Bilateral solar panels fail to take off. A technology from the 1980s wants to make them even more viable

As conventional crystalline silicon solar panels approach their theoretical efficiency limit, an option previously scorned for its installation costs is gaining popularity: bifacial solar panels. Reason: Latest models with HJT technology can pay off quickly.

What are bifacial solar panels used for? Unlike conventional solar panels that only capture light on one side, bifacial panels can capture light from both sides. It is capable of absorbing light reflected from nearby surfaces in addition to direct sunlight.

Three types are distinguished depending on the material of the second side: glass / glass, glass / transparent sheet and glass / opaque sheet. The first is a very efficient and robust model, but very expensive and heavy, which has so far reduced its interest.

Recent Technological Advances in Bifacial Technology Recent bifacial modules use heterojunction technology (HJT) of two different semiconductor materials: crystalline silicon and amorphous silicon. This advanced form of photovoltaic cell involves placing a layer of amorphous silicon on each side of a crystalline silicon cell, creating a heterojunction.

Amorphous silicon has a wide bandgap, allowing it to efficiently capture high-energy photons, while crystalline silicon takes care of low-energy photons. A heterojunction of the two achieves highly effective light absorption and minimizes efficiency losses due to electronic recombination.

An invention from the 80s. There were HJT panels Initially created Starting in the 1980s with the Japanese company Sanyo (now owned by Panasonic), several manufacturers brought and improved this technology into commercial production, reducing the photovoltaic industry's dependence on materials such as silver.

In 2020, the Italian manufacturer 3 Sun EGP demonstrated that bifacial heterojunction solar modules can achieve and exceed 24.5% efficiency. Recent panels from companies such as China Mason They use strong double sided glass and 210mm cells with 25% energy conversion efficiency. and similar mechanisms Soltec They maximize light capture by calculating the correct angle considering the radiation from both sides of the block.

More durable blocks. In the latest generation of modules, the HJT cell has a symmetrical front and rear arrangement, which increases the energy production of the rear area by 30%, leading to a quick replacement of the high installation costs typical of bifacial panels.

The new double-sided HJT modules suffer less degradation over time and are less sensitive to high temperatures than traditional solar panels, allowing manufacturers to offer decades-long warranties.

In what cases are they useful? A new generation of bifacial solar panels is useful in high-latitude areas, where the sunlight angle is low, to capture light reflected from snow and other surfaces. In areas with high ground reflection, such as desert sand or the white roof of a factory or large enough commercial building.

Following the same logic, double-sided panels can be used in agriculture, where crops benefit from sunlight passing through the glass. And in larger bodies of water, using reflected light helps protect them from rising temperatures.

It is true that double-sided panels are marketed as alternatives to awnings and pergolas to provide shade, but in their more efficient versions, they make more sense for general use in vertical installations such as canopies, bridges, facades and sound barriers on both sides. Road.

Picture | Soltec

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