Test standards for thermosyphon-type solar domestic hot water system: review and experimental evaluation

This communication presents a review of test standards based on steady-state methods and applicable to thermosyphon-type solar domestic hot water systems (TSDHWS). The theoretical basis, the technique of parameter estimation and the test procedure of each standard have been reviewed and compared. Three standards concerning solar-only systems have been evaluated experimentally in detail. Extensive studies have been carried out under a wide range of weather and operating conditions. Two commercially available TSDHWS (having two different collector technologies) have been used in the investigation. The tests were carried out at the same location under similar conditions. The characteristic parameters of the TSDHWS have been obtained on the basis of each procedure/standard. A sensitivity study has also been carried out in order to examine the effect of measurement errors on the values of the estimated parameters from different standards. There are no significant effects on CNS parameters. JIS is the simplest one to implement. The normalizing factor of 20 930 kJ/m2 day for the quantity of heat collected in this standard is not very clear. The ISO (part-2) is a very stringent standard as far as the operating and weather conditions are concerned. The combination of CNS parameters along with the overnight loss factor of ISO (part-2) forms an ideal set for comparing different TSDHWS.