PV Panels Efficiency Degradation Factors

Very important aspect of developing photovoltaic systems is the PV modules image thumb60 PV Panels Efficiency Degradation Factors efficiency drop over time due to scratching of the glass and other external influences like sand, salt, snow etc.

Here I am posting some practical findings and tips from several solar professionals:

ROGELIO NOCHEBUENA, Successful and Accomplished Management Consultant and Contractor:

For most Silicon based PV the main issue with efficiency drop is due to dust accumulation because in most instances they have a glass cover. So you need to wash them gently with soap and water. Also be careful because the glass has an anti-reflecting film. Make sure that you don’t drop water inside the glass cover that could short circuit the actual Silicon. In most cases you will never experience electron migration because the current density is relatively low and the operating temperature is below 100C, although junction temp may be as high as 140C

Douglas J.C. King, Chairman, Product Lifecycle Management Technical Group at Society of Manufacturing Engineers:

Crystalline modules degrade from .5% to 1% each year after an initial drop of 2-3%. Modules typically have a power warranty of 80% over their 25-year life which covers this.

Thin film modules also degrade. I’m not up to date on the latest thin-film testing but, several years ago, some technologies would degrade up to 50% over a short time.

There are differences between module brands based on materials used, manufacturing processes and quality control systems.

Here are some worthwhile articles:
http://www.homepower.com/article/?file=HP118_pg12_AskTheExperts_1

http://www.nrel.gov/docs/fy02osti/31455.pdf
http://pvcdrom.pveducation.org/MODULE/Failure.htm

Thierry Nguyen, Solar Energy Engineer at Barkam Engineering Services

You should consider weatherization phenomena of the glass. This is the attack of the glass by moisture. Industrial environments carry a lot of contaminants (Sulfur, chlorine, etc…) and they have been known to cause leaching of sodium from the glass. This typically leads to the formation of deposits on the glass surface, which overtime reduces the glass transmission properties.

Also not all glass are equal and I would advise to talk to Schott or Saint Gobain to have their input on how to best mitigate the problem.

There are also protective photo-catalytic coatings which incorporates Ti. These are self cleaning coating and have been developed to use light to break down deposits and dirt.

Last Updated On:30th September 2012

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