PV module manufacturers usually offer an 80-90% performance guarantee over 20 to 25 years. A research institute such as ZSW, which develops its own solar cells, modules and production processes, offers valuable assistance with its extensive testing capabilities in the laboratory and in the field when it comes to ensuring this level of quality.
Investors, banks, manufacturers and project developers rely on reviews and assessments of the performance, long-term stability and operational reliability of PV modules, as carried out by independent test facilities. Especially when verifying the suitability of PV modules produced using specific technologies and manufacturers for deployment in large international projects (bankability), it is sensible to have the modules randomly sampled and tested by third parties in order to minimise the risks for all involved parties.
The ZSW test laboratory for PV modules, SOLAB, provides the corresponding services. Most tests are conducted according to the standards IEC 61215 (crystalline Si modules) and IEC 61646 (thin-film PV modules), including measurements of the STC performance, low-light response, insulation inspections under wet conditions and potential-induced degradation tests (PID) according to IEC 62804. Depending on the location of the PV modules, it may be sensible to significantly extend the periods covered by accelerated ageing tests, damp heat tests (DHT), thermal cycling tests (TCT) and UV illumination tests far beyond the level required by the standard test. Another quality assurance measure is to assess the PV module manufacturer’s production site (factory inspection), which is something also offered by ZSW SOLAB.
In addition to laboratory tests, the operation and monitoring of PV modules in the field form indispensable parts of a comprehensive quality inspection. While the IEC standard requires only a few weeks of outdoor exposure, this test period should be at least six months or – even better – one full year. With its outdoor-test facility in Widderstall, southern Germany, ZSW offers its customers a perfectly suitable, well-equipped testing platform.
PV systems often exhibit yield losses and faulty components. In such cases, ZSW SOLAB carries out an analysis of the performance data, an on-site inspection of the PV system, IR thermography and performance measurements. This enables possible causes such as PID, microcracks, 'snail tracks', LID, defective bypass diodes, chalking, cracking or delamination of the backsheet to be quickly identified. In addition, individual modules can be precisely measured in SOLAB and then examined in detail in ZSW’s analysis laboratory. Together with the customer, an optimal recovery strategy can then be developed, such as for PID damage in PV farms.
Using experimentally measured parameters, ZSW has developed calculation models and methods to predict the expected energy yield for system operators and investors. We provide advice on site assessments and system planning, and check the yield quality of the installed PV systems. For more information about our services, which also include advice on the module, system and production level, see "PV module test laboratory" and "Solar test facility" under the keyword "Services".
Test development is a further field of activity provided by our photovoltaic experts. The continuous development of module technology and the ever-improving understanding of failure mechanisms (field errors) also require the further development of test procedures and methods, such as field-relevant PID tests or service life tests. Only then can the risks that every new technology harbours for manufacturers, users and the environment be minimised.
Many test procedures have been successfully described in international standards for several years. ZSW’s development work in this area is used as input in the standardisation process. ZSW’s 25 years of laboratory and field testing experience, and the correlation between indoor and outdoor characteristics, provide ideal prerequisites in this regard.