarantee a power output of 92 percent after 25 years.
The temperature coefficient of 0.26%/°C allows higher output production at high temperatures. This industry-leading rating beats competitor models. Panasonic panels produce more energy in warmer climates.
Panasonic solar panels use heterojunction technology. This allows maximum sunlight conversion and higher energy production. This technology minimizes electron loss while maximizing conversion efficiency. The result is consistently higher power output.
Panasonic offers a 25-year warranty on their AllGuard and TripleGuard EverVolt panels, including performance, parts, and labor. Although Panasonic solar panels are widely used in commercial applications, they are also suitable for residential solar systems.
How Efficient Are Solar Panels?
Solar power is marching toward the future. The next 50 years will see increased efficiency. As PV cell technology catches up with the dreams of physicists, we will see theory becoming a reality. With the race to create the most efficient panel, it is not unreasonable to hope that much of the world will convert to solar power by the end of this century.
Solar panels currently available are more than capable of providing sufficient electricity to power a vast majority of our existing structures. In conclusion, as efficiency continues to increase, smaller solar farm arrays will provide greater amounts of energy.
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