INFLUENCE ANALYSIS OF THE CHARACTERISTIC COEFFICIENTS OF SOLAR DOMESTIC WATER SYSTEMS TESTED ACCORDING TO THE STANDARD ISO 9459-2 REGARDING ITS LONG TERM PREDICTION

摘要

The Solar Thermal Testing Laboratory shared by CENER and GTER in Seville, performs outdoor efficiency tests for factory-made solar systems according to the international standard ISO 9459-2. This method (CSTG acronym for "Collector and System Testing Group", also called Input-output method) consists of three different parts: one part for determining mixing in the storage tank during draw-off, another part for determining daily system performance, and a part for the determination of storage tank heat losses. From the so-called CSTG test the following coefficients are obtained: the characteristic coefficients of the solar system in the daily performance (a_1; a_2, a_3), the normalized draw-off temperature profile (f(V)), the normalized mixing draw-off temperature profile (g(V)) and the storage tank heat loss coefficient (Us). After having tested some solar systems according to the CSTG method, the long term prediction of the system output is performed using a simulation program. Using the obtained test results as a starting point, we vary the parameters stepwise and observe how this influences the solar fraction f_(sol). Therefore, the purpose of the present paper is to analyze the influence of those parameter variations on the solar fraction f_(sol) obtained from the long-term prediction in different reference locations (Stockholm, Wuerzburg, Davos and Athens) and for various solar systems with different ratio Volume/Area. This paper presents the influence of varying values a_1, f(V), g(V) and U_s on the solar fraction in function of climate.