Solar trackers promise greater energy yield than their fixed-tilt counterparts because they keep modules constantly pointed toward the sun throughout the day. Similarly, bifacial modules can produce more power than their one-sided solar panel cousins because they have double the exposure level.
So, is there a benefit to pairing two technologies that each ensure greater solar yield? Some tracker manufacturers believe there is. At the very least, bifacial modules will generate more energy than their frontside power rating. When combined with certain environmental and design conditions, backside generation can be boosted even more.
Bifacial cells made up 50% of the world market share of solar cells in 2021, and that percentage is expected to increase to 85% by 2023, according to the International Technology Roadmap for Photovoltaics. Additionally, tracker manufacturers reported that the large majority of recent solar projects using their tracking systems include bifacial panels.
Besides the benefit of extra backside generation, the bifacial exemption from Section 201 trade tariffs has likely contributed to the technology’s proliferation in the market. But tracker manufacturers aren’t all in agreement on how to prioritize backside optimization.
“Your mileage may vary, and you need to do the math and figure out what’s best for a given project,” said Matt Kesler, director of solar technology at OMCO Solar. “The extra production that you get from bifacial is usually a good investment.”
Rotating solar irradiance on one axis
Single-axis trackers have quickly become a standard in utility-scale solar projects. They can be installed in similar project footprints to fixed-tilt racking, with the added production bonus of row-by-row movement to track the sun throughout the day.
The mechanisms that drive solar trackers and the controls that optimize positioning for energy generation and weather conditions vary by product. Manufacturers often develop in-house control software to accompany their trackers, but directing that software to focus bifacial arrays on backside generation isn’t necessarily the best move.
Array Technologies, a global manufacturer of single-axis trackers, tested optimizing backside irradiance gain with its proprietary control software SmarTrack. During the test and accompanying simulations, the company found that the energy difference between an array running typically and one focusing on backside generation was just 0.1% over a year.
Array found that the system moved erratically, rotating up and down almost hourly to encourage backside rather than frontside generation gains. The backs of bifacial modules are not as efficient as the front, so Array believes the focus should remain on frontside optimization.
“It’s always beneficial to try to maximize the irradiance from the sky with the front side,” said Kyumin Lee, VP of engineering for research and technology at Array Technologies. “That’s the best approach, because if you try to improve backside irradiance but lose on the front side irradiance, you …….