Most common solar panel defects and how to deal with them

To keep solar cells safe, manufacturers protect them with a layer of tempered glass and the plastic back sheet. These layers are sealed tightly to prevent the internal corrosion. However, sometimes they separate which is called the delamination of solar panels. It leads to corrosion and eventually to the failure of a PV module.

The reasons for delamination can be different: bad workmanship, poor manufacturing, high temperatures. Delamination often takes place in tropical climates, and semi-flex panels are especially vulnerable.

Usually the process starts at one angle or a side of the panel and then spreads across the PV module. You can detect the start of delamination by bubbles and creases on the plastic rear surface. Some owners try using duct tape and sealant to slow the process down, but such a panel isn't going to last long. So, once you've seen any of the signs of delamination, contact your installer immediately.

Microcracks are one the most widespread solar panel problems. They often occur in case of careless shipping or delivery and caused by excessive pressure. Unfortunately for the owners of solar panels, microcracks are hard to detect with the naked eye.

There are several ways in which microcracks can affect your solar panel:

• There can be almost no consequences at all. If microcracks don't cause electrical separation inside a PV module, then the efficiency might drop by only around 2.5%.
  
  
• If electrical separation does occur, it makes a cell or even a sector of a solar panel inactive. In this situation, power losses are huge. Since cells within a module are interconnected, the failure of one brings down the others.
  
  
• Microcracks can also create hot spots: a damaged cell heats more than others under the sun. It decreases the lifespan of a panel in the long run.
  

Preventing cracks is easy: follow the guidelines for transporting solar panels, don't step or drop anything on them. However, you aren't always in control of the delivery process. If some of your panels have arrived broken, document all the damage and contact the store.

Hot spots can stem from overshadowing, dirt or microcracks. When the sunlight hits solar cells, it is supposed to be converted into electricity. However, if the resistance of one solar cell rises, this part of the panel heats up. This is the hot spot – overproportional heating of one cell compared to the others.

You can detect an emerging hot spot with an infrared camera only. Eventually, hot spots in solar panels become visible to the eye: the problematic cell becomes brownish.

Hot spots lead to a faster solar panel degradation and can even start a fire on your roof. To avoid that, clean your panels from dirt every now and then. Before the installation, carefully pick a place without any shade. If some shading is unavoidable, opt for panels with a high shading tolerance and bypass diodes, like Panasonic HIT 330W or REC 365W Alpha.

Snail trails or worm marks are short thin dark lines on the surface of a solar panel. Just to clear it up: they have nothing to do with actual snails. They may appear several years after the installation along the edges and, most importantly, where microcracks are located.

If you've discovered snail trails on solar panels, it usually means that the PV modules are of a low quality. Snail trails are the products of oxidation, often caused by microscopic cracks in the panel or defective front metallization silver paste, which is used in the solar cell manufacturing process.

Luckily, snail trails by themselves only impact the appearance of a module and don't have any significant impact on its efficiency.

Potential induced degradation or PID is a result of so-called stray currents, which appear when the module's voltage doesn't match the earthing. The effects of PID are worsened by high humidity, high temperatures and high voltages of a system, so it can lower the power output of a PV installation by a third. Potential induced degradation in solar modules almost never happens if you use microinverters: they don't allow the voltage to go too high.

There are no visual signs of potential induced degradation of solar cells and panels, but it can be detected with an infrared camera, electroluminance or photoluminescence testing. So, if you suspect that PID might take place – for example, you get much less energy than expected – invite an expert for an inspection. PID isn't a rare occurrence: in 2013, solar panels of 19 out of 23 global solar manufacturers were susceptible to PID, according to ISE Fraunhofer.

A large share of issues with solar power stem from wiring problems. A loose connection can lead to corrosion, energy losses and shorter lifespan of a system. If you've connected solar panels in series, problems with wiring may lead to the loss of power in the whole string. Careless connection of panels can create an open circuit where you're likely to lose a substantial amount of energy. It is recommended not to try to deal with electrical issues of solar panels yourself – better call a certified electrician for help.

Surprisingly, solar panels are quite popular among birds and squirrels. They find the space between PV modules and roof to be perfect for their nests. It's needless to say that animals can effectively mess up the wiring of solar panels, damage important parts and, finally, bird droppings are hard to remove. If you find birds nesting under solar panels – call critter guards, no exceptions. Some companies, like BirdBarrier, offer metal nets that minimize the chance that some pigeons would settle down under your panel. Don't get us wrong, we love animals, but the solar panel protection comes first for us.

If you haven't purchased solar panels for yourself yet, don't let this list discourage you. The problems mentioned here might or might not happen to you, and most of them aren't fatal for a solar installation. Solar panels are a long-time reliable investment: the average life of solar panels exceeds 25 years. They can even survive a hurricane. What is true for all PV modules is that their power output naturally decreases with time by about 0.8% a year. It's called solar panel degradation. This is why most companies provide performance warranties, ensuring that the power output won't drop below a certain level in the future. With some brands like Silfab this warranty is issued for 30 years.