Modeling occupant behavior’s influence on the energy efficiency of solar domestic hot water systems

Abstract

Solar hot water (SHW) systems are widely used to save energy and reduce CO2 emissions. The domestic hot water (DHW) usage behavior of occupants has a significant influence on the energy consumption of SHW systems; the operation of SHW systems also affects the DHW usage of occupants. However, there is a lack of quantitative analysis for coordinating DHW behavior and the design and operation of SHW systems to maximize solar energy utilization and reduce energy consumption. Therefore, an information-driven stochastic DHW usage model that interacts with SHW systems is proposed. The optimal design and control strategies for SHW systems to match user behaviors were explored. Meanwhile, the effects of occupants’ sensitivity to water temperature and their energy-saving awareness on the energy performance of SHW systems were studied. The results showed that optimal design and control strategies based on the actual DHW profile can increase the annual solar energy utilization rate by 11.5%, and the corresponding electricity savings, CO2 emission reduction, and cost saving are 163.10 kWh, 145.52 kg, and 81.06 RMB, per household. The location of the reheater had a significant influence on the energy performance and optimal measures of the SHW systems. Moreover, based on technologies or policies to adjust hot water demand, the water supply capacity of SHW systems can be matched with the hot water demand, which can improve the efficiency of solar energy utilization, save 8.5% of electrical energy for reheating, and lead to a 107.55 kg CO2 reduction and 59.91 RMB cost saving per household per year.