What are bifacial photovoltaic panels?

Progress in photovoltaics has been accelerating enormously over the past few years. Manufacturers of photovoltaic panels are increasingly racing to come up with new solutions. An example of this race and a novelty on the photovoltaic market are bifacial panels.

The Advantages of Bifacial Solar Panels

Double-sided modules have been developed mainly to withstand the harshest weather conditions. In addition, energy producers were able to achieve much higher energy efficiency with little more money. Another advantage of these photovoltaic panels is their longer service life. The linear power drop guarantee for bifacial panels is up to 30 years.

In traditional photovoltaic panels, the front layer is covered with glass and the back layer is protected with a special film, while bifacial panels are distinguished by the fact that the front and back layer of the photovoltaic module is used, i.e. glass under which silicon wafers are located is at the front and back of the module. Hence, double-sided modules are also called glass-glass panels.

In their research, the Solarworld company presented that a 330 Wp bifacials can produce the same amount of energy as a traditional 410 Wp module, which together gives us about a 25% increase in generated energy.

Unfortunately, double-sided panels also have their “disadvantages”, if we can call them that, namely that they can only be mounted on the ground or on a flat roof. There are three ways to mount double-sided panels:

1. On a single-axis tracking system – this is the most cost-effective, but also the most expensive way to install double-sided panels.
2. On a fixed structure with panels facing south (at an angle from 25 to 35 degrees) – this way of installation can generate an additional 25% of power output
3. Vertical east-west – this is the least effective way of mounting, additionally the spacing between the panels must be at least 1.5 meters which strongly limits the number of modules that can be mounted on the surface.

Of course, apart from the installation method, there are several other factors which have a direct influence on the efficiency of the modules:

• Shading and uneven illumination of the back surface of the modules e.g. by elements of the mounting structure,
• Distance between modules,
• Tilt angle of the panels
• Panel installation height
• Degree of contamination of the substrate
• Albedo – the ability of the substrate surface to reflect crowded radiation.

White surfaces are the best sun rays reflectors. Below are the percentage albedo coefficients for white surfaces.

• White painted concrete – 60-80%
• Snow – 45-60%
• White roofing material 50-60%
• White sand 60%

However, it is not only white surfaces that can help us with higher energy yields for double-sided panels, as shown below:

• Grey roofing membrane – 62%
• Sand 30-40%
• Concrete 20-40% Summarising all the above information, the technology of double-sided photovoltaic modules allows us to increase the power of the photovoltaic system while keeping the same surface area, which makes it very interesting. However, it should be remembered that the features of these panels require appropriate fixing, which unfortunately excludes the use of these panels on sloping roofs. When considering the installation of such panels at your place, you will need to consult a specialist who will help us decide whether these panels will definitely be suitable for our installation and whether it will be profitable for us. Of course, in order to obtain such information, we invite you to contact us, because we are a company with specialists with experience and knowledge of broadly understood photovoltaics.

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