– Part 1: Standards and Failure Classifications
* Dumela Mma, Dumela Rra!
Would you buy your company car (or to some extent your personal car) on the pure and simple basis that it is the cheapest on the market? Regardless on any defect you may have noticed? Well, every rule has exception and I am sure we could always find a courageous person who will just do that for whatever motive but for the majority of us, I suspect the answer to this question will be NO. This does not make good business sense and this car could (literally) leave you on the road sooner rather than later.
The same applies to solar PV panels. So If you don’t particularly fancy the idea of ending up with a device which is more solar decorative rather than solar generative, I would strongly recommend that you visually check them at the time of purchase.
Before exploring in more details defects we could encounter, let’s have a look at the standards and the failure classification.
International standards
The International Electrotechnical Commission (IEC) has established quality standard certifications that are widely recognized throughout the solar industry and have gained acceptance in the past 15 years or so. These qualification tests do an excellent job of identifying design, materials and process flaws that could lead to premature field failures. Depending of the type, we have a specific type approval certification.
- IEC 61215
The IEC 61215 certification is for crystalline PV modules. It covers the parameters which are responsible for the ageing of PV modules. This includes forces of nature like:
- Sunlight including Ultraviolet (UV).
- Climate (changing of climate, coldness, warmth, humidity).
- Mechanical load (hail, wind suction, wind pressure, snow).
- IEC 61646
The IEC 61646 certification is for thin-film PV modules. It is in many aspects identical to the international standard IEC 61215 for crystalline modules. Additional tests take into consideration the degradation behaviour of amorphous silicon due to the temperature and the irradiance exposure.
It is worth pointing out both certifications are type approval standards aiming to identify the weaknesses of a product responsible for infant mortality. They are not test procedures to determine the working lifetime of a product.
Visual inspection
Visual inspection of a PV module is performed before and after the module has been subjected to environmental, electrical, or mechanical stress testing in the laboratory. Stress tests are usually used to evaluate module designs in the pre-phase of production, production quality, and lifetime of the module.
Importance of certifications
Passing qualification tests means the product has met a specific set of requirements. Nowadays, certifications are required for most national and international funding programmes. In West Africa for example, the ECOWAS Centre for Renewable Energy and Energy Efficiency (ECREEE) has been recommending the use of these standards as a measure of quality control. Although it is the responsibility of your developer and your EPC contractor to ensure they are using compliant modules, you should not hesitate to question them on this topic.
A good friend of mine, once president of a country I can’t name for privacy purposes has an old adage which says “Trust but verify”.
Failure Classifications
For clarity purposes, it is important in my view to be clear about what is considered a failure. I know it could a very sensitive point especially as this could lead to lengthy and heated (scorching in some areasJ) warranty discussions. In the view of the International Energy Agency (IEA), a PV module failure is an effect that degrades the module power which is not reversed by normal operation or creates a safety issue. A purely cosmetic issue with no consequence is not considered as a PV module failure. A PV module failure is relevant for the warranty when it occurs under conditions the module normally experiences.
Like any physical product, solar module issues could be classified in 3 categories:
- Infant failure (up to 2 years after delivery)
Infant-mortality failures occur in the beginning of the working life of a PV module. Flawed PV modules fail quickly and dramatically impact the costs of the module manufacturer and the installer because they are responsible for these failures.
From experience gathered, failures observed are junction box failure, glass breakage, defective cell interconnect, loose frame, and delamination.
- Mid-life failure (up to 11-12 years of operation)
An average of two percent of the PV modules is predicted to fail after approximately 11 to 12 years of operation.
Examples of issues include junction box and cables failures, burn marks on cells and encapsulant failures.
- Wear-out failure (from 13 years of operation)
Wear out failures occur at the end of the working lifetime of PV modules. They determine the maximum working life of a PV module. The working life of a PV module ends if a safety problem occurs or the PV module power drops under a certain level, which is typically defined between 80% and 70% of the initial power rating.
Failures encountered here are delamination, cell part isolation due to cell cracks, and discolouring of the laminate.
Having described the different categories let me come back for a second on the concept of failure under manufacturer’s warranty protection. On one hand, defects due to heavy snow load (in temperate climates) are considered as module failures as some modules are specified for heavy snow load and on the other hand, soiling of modules, which could be caused by polluted air or deposited dust is not considered to be a PV module failure. With the African market growing and the modules soiling deemed to be particularly important here, do you think that manufacturers should consider adding this issue into their warranty cover and protect the African customer? This would an important question for ECREEE and regulators to debate.
In followings posts, I will be going into more details about failures related to each type solar PV module, describing to you what they actually mean and how they look like.
I leave in peace for now. Do enjoy yourself and look after our planet…Switch this device off when you’re done!!
* Dumela mma, Dumela rra: “Hello Madam, Hello Sir” in Setswana, national language spoken in Botswana.
Summary
Notions to remember
- International Standards
- IEC 61215 for crystalline silicon modules
- IEC 61646 for thin film modules
- Visual inspection is important
- Failure classifications
- Infant failure (up to 2 years after delivery)
- Mid-life failure (up to 11-12 years of operation)
- Wear-out failure (from 13 years of operation)
Sources:
- Review of Failures of Photovoltaic Modules – Report IEA-PVPS T13-01:2014 – IEA
- Silicon Solar Module Visual Inspection Guide – Version 1.2, 2016-06-04 – K. Sinclair, M. Sinclair
- http://www.pveducation.org – Degradation and Failure Modes
- Catalogue of common failures and improper practices on PV installations and maintenance – Intelligent Energy Europe – 2011
- IEC 61215: What it is and isn’t – 2012 PV Module Reliability Workshop – John Wohlgemuth
- ecreee.org – Potentials, Opportunities and Barriers for the Deployment and Usage of Solar Energy Technologies and Services in West Africa – David Ato Quansah, Emmanuel W Ramde, the ECREEE-Secretariat.
Featured image: http://www.freepik.com/free-photo/robot-with-a-solar-panel_918549.htm , designed by Freepik.
