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ECN publication
Impact of inhomogeneous irradiance a the rear of panels on modelled biffacial energy yield
Published by: Publication date:
ECN Solar Energy 25-9-2017
ECN report number: Document type:
ECN-M--17-024 Conference Paper
Number of pages: Full text:
6 Download PDF  

Presented at: EUPVSEC, Amsterdam, , 25-29 september 2017.

The inhomogeneity of the rear irradiance of bifacial PV panels and its effect on the power loss due to current mismatch was investigated by modelling. We have found that the inhomogeneity of the rear irradiance depends on orientation, elevation, and tilt angle of the panel and on irradiance conditions. Typically the inhomogeneity of the rear irradiance is largest at a high fraction of direct light. Conversely, the inhomogeneity of the total irradiance is smallest when there is a large direct light component. The simulations indicated that the relative standard deviation (RSD) of the total irradiance will not exceed 5% even at albedo as high as 0.8, and is usually much smaller. Simulations mimicking near-field shading also showed that the RSD will be below 10% unless the beam component is small, i.e. at low light conditions. LTspice circuit simulations with an inhomogeneous current distribution showed that a current distribution with an RSD below 10% will not lead to cells going into reverse bias. This means the risk for hot-spots is small. A simple parametrization for the power loss as function of the RSD of the current distribution was established, which can be used for energy yield calculations.

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