Module Reliability with Changing Times

23 July 2021

Module Reliability with Changing Times

Authored by Amresh Mahajan, Head – Tech QA & EHS at O2 Power

“If we are not able to take care of our environment, the environment will not take care of us”. This has become a tag line in renewable sector across the world. We, in India, are possibly in best phase of our solar power journey. With huge emphasis for ‘Make in India’ by the Government, solar power tariffs are hitting an all-time low and targets till be 2030 being crystal clear, everything looks very rosy. Lower tariffs have direct correlation with low solar module prices and high efficiency. While higher efficiency can be attributed to technological advancement and optimized processes, the same cannot be said about lower solar module prices. Of course, like other industrial sectors it has direct correlation with scaling up of manufacturing capacities, more automation, optimized design and others similar factors.
But is it really the case or is excess optimization eating away the reliability factor?
The answer is tricky and needs more alertness on the part of developers while they negotiate with the supplier on this aspect. India is a very hot and humid country. Solar panel designs have to be in line with local weather conditions, and not generic IEC certifications. In our opinion, the most significant field failures over the last decade in India are:
  • Excess degradation
  • Moisture ingress
  • Junction box malfunctioning
With the passage of time, bus bars in solar panel have increased from 2 to 5 and now, the MBB (Multi Bus Bar) concept has taken over that have 9 to 12 bus bars. It means the width of bus bars have reduced. Additionally, TCI (Tin Copper Interconnect) height has increased up to 0.27mm to reduce I2R losses. This is a logical change for efficiency improvement. However, if this technical change is not compensated with increase in GSM of EVA, series resistance in hot environment will increase and will ultimately result in higher degradation. This can be simulated very easily in multiple thermal cycling tests. Moisture ingress defect can be majorly attributed to lower gel content specification which may cause delamination in field and also on quality of back sheet which, sometimes, is not conducive to Indian conditions. In our opinion, the three-layered back-sheet has better chance of survival than the coated back-sheet and double PET ones. Before zeroing in on options, multiple levels of damp heat test as per IEC/ BIS protocol is necessary to simulate the moisture entry defects to be followed by dry and wet insulation test. Generally, manufactures get multiple bills of material certified in CDF (Construction Data Form) but it for us to pick the right combination as there is nothing more important than securing plant life of minimum 25 years with expected power generation.

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