Know the Facts
Bifacial Myths vs. Facts
Balance of Systems
Myth: Costs, including balance of system and O&M, are the same for bifacial and monofacial modules.
Fact: When you look closer, you will notice additional costs for land, cabling design, taller tracker systems, financing, and vegetation and soiling control.
Additionally, bifacial energy gains are highly dependent on other factors such as albedo, row spacing, post height, torque tube thickness, etc. All of these factors increase the cost for the EPC by approximately +1-4 cents per Watt thereby increasing the variable costs of the power plant.
Myth: When utilizing energy yield prediction software for bifacial modules, it is okay to use the default/standard value for albedo.
Fact: Vegetation and the composition of the soil at your project site can have a significant impact on albedo, which can influence bifacial energy yield by 10% or more.
The extent of vegetation control required can vary significantly by project site, in many cases, O&M costs for bifacial modules will exceed costs for monofacial modules.
Myth: You can take the nameplate wattage of bifacial modules to the bank.
Fact: There is currently no international standard for measuring the nameplate wattage of bifacial modules.
While there are test specifications under consideration from the IEC, they are not yet required for certification. Read more about challenge areas the IEC test specification have had to date.
In order to mitigate risk associated with bifacial gains, financiers typically assume more conservative bifacial gains than are modeled in energy predictions.
Myth: What we understand about optimal tilt angle for standard systems can be applied to bifacial systems without risk of inaccuracies.
Fact: It is unknown whether accepted tilt angle best practices hold true for bifacial modules because impacts of tilt angle on bifacial systems have yet to be adequately studied.
More data is necessary to refine the algorithms used to calculate optimal tilt angles for bifacial modules on tracker systems. These algorithms are complex and must incorporate not only direct sunlight, but also reflected direct sunlight, diffuse sunlight, reflected diffuse sunlight, structure shading, row spacing, structure height, and more. These factors, and others, contribute to increased uncertainty about bifacial energy gains.
Myth: Bifacial modules are ideal for snowy conditions because they can absorb light reflected off snow on the ground.
Fact: Shading from snow contributes to energy losses estimated at 10% or more. Whether bifacial modules can make up for these losses has yet to
be conclusively tested.
Many assume bifacial modules are ideal for high albedo conditions (like snow, white sand, etc.) due to increased back-side energy gains of between 5-30%.
However, multiple, statistically representative samples of albedo at the specific project site are necessary to accurately measure albedo. According to a 2019 study by CFV, albedo can vary as much as 15-30% by season and by time of day. Because the site-specific albedo can vary so greatly, it can have a dramatic impact to predicted energy yield.
Myth: Bifacial yield estimates are just as precise as monofacial module estimates, so you can bank on the figures.
Fact: Known considerations such as albedo, view factor and mismatch losses are not yet conclusively studied for bifacial — not to mention unknown factors yet to be discovered.
Bi-facial c-Si modules are relatively new and there is currently insufficient data to validate the predictability of their long-term energy yield, which results in challenges with project financing.
Utility-scale bifacial performance data won’t be available for another 1-2 years.
Explore the following documents on bifacial technology.
The Weekend Read: Pursuing a 20 percent Bifacial Boost|PV Magazine | Charles W. Thurston
PVEL highlights industry trends and challenges in module manufacturing and technology|PV Tech | Finlay Colville