This is how bifacial solar modules increase the efficiency of PV systems

Bifacial photovoltaic modules can increase the electricity yield of solar systems and solar farms by up to 15 percent. But how do they work and what possibilities do they offer for solar power generation?

Conventional or monofacial photovoltaic modules are designed in such a way that they make optimal use of sunlight coming from the front. Bifacial (literally “two-faced”) modules, on the other hand, have photoactive cells on both sides. This property allows them to also convert reflected sunlight that hits the back of the modules into solar power. The production of the module types differs only slightly from each other, more precisely through a modification of the rear contacts. While monofacial modules have an opaque rear film, bifacial modules are usually transparent and therefore translucent. This allows the photons to penetrate the solar cells from both sides, thereby increasing the efficiency of the entire module.

What snow blindness has to do with photovoltaics

Surfaces of different brightness reflect sunlight differently. This is also known as the “albedo effect”. Snow, for example, reflects incoming sunlight particularly well, just as white surfaces generally have a high reflection factor. Therefore, without sun protection for the eyes, people can become snow-blind in snow-covered landscapes and in bright sunshine. The lighter the surface, the higher the albedo. The darker the surface, the lower the albedo, allowing a surface or object to absorb more heat and reflect less light. It is precisely this effect that bifacial photovoltaic modules make use of. The light reflected from the ground hits the back of the solar cells. In this way, solar energy can be used on both sides.

The construction of PV modules is important

For the successful use of bifacial modules, the type of installation and the environment, i.e. the nature of the subsoil, are particularly decisive. Simply put, bifacial solar panels only work if sunlight also falls under the panels. This is usually the case with a column or open space construction, such as with solar farms or on flat roofs. In the early and late hours of the day, for example, sunlight that falls flat from the ground can radiate particularly well onto the underside of the module. Experts also speak of a “buffer solution” for the times of day when the direct sunlight on the front of the module begins to decrease. To investigate how to increase the number of hours of available solar energy, the University of Leipzig is currently testing a pilot system with vertical bifacial PV modules. But even when the sun is high, bifacial modules increase the total yield of solar systems and solar farms.  

Why hep uses bifacial PV modules in North America

In some hep solar farms in North America, a double effect has a positive effect in terms of albedo. In summer, the ground is covered with dry grass or sand. In winter, there is snow under the photovoltaic panels. Both surfaces are correspondingly light and can optimally reflect sunlight. As a solar and investment specialist, the hep group almost exclusively uses bifacial modules in the construction of solar farms in North America. For example, in the case of solar farms in North Carolina, South Carolina, Oregon and Virginia. The next projects with bifacial photovoltaic modules are already planned in New York, North Carolina and in Alberta, Canada.

Sources: Fraunhofer Institute for Solar Energy Systems ISE,,,,,,,

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