The AC module performance for the entire system and the average per module AC performance, is shown in Figure 7. As is shown there, the system was bound by the AC output limit of the inverters, and “clipped” at the 166.5kW AC limit value early in March; this would indicate that under non-clipped conditions, the power/energy output of the system would be even higher.

CONCLUSIONS

An optimized bifacial system was installed in New York State and operated under snowy/winter conditions for much of February and March of 2017; during those months, the overall system output and performance ratio of the system were seen to be operating at much higher values than those traditionally associated with PV systems, and was designed to generate +22% annual energy compared to an equally rated monofacial system/offering.

Based on a Performance Ratio analysis of the seasonal measured bifacial values compared to typical annual monofacial values, the Prism Solar Bi60-368BSTC modules were collecting between 37.77%–61.04% more energy than what would be typically expected for an equivalent monofacial installation for the winter conditions, and between 11.11%–29.87% for the spring conditions. The median bifacial system performance ratio for the period Feb 22–Nov 12 was 1.02, the modeled annual value was between 0.97–0.98, not accounting for snow effects.

Additionally, based on the field peak power performance of the modules, it was shown that the bifacial modules achieved peak power production that was 12.70% to 21.45% above their STC (black background) rating late in March; considering that most PV modules operate at 8%–15% below STC condition even at full illumination, this shows that the Prism Solar bifacial modules were receiving a direct bifacial power boost. This direct power boost, integrated over time, translates into the additional energy generated by bifacial systems.

Both the PR and peak power metrics clearly indicate that the bifacial modules exceed the energy harvesting potential that would be expected from a traditional system.

White roof bifacial performance - Case study

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