View
2.200
Download
7
Category
Preview:
DESCRIPTION
Thermography on Photovoltaic Modules Термография на фотоэлектрических модулей
Citation preview
Committing to the futureCommitting to the futureCommitting to the future
Training forThermography on
Photovoltaic Modules
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
2/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Contents
Design of a Photovoltaic module
Why should measurements be carried out?
At which intervals should measurements be made?
Optimum measurement enviromment / conditions
Defect images
Observation alternatives
The "ideal" imager
Benefits
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
3/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Solar cell / solar system design (I)
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
4/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Solar cell / solar system design (II)
A photovoltaic plant consists of solar modules which are strung together into arrays (e. g. mono/polycrystalline silicon, thin film material )
Solar modules consist of light-sensitive cells which generate direct current
Alternating current converters transform the direct current generated by the solar modules into alternating current
Solar modules are fixed on appropriate structures, mostly on aluminum for heat transfer
A solar cell has an efficiency factor of approximately 5 to 20%
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
5/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Terms and effectivity
83 %
17 % 17 % direct current
83 % heat
Solar energy
Solar module
Alternating current
converter
94 % alternating current
6 % heat
Module
Cell
StringThe weakest cell in a serial string dictates the maximum power current!
Strings are serially switched!
Modules are usually also serially switched!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
6/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Serial / parallel connection of the modules
Parallel connection
Less sensitive to malfunction, modules work independently of
each other
Serial connection
The "weakest module" dictates the maximum current flow
Parallel connection less sensitive
Alternating current
converter
Alternating current
converter
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
7/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Which are the main reasons for maintenance?
Defective cells lead to considerable loss of performance from the system
A temperature increase of 10 °C above the operating temperature recommended by the manufacturer can lead to a 50 % shortening of its lifetime
Defective cells can lead to an enormous heat development, and thus to the danger of fire.
80% of all systems contain defects
In order to operate a plant efficiently, error sources must be localized and repaired!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
8/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Optimum measurement (I)
• Dry, cloud-free days
• Intense sunshine
• Irradiation value of 500-600 W/m²
• If the sun irradiation changes to below the minimum necessary irradiation value, the thermographic image is useless.
• Ideal measurement at low outside temperatures
Pto
t[%
ma
x]
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
9/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Optimum measurement (II)
PV module should be positioned vertically to the sun
Postioning of the imager to the module surface 60°-120° ideal at 90°
Distance of 2-3m between imager and PV module
Take emissivity of glass into account: however negligable, since ony temperature differences are evaluated.
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
10/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Optimum measurement (III)
Ima
ge
r h
eig
ht
1
,7 m
Ima
ge
r h
eig
ht
2
.2 m
60°
32°
23°
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
11/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Where can defects be determined?
Photovoltaic modules
Surface
Connectors
Bypass diodes
Corroded contact points
increased resistance heat develops
Plug-in connections
Cable contacts
Alternating current converter
Generators
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
12/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Which defects can be determined?
Module failure (also partial failure)
Defective wiring
Damp penetration
Delamination
Cracks in module
Defective bypass diodes
Cracks in wafers
Loose contacts
Wear and tear
Alternating current converters, junction boxes etc.
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
13/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Hot-Spot effect
Defective cell:
Converts power from the adjacent cells into heat!
Converts all incoming solar energy into heat
Known as the Hot-Spot effect
Defective solar modules, identifiable in the thermal imager as a Hot-Spot (approx. 15K above mean temperature)
Loss of performance of the system -danger of fire from overheating!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
14/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Overshadowing – dirt (I)
Overshadowed cell, or cell covered by dirt:
Converts power from the adjacent cells into heat!
Performance of all cells switched serially is affected (string)
Performance of all modules switched serially is affected (string)
Known as overshadowing
Loss of performance of the system -ideally comparable using a reference
image!INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
15/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Overshadowing – dirt (II)
1. OVershadowed or dirty cell, heats up more than the
others!
2. Entire string suffers peroformance loss, heats
up!
3. Heated string radiates, adjacent strings suffer
performance loss!
Dirt / overshadowing leads to considerable loss of performance!
There are module bypass diodes and string (bypass) diodes
Bypass diode avoids the effect string level
The bypass diode prevents power from flowing back into the module
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
16/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: defective bypass diodes
Defective bypass diode disables entire string / module
A "Hot-Spot effect" or overshadowing can no longer be countered
Power flows back into the module, it heats up
Intact cells can be damaged by the increased heat input
The warmer a solar cell becomes, the lower its degree of effectivity!
Loss of performance and danger of cell damage!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
17/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Cracks in the cell
Broken glass and cell rupture can be distinguished with the help of a thermal imager!
Broken glass does not lead to loss of performance
Cell rupture leads to a reduction in performance
Cracks in wafer
Ruptured cell
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
18/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Delamination
Contact errors between the conductive ribbon and the solar cell
Power cannot be transferred away
increased heat development
no thermal image in the module grid
loss of performanceDelamination is due to production errors
loss of performance
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
19/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Mismatch / patchwork pattern
Different performance data from solar cells within a module can lead to a loss of performance due to mismatch.
Mismatch not all cells in the module match each other
The weakest cell within a string dictates the maximum current flow.
