Let's fix it: find the cause of solar underperformance

Francisco CastroMay 7, 2019 2259 0

Find the Cause of Solar Underperformance 

A recent entry in an online message board dedicated to solar power questions presented this situation: “My SolarEdge inverter is rebooting nearly every day at 11 am. Note that it happens other times as well, just not as often. I know, pretty weird. The system is just over a year old and this only recently started happening (couple of months).”

The person says SolarEdge - the inverter manufacturer - blamed his installer for the problem, while his installer is blaming a combination of his utility’s smart meter and SolarEdge’s fault detection algorithm. 

“I suspect the production loss is minimal but this can't be good for the inverter's lifetime. I'm trying to figure out what I can do and to make someone take ownership of this issue. Any thoughts?,” he continued.

Identifying small problems early is critical to maximizing the long-term revenue of a solar power system. Even at pennies per kWh, when considering one bad cell in one module, the math over the life of the solar array can translate to tens of thousands.

But figuring out what the problem is may not be easy. 

Solar panel faults

Solar panels are very reliable and long-lasting, but this doesn’t mean they’re exempt from faults. Microfractures, also known as microcracks,  are small cracks that can appear in solar cells that represent a form of solar cell degradation.

Some microfractures can span the whole surface of the panel, whereas others appear in only small sections of a cell. These cracks can affect both energy output and system lifetime of a solar PV system.

Microfractures occur within cells and cannot be fixed without replacing the module. The potential causes could be extreme variations of temperature between night and day, humidity and freezing, heavy snowfall and hail. 

Another problem is degradation, which is harder to tell and requires an analysis to diagnose if the panel is producing less energy than it should. A solar panel's performance warranty will typically guarantee 90% production at 10 years and 80% at 25 years. An equipment warranty will typically guarantee 10-12 years without failing.

But the problem could be as simple as the positioning of the modules on the roof. In the Northern Hemisphere, they should be facing south. The pitch or tilt is also something to take into consideration. The installer should consider both of these factors when designing the layout and actually placing the panels on the roof. 

And let’s not forget shade, either partial or complete, which can adversely affect energy production. Homeowners need to make sure there is no obstruction between the panels and the sun. 

Inverter faults

As in the case of the question above, the problem could be the inverter. This piece of equipment, the brains in the solar power system that convert the DC (direct current) energy generated by the panels into AC (alternating current) that is used by appliances, have a much shorter life than the modules and is often the problem. 

Inverter faults account for almost 50% of major solar system failures. Typically when an inverter fails, the whole system shuts down and produces zero energy. There are many potential causes of inverter failure, and these will generally require a qualified solar electrician to rectify the issue. Fortunately, inverters have a 5 to 10-year warranty, so you should be able to get these faults fixed for free under warranty.

The problems can range from inverters that have been installed incorrectly, to their incorrect programming. 

Another issue may be overheating. Inverters have sensible electronic components and high temperatures may affect their production or functioning. That’s why its recommended they are placed in a garage or other area with plenty of ventilation and free of humidity or exposition to the elements. 

Isolation fault is another problem that could affect inverters. This occurs as a result of a short-circuit within the system. In these cases, the inverters will report an “isolation alarm.” 

A grid fault can also trigger a problem with the inverter, which should be able to restart on its own following a problem, such as voltage peaks in the electric grid.

Resolving the issue

The best advice when you notice any type of diminishing energy output from your solar power system is to call the installer who worked on your installation to conduct a test of the panels, wiring, and inverter. 

A thorough assessment as soon as possible is best to prevent further damage and/or correct the problem. Once the issue has been determined, it could be as simple as calling the manufacturer to get a new product if it's still under warranty.

Time is money when it comes to solar production. The less electricity your solar power system generates in a day, the longer the payback period when your installation will be paid off and you can continue reaping the benefits of solar for years to come, this time completely free. 

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