A new dynamic method for testing solar flat-plate collectors under variable weather

A new procedure for testing solar Aat plate collectors under unsteady weath er conditions has been developed. It is based on a model which lumps the th ermal capacities of the absorber plate, risers, headers and fluid together in one node referenced to the mean temperature of the fluid. The model is d erived from a general energy balance concept, and its solution gives the fl uid temperature in terms of the collector parameters and its response funct ion. The characteristic parameters defined in the model enable direct compa rison with results from steady state tests. The proposed method has been th oroughly validated under different weather conditions ranging from almost s teady to highly variable. During the tests, only the fluid flow rate needs to be regulated. Standard programs for non-linear optimisation are used to estimate the collector parameters from experimental data. The results obtai ned from the proposed method are close to those of the steady state ASHRAE 93-86 standard (within +/-3%); the scatter being within +/-2%, The theoreti cal predictions of the proposed model are closer to actual measured values when compared to other transient procedures. (C) 1999 Elsevier Science Ltd. All rights reserved.