ECN publication
PV-Wirefree versus conventional PV-systems: detailed analysis of difference in energy yield between series and parallel connected PV-modules
Published by: Publication date:
ECN Solar Energy 1-6-2004
ECN report number: Document type:
ECN-RX--04-074 Conference Paper
Number of pages: Full text:
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Presented at: 19th European Photovoltaic Solar Energy Conference and Exhibition, Paris, France, 7-11 juni 2004.


In the past several attempts have been made to measure the difference in energy yield between acmodules, string systems and array systems. Unfortunately measuring and comparing the output is difficult since the compared systems use different inverters, different modules and are operating at different locations. A new pv-system concept, called PV-wirefree, is based on parallel-connected modules using aluminium current carrying mounting frames. The expectations are that parallel connected systems will produce more energy due to less influence of partial shading and a better matching of individual modules. To check whether these assumptions are indeed correct, a test rig has been set up where, by means of relays, the module interconnection can be changed from parallel to series instantly. An automatic measuring system continuously measured and logged the complete I-V curve of the system and a web cam was used to provide pictures of the actual shading conditions. Measurements are executed over a period of several months under different shading conditions varying from virtually unshaded to partially shaded. The results show a significant increase of output ranging from 2 to even 50 % for the parallel connection.

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