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Emmerthal, Germany

Eitner U.,Emmerthal GmbH ISFH | Kontges M.,Emmerthal GmbH ISFH | Brendel R.,Emmerthal GmbH ISFH
Solar Energy Materials and Solar Cells | Year: 2010

An experimental technique to measure the deformation of solar cells in transparent PV modules is presented. This method uses the digital image correlation technique with a stereo camera system. Deformations resulting from thermal loading, where rather small deformations occur compared to tensile or bending experiments, are measured by viewing through the window of a climate chamber. We apply this method to measure the thermomechanical deformation of the gap between two crystalline silicon solar cells by viewing through the transparent back sheet of the laminate. Two PV laminates are prepared, each with three crystalline silicon solar cells that are embedded in transparent polymer sheets on a glass substrate. The first laminate (A) contains non-interconnected cells while the second laminate consists of a standard-interconnected cell string (B). We find the gap between two solar cells to deform 66.3±2 μm between 79.6 and -17.3 °C (laminate A) and 66.4±2 μm (laminate B) between 84.4 and -39.1 °C. We determine an accuracy of 1 μm in displacement for the gap experiment by measuring free expansion of a copper strip and averaging displacement values over regions with homogeneous deformation. Furthermore, the relative error contribution in strain due to the optical influence of the layers on top of the object surface is less than 1×10-6 for one camera. This is proven by a geometrical consideration. © 2010 Elsevier B.V. All rights reserved.

Potthoff T.,Emmerthal GmbH ISFH | Potthoff T.,Sysaic AG | Bothe K.,Emmerthal GmbH ISFH | Eitner U.,Emmerthal GmbH ISFH | And 2 more authors.
Progress in Photovoltaics: Research and Applications | Year: 2010

We introduce an approach to determine the operating voltage of individual solar cells in photovoltaic (PV) modules by electroluminescence (EL) imaging. The highest EL signal of each solar cell is proportional to its operating voltage. Moreover the sum of all operating voltages equals the externally applied module voltage. Thus the operating voltage of individual solar cells is determined from, the measured EL signal. The reliability of this relation is verified by measurements on specially prepared. PV modules allowing us to measure the individual operating cell voltage. The experimentally measured cell voltages are deduced with an uncertainty of ±1% from, an EL image. Moreover, the operating cell voltages determined from the EL image are used to calculate the module series resistance. Comparing experimentally determined values from the operating cell voltage and the total current flowing supplied to the module with calculated module series resistances using tabulated material and typical solar cell parameters, a very good correspondence is found. Copyright © 2010 John Wiley & Sons, Ltd.

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