Experimental and theoretical analysis of thermal solar collector systems for dhw in northern Italy

Abstract

Solar collectors performance evaluation has some established standards, represented by UNI 12976 and ISO 9806. Nevertheless, solar collectors are often installed as part of more complex Domestic Hot Water system (DHW). The aim of this work is to describe a methodology adopted for the experimental efficiency evaluation of Solar Collector systems for DHW production (SCDHW). In situ measurements of solar collector DHW system performance, including DHW storage and back-up heating system, have been compared with results from simulations performed using widely spread commercial software and f- chart method. In this paper ten SCDHW systems were analyzed. e. In situ measurements was carried out for at least 20 days for each plant, with sampling rate of ten minutes using ultra sound flow meter, and temperature probes. Almost all the plants had a previously installed heating power logger. Results show that generally the solar collector's area was exceeding actual DHW needing, resulting in measured lower efficiency (around 30%) than calculate by commercial software. Discrepancies between the measured and simulated data are probably due to unpredictable control system and end users behavior.