13Reasons for decreased Power and Yield of PV Generators 34
13 Reasons for decreased Power and Yield of PV Generators
Error To be detected by: Possible reason / workaround
System configuration chosen inadequately Measurement of mismatch losses Design fault / redesign
Erroneous match of strings and inverter Fed power too low for location and in
relation to nominal generator power
Design fault / redesign, replacement of inverters
Cast shadow I-V-curve shows "bulge", peak power too
low, optical check
Barrier near module (e.g. tree, chimney, birds
excrements) / remove barrier
Diffuse shading (may be hardly visible for
bare eye!)
I-V-curve is "impressed", peak power too
low
Barrier in some distance to module (high portion of
diffuse light) / remove barrier
Corrosion at plugs and cables Serial internal resistance Rs too high Material, planning or mounting fault / Clean,
replacement
De-lamination of cell embedding see shading diffuse Material / production fault / Replacement
Bubbling in resin see shading diffuse Material defect / replacement by supplier
Transparent covering material (glass,
plastics, resin) becomes blind
Optical check, peak power too low (s. a.
shading diffuse)
Material defect / replacement by supplier
Discolouring of the transparent cover
material (plastics, resin)
Optical check, peak power too low (s. a.
shading diffuse)
Material defect / replacement by supplier
Intrusion of water into the laminate, leads to
other problems (corrosion, discolouring)
Optical check Material or production fault / replacement by supplier
Faults in the crystalline structure of single
cells (hot-spot effect)
see shading diffuse Production fault / reduction of price, replacement by
supplier
Pollution of the module by dust Optical check, see shading diffuse High dust impact. Check modules periodically /
cleaning
Moss / algae on module, birds excrements see cast shadow Normal for several regions / cleaning
Broken cover glass, leads to other problems
(corrosion, discolouring)
Optical check Hailstorm, mounting or transportation fault /
replacement by supplier
Break of single cells in module Peak power too low, possibly deformation
of I-V-curve
material defective / replacement by supplier
Improper electrical connections in module Peak power too low, internal series
resistance Rs higher than calculated
Fault in soldering, material defective, corrosion /
replacement by supplier
Bypass diode defective (short circuit) Peak power of strings reduced by module
power
Overload, material defective / repair
Bypass diode mounted the wrong way Peak power of strings reduced by module
power
Mounting fault / repair
No bypass diode mounted or diode defective
(high resistance)
Shading of one module reduces power of
the string dramatically
Planning / mounting fault / repair
Dimension of cabling too small Internal series resistance Rs too high Design fault / replacement of cables
Cable defective (e.g. break, corrosion) Internal series resistance Rs too high Mounting fault / repair
Insufficient mounting of connectors Internal series resistance Rs too high Mounting fault / repair
Corrosion in screwed or plugged connectors Internal series resistance Rs too high Mounting fault / cleaning, repair
Insufficient preselection of modules
regarding peak power
Peak power of plant too low Planning or mounting fault (match losses) / New
preselection of the modules after peak power
measurement
Insufficient preselection of single cells
regarding power during module production
Peak power of module too low Production fault / reduction of price, replacement by
supplier
Short circuit between cells in the module Peak power of plant too low, open circuit
voltage U
oc
too low, shape of curve
Production fault / replacement by supplier
Fabrication tolerances in cell production Peak power too low, shape of curve Production fault / reduction of price, replacement by
supplier
Please notice: some faults may appear only under special operating states, e.g. high module temperatures.
This compilation does not claim to be complete or free of failures.
Operation manual for PVPM devices PV-Engineering GmbH
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