Hi,
What could cause panels to reduce output by 30-50% year over year?
Some plants I oversee have strings showing reduced output of the above mentioned percentage comparing production from sunny days the previous year.
Difference from expected PV*Sol simulations could be as high as 50%. There also seems to be a pattern where the production peaks too early in the day, and then goes of a hill.
Panels are rather small(Physically) so stringlengths of up to 30 panels, often in parallell - Up to 4x30 panels. Panels have glass on both front and back.
E.g from a few panels' flashtesting when new:
Voltage checks are reading same as when installed, but the amps are much lower than expected. Still a parallell string with 2x-3x-4x is reading approximately 2x-3-x-4x amps of 1x strings on the same installation (So amps drop significantly year over year).
Thermocamera reveals some panel with hotspots, but delta-t is most often not even 20 degrees celsius even in sunny weather.
Replacing all panels that show some indication on the thermal camera works sometimes, some times not.
Most of the reduction seems to have happened during the panels first summer, so after first real heat and proper production period. E.g June 23 production is bang on expected from simulation, while July-Aug is well below.
Panel technology is shingled. Could shingled panels be a factor here if ventilation is bad, and permanent damage caused?
Ambient outside temperature is never more than 30 degrees celsius.
Due to some installers having closed up the ventilation areas (deviating from mounting instructions)the temperature below the panels on some installations could theoretically reach as high as 90-95degrees celsius on a sunny day. Most installations never go above 80 degrees celsius. But will panels take permanent damage from this?
When checking the panels taken down in a lightbox almost 80-90% of the ones showing hotspots on site perform fine, but the remaining 10-20% have really low LSC values compared to good ones under same conditions. Voc is identical.
Any suggestions on cause, why, and how to better be able to identify the troublepanels without having to dismount them first would be much appreciated.
What could cause panels to reduce output by 30-50% year over year?
Some plants I oversee have strings showing reduced output of the above mentioned percentage comparing production from sunny days the previous year.
Difference from expected PV*Sol simulations could be as high as 50%. There also seems to be a pattern where the production peaks too early in the day, and then goes of a hill.
Panels are rather small(Physically) so stringlengths of up to 30 panels, often in parallell - Up to 4x30 panels. Panels have glass on both front and back.
E.g from a few panels' flashtesting when new:
| lsc | vos | pm | lpm | vpm | ff |
| 6,3549 | 24,6094 | 117,3524 | 5,7526 | 20,0183 | 73,63% |
| 6,2654 | 25,3331 | 115,8632 | 5,6796 | 20,525 | 73,45% |
| 6,2687 | 25,0463 | 116,1194 | 5,6921 | 20,2723 | 73,49% |
Voltage checks are reading same as when installed, but the amps are much lower than expected. Still a parallell string with 2x-3x-4x is reading approximately 2x-3-x-4x amps of 1x strings on the same installation (So amps drop significantly year over year).
Thermocamera reveals some panel with hotspots, but delta-t is most often not even 20 degrees celsius even in sunny weather.
Replacing all panels that show some indication on the thermal camera works sometimes, some times not.
Most of the reduction seems to have happened during the panels first summer, so after first real heat and proper production period. E.g June 23 production is bang on expected from simulation, while July-Aug is well below.
Panel technology is shingled. Could shingled panels be a factor here if ventilation is bad, and permanent damage caused?
Ambient outside temperature is never more than 30 degrees celsius.
Due to some installers having closed up the ventilation areas (deviating from mounting instructions)the temperature below the panels on some installations could theoretically reach as high as 90-95degrees celsius on a sunny day. Most installations never go above 80 degrees celsius. But will panels take permanent damage from this?
When checking the panels taken down in a lightbox almost 80-90% of the ones showing hotspots on site perform fine, but the remaining 10-20% have really low LSC values compared to good ones under same conditions. Voc is identical.
Any suggestions on cause, why, and how to better be able to identify the troublepanels without having to dismount them first would be much appreciated.
