Understanding the degradation phenomenon in solar panels

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Understanding the degradation phenomenon in solar panels

Some things get better as they age, but there are also things which get deteriorated as they have a finite life span i.e. the machinery and electronic devices. Even the extravagant investments like houses, farms and solar bear the brunt of time.

So, before switching to solar, investors should understand the lifecycle of the solar modules. You should be able to weigh the pros and cons of solar investment. It will help you in comprehending how long the solar system will last, the effect of time on panels and what you can do to make the most out of your investment.

The “useful life” of the solar solution solely depends on the manufacturer, the type of raw material used and standards of quality measures followed during the production process. Manufacturers offer a guarantee of 25-30 years, but panels are likely to perform even after that, if they have exceptional quality.

But, just like other equipment, solar panels also can’t perform at 100% capacity for their entire operational time. Rather, at a very slow rate, the energy harvest ability reduces as the solar modules age – this phenomenon is called degradation.

Solar panels degrade over time, meaning their energy generating potential reduces, they produce less electricity from the same amount of sunlight. There are several external factors which contribute to that and affect the overall power production.

In this blog, we will discuss the various types of panel degradation and their effect on the solar system. Let’s begin!

Microcracks

The most common degradation seen in panels is microcracks. They develop on silicon of the solar cells because of the thermal cycling process. In hot weather, things expand and in cold weather, they contract.

Solar panels are not immune to endure these frequent weather changes. The constant expansion and contraction phenomenon put them under strain and then they form cracks.

Due to these microcracks, the electrical connections collapse in the module. There are only a few paths to travel for the electrons from the sun and that influences the low energy yield to power your business, farm and home.

Solar panel discolouration

The brown and yellow pigment on modules develop due to Ethyl Vinyl Acetate (EVA). A result of an uncontrollable chemical reaction from materials within the panel.

EVA browning occurs when several additives, used to avert the browning and strengthen the UV tolerance, begin to disappear after losing strength against UV rays. This usually happens because of poor storage and handling conditions, causing bleaching and blistering of the EVA film and the back sheet which set off corrosion in the cell.

The two main causes of discolouration in EVA are;

Acetic acid formation: It is the prime reason for solar panel discolouration. As per the studies done in the solar industry, acetic acid turns EVA encapsulate yellow. It mainly occurs on the PV cell surface in a chemical reaction involving the chemicals used in silicon solar cell surfaces and chemicals used in treating the glass.

As this yellow discolouration occurs, the UV absorbers break down and the percentage of cross-linked polymers increases. The formation of acetic acid is the prime reason for the module’s inner layer discolouration.

Sun exposure: The back-sheet of the panel is designed to resist the harsh UV rays and to prevent the browning. When the poor quality of raw materials used in panels, the structure of EVA changes when exposed to UV radiation and temperature. As a result, it initiates the process of discolouration.

Besides the aesthetic issue, discolouration affects the output and decreases the module performance due to high absorption in EVA film as shown below ;

This is why you should invest in panels with promising quality standards. Buy panels from manufacturers that follow a relentless back-sheet qualification procedure, as back-sheet is generally the first component to break down in UV exposure.

LID (Light Induced Degradation)

 

The degradation which transpires in the initial few hours of sun exposure, without the flow of electrons across the p-n junctions is known as LID. If left untreated, LID can reach up to 10% in the first month itself.

After that, power stabilization happens, which indicates the lower level of performance loss in subsequent years of usage.

During the manufacturing process of PV cells, manufacturers tend to make use of PERC (Passive Emitter Rear Cell) technology to do mass production of solar cells with efficiency above 20%. But they utilize the same machinery for that with minor adjustments.

The presence of defective Boron-oxygen complex in the wafer used during the production of PV cells can be accredited to light-induced degradation. It affects 90% of the silicon wafers prepared through the Czochralski process. LID is one of the most discussed reliability indicators, as it ensures that the solar system can sustain outdoors.

There are three categories of LID;

  • BO-LID – which occurs due to boron oxygen complex
  • LeTID – Light elevated and temperature-induced degradation
  • UVID – which happens after UV exposure.

