Fretting over junction boxes

The story of Scheuten Solar is one that exemplifies the tale of bankruptcies, consolidation and market downturn in the solar sector. The company Scheuten Solar Holding BV filed for insolvency in March 2012, and was "saved" through acquisition by Chinese cell manufacturer Aikosolar in June 2012. Chief operating officer at the time, Perry Verberne, told <b>pv magazine</b> that the Chinese investor's takeover was the best way forward for European manufacturers in trouble. But little did the company know that lightning can strike twice as Scheuten was forced to declare bankruptcy for the second time, this year. One major issue that hurt the company even more was the attestation made by the Dutch Food and Consumer Product Safety Authority (NVWA), which declared thousands of Scheuten's modules were fire hazards due to design flaws that affected the junction boxes. As many as 650,000 Scheuten Multisol PV modules that were distributed between September 2009 and October 2010 were allegedly affected by such flaws that led to fretting corrosion of the tin-plated contacts in the junction boxes. Numerous fires in in-roof systems were reported in France and Italy where the higher solar irradiation played a significant role.
German company Suncycle was assigned to unfold a repair program for these modules. Suncycle started off by proactively inspecting in-roof PV systems, identifying and reviewing the deliveries and thereafter communicating with both installers and end customers.
Suncycle's CEO Dr Mischa Paterna explained to <b>pv magazine</b> that the risk is particularly focused on Multisol modules and Scheuten has provided Suncycle with a list of serial numbers that can be matched against customer registrations. Suncycle developed a separate Scheuten Solar service portal on their website where customers with these affected modules on their roofs can inform themselves, check their module serial numbers, register their site, and generate a cost calculation for the repair. Hereby, "knowledge about the location of the affected modules is generated," added Paterna.
These modules unfortunately span Europe on the roofs of more unfortunate customers of the bankrupt company. Paterna breaks it by geographical location of the modules as such:

• 30% in Germany;
• 20% in Italy;
• 20% in France;
• 10% in Greece;
• 5% in the UK;
• 5% in Benelux; and
• 10% in the rest of Europe.

The fault and the repair process

While it seems easy to keep flogging a dead horse, the horse in this case being Scheuten Solar, the fault was also widely reported in the media to lie with the Solexus junction box, something junction box manufacturer Alrack contested. Alrack stated on its website: "NVWA gives the impression that the problem would only occur with Alrack Solexus junction boxes" and refuted the allegation, saying that this problem was one that can arise with other junction boxes as well and has been caused by Scheuten Solar's design error.
"The problem seems to be rather attributable to the design than to the manufacturing of the junction box, Paterna added. "Maybe it is accelerated through the choice of materials used."
Suncycle summoned an expert discussion to decide upon extended tests that went beyond the standard requirements. This was because the affected module types did pass the standard tests, but failed in application. Paterna explained that these new tests were undertaken at the Fraunhofer IZM.
Instead of undergoing the IEC norm test of 200 cycles over a maximum of six hours for thermal cycling where the module is subjected to temperatures between -40°C and 85°C in a climate chamber, the new tests stipulated that the modules undergo 1,000 cycles in a dual climate chamber with only one-hour cycle times, explained Paterna. The regular tests are performed in a single chamber and the temperature change is gradual. With the new test, the samples are transferred from one chamber which is cold into another which is hot so the temperature change is no longer gradual. "This can only be done with two chambers. This increases the stress on the module," Paterna said.
The cause of the failure and the reliability of possible repair methods were tested under these stricter test conditions. Apart from visual tests and online measurements of the contact resistance, analytic methods such as scanning electron microscopy were also used to determine the cause. Fretting corrosion occurred in the junction boxes and led to a quick increase in contact resistance.
A repair process was then developed by Suncycle with Fraunhofer IZM where the connectors were soldered to the contacts of the circuit box. A highly flexible connection between the connectors and the module cable prevents undue mechanical stress of the solder joint due to temperature extremes. If damage has already been done to the printed circuit board, then the boards have to be partly exchanged since repair is not possible. The damage
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has been recorded to be higher and more advanced in southern European countries, namely due to the higher temperatures and irradiation conditions. The number of non-reparable modules was also more than double that of Germany. Though Suncycle has been undertaking the repairs now for a while, the seasons are a halt-factor in Europe. "The repair itself can be done in all seasons, but it makes life harder in winter when there is ice and snow on the roof," Paterna explained. The company is thus focusing on Greece, Italy and Southern France in winter. The repairs are expected to carry on for another two years.

Who pays?

