This article was originally published in pv magazine – March 2022 edition. Learn more about the pv magazine test here.

This article presents the next batch of energy yield results from the pv magazine outdoor test field in Xi’an, China. In this issue, we present data for December and January, as the pandemic lockdown delayed the publication of yield results for the final month of 2021, alongside analysis from George Touloupas, Senior Director of Technology and Quality at CEA.

As GSolar’s facility in Xi’an could not be accessed until Jan. 21, maintenance checks and reset procedures were conducted for the whole facility. Figures for Jan. 21-26 were impacted or missing, and are omitted from the analysis. The first chart to the right shows the meteo station data for these two months.

Three new products were added to the outdoor test field (see table below). They are all mono PERC modules, from JA Solar (#36), LONGi (#38), and Trina Solar (# 40). Energy yield figures were corrected to account for diverse resistive losses of different products due to the cable length connecting them to the microinverters.

Bifacial Boost

The average bifacial boost for December 2021 is 4.6% and for January 2022 is 5%. Bifacial boost is defined as the extra energy yield of the bifacial products compared to the average energy yield of all mono-facial mono PERC products.

The chart below (Figure 1) shows the comparison between different PV module technologies for the two months on a rolling average basis. Bifacial modules are steadily performing above all the other technologies, with multi modules having the lowest yield. [Read: LCOE of Monofacial vs Bifacial Modules: Are Bifacials Worth the Extra Cost?]

*Figure 1: Relative yield of different technologies (Dec. 2021 - Jan. 2022)*

*Table 2: Energy yield ranking - October 2021 to January 2022*

Notes on energy yield results

The energy yield comparison among various technologies, including bifacial boost, will be analyzed using products installed after the beginning of 2019.
The energy yield is given in Wh/Wp and calculated by dividing the energy produced by the Pmax at STC of the module. This Pmax is the maximum STC power after a process of stabilization.
The results are grouped into categories, per module type.
The bifacial boost depends on many parameters: the bifaciality factor, the installation geometry, the albedo of the ground, and the sun angle and diffuse irradiance. The ground in this case is gray gravel.

*Figure 2: Total energy yield - Dec. 2021 and Jan. 2022*

*Figure 3: Daily temperature and irradiance data - Dec. 2021 and Jan. 2022*

Test Cooperation

pv magazine test is a cooperative effort involving pv magazine, APsystems, CEA, and Gsolar. All testing procedures are carried out at Gsolar’s test laboratory in Xi’an, China. CEA supervises these tests and designed both the indoor and outdoor testing procedures.

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