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Longevity

 

 

The price reduction in the photovoltaic industry endangers the quality and longevity of solar power plants – the daily life of a PV-expert

 


The fast reduction in investment cost has brought photovoltaic where we wanted to have it 25 years ago: close to grid parity of even beyond grid parity for self consumption. But the price reduction has it's price: quality!

25 years ago no one doubted that the technology would last 20 years or more. This certainty has gone lost in the recent years. The price reduction is not only due to higher efficiency in the production and the dislocation of the production to low cost countries. The process to reduce costs have also affected quality management in the production. It’s fact for the solar modules, but as well for the structures and execution, where you find mistakes that reduce the value of a solar power plant.

 

What we see in our work as PV experts is often surprising. You find mistakes that are very often an obvious violation of the state of art.

 

Some examples:

Solar Modules with hidden production defaults

 

In a thermal imaging campaign we found “cold soldering“ on cells and damaged junction boxes. Both mistakes were each found on roughly 10% of the modules. Both damages have the potential to reduce the production or severely damage the module by overheating in the junction boxes.

cold soldering bad connection

 

Ill. 1: these two problems can reduce the production or damage the modules

Another problem on modules are „third party mistakes“, caused by subsuppliers.

In this example the supplier of the silicon material to glue the junction box delivered faulty material. Moisture entered into the junction box. Some boxes were damaged, some boxes fell down.


 

Ill. 2: damaged junction box

 

       Potential Induced degradation PID

We were called to check a power plant with unsatisfying production, far below expectation. Through evidence of several criteria we could show that the modules are PID-sensitive. The finding war approved with a laboratory test. Thermal imaging was an important part of the diagnostic. PID is reversible with suitable treatment of the modules. It's possible to earth the negative pole of the strings, as long as the inverter allows it. Another solution is the installation of a device that gives a corrective tension to the modules during the night.

 
Ill 3:Typical Thermal Imaging patterns of PID-affected modules

 

Unsuitable structures

The structures as well have to contribute to the cost reduction. The results are not always satisfying. Cheap and thin materials, unproper corrosion protection will cause a loss of functionality before the end of the planned lifetime of the power plant. Only good quality will withstand the climatic attacks during more than 20 years.

 
 

Ill. 5, 6 and 7 Very thin beams, rusty shortly after commissioning, not screwed correctly, unsiutable structure

 

dirt

Dirt on the modules is another underestimated problem. Cost reduction has led to the installation of modules in non optimized conditions. In many cases for example the modules are mounted almost horizontal. Economically is can be sufficient. But the impact on the production can be much higher than just the reduction of the transmission through dirt. Dirt accumulation on the lower edge can create "dirt hot spots" that will reduce the production in a much higher extent.

 

 

Bild 8: Dirt-Hotspot

 

Design faults

It’s hard to believe to see the mistakes that are made in the design of the power plants. The cheap modules have lead to the situation that design and planning are not done any more with the desirable care. In many installations we analyze we see hard shades on the modules due to many reasons or green roofs with unsuitables structures.
ill. 9: shade by chimney ill 10: shade by ladder
ill. 11: modules on the nort side of a facade ill. 12: too much greenery, and this is just the beginning

Quality management during execution or latest at commissioning will prevent mistakes or at least the supplier can be made responsible for it. Qualified know how is necessary to make this work.

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