Kwaliteit zonnepanelen

To continuously check on the performance of solar panels or inverters, professional monitoring is required. Its value becomes apparent as soon as components become faulty – and the arguments over warranty start.

Peitz near Cottbus near the Eastern border of Germany is generally more of a quiet spot. This area along the eastern edge of Germany is usually better known for the Peitz Ponds, where carp are reared for New Year’s Eve. But we are more interested in the photovoltaics installation of Sven Minetzke. He deals in spare parts for HGVs. “In late 2011, I had a solar array installed to the roof of my warehouse,” he recounts. “Back then we installed 267 solar panels from S-Energy.” Installing the PV has helped him to refurbish his roof, formerly made of asbestos, with sheet metal and solar panels.

The panels were bought from Donauer, a distributor that has since gone insolvent. “Half of the panels are currently defective,” Minttzke complains. “In 2016 alone we lost about 6,000 euros.”

Minetzke’s story is a textbook example why proper monitoring is important. “At first, all seemed to be going well,” he remembers. “The inverters were showing yields, there were no failures.” Four Sunny Boy Tripower 18,000 and three 15,000 combine the strings and feed the AC power into the regional grid. “When I accounted for the yearly values at the end of 2015 I realised that yields were going down.”

At the beginning of 2016, technician installed a Solarlog 1,000 in order to systematically monitor the system. The firmware of the data logger was updated in February 2016. Since then, the Solarlog can access the reference values of similar installations in the area which are also being managed by a data logger. “That took me by complete surprise,” Minetzke says. “We saw a deviation of minus 25 percent. We then subjected the the installation to a thorough inspection.”

Minetzke’s technician noticed hotspots at the solar panels. These were clearly due to suspected serious production faults in one of S-Energy’s factories, because installing companies all over Germany have been reporting similar occurrences. The soldering joints at the connectors of the cell strings are poorly executed, as is obvious from the soldering head. “That was where the discussions started,” Minetzke continues. He now knew what the cause of the loss in yield was, but a major odyssey followed. Donauer had gone insolvents, and nobody was left there to pick up the phone.

S-Energy products are still being sold by two distributors in Germany, but they are not responsible for past cases. The Korean manufacturer does not officially have a branch office in Germany or even Europe. After weeks of e-mails back and forth, Minetzke was directed towards the service provider Suncycle that operates a large-scale repair shop in Thuringia.

Normally, the manufacturer’s warranty that the output of the panels would not fall below a certain value within 10 or 20 years would take effect in such cases. Referring to their terms and conditions, S-Energy sent some replacement panels to the stricken customer. The cost of inspections, demounting the faulty panels and remounting the new ones was going to be left to the customer. “This has been going on for over a year now,” Minetzke states. “Suncycle delivered 20 repaired panels that I had to put up onto the roof at my own expense – including the scaffolding.”

S-Energy’s panels all have their serial numbers on a sticker applied to the rear foil. Of course, it is possible to find affected panels by thermography, for example, but to ascertain their serial numbers and submit them to the manufacturer, the panel still has to be physically unscrewed from the mounting frame – as good as completely demounted.

And after all, Minetzke cannot even be certain if the rest of the panels will not end up being affected by hotspots this summer: The curse seems to slowly spread over the entire panel array. “So far, 60 of 267 panels have been replaced,” he complains. “Am I supposed to keep checking if the other panels are also faulty – or are developing faults?”

Assessments from similar cases have shown fairly conclusively that these are manufacturing faults committed by S-Energy. 2011 and 2012 were boom years in PV, manufacturers were struggling to put out their products fast enough to meet demand. S-Energy used subcontractors that clearly botched things up. In the meantime, the Korean company has parted ways with their erstwhile partners. On the other hand, any botched-up panels are, of course, still out there.

It is a little like with children. When they are young, they can out of the blue catch a fever, a rash or miliaria – but that goes away. S-Energy’s panels have also not had any issues since 2012. Quite the opposite: They have been and still are very popular with many installing companies because of their quality and stability. And beyond those cases where there have been issues, there are many installations out there that are running flawlessly.

The defective panels seem to all be from one specific distributor. This becomes apparent from the serial numbers. We have information that indicates that as much as several megawatts’ worth of panels may be affected. They should never have been distributed, much less installed. But what is worse, here and now: “The way S-Energy are handling this is a catastrophe,” thunders. “It would be best if S-Energy were to take responsibility for their mistakes and exchange the entire array with new panels. Otherwise, the cost will keep escalating.”

Because issues keep coming up. Within two weeks, the repaired panels – 10 out of 60 so far – have also experienced hotspots. “Now I am at the end of my tether,” he says. “I will no longer accept repaired panels. The Koreans have to supply me with new ones. For the entire array.” Indeed, anything else makes little sense: In 2011, the frame of the panels was 50 millimetres high. Now they only measure 40 millimetres.

All the same: Minetzke did not experience a complete disaster. He is insured through the Allianz and at least they cover his loss in yield. Markus Merkle, solar technician in Reckingbach very far in the south of Germany, was less lucky. He installed a number of arrays by S-Energy – adding up to between 200 and 300 kilowatts. He was also a customer of Donauer.

He is with the Gothaer Insurance, who have since cancelled their coverage. “At first we thought the damage was caused by overvoltage,” Merkle, who was very professional in locating the fault, reports. “We supposed that the bypass diodes were broken.” So he replaced some of the panels at his own expense. That was in 2013. “Back then, the Koreans built 54-cell panels with an output of 205 watts. Suncycle does not supply replacements for these anymore. They are very hard to come by and replace.”

In the meantime, his installations are also experiencing insidious losses in output, as if hotspots were the fever rash of photovoltaics. “In one array, all panels are affected, one fifth in another and, so far, six to seven percent in the third.”

Merkle is liable to his customers. After all, it was him who originally put the array up to their roofs – assuming that the promises of the Koreans were to be trusted. S-Energy’s warranty also seems to be of little use. “We could go to court,” he remarks. “But it just is not right that our customers are left in the lurch and having to foot the bill. And we as the installing company also do not have the capacity to spend weeks looking for faults. Just the cost of setting up scaffolding is quite substantial.”

He also used thermography to find the hotspots. Since then, the replacement happens in stages, and only after tedious e-mail exchanges. “It seems that the replacement panels are also faulty,” he complains.

In the case of one installation (70 kilowatts), eight panels had to be replaced. The insurance company (Gothaer) at first okay with that. But once it turned out that another 13 panels were faulty, they cancelled the policy. “Now I have serious difficulties in re-insuring this installation. And now I somehow have to get that through to my customer.” And now he has 13 repaired panels on his premises that were delivered by Suncycle. Merkle is adamant: “We will not put them on the roof. What if they are also faulty?”