Broken glass
No value at all, panel is recycled.
Moister enters and affects PV cells, expanding the damaged glass surface. Only option is to recycle the panel.
Isolation
error
Depends on the level of the isolation error.
A PV isolation fault is usually an earth fault on the DC side (the PV panels side) of the system which is usually caused by moisture ingress or damage to the system or the panel.
1. Low.
2. Medium.
3. High.
Delamination
Delamination of a PV panel is the detachment, even if partially, of the encapsulant from the glass or the backsheet.
Different types and levels:
1. Bubbles inside modules.
2. Low isolation resistance.
3. Ribbon / busbar corrosion.
4. Forming a continous path between any part of the electrical circuit and the edge of PV panel.
Backsheet
cracks
Backsheet cracks is the degradation of the outermost “layer” of a PV panel and occurs at different stages.
Stage 1: Not visible yet, backsheet gets pouros.
Stage 2: Beginning of cracks – light impact.
Stage 3: Full cracks around the cells.
Stage 4: Backsheet disintegrates.
Snail
trails
Snail trails are discoloration of the PV panel, which builds up over years of power production in the field. Moister can enter through the back sheet and diffuse to the cell surface.
Different levels:
1. 1-3 cells affected.
2. 4-6 cells affected.
3. More than 6 cells with snail trails.
Dust
build-up
Accumulation of dust on the surface of the PV panel.
Reduces the glass cover transmittance and hence decreases the amount of solar irradiation reaching the cells.
Cracked
cells
They are triggered by mechanical and chemical environmental factors causing stress to the PV panel during operation.
Further stress factors are geared to the thermal cycles of the cells involving contracting, expanding and flexing metal contacts, solder and wire interconnects.
Poor
string
connection
Failures due to improper installation and operating stress are both avoidable.
Inadequate wire terminations, undersized conductors, environmental conditions that are outside of the equipment rating, inadequate protection from surge voltage and inadequate protection from physical damage.
Potential
induced
degradation
Potential induced degradation (PID) is a performance degradation in crystaline PV panels.
Caused by so called stray currents. This effect may cause power loss of up to 30%.
Chalking
Polymer degradation in paints and coatings affecting reliability and performance.
Backsheet chalking is a failure mode of field exposed PV panels and is observable as a white powder on the outer backsheet layer.
Hot spots
Hot spot heating occurs in a PV panel when its operating current exceeds the reduced short circuit current (Isc) of a shadowed or faulty cell or group of cells.
When such a condition occurs, the affected group of cells is forced into reverse bias and dissipates power, which can cause local overheating with different levels:
1. 1-3 cells affected.
2. 4-6 cells affected.
3. More than 6 cells with hot spots.
Junction
box
The junction box of PV panels fails in the field mainly because of fault current passing through the junction box.
The main failures of junction boxes are:
1. Burnt bypass diode.
2. Burnt off junction box.
3. Lost connection.
4. Malfunction.
5. Connection cable cut / broken.
Micro
cracks
Micro fractures, also known as micro cracks.
The silicon used in the PV cells is very thin and expands and contracts due to thermal cycling. During the day, the solar panels expand because of higher temperatures.
Holes
Different types of holes.
Moisture enters and affects PV cells.
Holes tend to expand and get bigger.
Scratches
Damage or scratches will result in a reduction of efficiency.
The wrong cleaning tools and improper cleaning methods can scratch PV panels or make the glass cloudy.
