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19 th European Photovoltaic Solar Energy Conference and Exhibition

wirefree. PV. PV-wirefree versus conventional PV-systems: detailed analysis of difference in energy yield between series and parallel connected PV-modules. Henk Oldenkamp OKE-Services, The Netherlands 8 June 2004 Web: www.pv-wirefree.com.

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19 th European Photovoltaic Solar Energy Conference and Exhibition

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  1. wirefree PV PV-wirefree versus conventional PV-systems:detailed analysis of difference in energy yield between series and parallel connected PV-modules Henk OldenkampOKE-Services, The Netherlands8 June 2004Web: www.pv-wirefree.com 19th European Photovoltaic Solar Energy Conference and Exhibition

  2. Overview presentation • Definitions • What is PV-wirefree? • PV-wirefree claims … • Focus of this presentation • Test setup • Explanation of the graphs • Measurement results • Conclusions • Finally

  3. Definitions • PV-string: series connection of PV-modules of which all cells are connected in series Duality of a PV-string is: • PV-shunt: parallel connection of PV-modules of which all cells are connected in parallel But all cells of a PV-module connected in parallel is not practical due to high currents and its associated losses

  4. Definitions • PV-string: series connection of PV-modules of which all cells are connected in series • PV-shunt: parallel connection of PV-modules of which all cells are connected in series

  5. What is PV-wirefree?PV-wirefree = PV-shunt(s) • Large numbers of PV-laminates connected in parallel using a current carrying mounting frame (= mounting bus) • Each group of PV-laminates connected to one set of mounting busses has its own inverter, and is called a subsystem

  6. What is PV-wirefree?PV-wirefree = PV-shunt(s) • Large numbers of PV-laminates connected in parallel using a current carrying mounting frame (= mounting bus) • Each group of PV-laminates connected to one set of mounting busses has its own inverter, and is called a subsystem

  7. What is PV-wirefree?PV-wirefree = PV-shunt(s) • Large numbers of PV-laminates connected in parallel using a current carrying mounting frame (= mounting bus) • Each group of PV-laminates connected to one set of mounting busses has its own inverter, and is called a subsystem

  8. PV-wirefree claims • Increase of annual energy yield especially in suboptimal conditions • Considerable decrease of costs

  9. Focus of this presentation • This presentation proves the first claim: a significant increase of annual energy yield How? • By measuring the full P versus V curves of nine PV-modules continuously switched between shunt and string under varying shading conditions, excluding any other influences on the array power

  10. Test setup Every minute the lower 9 pv-modules are connected in shunt and in string, and a photo is taken. A 1000 points power versus voltage sweep takes 7 seconds

  11. Explanation of the graphs Red line = average shunt power per module versus shunt voltage Purple line = irradiation during the 7 seconds sweep time

  12. Explanation of the graphs Red dot marks maximum power point of the shunt

  13. Explanation of the graphs Blue line = average string power per module versus average module voltage Green line = irradiation during the 7 seconds sweep

  14. Explanation of the graphs Blue dot marks maximum power point of the average string module

  15. Explanation of the graphs Black dot marks maximum power point of the string when loaded at 81.5% of Voc (expected MPP)

  16. Measurement resultsDefinition of three types • Very lightly shaded: the shade covers roughly the area of one cell • Lightly shaded: the shade covers several cells • Moderately shaded: the shade covers several modules

  17. Measurement resultsVery lightly shaded •  P shunt/string = 0.3% •  P shunt/string at V=81.5% Voc = 0,4%

  18. Measurement resultsVery lightly shaded •  P shunt/string = 4.9% •  P shunt/string at V=81.5% Voc = 9.6%

  19. Measurement resultsVery lightly shaded •  P shunt/string = 2.4% •  P shunt/string at V=81.5% Voc = 8.7%

  20. ResultsVery lightly shaded • Minimum gain: 2-5% • Expected gain in practice: 5-25%

  21. Measurement resultsLightly shaded •  P shunt/string = 1.5% •  P shunt/string at V=81.5% Voc = 2.0%

  22. Measurement resultsLightly shaded •  P shunt/string = 10.8% •  P shunt/string at V=81.5% Voc = 12.0%

  23. Measurement resultsLightly shaded •  P shunt/string = 10.6% •  P shunt/string at V=81.5% Voc = 27.0%

  24. ResultsLightly shaded • Minimum gain: 10-20% • Expected gain in practice: 10-40%

  25. Measurement resultsModerately shaded •  P shunt/string = 3.8% •  P shunt/string at V=81.5% Voc = 53.9%

  26. Measurement resultsModerately shaded •  P shunt/string = 0.4% •  P shunt/string at V=81.5% Voc = 226.6%

  27. Measurement resultsModerately shaded •  P shunt/string = 23.9% •  P shunt/string at V=81.5% Voc = 176.0%

  28. Measurement resultsModerately shaded •  P shunt/string = 49.6% •  P shunt/string at V=81.5% Voc = 174.2%

  29. ResultsModerately shaded • Minimum gain: 0-50% • Expected gain in practice: 30-400%

  30. Conclusions: measurement resultsOverview shading effects

  31. ConclusionsShunts always perform better Since: • The MPP voltage nearly constant • And simple and efficient MPP tracking possible Additional advantages of shunts • Inverters can have significantly narrower input voltage windows, which will reduce costs and/or increase efficiency of inverters • MPP tracking efficiency will always be significantly better

  32. Finally: shunts = PV-wirefree • More information available at • Stand T22 • www.pv-wirefree.com • Partners PV-wirefree • Bear, ECN, OKE, OJA, Oskomera. TNO • Connector: Multi-Contact, • Acknowledgements • Nico van der Borg, ECN

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