How Microcracks Damage Solar Panels

Written by Tony Chang

November 30, 2020

How Microcracks Damage Solar Panels

As part of the common solar panel defect series, we will be looking at solar panel damage caused by microcracks in this article.

You will learn about the typical causes of microcracks in solar panels, and all the different ways to prevent microcracks from degrading the energy production of your rooftop solar installation.

What Are Microcracks?

Microcracks are tiny fractures on solar cells that are invisible to the naked eye.

Even though you cannot see microcracks, but they are indeed broken solar cells held in place by the solar module laminate.

As the module bend and flex due to external pressure, the fractures on the cells stop conducting electricity, causing degradation in the damaged solar panel.

What Cause Solar Cells to Crack?

Solar cells are thin and brittle by design, no more than 170 micrometres in thickness, and they break easily without the protection of glass, EVA, backsheet and frame, other key components of a solar panel.

While solar panels improve the survivability of solar cells in the field, when large mechanical stresses, such as wind and other impacts, cause the panel to bend, the solar cells can break, leaving traces of cracks invisible to the eye.

How Do Microcracks Damage Solar Panels?

Microcracks can reduce the energy output of solar panels.

A perfect solar cell can absorb sunlight across its whole surface, and convert the light into electrons that flow out through the nearest ribbon.

When microcracks appear, the shortest path between any point of the cell to the nearest ribbon can be interrupted by the crack, ceasing the flow of electrons.

When the electron flow stops, areas of the solar cells become inactive, and the power output suffers.

solar panel microcracks
EL picture of microcracks on solar panels due to poor handling practices.

Inactive solar cell areas can be easily detected through EL, where the brightness correlates positively with the conductivity of solar cells, with microcracks and other defects marked as dark areas.

A new, perfect solar panel should appear uniformly bright in EL, while a weathered and beaten old solar panel with scattered dark areas of microcracks can reduce power output as much as 20%.

Can a Damaged Solar Panel Be Repaired?

Solar cells, glass, EVA and backsheet are heated and fused into a waterproof laminate during manufacturing, and they cannot be separated without causing severe damage to the solar cells.

So when cell cracks start to appear inside a panel, there is no easy way to replace the broken cells without destroying the solar panel.

Once microcracks appear in the solar panel, the power output can only get worse from here.

So the best way to keep your solar panel energy production high is by preventing microcracks in the first place.

How to Prevent Microcracks in Product Design?

Microcracks are usually created by external impact to the panels, so a good way to prevent microcracks in solar panels is to toughen up the overall product by design.

Key components that add strength to a module are glass and frame.

By choosing the tempered glass that can withstand the impact of advanced hailstone tests, WINAICO modules can withstand the collision of 35 mm ice balls launched at 100 km/h.

This advanced test contains more than 4 times the kinetic energy of standard IEC hailstone tests and makes sure WINAICO systems can survive the impact of stray golf balls.

WINAICO modules’ frames are constructed using L-shaped corner keys to lock frames in place, and can withstand up to 5400 Pa of mechanical load, more than 900 kg, and spread evenly across the panel.

WINAICO’s sturdy solar module design reduces the possibility of microcracks in well-maintained solar installations, and make sure your system continues to perform even in harsh weather conditions.

How to Prevent Microcracks During Production?

Despite high precision and finely tuned production processes, the heat and pressure experienced by solar panels during manufacturing can occasionally leave microcracks in panels.

A great way to prevent microcracks from shipping out the factory is by adding multiple EL stations in the production line and just before the panels go out the door.

solar panel EL inspection
A quality inspector checks the EL picture for defects.

This way, all our customers receive perfect WINAICO panels free of defects.

How to Prevent Microcracks During Transport?

Transportation, if done incorrectly, can create microcracks in panels.

We see examples of installers strapping inverters and toolboxes on top of a solar panel stack, which we suspect could cause microcracks.

An experiment was performed internally to measure the impact of incorrect transportation:

  • A 5 kW inverter weighing 31 kg was placed on top of a 320 W module.
  • A forklift drove the pallet carrying the module and inverter around the car park at 10 km/h.
  • Total distance travelled, 1 km.
  • The module power was measured before and after for comparison.

transport inverter on solar panel
An experiment of transporting an inverter on top of a solar module that can cause microcracks.

The before (323.9 W) and after (316.0 W) power measurements showed a -2.44% decrease in module output.

If travelling 1 km at 10 km/h can degrade a panel’s output, imagine how much solar panel damage a 30 km drive through a bumpy country road at 50 km/h can do.

How to Prevent Microcracks During Installation?

Do you know there are wrong ways to carry solar panels up the ladders?

Our team investigated the impact of leaning your head against a solar panel as you climb up the stairs/ladders, to see if you can cause microcracks:

  • A module was carried up 24 steps of stairs with the glass against the shoulder/head.
  • A module was carried up 24 steps of stairs with the backsheet against the shoulder/head.
  • The module power was measured before and after for comparison.

carry solar panel up ladder
Incorrectly putting shoulder and head against the panel during the climb caused 1% power drop.

The before and after power measurements showed between -0.97% (leaned against the glass) and -0.86% (leaned against backsheet) decrease in module output.

The correct way of carrying the panel is to balance the weight in your hands against the panel frame.

Knowing how to carry the panels without putting pressure on the solar cells is the first step in a quality solar installation.

correct way of carrying solar panel
The correct way of carrying a solar panel.

Can You Walk on Solar Panels?

No, you cannot walk on solar panels in any circumstance.

Despite the sturdy construction of solar panels, when frames and glass flex under the weight of an adult, the concentrated pressure on ones’ feet can still break solar cells and damage solar panels.

The following video from NREL illustrates solar panel failure by microcracks with the aid of EL.

We recommend leaving enough room in rooftop solar designs to prevent walking on panels during installation and maintenance.

How to Detect Microcracks After Installation?

The most efficient way of detecting solar module defects onsite is using infrared cameras to monitor the temperature differences on the module surface.

When the sun shines on a damaged solar panel, the cracked cells become a high resistance region with a higher temperature than surrounding cells.

An infrared camera can efficiently point out areas with high-temperature differences, and alert the maintenance team to actively troubleshoot the suspicious panels.

Now you know microcracks can reduce the power output of a panel by 3% in the short term and up to 20% in the long run, it’s very important to adhere to the correct solar module handling practices to create a perfect solar installation that lasts for a long time.

To learn more about how WINAICO solar technologies can help with your rooftop energy production, please get in touch with us.

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