The same effect can occur at module level
The reason for this is the serial switching
Mismatch is only an error if the manufacturer's specifications are not reached
If a solar module does not match a string, it
reduces the total performance of the
string!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
20/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Non-functioning modules - miscellaneous
Non-functioning modules appear with regular heating, and warmer than the adjacent modules
Miscellaneous defects
E.g. due to incorrect connection, animal bites, module failure
Damp penetration, danger of delamination
Loose contacts
Wear and tear
Defective wiring
These errors cannot be generalized using an exemplary thermal image
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
21/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Example images: Not every Hot-Spot is a defect
Aluminium support brackets lead to heat transfer
Connection sockets are sometimes warm, and visible in the thermogram
Continuous discrepancies do not indicate a defect
Not every Hot-Spot is automatically a defect!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
22/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Summary – example images (I)
Pattern Description Possible error Possible cause Electrical measurement Comment
One module regularly
warmer than others
Non-functioning
moduleModule disconnected
Module usually fully
functional
Warming of a module
by line ( 1string)
One cell string short-
circuited
Bypass diode defective
Internal short circuit
Loss of performance of sub-
string
Hot-Spot detected by
IR measurement
Single random cells
considerably warmer
Module is short-
circuited
All bypass diodes
defective
Performance of module
almost nil
Voc reduced
"Patchwork pattern"
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
23/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Summary – example images (II)
Pattern Description Possible error Possible cause Electrical measurement Comment
One cell considerably
warmer
Overshadowing
Defective cells
Not necessarily loss of
performance
Visual inspection
required
Part of cell
considerably warmerCell rupture
Outside mechanical
influence
Drastic loss of performance
Reduction of Isc and FF
Artefact
Overshadowing (due to
bird droppings...)
Reduction of performance,
depending on size and
overshadowing of cells
Visual inspection
required
Cell crack Construction errorReduction of performance,
depending on size of crack
Crack is detected only
by Hor-Spot IR
measurement
Spot heating
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
24/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Examine front and back
No problems with reflections
Higher emissivity
Heat distribution can be evaluated almost as well from "below"!
As a thermographer, extend your field of view!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
25/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Measurement with a telephoto lens
Distance measurement
High geometric resolution thanks to telephoto lens
Telephoto lens measurement, and you no longer need to climb on to the roof!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
26/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
The ideal thermal imager (I)
Testo, of course!
testo 876
Fulfils all the requirements of Photon magazine for an thermal imager for use in photovotaics
Offers additional features for make work easier,e.g.. Hot-Spot, speech recording, …
Characteristic Requirement according to Photon876
Temperature range -10 to +100° C -20° to 100°C / -20° to 280°C
NETD < 100 mK < 80 mK
Temperature accuracy < 5 % +/- 2°C
Operating temperature -10° to +40° C -15° to 40° C
Protection class IP 54 IP 54
Image frequency > 5 Hz 9 Hz
Battery life min. 2h approx. 4h
Shield for overshadowing display desirable Rotatable display
Auto focus desirable Motor focus
Orientation by laser or (better) digital image Real image
Weight < 1.5 kg 0.9 kg
Detector resolution min. 120 x 120 pixels 160 x 120 pixels
Lens < 35° 32° Standard + 9° Tele
Manufacturer's service. desirable present
Training by manufacturer desirable present
Price (net) < 10.000,- € 5.000,- €
Requirements for thermal imagers for use in solar installations
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
27/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
The ideal thermal imager (II)
Motor focus offers real one-hand operation, ideal for ladders, etc.
Rotatable display can be read optimally even when using a tripod, no sun reflexions on the display
Exchangeable lenses allow two analysis versions:Close analysis(wide-angle, optimal with 32°)distant analysis (telephoto, optimal with 9°)
Speech recordingsimplifies analysis and supports one-hand operation
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
28/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Benefits for solar engineers / photovoltaic system fitters
System can remain in operation, does not need to be switched off for analysis
Identification of manufacturers errors after commissioning
Fast and meaningful defect detection
Well correlated with electrical measurements
Theuse of a telephoto lens allows an estimate to be made as to whether the system needs to be examined more closely
Invisible defects can be deteected
Comparison with reference images after commissioning
Ideal for evaluation when purchasing used PV modules
The use of a thermal imager is a MUST for all solar engineers!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
29/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
When should the solar engineer come to carry out the measurement?
Recommendation of a solar engineer to his customers regarding measurement frequency:
1. Testing directly after commissioning
Any defects can be eliminated right from the beginning
Good reference for later follow-on measurements
2. Testing shortly before the end of the guarantee period
Guarantee claims can be made if defects are discovered
• Regular tests in order to achieve the optimum effectivity of the PV system
• For evaluation purposes when purchasing used PV modules
The more regular, the more secure are the highest yields!
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
30/30testo AG,
Committing to the future
Div TI, vl, Photovoltaics training, 29.4.2011
Advantages for the manufacturer of the photovoltaic system
The use of a thermal imager is a MUST for every manufacturer!
Invisible defects can be detected
Fast and meaningful defect detection
Testing correct installation
Well correlated with electrical measurements
INNOTEC LLC (INNOTEK MMC), tel:+99455 6610664, +994124087047 email: sales@innotec.az, www.aztesto.com
Recommended