The Long-Term Sequential Test was developed by TÜV Rheinland and is a new testing methodology designed to simulate long-term operational conditions that solar PV modules experience throughout their lifetime. An accelerated test sequence for PV modules is designed to more accurately approximate real outdoor solar module behaviour in a laboratory environment.
This sequence has been designed specifically for this purpose and allows both manufacturers and end users to increase their confidence in the quality of PV modules.
The test evaluates solar modules with four sub-tests:
- Damp Heat;
- Thermal Cycling;
- Humidity Freeze;
- Bypass Diode.
These test the module’s overall performance and quality by putting it under harsher conditions than those standardised by the International Electrotechnical Commission (IEC). Furthermore, while conventional testing dictates that a separate individual module be used per sub-test, the Long-Term Sequential Test carries out all four sub-tests on the same module, thereby evaluating it under conditions closer to those a product faces over its actual lifetime.
Kyocera's solar module KD210GH-2PU (comprised of 54 polycrystalline silicon photovoltaic cells; mass-produced since 2008) has passed TÜV Rheinland’s major sub-testing for Damp Heat and Thermal Cycling — and Kyocera’s module has proven to maintain a constant level of power output throughout.
Furthermore, reports the company, compared to conventional industry testing methodology, these two sub-tests evaluate modules over a longer time period. Currently, the company’s module is undergoing the remaining sub-tests — Humidity Freeze and Bypass Diode — with the full Long-Term Sequential Test planned to be completed by December 2010.
“Now that the market is promising up to 25 years of life for a PV module, end users are asking for more evidence to give them confidence in a solar investment,” says Mr. Stefan Kiehn, head of the PV testing facilities at TÜV Rheinland Japan. “TÜV Rheinland’s Long-Term Sequential Testing does not guarantee that the product will be as perfect in 25 years as when it was purchased, but it can help manufacturers to better understand how their modules may behave after being in use for a long time. Until now this was only possible through real outdoor lifetime testing.”