Bifacial solar modules offer many advantages over traditional solar panels. Power can be produced from both sides of a bifacial module, increasing total energy generation. They’re often more durable because both sides are UV resistant, and potential-induced degradation (PID) concerns are reduced when the bifacial module is frameless. Balance of system (BOS) costs are also reduced when more power can be generated from bifacial modules in a smaller array footprint.
Some companies with bifacial modules currently on the market include LG, LONGi, Lumos Solar, Prism Solar, Silfab, Sunpreme, Trina Solar and Yingli Solar. As more manufacturers begin production, bifacial modules look to be a niche product entering the mainstream.
What is a bifacial solar module?
Bifacial modules produce solar power from both sides of the panel. Whereas traditional opaque-backsheeted panels are monofacial, bifacial modules expose both the front and backside of the solar cells. When bifacial modules are installed on a highly reflective surface (like a white TPO roof or on the ground with light-colored stones), some bifacial module manufacturers claim up to a 30% increase in production just from the extra power generated from the rear.
Bifacial modules come in many designs. Some are framed while others are frameless. Some are dual-glass, and others use clear backsheets. Most use monocrystalline cells, but there are polycrystalline designs. The one thing that is constant is that power is produced from both sides. There are frameless, dual-glass modules that expose the backside of cells but are not bifacial. True bifacial modules have contacts/busbars on both the front and back sides of their cells.
How are bifacial modules installed?
The way a bifacial module is mounted depends on its type. A framed bifacial module might be easier to install than frameless, just because traditional mounting and racking systems are already adapted to framed models. Most bifacial module manufacturers provide their own clamps to mount their specific brand, taking away any installation hesitations.
For frameless bifacial modules, the module clamps will often feature rubber guards to protect the glass, and special care must be taken to prevent overtightening bolts and damaging the glass.
The higher a bifacial module is tilted, the more power it produces from its bifacial properties. Bifacial modules mounted flush to a rooftop block any reflected light from reaching the backside of the cells. That’s why bifacial modules perform better on flat commercial rooftops and ground-mounted arrays, because there is more room for tilt and bouncing reflected light to the rear of the modules.
The mounting system itself can affect the performance of the bifacial modules. Racking systems with support rails usually covered by a monofacial module’s backsheet will shade back rows of bifacial cells. Junction boxes on bifacial panels have become smaller or separated into multiple units positioned along the panel’s edge to prevent shading, too. Mounting and racking systems specially formatted for bifacial installations take out the question of backside shading.
What is the outlook for bifacial modules?
Last year, Vincent Ambrose, Canadian Solar’s general manager for North America, told Solar Power World that bifacial modules were really going to take off in the next few years.
“The challenge with bifacial has always been the unpredictability of the power output because it’s dependent upon the substrate behind the modules—a white commercial roof, a dark comp shingle, grass, gravel,” he said “It’s hard to model what the module is going to produce. The financing community is coming around on bifacial and the cost structure is coming down. We’ll be hearing more about that technology in the coming two or three years.”
Chinese panel manufacturer LONGi Solar believes we’re entering a new era of PV, one where high-efficiency modules are supreme. Bifacial technology supports the concept of using quality materials for high-energy yields.
“Bifacial modules are the future of the industry,” said Hongbin Fang, technical director of LONGi Solar. “It inherited all the advantages of mono PERC modules: high power density resulting in significant BOS savings, high energy yield with better low light performance and lower temperature coefficient. In addition, bifacial PERC modules also harvest energy from the rear side, demonstrating higher energy yield. We think bifacial PERC modules are the best approach to realize lower LCOE.”
Since the panels are not made opaque, do bifacial solar panels inherently run cooler since a portion of the sunlight at least is passing through and not striking opaque surface? Thanks
Premchand Dalvi says
For Bifacial panel what is maximum height we can take so will get solar output from both side
After which height from ground ,we will not get output from backside of panel.
Chris Hinds says
half of distance to sun. Sounds like smart ass comment, but full of truth, fall off ratio of light, source twice the distance 1/4 of light
Owen Parker says
I’m going to try a couple of 450 bifacials on the top of my van. They will rest on a rack atop a box that will be lined with highly polished stainless steel lining and will use actuators to be set at the best angel for the latitude I am presently at. It may well all be for naught, but the difference in price is nominal and the upside potential seems worth a shot.
Seems a vertical installation could help in an off grid situation where early and late power generation is more important. I could also see them as vertical windbreak walls on a deck or patio.
Has anyone used a ground mount system next to a metal sided building (pole barn). I am also going to place white rock under my system in hopes of gaining all the reflection I can get. What are your thoughts?
I am ln Canada at 48th parallel and have a 2.04 kw system(8x255w) top of pole mount(14ft up at pole top).Panels are tilted 15 deg. for winter.
