An integrated simulation of intermittent heating of multi-zone buildings by heat-pump heating systems with different terminal types

Abstract

Intermittent heating has been considered to be an effective way to achieve energy savings compared with continuous heating. However, recent studies have found that actual energy savings from intermittent heating vary greatly, depending on actual building conditions, terminals and heating supply systems. For multi-zone buildings adopting heat pumps with specific terminals, a comprehensive analysis of energy savings resulting from intermittent heating still needs to be done. In the present study, an integrated dynamic model is developed by considering the interaction of thermal processes among building envelopes, terminals, and heat pumps. Its reliability is verified in field tests, and a better accuracy was achieved when considering the radiant heat ratio of terminals. On this basis, the model together with a source and terminal control strategy is applied to simulate the thermal behavior of heat pump heating systems for buildings under various conditions. The effect of different terminals and building envelopes on room temperature variation and energy utilization by intermittent heating is analyzed. The simulation results and practical projects indicate that heat pump power consumption under intermittent heating may be lower, close to or even higher than that under continuous heating. The factors that affect the efficient of intermittent heating, including building and system thermal inertia, heat pump operation COP, the radiant heat ratio of terminals, need to be systematically considered. Specifically, fan-coil heating systems could use 16.48% less energy, while radiant floor heating systems consume more energy under intermittent heating. Heat pumps under continuous heating are more efficient in buildings with radiative heating systems and heavy envelopes.