Development of Energy Efficient Domestic Hot Water Loop System Integrated with a Chilled Water Plant in Commercial Building

This study investigates a novel approach to reduce energy consumption in large commercial buildings by recovering waste heat from the condenser of a chiller and utilizing it to preheat domestic hot water (DHW). While numerous energy-saving strategies have been developed for building heating and cooling systems, the energy efficiency of DHW systems has lagged behind due to the increasing demand for hot water driven by improving living standards and hygiene concerns. By integrating a heat exchanger between the chiller and the DHW system, the proposed system effectively improves the chiller’s performance and significantly reduces the energy consumption of the DHW heater. Simulation results demonstrate that during the cooling season (June–August), the chiller achieved a 3% reduction in energy consumption, while the DHW heater experienced energy savings exceeding 70%. Additionally, the operating frequency of the DHW heater was substantially decreased. Notably, despite the significantly higher energy consumption of the chiller compared to the DHW heater, the reduction in greenhouse gas emissions from the DHW heater accounted for more than 50% of the total reduction. This finding highlights the significant contribution of energy savings in the natural gas-fired DHW heater to improving the building’s overall sustainability.