Bifacial solar panels have solar energy cells on both the front and back side of the solar panel

Bifacial solar panels have solar energy cells on both the front and back side of the solar panel. This allows solar energy to be collected on the backside of the panel and enhance the energy output of the solar energy system. Traditional solar panels utilize a layer of solar cells on the front side of the solar module, and have a white or black back-sheet on the back. Under the correct installation conditions, bifacial gain can more completely take advantage of solar energy collection by capturing light through this dual energy capture process - Both on the front side, and the back side of the solar panel.

Bifacial solar panels utilize technology across modern advancements in solar module and cell development, such as, high watt modules, higher efficiency panels, half cut cell designs and more. Many solar panel manufacturers such as LG Solar, Longi, and Canadian Solar are producing new panels over 300w+, with 400w+ modules on the market. High watt solar panels allow you to obtain further cost advantages through both lowering the bill of materials and driving down installation costs.

The higher efficiency rating of solar modules not only increases your overall energy output, but the output of your solar energy system under less than ideal sun conditions. While half-cut cell technology reduces the risk of “hot spots” developing on your modules, extending the lifetime of the module and increasing the output of your modules.

Bifacial solar panel technology takes advantage of all three of these technologies, and combines them into a singular module, capable of producing up to 30% more energy output. Bifacial solar panels are designed with solar cells on both sides of the module, unlike traditional modules. If you are looking to maximize the output of your solar energy system, bifacial solar panels may be one of the best solar panel options for you.

To find out more about Bifacial Solar Panels, we will be analyzing the following:

Bifacial Solar Panel Technology

Recommended Installation Conditions

Bifacial Solar Panel Comparison

Solaris Recommendations

Bifacial Solar Panel Technology

Bifacial modules double-sided solar cell design and transparent back-sheet allow light to be captured by both sides of the solar panel. This is accomplished by the backside of the panel capturing light that is reflected onto the underside of the module off the ground beneath the panel. This means that there must be enough space between the underside of the panel and the ground to allow light to reflect onto the module.

Bifacial panels are listed at their front-side output rating, expected bifacial output varies by solar panel and manufacturer as well as environmental conditions. For example, Canadian Solar can achieve up to 30% bifacial gain but may only achieve 5% depending on outside lighting conditions. Bifacial gain is largely determined by the amount of light that hits the back of your modules.

Bifacial modules are manufactured to be compatible with market ready power converting solutions like string inverters and microinverters. Furthermore, bifacial panels perform better under low light conditions. LG Solar’s NeON2 bifacial panels have been tested to produce up to 64.4% more energy over three-day period following a snowstorm. Their study also showed that the modules performed slightly better or on par with single sided modules during days in which it was actively snowing.

Recommended Installation Conditions

Due to the fact that bifacial panels obtain their gain from reflected light on the back side of the panel, they are not recommended for the majority of roof mount installations. For flush mount and most tilt mount roof top solutions, there is not enough space between the module and the roof face to reflect light onto the underside of the panel. Therefore, the dual energy yield will either under-perform, or not perform at all. Installations using flush mount solutions should avoid using bifacial modules, while tilt mount installs should review their site and roof for feasibility.

Bifacial modules work best for ground mount, top of pole and awning installations. Bifacial gain is further enhanced if the surface that the system is installed on is reflective. Homeowners interested in utilizing pergolas or deck overhangs may also benefit from dual-sided technology.

The modules work well under a number of extreme environmental conditions. As mentioned in the case of LG, bifacial modules outperform traditional modules in the days following a snowstorm. This is because the underside of the panel actively captures the light reflected from the white of the snow and produce energy. As an added bonus, this will also heat the panel and assist in melting snow on the front side of the module.

We recommend bifacial modules for installation sites that can benefit for bifacial gain, meaning, that residential homeowners with roof mount installations are advised to seek other solar panel solutions. Under the right conditions, bifacial modules can produce more power with less equipment, saving in both initial investment cost, and increasing your return on investment.

What About East- or West-Sloped Roofs?

For roofs that slope to the east or west, tilting to the south does not help much. Your solar panels will still be somewhat angled east or west, unless you build a very elaborate wing-like structure to flatten out that east or west tilt. This is not very practical and will likely result in high costs and unhappy neighbors.

On a west-facing roof, this is especially unnecessary because west-tilted solar panels produce more power in the afternoon. Furthermore, you would benefit from the TOU electric rate since afternoon kWh rates are the highest.

Tilting Solar Panels on a Flat Root

If you have a flat roof or plan to mount solar on the ground, you’ll encounter a slightly different situation. The overall annual energy loss for flat solar panels versus solar panels tilted at the perfect angle is about 10% in the southern states and 15% in the northern states. That much loss might be worth the extra hardware and effort.

Flat roofs also have ballasted racking options that require fewer (if any) holes, so the added wind load of tilting the solar panels does not necessarily mean more attachments to install. Aesthetics are usually less of a concern, as flat roofs are often taller and hidden from view by parapet walls.

With a flat roof, your biggest consideration is the inter-row spacing required to avoid shade on the solar panels. But there is a trade-off: you will get higher kWh production per square foot if you mount the solar panels flat versus tilting them and spacing them apart. On the other hand, if you tilt them, you will get more kWh per solar panel with a better ROI of your upfront cost.

The decision to tilt solar panels on a flat roof depends on your priorities:

If you want the best ROI and you have plenty of roof space, tilt the solar panels

If you want the most energy possible from a limited amount of roof space, install the panels flat.