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Title:
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Near-field partial shading on rear side of bifacial modules
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-10-2017
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ECN report number:
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Document type:
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ECN-W--17-030
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Article (scientific)
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Number of pages:
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8
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Published in: Energy Procedia (Elsevier), , 2017, Vol.Volume 124, p.532-539.
Abstract:
It is well-known that near-field shading reduces the power output of a PV system drastically, especially when inhomogeneous shading creates a large current mismatch between series-connected solar cells. Typically, the front side irradiance is very uniform and near-field shading is avoided. In contrast, for bifacial panels, the rear side contribution is effected much more, both by the inhomogeneity of the rear irradiance and by (unavoidable) near-field objects, including the mounting system. In this paper, outdoor and indoor irradiance and IV measurements are combined with LT-spice modelling to show the limited effect of rear side shading on the performance. We will show that the actual rear side irradiance for an actual, tilted, equator-facing system, with cell-size resolution, varies between 47 and 83 W/m2. Varying distance and position of near-field objects, the drop in current is in good quantitative agreement with the measured reductions in rear side irradiance. Increasing the reflectance of the near-field object strongly reduces the effective shading, the measured loss in rear irradiance and the current drop in the IV curve.
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