The conversation surrounding solar modules in 2018 is understandably focused on the ramifications of the Section 201 tariffs. But there is another trend that could also reverberate through the market: the growth of high-efficiency modules.

In particular, monocrystalline and bifacial modules that use passivated emitter and rear cell (PERC) technology have demonstrated the potential to increase energy yields, potentially enough to erase the price hike inflicted by the tariffs.

According to GTM Research, PERC cell capacity rose from a few pilot lines just five years ago to more than 35 gigawatts in 2017, or nearly one-third of total global cell capacity.

The large ramp-up in capacity has been driven in part by policy. China’s Top Runner Program was designed to encourage the production and installation of high-efficiency solar equipment. The most recent round of the Top Runner Program required monocrystalline cells and modules to have efficiencies of 21 percent and 18 percent, respectively. GTM Research estimates that the program has driven a total of 6.5 gigawatts of demand.

The use of high-efficiency modules can have a significant impact on a solar power plant’s production and economics. “Because of high-efficiency modules, if you have the same 100-megawatt PV system, you require fewer modules for the same system output,” said Hongbin Fang, director of technical marketing for LONGi Solar, the world’s largest producer of high-efficiency mono wafers and modules.

“Compared to state-of-the-art multi modules, you require 10 to 12 percent fewer high-efficiency modules because they are 10 to 12 percent more efficient," he said. At the same time, balance-of-system costs for cables, racking, labor and land are also proportionally reduced because fewer modules can produce the same amount of energy.

The emergence of bifacial PERC modules, which produce energy from the rear side of the module as well as the front, is widening the energy production gap when compared to traditional multi modules.

LONGi recently conducted field tests comparing the energy yield of bifacial, mono and multi modules installed in China. In one test, two roughly 18-kilowatt installations were monitored for three months. Both were installed in a fixed-tilt configuration and one had standard mono modules while the other used bifacial panels. The result was a more than 11 percent higher energy yield for the system using bifacial modules.

The difference was even starker when LONGi compared the energy yield of a 336-kilowatt system using bifacial modules and a tracker with a similar size system using multi modules and no tracker.

“The energy yield gain of the bifacial module and tracker is 27 percent,” said Fang, who will be discussing the outlook for solar modules during an upcoming panel discussion at GTM’s Solar Summit in San Diego in May. Even when equipped with a tracker, the multi modules still had an energy yield 14.3 percent less than the combination of a bifacial modules and a tracker.

These energy yield benefits would be of little consequence if high-efficiency modules were dramatically more expensive than their multi counterparts. But the price difference between mono and multi has narrowed dramatically in recent years.

According to Fang, what was once as much as a $0.40 per piece price difference between multi and mono wafers back in 2012 is now in the $0.10 to $0.15 range, which translates into a $0.02 to $0.03 per watt difference on wafer cost. The $0.02 to $0.03 increase is offset by the high efficiency on the cell and module level, he added.

The ever-shrinking cost difference between mono and multi wafer has been enabled in large part by LONGi’s consistent investments in R&D. LONGi invested about $170 million in the development of mono ingot, wafer, cell and module technology last year, and spends 5 percent to 7 percent per year of its revenue on R&D annually.

LONGi expects to hit about $0.16 per unit by 2020 for mono wafer non-Si cost. LONGi improved its cell efficiency by 1.5 percent last year and demonstrated a p-type mono PERC cell with 23.6 percent efficiency in 2018.

“It is promising that 23 percent cell efficiency will be realized in high-volume manufacturing in the near future,” said Fang. "We believe mono PERC, including bifacial PERC, is the best solution to realize lower [levelized cost of energy] for solar projects in the next few years.”