Would bifacial panels contribute some heat to panels and help melt snow from panels? …..thank you
Larry S. Odom says
I have a large amount of mirrors to reflect solar to bottom side. Would this be a great advantage or would it overload the system ??
Mirrors might cause hot spots. IF this form of reflection is actually advantageous (I haven’t tried it), It might be better to try diamond Mylar, like that used in grow rooms, that will more evenly distribute the light.
R. Foster says
Mirrors will overheat the modules and cause early degradation (solar brownies). You need to use a heat sink to cool the module like on CPV. Otherwise you are repeating an early mistake made on Carissa Plains CA solar system in the ’80’s.
Dean Barlow says
Can you use and anchor down bifacial matting? Any form of white, high albedo rubber matting will do.
I have had enough sunburns on the bottom and inside of my nose after a day on the snow to know that this is great for high altitude and high latitude places.
Jijo Pazhayattil says
Are these panels rated for their top side production capacity or total for both sides? In other words, does a 400W panel produce 400W plus the potential 30% from the underside? This is important information when designing a system. How do we plan for the additional production is a big question. Also, planning for an additional 30% production could drive up the cost of inverters/batteries – all for an extra production that might never come.
Tom George says
Hi Jijo, Hope you got the answers for your questions. I am going to try it out on an experimental basis soon. Thanks!
M. Ibrahim Khan says
The rating is based on front side as we don’t know what surface is reflecting energy on back side. So the back side production of electricity is your bonus which offset the extra cost.
Pratyusha Yadav says
Hi, I wonder what shall be the feasibility of bifacial modules with ballast type structures on RCC roof with lower tilt?
Mario Cachia says
Good article. But it is one thing about the panel rating and another about its productivity.
How can the back side be expected to generate enough electricity if in the first instance it is looking away from the reflected light ? or rather has a plane that is parallel to the reflected light rather than perpendicular to it ? Moreover, when installed on flat rooftops and at lower angles, like 5Deg or 10Deg, with a ground cover ration that is quite high, there will hardly be any reflected light reaching the back of the panels anyway. So is this really overrating the benefits?
The only benefit I can see is if these are installed elevated from the ground on ground mounted systems with a very reflective surface like sand or snow. And then again we can’t really quantify the uplift in energy. So has anyone shared data about the new power rating of a bi-facial panel and its uplift in energy yield vs a normal single faced high efficiency panel and its energy yield?
I’m about the install LG Bi Facial Panels on my rooftop (4Kw- 400WX10 to start with). We’ve decided to paint the slate roofing underneath the panels white.
They will be installed on South, East and West facing roofing here in London. I’m curious to know how much the system will yield. Anyone actually installed these on a roof?
David Nadaud says
I still don’t understand why the various bi-facial projects aren’t considering laying mirrors on the flooring.
Michael McCool says
I think the biggest use-case is in snowy climates, in ground-mount situations, such as pole mounts. The albedo of freshly fallen snow is over 90% and snowy climates are also often overcast in winter. In this situation the diffuse reflection from the snow illuminating the backside of horizontal panels may actually equal the light from above! One trick though is mounting them. Pole-top trackers include a bunch of hardware which can block light from the back. On the other hand, a tracker that can tilt panels around at least a horizontal axis is handy for dumping snow, then returning the panels to a horizontal orientation (for overcast winter days…). I’d be interested in knowing if anyone has some up with a dual-tracking arrangement that would not shade the back of bifacial panels, though. A central pole-top mount would, unfortunately.
yes – IDEEMATEC L-Tec is specifically developed for Bifacial use 1P or 2P
Susan Boucher says
Very informative, thanks!
Lili Francklyn says
They can be gorgeous in certain architectural situations. I think there is still a “wow” factor since they are new and unusual, when used for shade, canopy, or integrated w/ architectural design. In these cases there is a value add that is more than just the solar gain.
Rodney ONeill says
If installed over water or in snowy areas, this may have benefits.
If the backside material is important why isn’t it installed with a layer of mirror?
From a normal solar panel, indirect sunlight produces way less energy that doesn’t make economic sense. Unless the backside cells are different type, I don’t see how it can produce 30% more.
As you said, the back side produces a lot less; 70% less according to this article.
Which means that by having a back face collecting reflected light as well as a top face collecting direct light, it increases the overall production by 30%. Makes sense?
james ward says
The reflected light is also transmitted light weighted red. The top cell is very thin.
RAMESH KRISHNAMURTHY says
Installers will normally prefer PERC modules to BI FACIAL modules for ground mounted installations because BI FACIAL modules require a higher tilt angle .This will drive up the cost of the Module mounting structures.In Installations of 100MW and above the number of module mounting structures are significant. A small increase in the individual MMS cost will significantly impact the Project cost.
As of now PERC modules appear to be cost effective for large ground mounted installations compared to BI FACIAL.
