In order to achieve energy conservation and emissions reductions

an air source/sewage source heat pump hot water system was designed. Field tests were conducted in a demonstration project on Tunxi Road at Hefei University of Technology. The results show that at an ambient temperature of 8 ± 1.2 ℃ and a water supply temperature of 50 ℃ condition

the wastewater temperature is decreased from 30.6 ℃ to 15.5 ℃ through preheater and waste heat recovery. Heat recovery energy accounts for about 1/3 of the total energy for hot water heating. At an ambient temperature of 10 ± 1 ℃ and a water supply temperature of 45 ℃ condition

the energy efficiency of the composite heat pump system was 3.45. Compared with a separate air source heat pump

the energy efficiency is increased by 18%. Compared with a gas water heater and an electric water heater

the composite heat pump system can reduce operating costs by 53.3 and 72.4%

respectively. The results show obvious advantages of composite heat pump system on energy saving

environmental protection

and cost reduction.