Influencia real de la inercia térmica de los elementos de un captador solar plano de baja temperatura

Abstract

The thermal inertia of the elements which compose flat plate solar thermal collectors (FPSTC) is mainly used to make previsions of temperature in order to obtain the collector performance and other related parameters. Consequently, the accurate determination of this parameter is of major interest to provide the collector performance indicators. EN 12975-2:2006 standard, establishes the procedure to obtain the thermal capacity of a FPSTC from experimental or simulated data. This standard applies a coefficient for every layer of the assembly, decreasing the role of the glass cover to less than 4%. However, the obtained experimental inertia of the glass cover was around 10%. The calculations were made using data obtained in thermo-solar experimental facility of the Solar Laboratory of the University of Murcia. Two solar collectors of different typology belonging to this facility were provided with a set of 28 thermocouples each, divided into four measurement sections. This arrangement allows the continuous measurement of the collector temperature field, as well as of fluid temperatures and other data related with collector performances. The thermal inertia of each component of one of the FPSTC has been represented in bars diagrams, during the daylight period, in steps of 10 minutes. In most cases only a slight difference of about 0.2 to 1.2 ºC between forecast temperatures, considering new elements or not, were obtained, leading to the conclusion that for general purposes the EN-12975-2:2006 standard definition of collector mean temperature is sufficiently accurate, but it could be improved.