Jeff Noble says
There are instances where a client may want to put off doing solar as they are planning to do a new roof in 2-5 years. With the Bi Facial panels, you can conceivably roll in the cost of a new roof into the solar cost and receive the 30% ITC on both roofing and solar costs.
Michelle Owens says
I am in Canada and I am very curious as to how the modules will perform in different situations. Flush mount on shingles, flush mount on lightly coloured metal roofs, ground mount and rooftop mount. Is there racking systems specifically designed for a flush mount bifacial system? And do clear back sheets allow for more light to pass through the module and add reflective light to the backside or is it just not worth it to use a bifacial module on a flush mount system? I have only been able to find racking systems specifically design for bifacials on ground mounts and flat roof systems and nothing for flush mount. Would be awesome if there was some hard numbers on additional backside gain!
Kelly Pickerel says
In general, bifacial modules are not recommended for flush-mount systems, because then there isn’t enough room to reflect light onto the backside. Even with a light-colored roof, there still isn’t room for reflection.
Ihab Mousa says
Do you have results for studying the optimum room volume in the backside of bi-facial solar power cells, in terms of maximum power generation and minimum cost impact of using this room with specific specifications (such as size, material, color…etc.).
bifacial modules are definitely going to produce more energy form conventional and this is game changer, however the cost matters off course . how much 30 or upto 30% they will produce and how much additional cost we have to pay that will actually set the tone that they will be commercially viable or not . at lot of high efficiency modules are available in market but they are not able to contribute more only because of their commercial viability. they will be used in some % of market in a limited segment till the crossover point are not reached
David Reichard says
I can see a strong benefit if an additional efficient concentrating reflector is placed to shine on the back side.Additional expense would be incurred but possibly not too much to be quickly offset by the higher power yield.
nobody of importance says
Maybe break from the traditional picture fame style panel to one with cells parallel to the light source and reflectors directing light to cells from both sides.
Ferran Garrigosa says
For me the problem is not about the overgain you have but how to known which plus you’ll have in your specific facility. At the end you will pay more but, how much energy you’ll generate? What does it means up to 30%? It will be with the best conditions but in other cases? There are two many kinds of grounds and roofs. How can I guarantee the customers the % extra gain?
Hank Roberts says
I am confused. I own a solar business and I can’t see the benefit of a bifacial PV panel that only produces, according to this article, 30 % more power than the older type. If you were to place 2 PV panels side by side and connected to each other, you would produce 100% more power. The only advantage that I see is where there is a very limited amount of space to mount the panels.
Kelly Pickerel says
Overall, bifacial panels can give you more energy gains. I don’t think the aim of bifacial panels is to get you to use fewer panels on an array, but they provide the option to produce more power using the same amount of panels (as long as the installation conditions support bifacial modules). If you have the option to install bifacial panels, why not?
Lars Bagman says
Have to define what “delivers up to 30% more power” really means; is it the same as “guaranteed not to exceed 30% more power” or is it “delivers 15% more power +/-100% depending on environment?”
It all comes down to cost.
+ If the bifacial panels cost 30% more and actually deliver 30% more power, then I am indifferent to which panel I choose unless I have an installation space constraint.
+ If the bifacial panels cost 30% more and might possibly deliver up to 30% more power under just the right installation conditions, then I would never choose bifacial panels because this would be like making a bet where the best I could do is break even and that is everywhere and always a suckers bet.
+ If the bifacial panels cost 50% more and actually deliver 30% more power, then I would never install them unless I had an installation space constraint. The cost per KW of installed capacity would be higher.
The increase in capital cost is once off, the increased yield is for the life of the system. One cannot be simply traded off against the other.
William Mollett says
Yes you can. Example: if the cost is double but the output is only 80% more it will never stack up.
The increased cost is approaching only 4% . So 15-30% more energy for a panel that costs only 4% more is an attractive concept. Add the exception to tariffs for bifacial modules and that actually makes bifacial significantly cheaper. While traditional panels are subject to tariff makes a bifacial a less expensive product that produces more energy. That currently makes bifacial the current winner no matter what the increase in performance works out to be.
It depends on how much panels cost relative to total capital. Racks and such are probably about the same cost, regardless of single or bifacial panel.
So, what would be needed then to support this installation?
William Mollett says
Not 100% if one side is facing the sun.
Aimo Ihanamäki/RPU Thermo says
Intersolar.de was introducing frameless and bifacial panels nicely!
I’m from Finland and as U know, our sun is located very low during wintertime; as all nordic regions.
We still have a lot sunny hours, also based on our location.
Frameless, bifacial (double glass) panels would be good solution, because of white snow, vertical installation, lots of space, wall constructions etc.
Should be developed/found better installation and fixing systems to get further. My customers would be ready start piloting/testing “Clever Fixing”!
Keep on discussion, please! Kind regards.