The growth in solar photovoltaics (PV) plants in South Africa in the corporate and industry space is huge and many operations are finding their PV plants have large numbers of solar modules or solar panels as they are commonly called, which are underperforming.
It is a significant financial investment and investors and insurers should require that independent testing is done as part of Operations & Maintenance (O&M) contracts.
Solar modules should be independently tested pre-installation, on-site once installed, during the warranty period and over time.
Large PV plants have hundreds of thousands of modules, the majority of which are imported, mainly from China and Vietnam. For a large PV plant with, for example, 300 000 modules, 300 – 500 modules need to be independently tested to give the purchaser greater peace of mind that the PV modules are without defects or that they meet the manufacturers specifications in terms of quality, power output and lifespan.
What is extraordinary is that multiple millions are spent on PV plants while the tests cost in the thousands, but many companies, insurers and investors do not include independent testing in their contracts. Many are not aware that independent testing is available and why it is essential.
The EL testing side is making great strides: “With our previous setup, we could test 100 modules per night and we can now do 500 to 800 per night, which is the best testing rate in South Africa, and the increase allows us to expand the sample size and provide statistically meaningful results to our clients,” explains Dr Jacqui Crozier McCleland who has a PhD in physics, and is the quality and technical manager of PVinsight (Pty) Ltd (PVi) – the only accredited mobile laboratory testing service in South Africa, offering in-lab and on-site PV testing services.
“We test the modules at night so that the EL camera can detect the emitted EL light without interference from other light sources. Testing at night also means the PV plant does not lose production during the day,” Crozier McCleland explains.
To advance testing in South Africa and achieve far higher volumes per night, the company has formed a strategic partnership with the German company AePVI (Aerial PV Inspection GmbH) and invested in new EL cameras and other specialised equipment from them, which they started using in January this year on in situ inspections in South Africa.
Andreas Fladung, co-founder of AePVI, who joined PVi for the January launch, says: “Today, innovative high-volume EL measurements in the field enable clear and meaningful quality analyses at cell level with regard to production, transport and installation loads, ageing processes and environmental events. No other measurement method currently offers this depth of analysis.”
The managing director and founder of PVinsight is professor of physics, Ernest van Dyk who established the company in 2017 after it was spun out of the Photovoltaics Research Group (PVRG) in the Department of Physics at Nelson Mandela University. “We have over 30 years of experience and knowledge of PV systems and device research,” explains Prof van Dyk.
“We test modules at all levels, from the utility scale that feeds into the electricity grid to plants that power industries, companies and communities. Our testing is done according to the International Electrotechnical Commission (IEC) standards and we are accredited as a testing laboratory with the South African National Accreditation System (SANAS).”
PVinsight is run by a team of physicists and researchers from Nelson Mandela University and one of their key tests is the EL imaging test to see if the modules are damaged in any way. Damage can happen during the manufacturing process or when they are transported, handled and installed.
The EL method powers the modules by night. The light then emitted by the modules is not in the visible spectrum and it’s impossible to see small defects with the naked eye but the EL camera picks up all cracks or defects in the cells, even minute ones. Previously they had to take two images per module, but with the new camera they take one image per module, which considerably speeds up the process.
“With broken cells (which show up in the image as dark areas), the module won’t produce as much power as if they were all uniform,” says Crozier McCleland. “There are also sometimes manufacturing defects that decrease the module’s performance.
“Defects can creep in at the manufacturer level, such as soldering or bus bar issues, or be caused by poor handling. Generally, if there are cracks in a module it is because at some point it was not transported properly or dropped or handled incorrectly,” she explains.
“Cracks can also occur at the mounting stage if this is not done properly, and there have been numerous issues with rooftop installations where modules have been walked on during installation or when cleaned. Even small issues with the modules can lead to significant power loss.”
Which is why testing is essential. The tests can also be used in warranty claims. When clients are armed with an accredited module evaluation, it greatly empowers them in terms of recourse with the manufacturer or project developer should any problems be detected.
The significant increase in large PV installations has resulted in an increase in the number of insurance claims, ranging from hail and handling damage to inferior quality modules to defective performance – there are all sorts of reasons.
Crozier McCleland explains that when there is an insurance claim, some insurers require that every single module is tested, others require a percentage of modules. “This needs to be done in situ because if you remove them, you cannot say with absolute certainty where the damage occurred. What if they were damaged in transit to testing? A recent test PVi did was on all the modules inside a shipping container that had fallen over.
All modules have certification at a factory level and large international companies do factory audits, but best practice is an independent, third party assessment of the modules on arrival. What has worked well for companies is they have a pre-and post-installation contract with the manufacturer that they will have their modules independently tested before they are installed, and at 12 months, 24 months and annually after that.
“A lot of PV plants have 10-year warranties and if the manufacturer knows we are going to test the modules, they have to make sure the quality is according to specification across the entire range of modules,” Crozier McCleland explains.
“It’s possible that modules are constructed differently even though they are the same module type because the bill of materials can be different. We do a range of tests at PV plants and in our lab to check this, such as UV tests where you can see that different materials have been used in the modules for the same plant.”
The PVi team’s close involvement in PV research at an international and South African university level, and their partnership with AePVI, ensures that they keep abreast of the latest developments in manufacturing processes, solar module types and characterisation techniques. PVi collaborates with their business partner GeoSUN in offering the service to the PV industry. GeoSUN is a 2012 spin-off company from Stellenbosch University and one of PVi’s shareholders.
As important as testing the new modules coming onto the market is to test the original utility-scale PV plants that are now 10 years old, commissioned in 2014. Performance issues and degradation can naturally occur over time so it’s important to check these plants so that good decisions can be made about how to improve their performance or replace and update modules.