15 Reasons for decreased Power and Yield of PV Generators
-35-
15 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 / r
edesign, 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 / r
epair
No bypass diode mounted or diode
defective (high resistance)
Shading of one module reduces power of
the string dramatically
Planning / mounting fault / r
epair
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 / r
epair
Insufficient mounting of connectors
Internal series resistance Rs
too high
Mounting fault / r
epair
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 / r
eplacement 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
