Two different types of PV MIPS systems have been mounted on the roof of two research houses at the ECN site in Petten, the Netherlands. The PV-MIPS systems, which consist of AC-modules with an inverter fixed on the rear, have been integrated in sloped roofs. Various types of inverter integration in the module have been applied in order to test the heat load and influence of natural ventilation on the delivered power and durability of inverters.
Prior to installation, outdoor tests of the HV CIS PV-MIPS systems have been done in order to detect defects on a system level. Exchange of failed inverters of AC-modules integrated in sloped roofs is supposed to be labour-intensive and expensive. Two IWES/Steca inverters failed outdoor test and were returned for reparation.
Measuring period was 15 months for HV CIS modules with IWES/Steca inverter and 12 months for a-Si modules with Delta inverter. Apart from one of the 24 a-Si modules, both combinations of modules and inverters have been operating without problems.
No clear influence of the mounting of the inverter can be seen on electricity output and module temperature. For the inverter temperature, influence is small as well, i.e. inverter temperature is a bit lower if mounted on a support. On the other hand, temperature gradients for outdoor inverters are much larger than for inverters installed indoor. A much more detailed indoor laboratory test setup of a complete PV-MIPS system would be needed to reveal the connection between PV system performance and all these system and ambient aspects.