Solar Panel Lifetime – How long do solar panels last

Solar Panels last for a minimum of 25 years, but that does not mean the panels will stop producing energy after 25 years. The Solar panels will still produce appreciable energy for a couple more years till they start degrading significantly.

how long do solar panels last
How long do solar panels last

This is a recurring question installer hear from Homeowners are, how long do solar panels last once I buy and install? The customer is looking at different options to buy during the sales process, whether to buy a polycrystalline or a monocrystalline solar panel.
It is a truly relevant question when you are thinking of spending a couple of thousands of dollars on getting electricity for your house and plan to use it as the main source to generate electrical energy.
This article on how long your solar panels last will explain how to keep your solar panels producing the optimum energy as prescribed and what causes the degradation in the panel and how to prevent it.

Solar Panel Degradation

According to NREL[1], solar panel degradation rates are accurate quantification of power decline over time. Degradation rates are significant because they will predict power delivery during the panel’s lifetime accurately and is essential to all the stakeholders involved – utility companies, investors, and researchers alike. Few reasons encapsulate why the degradation of solar panels is important.

  1. The higher degradation rate of Solar panels results in less power and thereby results in reduced cashflow.
  2. Understanding the rate of degradation and the causes of degradation results helps us to determine the cause of failure.

Although other factors also contribute to the electricity production of solar and the life of the solar panel, e.g., climate, module type, and racking system. It is primarily the degradation factor that matters the most. Solar Panels, in general, have a 0.5% degradation rate year over year. Still, it is mainly on the higher side in hotter climates and for rooftop systems. A degradation rate of 0.5% per year means that by year 20, the module will produce 90% of the electricity in year 20 compared to year 1. However, solar modules are warrantied to produce electricity till year 25, but beyond that, the output level is no longer guaranteed. Although this may sound good for a homeowner, a 20 or 30 panels system is still producing electricity after 25 years at 90% of its original capacity; it is not the case for large-scale solar farms like utilities and commercial. This translates to a significant decrease in power output and cash flow, which will ultimately be the time to retire those panels.

What Causes Solar Panel Degradation

A typical solar panel is made of four different materials: Glass, metal frame, silicon semiconductor, and polymers.

  • One of the most common types of failure that is induced in solar panels is Climatic Stress. Although solar panels need to be exposed to sunlight for solar irradiation to create the electron-hole pair that generates electricity, much of the solar irradiation is absorbed by the solar panels and dissipated as heat, and the high energy radiation, like the Ultra-violet irradiation, can cause the degradation of the polymers (Back sheet on the panel and Humidity is another factor that can impact the performance of polymers. As a result, it can affect the solar module’s output and especially when the humidity enters the solar module sealed package and reaches the metallic elements within the package.
  • Humidity freezing causes the junction box adhesion to fail.
  • Hail can have an impact on the solar panel. Although solar panels can withstand hails, a certain hail size or bigger can have an extremely high local on the module’s performance, depending on their size and velocity.
  • Salt concentration can cause corrosion of the metallic components within the solar panels and the back sheet. Hence, there are high chances of solar panels failing near the coastlines.
  • Acidic corrosion can happen if solar panels are installed close to roads and industries. Hence, they are exposed to certain types of gases, like g. O3, NH3, SO2, NO2, H2S, Cl2.
  • Some of the other unavoidable factors that can affect solar panels include thermal cycling, damp heat, humidity freeze.
  • The silicon in the solar cells is wafer-like material. It can expand and contract due to thermal cycling, i.e., temperature variation between night and day. During the daytime, the solar cell expands because of higher temperatures, making small imperfections in the silicon cell that can lead to larger micro cracks. The length of micro-cracks can vary; some span the whole cell, whereas others are in certain sections. Thermal cycling can cause solder bonds to fail.
  • Damp heat has been associated with the corrosion of the solar cell and the de-lamination of encapsulants.
Aged PV Module after Damp heat test (left) vs unaged
  • In addition to this, there is a chance that an inverter can contribute to the degrading factor. The use of transformer-less inverters has increased potential induced degradation (PID) for solar panels. Potential induced degradation (PID) happens when different components of the solar panels are at a different voltage, such as the frame and the solar cell, which results in the leak of electric current. Hence, the module starts to lose its peak performance. This can be avoided if the system is negatively grounded, but transformer-less inverters are ungrounded. Frameless modules can help to reduce the PID possibility because there is no metal frame to disrupt the voltage.

