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Understanding solar panel degradation

Francisco CastroMay 21, 2019 1324 0

Understanding solar panels degradation

Ever bought a brand new car at a dealer just to see it drop in value as soon as it drives off the lot? It’s called depreciation and according to CarFax, vehicles lost more than 10% of their value during the first month after you drive off the lot. And it will keep falling, as much as 20% after the first 12 months of ownership.

Cars depreciate because they’re no longer in pristine condition as you drive it, their parts now working and -as with any machine - losing their brand new capabilities with each mile you put on it.

Solar panels suffer a somewhat similar fate, but in their case, it’s not depreciation, but degradation.

It’s basically a decline in output that all solar panels experience over time. And it’s inevitable.

On average, solar panels decrease 1%-3% in output the first year and about 0.5% per year after that. Why such a sudden drop in the first year? Simply because they are finally exposed to ultraviolet rays and real weather.

It is called “Light Induced Degradation” and it occurs during the first few hours when the solar panel is in use.

All solar panels degrade, but not all degrade at the same rate.

This means that if a panel experiences a 3% degradation in the first year, it will be operating at 97% of its labeled efficiency in its second year. Assuming a 0.5% degradation every year after that, by year 25 - the expected lifetime of a photovoltaic (PV) module - it will still be producing at 86% capacity.

That loss of power might not seem substantial, but it equates to hundreds of kilowatt-hours lost every year, depending on the number of panels in your domestic solar power system and how long they’ve been generating electricity.

That’s why it’s important to select higher-quality panels that degrade more slowly.

It is also important to size your home solar energy system correctly to match your electricity needs now and into the future, so that the drop in electricity production won’t affect you in the long run.

If you don’t know what the correct size of your solar power system should be, you can easily find out with the Hahasmart price checker. Just provide your address and your average monthly utility bill and you’ll get the actual price of solar panels and inverters - which are the most critical parts of a solar powered system - as well as provide you with an estimated cost of installation based on thousands of completed solar projects in your area.

They’ll even provide you with an estimated buyback period, the point where the electricity savings achieved with your solar array cover the purchase of your residential solar panels and your system becomes free.

In addition, they’ll connect you with their installer network to get your residence equipped with solar power as possible.  

Causes of degradation

Solar panels are extremely reliable and strong, but exposure to the elements is the most common cause of degradation. High winds and humidity, scorching hot weather and freezing snow storms may contribute to faster degradation.

Humidity and moisture are especially problematic because they significantly increase metal corrosion and breakdown of plastics in solar panels. When water vapor seeps through a typical module’s backsheet and into the panel, acetic acid is formed. This acid weakens the bonds of the front-side silver contacts and rear-side aluminum metallization, which decreases the ability to carry a charge and decreases performance.

Sudden and dramatic changes in weather and temperature also affect Thermal Cycling, the alternate heating and cooling of a material. Due to differences in temperature between day and night, Thermal cycling occurs at least one time per day in the life of a module.

Another culprit is dust, pollen and dirt accumulation. You should clean your residential solar panels regularly to keep them working at their top peak. Also check them annually for physical damage, such as trees or branches that may have scratched them.

You should also conduct a routine maintenance check by your solar installer to make sure all the parts, connections and wires in your home solar energy system are working properly.

Types of degradation

Solar panel degradation can take on many forms.

It could be a “hot spot,” where cracks in the solar cell leads to a discharge of power in the form of heat. It leads to cells becoming inactive.

Another form is “snail trails,” linear discolorations on parts of the solar cell surface that will also cause hot spots.

There’s also interruption of/or between cells often brought on by expansion of high temperature, hailstones and damage through production and assembly.

In addition, it could be caused by problems in the wiring that connects the solar panels.

Something else is “delamination”, when imperfections or damage to the lamination that covers solar panels occurs.

The solar industry acknowledges degradation, and that’s why solar panel manufacturers account for it in their warranties. The guarantee is that panels will produce electricity at least at 80 percent of their original capacity at the end of the 25-year warranty period. 

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