NEXTracker, the fastest selling solar tracker in the world, inaugurated its expanded bifacial solar test facility at its Center for Solar Excellence in Fremont, CA, April 22 to celebrate Earth Day. The test bed includes 20 different bifacial test scenarios, including multiple panel types from Longi, JA Solar, and Jinko, says Dan Shugar, the founder of the company.
NEXTracker is partnering with Groundwork to measure and monitor the test array, using utility-scale sensors and analytics. The goal of the testing is to optimize the configuration of bifacial panels on the company’s NX Horizon trackers for future deployments globally. Factors being tested include the albedo — or ground reflected light, height of the torque tube, elevations over time, and front and rear energy yield ratios, among others. The bifacial boost expected from the array is in the 8 to 10% range, minimally.
The self-powered NX Horizon rotation comes from a small solar panel on the motor, eliminating captive energy from the design yield. The so-called “distributed design” of the system is attributed to the ratio of one motor per eight-panel solar table.
NX Horizon is built at rotation-axis elevations up to 100% of the total PV panel width, and its large height-to-width aspect ratio maximizes module rear-side irradiance, the company says. The design also helps maintain consistent irradiance along the underside of the modules, something which is difficult and costly to accomplish with larger-format trackers, it says.
The company already has a pipeline of 800 megawatts of bifacial tracker systems in place, and that number is expected to rise. “The 10 percent increased energy yield from bifacial solar panels is one reason that solar continues to be the leading source of new energy installations,” says Shugar.
The bifacial boost, as the rear panel contribution is often called, is likely to open up new US geographies to the use of solar energy, particularly with bifacial panels on single-axis trackers, suggests Sheldon Kimber, the CEP of Intersect Power, present at the inauguration. “This combination of technology can be adopted in the middle of the country, where coal and nuclear plants are being closed down,” he says.
Apart from testing off-the-shelf bifacial solar panels, NEXTracker also is co-developing some bifacial panel versions in cooperation with the manufacturers like Longi. For example, the two are testing half-cell bifacial panels with center busbar locations and optimized wiring pathways. The half cells generate more energy than a whole cell, and operate with greater tolerance to temperature limits, among other factors.
The bifacial panels under test at the facility are all framed solar panels. “There have been some colossal failures with unframed panels on trackers in China,” Shugar notes.
The test array is utilizing Delta inverters, with a distribution of one inverter per NX Horizon unit of eight panels. The panels are spaced so that they do not cover or shadow the top of the torque tube bearings, piers, or slew gear. This design feature eliminates direct shading and greatly reduces mismatch losses in energy between the panels and the inverters, the company points out.
The test facility is also testing five types of energy storage systems, including lithium batteries and utility-scale vanadium flow batteries.
Shugar points out that the combination of bifacial panels and the company’s Artificial Intelligence-driven algorithms, branded True-Capture, can translate to as much as 20% more energy harvest than traditional single-axis trackers using monofacial modules – as well as a lower system Levelized Cost Of Energy.
Bifacial panels may soon grow to represent 25% of all solar tracker systems the company sells, reckons Shugar. And in a few years, bifacial panels could represent 50% of all solar tracker systems, he calculates.
Kimber sounds even more enthusiastic about the future of bifacial panels on trackers: “Let me be clear: as a developer of utility-scale projects, we are very bullish on bifacial. We see bifacial as the next major evolution in solar module technology,” he says in a recent blog. “Even if bifacial modules trade at a slight premium for the time being, many manufacturers tell us they intend to make even their monofacial panels with bifacial cells. Once they move their production lines over to bifacial, there won’t be a huge marginal cost difference and the prices will equilibrate — as a result, the module market norm will increasingly evolve to bifacial cell and module technology,” he expects.
NEXTracker, a Flex company, “advances the power plant of the future with smart solar trackers, energy storage systems and TrueCapture advanced control software that yields additional energy, optimizes performance and reduces costs for project and plant owners,” the company says. “As the number-one tracker supplier worldwide with over 17 GW delivered or under fulfillment, NEXTracker is globally recognized for delivering smart and connected energy systems for hundreds of projects across five continents,” it adds. Headquartered in the San Francisco Bay Area, the company has offices in Australia, India, Latin America, and Europe.