Energy, environmental and economic assessment of wastewater heat recovery systems in hotel buildings

Abstract

Wastewater heat pump system has been extensively researched due to its benefits in terms of energy conservation and environmental preservation. Most of these studies, however, use R134a or R22 as refrigerants, which are being phased out. This research selects the transcritical CO2 heat pump for wastewater heat recovery, the model is built in TRNSYS software, and the energy, environment, and economy analyses of the three systems are examined. The results reveal that the regenerative heat pump system (RHPS) can save 76.67% more energy than the regenerative boiler system (RBS). The RHPS has a larger initial investment than the RBS, but the yearly carbon dioxide emission is reduced by 33.99 tons, and the life cycle cost is lowered by 1452.55 thousand CNY. Furthermore, RHPS can reach the peak of the annual average cost difference earlier with the support of government policy, and the annual average cost difference has increased by around 21–29% more than that without the subsidies. This research will help to promote the combination and implementation of the transcritical CO2 heat pump in wastewater heat recovery technology.