Reasons for decreased Power and Yield of PV Generators
Page 35
14
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
Discoloring 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, discoloring)
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, discoloring)
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.
PVPM 1000X / 1040X
User Manual
PV-Engineering GmbH
