Unlike wine, which tastes better with age, most of the appliances degrade with time; and so does solar panels which are responsible for production of 3.6% of world’s electricity through solar energy in year 2021.
Have you ever had the chance to install solar panels in your home or offices, you would know by now that a standard solar panel warranty period provided by the solar panels manufacturers is 20 – 25 years. But does it mean that the solar panels completely degrade after 25 years? Or is it that they don’t degrade in the warranty time span at all?
Solar Panel Degradation
On average, solar panels degrade 0.5 % every year constituting to an average decrease of 10-11% in 25 years of age. That being said, the companies claiming warranties for first 25 years of solar panel’s life is because of this reason that lesser the degradation in first 20 -25 years, lesser the maintenance cost.
This also broadens the spectrum for understanding solar panels degradation after their stipulated life span. An average degradation value after 25 years of age is still expected to be 89% according to a study conducted by NREL.
Interestingly, world’s oldest solar panel is aged at 60 years. That being said, you may want to replace them after passing solar panel’s useful life to have electricity produced at a better panel’s efficiency and with a less degradation rate.
While you may brainstorm the reasons on what could be the factors for global solar panels degradation and how to effectively curb this situation, a much needed understanding is required on what exactly is solar panel’s degradation?
Solar Panels’ Degradation is a terminology defined when a constant average solar irradiance value per annum is maintained while having a fixed solar panels assembly, the corresponding amount of electricity generated by these panels is decreased every year.
Although a lot of work in this field is being done by the National Renewable Energy Laboratory and in many other research facilities available worldwide and so far the efficiency of solar panels have increased about 20% over the last five years. But there are multiple factors that still contribute to solar panels degradation despite new innovations in this field. Some of the factors outshine the others based on their severity and complexity and are highlighted in the next paragraphs.
Thermal Cycling
Lets recall what we all studied in structures in physics class as a child, Why do we make bridges with gaps in between them? So as to ensure, that during hotter months when the metallic beam expands, the gaps provide enough space to cater for the expansion.
Unlike bridges, solar panels are made up of tiny silicon particles intricately connected with each other. So what would happen if a solar panel is exposed to a temperature of 40 degrees? And later in the night when the temperature cools down?
This constant process of expansion and contraction owing to heating and cooling of the panels also known as thermo-mechanical stresses puts a strain on the surface thus causing micro cracks.
Light Induced Degradation
The solar panels frame is composed of 07 layers comprising of frame, glass, encapsulant, solar cells (internal circuit), encapsulant, backsheet and junction box. These solar cells in the fourth layer of the solar panels being composed of polymeric materials are highly susceptible to UV light.
It is because of the fact that in UV rays, the photons are of the highest energy, sufficient enough for breaking the main chain of the polymer assembly of solar cells. This degradation varies with the incident light and will be maximum under maximum sun light exposure.
Soiling
Soiling, a phenomena that has kept the researchers in the field of solar energy extremely busy. A phenomena that has constituted to various techniques in cleaning of solar panels. In simple words, soiling is the process of accumulation of foreign particles on the surface of solar panels. These particles range from algae growth to dust to bird droppings and to the air pollution.
When the particles are not removed from the surface of the panels using the cleaning techniques as advised for solar panels, they lead to the creation of a destructive phenomenon known as “hotspot”.
The solar panels being connected in series circuits will have the currents in all of the panels add up while having constant voltage across them. However, with the blockage of sunlight on the dusty panel, large reverse biased current on it causes “hotspots” to form leading to glass cracking and material degradation
Moisture
Solar panel degradation is majorly caused by unwanted moisture contents present everywhere. Moisture is present in all weather conditions starting from humidity, rain, dew, snow and ice. Each of them have a different but degrading effect on the health of panels.
For solar panel installed in the humid regions, the water gets absorbed by the surface and gradually starts hampering the module construction leading to material degradation.
Colder regions having extreme temperatures where the panels undergo freeze-thaw cycles, the ice on the panels cause mechanical stress on the solar cell and causes physical damage in the form of delamination of the panels surface.
Mechanical Stresses
Despite all of the precautions that are taken to protect solar panels against extreme weather conditions, it is understood that majority of these factors are unavoidable. For extreme cold and windy regions, a significant amount of mechanical stress is bored by the solar panels irrespective of having a protective encapsulate, back sheet and glass frame. Further, such solar panel degrade at a higher rate if already affected by solar irradiance and moisture.
Compatibility of Solar Panel System
There are some internal factors as well which also determine the lifespan of solar panels. Modern solar panels produce electricity at a higher rate as compared to the older ones. This is attributable to the factor on how the solar panel module was manufactured.
A key component in determining the rate of solar panel degradation is its manufacturing process. Most solar panels loose efficiency in the field because of poor processing techniques resulting in maximum failure.
Also, another major factor effecting solar panel life span is the compatibility of modules within the solar panel system. The encapsulant and the backsheet in solar panel need to have their designs matched with eachother. These two play the most important role in determining the reliability, stability and durability of the panels.
How to extend the life of solar panels?
Although degradation with the passage of time is bound to happen, there are number of measures that one can take in order to delay the degradation process in modern solar panel. One of them could be working with certified solar panel manufacturers so that during installation, the assembly is mounted correctly in order to bear the harsh weather conditions.
Similarly, while purchasing solar panels, higher quality panels having least amount of manufacturing issues will also ensure better solar panel lifespan with reliability, increased energy output and less solar panel degradation over time.
