Bifacial tracking grows on new designs


A host of tracker companies have released or are releasing new model designs that are optimized for bifacial panels. The global leaders in tracker supply have all released bifacial-optimized systems. One new manufacturer design scheduled for commercial availability in early 2020 is Arctech Solar’s SkySmart2 tracking system. Indeed, the Chinese manufacturer expects to improve its global tracker sales position – currently fourth in the world by volume – as demand for bifacial systems increases.

“Bifacial tracker systems will become much more popular, because of the yield increase. These bifacial panels and our new tracker – which has a lower capex requirement – will make far more projects viable,” reckons Guy Rong, the president of Arctech Solar’s global business. “The major reason we designed SkySmart2 was to offer a better economic return for projects.”

One basic reason that bifacial tracker designs will become increasingly accepted as cost beneficial is that less DC equipment is needed to provide the same energy yield as a single-axis tracker or a fixed-tilt system. The use of less equipment to produce an equal or superior yield lends an overall efficiency of up to 5% across a bifacial tracker system, according to Peter Johnson, a senior project engineer at AWS Truepower, the recently acquired advisory unit of Underwriters Laboratory.

Ongoing industry research and field tests of bifacial panel optimization shows that the number of variables in enhancing performance is substantially higher than in a simple mono-facial solar system, whether fixed tilt or tracker-supported. Key factors include those that affect albedo, or ground-reflected light, which has already been shown to boost yield by 15-20% or more. Early research in Europe by Fraunhofer ISE suggests that further system optimizations could push the bifacial boost as high as 30%, or even more.

Modeling performance

Software modeling of the performance of bifacial tracker systems has been a particular challenge, and close to a dozen field tests of the tech combination are now underway at US Department of Energy-supported laboratories, across both universities and private sites. These tests are aimed at reducing the difference between modeled performance predictions and actual performance.

Major US bifacial tracker research players include Arizona State University, Black & Veatch, CFV Solar Test Laboratory, DNV GL, University of Iowa, National Renewable Energy Laboratory, and Sandia National Laboratories. Others are joining the work in an effort to help develop standards for design.

The first waves of bifacial tracker performance figures are already out, and more extended data sets are expected by the end of this year. As more field data is analyzed and performance modeling is further tweaked, bankers will become more willing to risk project loans using bifacial tracker technologies.

The growth rate for bifacial tracker adoption is expected to take off rapidly over the next decade. The International Technology Roadmap for Photovoltaic (ITRPV), produced by the German Mechanical Engineering Industry Association (VDMA), predicts that bifacial modules will account for 10% of the total world market share of PV modules by 2020, and more than 30% by 2028.

The long list of factors affecting bifacial tracker systems begins with the basic concepts of solar light capture. “Bifacial performance is very project specific, depending on the soil conditions, the topography, the field layout and shading,” explains Rong. “We have conducted extensive research and testing of these factors on our new system, to make sure it is really robust.”

The type and color of ground cover is crucial to albedo value enhancement. While standard desert soil may provide only a 20% addition of reflected light, snow can provide 90% or more ground-reflected light. As a result, many of the ongoing field tests are including several different ground cover types to determine the cost/benefit of modifying the ground cover at a potential bifacial tracker site. Some researchers are testing metallic and plastic reflective surfaces as well.

The high albedo that snow presents also means that bifacial trackers may penetrate vast new geographic zones of low insolation, like in the northern United States, where single-axis trackers often do not perform well enough to justify the additional cost over a fixed-tilt solution. The University of Alaska is conducting field tests with vertically mounted bifacial solar panels in an effort to determine whether the state should adopt the technology.

Ground shading from the tracker structure is therefore a major consideration in bifacial tracker design. While some manufacturers, such as Arctech Solar, have settled on the two-in-portrait (2P) panel table design with horizontal spacing between the panels over the torque tube, other tracker manufacturers have opted for one-in-portrait designs centered over the tube, and are still coping with the issue of tube shading. Research on the impact of the specific shapes of various torque tubes on shading is ongoing.

As more 2P designs emerge, another research factor to be considered for bifacial tracker designs is wind resistance, because panels are extended further from the central support of the torque tube. “We are continuing to do wind tunnel testing and working heavily with the data. Wind tests can help us understand the fundamentals of the tracker product better and in this industry there is a need to analyze fundamentals before adding bells and whistles,” says Rong.

Beyond bifacial trackers

Arctech Solar may be best known for its new SkySmart2 bifacial tracker, but overall company sales thus far have been dominated by fixed-tilt and monofacial panel systems.

“About 50% of our sales were trackers last year, and the percentage for 2019 will be higher,” adds Rong.

Export sales are growing rapidly for the company. “Two years ago, our exports amounted to about 25% of overall sales; last year, exports were up to 30%, and based on our sales from the first half of this year, exports will likely represent more than 50% of total sales in 2019,” says Rong.

He expects global growth in all geographies. “We now have seven regional offices worldwide,” Rong says. “Several major markets are moving very fast for us in Latin America, including Mexico, Brazil and Chile. The next big regional market for us will be the Middle East, where we already have a good position,” he says. Arctech also has shipped trackers to projects in Vietnam, Mexico, Australia, Turkey, Kazakhstan, Brazil, China, Greece, India, Indonesia, Japan, Namibia, Oman, Jordon, Malawi, Spain and Thailand.

To continue financing such global growth, Arctech Solar is launching an initial public offering of its shares on the Chinese stock market, with plans for trading to start by early 2020.

“We have been working with private equity investors for several years, but we want to build up a bigger financial platform, to raise more capital,” Rong says.

And he hints that the IPO in China may be followed by further offerings on other international stock exchanges.

“We want to launch in China first, then we will see what we may do in other markets.”

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