LAUSR

The main objective of this article is to investigate the effect of a control scheme on the behavior of a solar domestic hot water system, consisting of two evacuated tubes with compound-parabolic concentrator (CPC) collectors and a storage tank. In this regard, a transient thermal analysis of the system was performed using an original mathematical model. The developed model was validated by comparing the results with the data provided by the manufacturer. Simulations were conducted during a 48-h period in the meteorological conditions of Bucharest, Romania (latitude 44°24′N, longitude 26°05′E). The second objective of the present work relates to the working fluid thermal inertia. An analysis was made to determine whether the solar collectors’ fluid thermal inertia has an impact on the storage tank water temperature. Three different working fluids have been considered. The results showed that for the entire 2-day period in which simulations have been conducted, differences between the useful energy delivered to the storage tank water in the case with mass flow rate adjusted depending on the incident solar radiation and the cases with constant mass flow rate were approximately 1 kWh in summer and 0.72 kWh in winter. In addition, it has been concluded that the time required to heat the storage tank water from 30 to 60 degrees centigrade is approximately an hour less when the system is working with water compared to the propylene glycol case.