Lezaca et al. presented their new algorithm at the SolarPACES conference. It allows to continuously calibrate Rotating Shadowband Irradiometers (RSI) in situ
Applying a thermopile pyranometer of high quality – fulfilling Class A IEC29500:2008 the spectral error induced by the limited sensitivity of the photodiodes used in RSI instruments is minimized. Compared to the traditional calibration at reference stations, the Lezaca-calibration has the advantage to be much more site-specific as it traces back to a high level instrument, operated at the same site. This in situ method avoids errors induced by differing atmospheric conditions between calibration site and the actual location, where a RSI is operated.
The sliding calibration, over approx. the past month, has the further advantage that the calibration adjusts itself to changing atmospheric conditions. As the atmospheric composition usually varies in the course of the year, the Lezaca-calibration allows for a better spectral correction. The validation results show good results of the new method for Global Horizontal (GHI) and Direct Normal Irradiance (DNI). Moreover, the new correction algorithm does not require lengthy outdoor calibration at a reference site. Therefore, RSIs can now be calibrated much faster and without sending back to the lab.
The set up allowing for application of the new method is now available in our HelioScale phi advanced station.