Solar Builder

SEP-OCT 2018

Solar Builder focuses on the installation/construction of solar PV systems. We cover the latest PV technology (modules, mounting, inverters, storage, BOS) and equip installers/contractors with tips and tools to make informed purchasing decisions.

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Page 39 of 55

40 S E P T E M B E R / O C TO B E R 2 0 1 8 design variance. An important objective of this testing is to validate ray tracing simu- lation programs which will aid in the accurate modeling of bifacial performance in site-specific applications. "We are working closely with the mod- ule manufacturers in a way we've never done before for exactly that reason," Corio says. "When you design the module and the tracker as one system, you get a better result." In a comparative one year test, con- ducted in 2017, Array saw a 9 to 10 per- cent yearly gain for bifacial over monofa- cial at the same test site. The difference in Soltec and Array's testing approaches is in line with the dif- ference in their tracking approaches — Soltec uses distributed tracker rows and Array supplys centralized drive. All of the performance gains reported will need to be considered within the already established LCOE of each tracker design. Example: The torque tube impact is an early point of differentiation depending on who you ask. The Soltec testing team has seen the shadow from the torque tube in a 1x configuration hurting irradiance harvest in a way it does not when posi- tioned in a 2x configuration, so its SF7 tracker includes an intentional gap between modules at the torque tube loca- tion that avoids shadowing on the back- side of the module. Preliminary measure- ments have shown that up to 38 percent of reflected light does not reach the center of the bifacial modules compared to the edge due to the torque tube shadow of the 1x configuration. Array is quantifying the impact of the torque tube to harvestable rear side irradiance and testing modules with design characteristics that may use the torque tube as a performance advan- tage. All of Array's test data will be com- piled in an LCOE comparison. The difference in testing isn't really the point. The Lawrence Berkley National Lab noted during the Market Trends panel at Intersolar that the cost premium associated with tracker projects is all but gone with 79 percent of newly installed capacity being trackers. When all of this testing is done, the choice will still be the same centralized or distributed tracker decision its always been, just with these new bifacial performance gains to plug into the equation. Chris Crowell is the managing editor of Solar Builder. Array Technologies already sees a 9 to 10 percent gain in bifacial tracking performance.

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