S. Fischer, H. Muller-Steinhagen

Universitat Stuttgart, Institut fur Thermodynamik und Warmetechnik (ITW) Pfaffenwaldring 6, D-70550 Stuttgart Tel.: 0711/685-3231, Fax: 0711/685-3503 email: fischer@itw. uni-stuttgart. de

In the European Standard EN 12975 /1/ two different approaches for the determination of the thermal behaviour of solar collectors are described: The test method under steady state conditions and the method under quasi-dynamic conditions. Although both approaches are quite different one common item exists: a test is considered complete if all required test sequences have been performed. A validation of the determined parameters, in the way done for the testing of hot water stores, is not foreseen for collectors.

The present paper describes the selection and evaluation of a suitable validation sequence. In addition, criteria are introduced that help to decide whether the found parameter set describes the thermal behaviour of the collector satisfactory or not. The procedure is introduced for the example of a CPC collector with vacuum tubes.

1. Introduction

The reason why a validation procedure may be necessary for collectors is shown in Figure 1, where the measured collector output is plotted together with the calculated collector output.

The collector parameters obtained during the test can be used for performance predictions by a dynamic system simulation /2/. The results of the performance predictions are used to compare the collectors and are often the basis for the decision which collector will be installed. In Germany the results of the performance prediction serves, in addition, as a criterion whether a collector qualifies for government subsidies or not. Taking this into account it is reasonable to introduce a validation sequence within the thermal performance testing to prove that the dynamic behaviour of the collector in operation can be described by the determined collector parameters.