Certain module manufacturers try to lower their prices by making their frames thinner by adding less aluminum. As a result, stress is induced on the solar panels, e.g., when the snow melts. As the temperature drops again, it refreezes on the edge of the solar module, which can strain the solar panel. As a result, the panels can become less mechanically robust and cause the solar panels to fail.

Another reason why solar panels fail is because of busbar solder bond failures. With more busbar and solder bonds, there is a high probability of failure. But with more than one solder bond failure, additional busbars can pick up the slack.

Based on the research done in the last decade by the Fraunhofer Institute for Solar Energy Systems, Heidenhofstrase, Germany [2], the Following are the most common failures that have occurred during operation

  • Yellowing/browning of encapsulants and back sheets with and without power loss
  • Delamination of encapsulant and back sheet
  • Bubble formation
  • Oxidation of busbars
  • Discoloration of busbars
  • Corrosion of connections
  • Cracking of back sheet
  • Hot spots
  • Cell breakage
  • Micro cracks
Hot Spot Tests – Bubble formation on the front side (left), Bubble formation on the front side (middle), Disintegration of Polymers after hot spot test (right)

Although, some of them have effects on the electrical characteristics of the PV module, like increasing series resistance. While others, like Microcracks and cell breakage, have a higher impact on performance.
In the years between 2006 and 2009, the research concluded that hot spot test (HS) with a failure rate of 20%, followed by mechanical load test at 17%, humidity freeze (HF) at 16%, Damp Heat Test at 15%, and finally thermal cycling at 7%. These 5 tests were responsible for 75% of all PV module failures in the 105 projects conducted by the researchers.

Exposed Connector on a Solar Panel

How long do solar panels last and Can you extend the life of your solar panel?

There are few ways by which a customer can extend the life of your solar (PV) panels.

  1. Get well-known solar installers in the area with all the required licenses to ensure that you get a clean install. This is necessary because, without a clean install, there are high chances that you may not be able to get optimum solar output.
  2. Once installed, the customer can buy solar panel monitoring devices that monitor the solar electricity generation daily or monthly.
  3. Understand the amount of electricity generated by the Solar (PV) panels monthly because this will help you determine if there is any drop-off in the production.
  4. Do a regular yearly maintenance check on the solar PV system, like any HVAC system or so, because it will enable you to catch any issues early on, like any wiring getting burnt or damaged, or if the inverters are overheating, etc.
  5. Keep your solar panels clean by spraying them down with water if they are dirty. This will eliminate any false notion of lower production. Also, debris like dust and sand can cause micro-cracks on the panels and multiply into bigger cracks.
  6. Ensure to clean off the snow left on the panels because any regular freezing or thawing can affect the solar panels and create micro-cracks in the extreme cold. Also, the undue pressure from the freezing of snow can cause the glass to break.

Ensuring to follow the steps mentioned above will help reduce the strain on the solar panels and take precautionary measures in advance if something goes awry.

When is it time to replace the solar panel?

The good news for customers is that based on the NREL Researchers, the median solar panel failure rate is around five panels out of 10000 annually for installations between 2000 and 2015. While, for panels installed between 1980 and 2000, the rate was twice as high. Generally, well-built Solar panels have demonstrated reliable performance for 30 years outdoors. As a result, manufacturers have provided a reliable 25-year warranty for these modules. As a result, all-weather damages associated with any panel failures can be recouped by contacting the manufacturer for any weather-related issues.
So, if the customer notices any drop off in the solar production via the monitoring system, make sure you contact your solar installer to get replacement parts necessary to keep your system running with ease. Also, the solar installers can contact the manufacturers or dealers for any replacement of the solar panels. Also, note that some installers only provide a 5 – 10-year warranty for workmanship. So, if any damage happens to the solar panels beyond that period, you will need to contact the manufacturer for replacement parts.

Should you replace your solar system after 25 years?

Solar energy systems keep producing energy after 25 years provided, they are well maintained, but it is important to note, though they are maintained they will not be as efficient at energy production cause the cells have 0.5% annual degradation rate. After 25 years, it is expected that a well-maintained system will produce energy at 90% capacity as to when it was installed.

If the system is not producing enough power as per the technical specifications outlined, it might be a good time to replace the panels. If some of your solar panels are broken and the rest of them is functioning quite well, it would be a good time to replace those panels. Working with a reputable installer is the best way to go about replacing those panels. [3]

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