ECN publication
Relation between indoor flash testing and outdoor performance of bifacial modules
Published by: Publication date:
ECN Solar Energy 22-9-2014
ECN report number: Document type:
ECN-M--14-054 Conference Paper
Number of pages: Full text:
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Flash tests under standard test conditions yield lower power for bifacial modules due to transmittance of the transparent back sheet or glass. Nevertheless, these bifacial modules are expected to outperform their monofacial equivalents in terms of yearly energy output in the field, depending on local climate conditions, albedo, orientation (relative to South) and tilt angle. Modules with transparent back sheet on the rear give very similar power output in standard test conditions and with extra background scattering when compared to bifacial modules with AR glass as rear cover. This gives the freedom to design either a glass-glass or a glass-back sheet bifacial module, depending on other considerations. For a location with low albedo, bifacial modules produces more kWh/Wp than monofacial modules in the early and late hours of the day, when the sun is more or less parallel to the plane of the modules. With increasing albedo, the bifacial gain increases from 5% to 20%; the gain is constant for a broad range of irradiation conditions.

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