CdTe Spectrally Matched c-Si PV Reference Cell for PV Plant Monitoring

Spectrally matched PV reference devices can aid in performance monitoring of PV power plants by improving correlation between measured irradiance and system power output. This is especially beneficial for PV technologies such as CdTe where spectral mismatch to thermopile pyranometers and unfiltered Si reference cells can be significant. Here we evaluate a CdTe spectrally matched filtered c-Si PV reference cell designed by Atonometrics. The cell includes a filter specifically selected to minimize the relative impact of typical variations in solar spectrum due to atmospheric precipitable water vapor content, which is the most significant factor affecting CdTe spectral mismatch. We review the design of the cell and the filter selection and present evaluation data comparing the cell's performance versus a First Solar Series 6 CdTe module in a 3-month outdoor test. The results indicate that the filtered reference cell response to precipitable water vapor closely matches that of the CdTe module.