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AKE: Energie

AKE 7: Energietechniken - Einzelentwicklungen

AKE 7.5: Talk

Thursday, March 29, 2001, 16:45–17:00, S4

Correcting the error due to non-parallel irradiance during calorimetric measurements of g — •Simon Pick, Werner Platzer, and Tilmann Kuhn — Fraunhofer-Institut für Solare Energiesysteme ISE Oltmannsstrasse 5 79100 Freiburg Germany

A new method is presented for the correction of systematic measurement errors caused by non-parallel irradiance during calorimetric measurements of the total solar energy transmission g. This method improves the accuracy of evaluation of facade elements and thus allows for a more precise calculation of solar gains in buildings. This enables a more exact assessment of heating and cooling systems. Construction costs as well as energy consumption are thereby reduced. This is of particular importance for the large and growing group of facade elements (venetian blinds, daylighting systems,…) exhibiting a noticeable dependency of g on the direction of the solar irradiance. Our method employs radiance measurements performed with a CCD-camera on the radiation source and transmission (and in some cases absorption) data of the facade element measured optically with nearly parallel irradiance. The formalism corrects in a simple manner errors caused by direction-dependence of the solar transmittance and absorptance. If the distribution of the absorption over the samples depth also changes with the direction of the solar irradiance, a second correction applies, requiring additional low-level modelling. The method has been validated on several different kinds of facade elements. In all cases the systematic measurement error was reduced substancially.