New Study Tackles Hidden Solar Panel Dilemma
Instead, the study found three major reasons for panels to be grouped in the long tail.
The first is interconnected failures. This highlights a scenario where different types of problems can interact with each other on an individual panel.
For example, if the backsheet (a protective layer on the rear of a module) is damaged, moisture can get in possibly causing a failure of the electrical junction box and other problems such as cell cracks or corrosion.
This domino effect, where the issues don’t just add up but instead multiply, can be seen to make panels degrade much faster than predicted.
The second reason is rapid failure when modules are relatively new, dubbed infant mortality. Modules tend to have a slight recovery and slower degradation rate after the initial period of installation.
These panels likely have critical manufacturing defects or material flaws that are not discovered in quality control or testing and therefore fail rapidly — sometimes within just a few years of installation.
Finally, there are minor flaws that may not cause a problem initially, but then result in a sudden severe performance loss at a random point.
This could be a tiny hairline crack in a cell, or slightly imperfect soldering that goes unnoticed until complete failure.
Climate variation ruled out
Importantly, these three factors occur regardless of the location where the panels are installed.
This highlights the fact that climate is not a factor in the long tail of degradation rates, which was one hypothesis being considered.
Dr Poddar, a co-author of the paper, said: “A subset of the data shows information specifically related to solar modules in very hot climates which we know causes higher degradation.
“However, in other climates, when those hot regions are being excluded from the analysis, we see similar long-tail pattern in the probability distribution of performance degradation rate. This suggests that the issue is consistent regardless of where the panels are operating.
“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).
“But when they are actually operating in real-world conditions there are so many different factors coming into play, and those cascading failures 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 research is important for solar panel manufacturers and those spending many millions of dollars to build large solar arrays to provide clean energy.
The long tail phenomenon challenges the financial models that underpin the industry’s growth, creating uncertainty in long-term energy yield and operational budgets.
If the real-world failure rate is much higher and panels degrade much sooner than expected, as shown in the UNSW study, there will be unforeseen expenditure required by operators for repairs or module replacements.
“With this research, we are hoping to make real impact in three ways,” said Dr Poddar.
“We would like to get even more data from large-scale solar farms to analyse real-world failure rates in even more detail, so we can then make recommendations to the manufacturers of these modules.
“Secondly, we aim to understand different factors contributing to module failures in different climate types to develop early detection system and recommend manufacturers to improve design robustness.
“Thirdly, testing authorities should be informed of real-world degradation patterns across diverse climates and consider combining stress tests to better replicate outdoor operating conditions.”