Recent developments in PV module technologies require new,long illumination,test methods to achieve scientifically sound results that are representative for outdoor conditions.There are two major challenges in testing this next generation PV modules:1.PV modules that exhibit a longer response time to light pulses than the common 10 to 50 milliseconds of flash tests.This effect is visible in capacitive high efficiency c-Si and thin-film modules,in modules involving chemical reactions and in modules with integrated electronics.To perform accurate measurements,long pulse solar simulation with an illumination time of 1 second or higher is required.A point of attention when using longer illumination is heating of the solar modules during the Ⅰ-Ⅴ sweep.However,it has been shown that at 1 sun illumination the temperature increase is usually in the range of 0.2-0.6 ℃/s.This effect can often be neglected or compensated for by simple means.2.The need for additional test procedures,including testing in different conditions and testing for power instability.Installation companies nowadays use sophisticated yield estimation tools that require more performance data in different conditions as input.Furthermore,the performance of many new PV technologies over a longer time is not stable and difficult to predict mathematically.Therefore test procedures such as Performance at NOCT,Low irradiance testing,Pre-conditioning and Light soaking are of increasing importance.Some of these tests require high accuracy continuous solar simulation to achieve reproducible and representative results.