Swiss Mobile Flasher Bus: Progress and New Measurement Features

Abstract

The Swiss Mobile Flasher Bus (SMFB) was developed in July 2009 and is equipped with a standard high-quality Pasan flasher. In the past year several measurement orders were carried out and a very high throughput of up to 200 PV modules per day could be reached at customer site. The measurements of the SMFB are calibrated with a set of four 230W standard polycrystalline silicon modules, each tested at ISE, Freiburg by a precision performance measurement with an uncertainty level of 2% (95% confidence level). A calculation of the SMFB measurement uncertainty budget is presented based on the uncertainty of this four reference modules. Additional test measurements with the SMFB were performed, to estimate the sensitivity of parameters, responsible to further increase the overall uncertainty budget. For instance the non-uniformity was measured over the whole area of 2m by 2m, the module temperature was varied in the range of larger than 5°C around STC and module inclination was systematically changed to account for unknown variations due to not identically mounting situations of the module position and the reference cell. The resulted expanded combined uncertainty is ±3% at a 95% confidence level for standard crystalline Silicon modules. This uncertainty value is about 1% larger than values of the best stationary test labs but enables still very accurate measurements at ambient temperature conditions with the advantage to make more measurements directly on customer’s site. Particular regard was set on the measurement of module efficiency from STC down to low-irradiance of 70 W/m. Thin film technologies like CdTe modules come up with an efficiency characteristic with about 4% relative higher values in the range of 400 W/m compared to standard crystalline Silicon modules. Since summer 2010 the SMFB offers the measurement of the spectral response characteristic on module scale. This is realised by placing optical band pass filters of 50nm spectral width, in front of the flasher light source in steps of also 50nm from 400nm to 1100nm. The spectral response measurement will allow even more accurate measurements of the power performance because the spectral mismatch factor can be quantified und thus this spectral uncertainty contribution will be minimised. Successful spectral resonse measurements could be performed using single junction devices like standard cr-Si modules CdTe and CIS modules.