Techno-economic and environmental assessments of a shower wastewater source heat pump assisted by an air source heat pump based on actual operational data validation

Shower wastewater of human daily life actually contains a large amount of low-grade thermal energy. Despite the significant potential of shower wastewater source heat pump (WSHP) in saving energy and reducing carbon emissions, it has not yet been widely adopted. To expand the market application, this paper presents a comprehensive assessment of a WSHP coupled with an air source heat pump (ASHP) system used for providing shower hot water, covering energy performance, life cycle cost ( LCC ) and environmental impact. Based on one year of operational data, a dynamic simulation model was developed and validated. The results show that the maximum relative error in hourly tank temperature does not exceed 9%, and the relative errors in monthly power consumption are within 6%. The simulation of the WSHP-ASHP in TRNSYS shows that, contrary to the ASHP, the COP of the WSHP is the highest in winter and the lowest in summer. And the monthly COP of the WSHP-ASHP is relatively stable over the year, ranging from 3.4 to 4.1. Moreover, the WSHP-ASHP exhibits significant advantages over conventional boilers in terms of life cycle cost ( LCC ), and also achieves the lowest CO 2 emissions, with annual CO 2 emissions reduced by 77.77% and 60.76% compared to electric boiler and coal-fired boiler, respectively. Additionally, the LCC difference contour plot performs that the WSHP-ASHP maintains an economic advantage over the gas boiler under typical market conditions. The findings highlight the WSHP-ASHP coupled system's substantial potential in supporting carbon neutrality goals and advancing sustainable building energy systems.