As of February, the insurance company was supposed to pay for repairs to all ‘high-risk' systems. Since the NVWA sent out their warning, the number of claims has skyrocketed. This may sound good, but there is an issue now pertaining to payment from the insurance side. Dutch insurance law allows an insurer to suspend payment in order to protect against the limit being exceeded. The insurance company, in other words, is not willing to pay more than the maximum obligated sum. Therefore the past policy has been stopped and even ‘high-risk' systems have no coverage now.
"We are also not happy about this," said Paterna. "AIG, which is the insurance company of Scheuten, tried to use the €5 million coverage responsibly and do some proactive repair. We did this in 2012 but this stopped when the NVWA said additional testing was required. Thereafter, AIG claimed that the number of claims was now over the limit, over the €5 million mark, and payment will be stopped. They added that if they selectively looked at high-risk installations, then other customers could sue them for not taking care of their systems. So the distinction between high and low risk which was developed by Suncycle and AIG would not possibly hold in court. So in the end the insurer will indemnify each individual claimant on a pro rata basis under Dutch law. In three to four years, installers may receive 3-5%. Clearly it would be easier if insurance covered the repairs, but this is not the case any more."
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In August, German media 3Sat reported on a home owner with problematic modules in Germany. Manfred Scholtes was told to remove his PV installation from the grid by his system operator. The repair works are to cost around €2,000 for Scholtes. So who pays for the repairs? The installer can be made liable in the case that the installation is less than two years old. If not, the end customer ends up digging into his own pockets. Paterna adds that, in reality, installers are often willing to split the costs or perform the repairs at reduced charges thanks to the strong relationships with end-customers.

Technical solutions in junction boxes that detect faults like arcing can make PV systems safer. Many junction box manufacturers are working on or have already released products with such safety electronics integrated. Some examples are as follows: The Huber+Suhner Radox HM-Blue-Safety consists of smart integrated electronics that consist of a safety switch and wired communication. There is an inbuilt temperature sensor on the HM-Blue-Safety that detects overheating of the junction box itself, or in the vicinity, and automatically switches off PV module voltage and string current, in turn preventing fire ignition from arcing. The monitoring feature allows performance monitoring of each individual PV module and thus improves the probability of early detection of defects.
Trina Solar launched the Trinasmart module that integrates a module optimizer into the junction box. The power electronics from Tigo Energy aid in the reduction of arc, fire and safety hazards. Tigo Energy's optimizer is also found in Amphenol's new junction box. The HBFMMJ-ES50, also known as the Tigo-Amphenol Optimizer, has received a CSA certification for integrated Smart Module technology.
SolarEdge also has power optimizers that provide safety features. The new optimizers provide arc detection and termination capabilities, which can reduce the risk of solar PV-related fire and electrocution. Module manufacturers can embed these optimizers into each module and replace the junction box completely, SolarEdge states.
Synapse Wireless and Shoals Technologies Group partnered up this year to design and develop an arc fault detector solution that can be integrated into Shoal's wireless smart combiner boxes. "This is an exemplary way of harnessing the powerful potential of cloud-enabled software," says Jason Whitaker, chief technology officer of Shoals Technologies Group. "The ongoing collaboration between our companies is expected to result in reducing the amount of unwanted deaths and injuries and billions of dollars of costs directly stemming from a lack of being able to properly and proactively detect arc faults." The company Sensata Technologies announced the release of its UL-recognized arc fault detectors in July. The PVAF family is a series of UL 1699B recognized, pre-integrated arc detection solutions for use in inverters or combiner boxes on new arrays, or retrofit boxes on existing arrays. "Though NEC 2011 included an arc fault requirement, the lack of UL-recognized equipment made compliance with the code extremely challenging, so it was not enforced in many areas," said John Kluza, solar strategic marketing manager for Sensata. The U.S. National Electric Code, for one, requires the implementation of arc fault detection and interruption in PV systems that are installed on buildings.
<b>pv magazine</b> also spoke with Thomas Hoffmeister, head of photovoltaics at Lapp Group, who stressed the importance of keeping humidity out of the junction box, as it can generally lead to corrosion. Corrosion build-up leads to higher resistance as well. "We have IP67 protection rating in both our plastic and aluminum junction boxes. There is a pressure valve that allows the junction box to breathe and keep humidity out as well. Especially for our aluminum boxes, the material does not get brittle over time, as brittle junction boxes also allow humidity and water inside. This can lead to corrosion and thereby, arcing," Hoffmeister adds.
In the case of Solexus, there were no such mechanisms integrated, Paterna told <b>pv magazine</b>. "There are different approaches available or that are in development to reduce arcing risks in PV installations. Module-integrated solutions like DC/DC converters, DC/AC inverters or safety electronics with integrated arcing detection are options. So far there is not much field experience related to arc fault detection. The devices need to be reliable and detect different types of arc faults. At the same time, they should not produce too many nuisance alarms either,” Paterna added.