Three reasons explain why one in five solar panels deteriorates and fails prematurely, a new analysis has found.

(image: AI generated via freepix)

In their latest paper, a team from the University of New South Wales has analysed data in respect of 11,000 solar panels from around the world.

The research aimed to determine the rate of solar panel failure and to identify common causes of early panel degradation.

Across the data set, the report found that on average, solar panels degrade by around 0.9 percent per year.

This means that average panels are still operating at 77.5 percent performance by the end of the 25 years over which most systems are designed to last according their warranty period.

However, a significant number degraded much faster than this.

Indeed, according to the research:

• At least one in five (20 percent) of the systems that were analysed degrade at a rate which is at least 1.5 times faster compared with the typical rate. This reduces their useful life from 25 years to around 18 years.
• As many as one in twelve systems degrade at twice the average rate or more. These systems lose up to 45 percent of their output by the 25-year-mark. Such degradation could slash their useful lives by more than half from 25 years to 11 years.

The analysis comes as solar power forms a critical part of Australia’s clean energy transition.

In the latest edition of its Integrated Systems Plan published late last year, the Australian Energy Market Operator called for a five-fold increase in the amount of installed capacity of utility-scale solar as well as wind assets across Australia between now and 2050.

This will see the installed capacity of utility-scale solar/wind generation increase from 23GW to 120GW over that timeframe.

By that time, AEMO hopes that the nation will also have 87 GW of installed capacity in rooftop and other small scale solar.

The research also comes amid concern that early panel degradation may compromise both the cost and performance of solar power generation.

With large-scale solar farms requiring hundreds of millions of dollars in up-front investment, unexpected costs in terms of repairs or module replacements in the event of premature degradation pose a significant concern to the viability of these projects.

Causes of failure

In their study, the researchers found that three common factors are responsible for most cases of solar panel degradation.

These are:

• Interconnected failures. This occurs where different types of problems interact with each other on a single panel. For example, consider what would happen if the backsheet (a protective layer on the rear of a module) is damaged. Potentially, this could lead to moisture getting in and could possibly result in a failure of the electrical junction box and other problems such as cell cracks or corrosion. This creates a domino effect whereby combinations of individual problems multiply. It can lead to panels degrading much faster than predicted.
• Rapid failure of new modules. A second reason for failure is rapid failure or modules which are relatively new. Whilst most newly installed modules tend to have a slower rate of degradation, a small number fail rapidly after installation. These typically have manufacturing defects or material flaws which have not been discovered during quality control or testing.
• Minor flaws. Finally, some modules fail as a result of minor flaws which may not cause a problem initially but may subsequently result in a sudden, severe performance loss at a random point. Examples might include a tiny hairline crack in a cell or a slightly imperfect soldering that goes unnoticed until complete failure.

Climate not a factor unless extremely hot

The study has also ruled out climate as a factor in premature degradation outside of very hot climates.

According to the study, solar modules in very hot climates showed higher rates of degradation. As had been previously known, very high temperatures decrease solar panel efficiency and accelerate the physical breakdown of internal components such as encapsulants, wiring and solder joints.

When these extreme climates were excluded, however, there was no significant correlation between climate and degradation rates.

Furthermore, the three aforementioned problems were shown to occur regardless of the location in which panels are installed.

Rethink testing standards

Dr Shukkar Poddar, a post-doctoral researcher in the School of Photovoltaics and Renewable Energy Engineering at UNSW and a co-author of the paper, said that the research highlighted the need to re-think testing methods and standards.

Going forward, Poddar says that the research would like to gather even more data from large-scale solar farms.

This would enable a greater understanding of the factors which contribute to module failures across different climate types.

The information will assist manufacturers to improve design durability.

It will also provide testing authorities with an evidence base of real world degradation patterns across different climates. From there, authorities will be able to consider combining stress tests to better replicate outdoor operating conditions.

“Current testing standards focus primarily on three parameters: the modules’ response to mechanical stress, extreme temperatures, and exposure to ultraviolet radiation – as well as often testing for humidity and response to a standardised amount of sunlight (AM1.5 spectrum),” Poddar says.

“But when they (the solar panels_ are actually operating in real-world conditions, there are so many different factors coming into play, and those cascading failures (referred to above) can be very significant.

“So I think we need to start thinking about different testing standards which would help to ensure we have more resilient types of modules.”

The study was undertaken by the UNSW team, which included Dr Fiacre Rougieux, Dr Shukla Poddar, Associate Professor Merlinde Kay and PhD student Yang Tang from the School of Photovoltaic and Renewable Energy Engineering.  School of Photovoltaic and Renewable Energy Engineering.

The team analysed information which had previously by Dr Dirk Jordan from the US Department of Energy’s National Renewable Energy Laboratory. This is a collection of the annual production data from tens of thousands of photovoltaic systems produced globally and includes statistics on performance and maintenance.

The paper was published in IEEE.

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