Exergy- based sustainability analyses of a wastewater source heat pump system

Heat pumps are environmentally friendly technologies compared to various conventional systems since they enhance energy utilization efficiency and sustainability of the system by using renewable energy sources. They have also had a wide range of uses from residences to public institutions and industrial applications in the developed countries for years. There are different thermal energy sources for heat pumps, such as water, air, and ground energy. Wastewater can be considered as a renewable heat source for heat pumps due to its high availability, easy accessibility, and sustainability, especially in large settlements. Exergy analysis is seen as a useful tool for analysis and performance assessment of energy systems due to determining the magnitudes and locations of the exergy destructions in the system. These irreversibilities should be reduced to acquire sustainability. This paper aims to present various exergy-based sustainability indicators of a wastewater source heat pump system. Experimental data were obtained from a wastewater heat pump system and utilized to perform an exergy-based sustainability analysis. Comprehensive exergy analyses were performed while the investigated sustainable indicators were calculated by using exergy analysis outputs for the wastewater heat pump system. The indicators of the wastewater heat pump related to exergetic analysis and sustainable development included exergy efficiency, waste exergy ratio, exergy destruction factor, recoverable exergy rate, environmental effect factor, and exergetic sustainability index, which were proposed by other investigators. The aim of researching sustainability indicators was due to sustainability being relevant to economic problems, human factors and environmental effects, which become more important day by day. These indicators were applied to the wastewater heat pump system considered and the results are presented and discussed.