Improved differential control for solar heating systems

► We investigate an improved differential control for active solar heating systems. ► The improved differential control is compared with the ordinary differential control. ► The comparison is based on both measurements and simulations. ► The improved control provides increased utilizability and less pumping switches. ► The improved control recommended generally can be easily adapted in practice. One possibility to exploit solar energy better is the efficiency enhancement of the control of solar thermal heating systems. In this paper an improved differential control and the generally used ordinary differential control operating with fixed switch-on and switch-off temperature differences are compared in different efficiency viewpoints. The comparison is based on measured data of a particular system at the Szent István University, Gödöllő and on a TRNSYS model developed for solar heating systems. According to the results the improved control provides a higher value of utilizability and brings forth fewer switch-ons and switch-offs for the pumps. These advantages nevertheless result in extended operation time and thus extended parasitic consumption of the pumps. This drawback can, however, be moderated or even extinguished by modern pumps with low energy consumption or if supplied by renewable energy source. Comparing the amount of utilized solar energy and consumed parasitic energy increments, the improved control can be generally recommended.