LID naturally develops as a stabilization procedure, primarily for the p-type solar cells and light intensity exposure of panels defines the speed of the stabilization process. Whereas in LeTID phenomenon, module operating temperature plays a vital role to regulate at what speed the phenomenon may develop.

To combat the adverse effect of LID, installers use the “re-cooking” process of the solar cells to reduce LID to zero. If the module is kept at 200 degree Celsius for 30 minutes, the defected boron-oxygen complex can be separated.  Although the regeneration process may vary depending on the quality of wafer used.

PID (Potential Induced Degradation)

PID  is an unwanted degradation effect on solar modules caused by factors like voltage, heat and humidity. Most modules are vulnerable to face the combination of these factors during their operational time.

In a solar project, multiple panels connected in an array are called a string. A string has two sides – negative and positive, connected through an inverter which produces AC voltage. If we compare it with the ground, the voltage has a negative and positive potential. The negative potential triggers PID in a solar cell. Usually, photons let electrons flow towards the cell’s connector and generate the current.

However, the negative potential attracts positive ions in the cell such as sodium ions which stimulate surface polarization and shunting. The movement usually happens from the glass plate through the encapsulation and the anti-reflective coating to the cell. The electrons then stop flowing and generate electricity which results in a disruption in a junction functionality meaning the decline in the power capacity of the panel.

A thermal image of solar strings showing signs of PID, the strings on the left side are less affected than the strings on the left side. 

Another thermal image representation of advanced level of PID

 

After a few weeks or months, PID occurs at the entire negative side of the string. The most negative panel loses 30-80% of its yield. PID is contagious, more cells get affected by it over time, it turns the cells black. The speed of PID depends on – the system voltage, humidity levels and cell temperature. It can be reversible or irreversible. Therefore, it has devastating effects on all installation levels of a PV system – financing, operations and economies. The solar investor must address PID effects in the early stage to ensure the PV system works well in its entire life cycle.

The performance loss in PID is up to 20% or more in the initial few months. Panels which are affected by PID, contain non-functional black cells (often from the negative pole side) which are typically found near the frame. It emerges because of the massive flow of electrons through such solar cells and the difference of voltage across the panel.

How can you increase the life expectancy of panels?

Generally, panels degrade at a rate of 1% each year. While they lose their production capacity to LID in the initial few hours, the degradation reduces drastically for the remainder of their lifecycle.

The degradation is unavoidable, it will happen to panels sooner or later. Your best line of defence against degradation is to use products from a trustworthy manufacturer who is also a certified expert.

Even when you buy high-end products which can survive in any weather conditions, they could suffer a lot during a rough installation.

Choose an installer who provides you panels which promise high-performance, does location analysis and handles the panels with the utmost care during installation. With that, periodic maintenance can aid in extending the lifespan of modules.

All things considered

To fight these various degradations, Novergy with its continuous R&D, innovation and up-gradation, has introduced monocrystalline and polycrystalline panels with PERC cells and 5 bus-bars. Our panels eliminate the light and  temperature-elevated degradation without compromising on performance and quality in the solar cells . Our panels are sturdy and reliable to function in harsh weather situations. We are an integrated player with in-house expertise in designing, engineering, production and installation.

Owing to the unavoidable panel degradation, many manufacturers warranties tend to change as the solar system gets older. As per the standard warranty, in the first decade, manufacturers typically guarantee 90% of panel production. After that, the production performance drops down to 80% for the rest of the 15-20 years.

We offer a 25-year of linear warranty on all our products, meaning for the first year, panels will maintain at least 98% of their rated power. Subsequent to the first year, the solar panels would not exhibit degradation of greater than 0.67% per annum. You can derive greater value from your investment as the panels will keep up their power output.

With Novergy, you can be rest assured your investment is safe. Accomplish your financial goals and get complete energy independence! To explore our solar solutions, visit novergysolar.com now!

By | 2020-07-29T10:57:11+00:00 July 29th, 2020|Solar Modules, Solar Panels|Comments Off on Understanding the degradation phenomenon in solar panels

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