Application and Analysis of a Heat Pump System for Building Heating and Cooling Using Extracting Heat Energy from Untreated Sewage

Heat pump technology can extract low-level heat energy from urban sewage to heat or cool buildings, which can alleviate the two major problems of energy shortage and environmental pollution to a certain extent. This paper introduces the principle of wastewater source heat pump technology and summarizes the current common system forms and their key core technologies. The proposed special heat transfer technology for sewage can effectively solve the problem of blockage and corrosion in the process of sewage heat transfer. Taking the system of an office building in Qingdao as an example, the system design parameter is introduced in detail. The operation monitoring of the heating and air conditioning seasons of this project was completed through a data collection system, and various performance parameters of the system were studied and analyzed. The data was obtained using measured data from one year of system operation. The testing results show that the sewage temperature of the heat pump system in winter is approx. 13.5 °C, the hot water supply temperature is approx. 50 °C, the average COP of the unit is 3.95, and the average COP of the system is 2.96. The calculation results show that the heating energy consumption of the heat pump unit is only 50.81% of that of a traditional heating mode coal-fired boiler and 57.57% of that of an air source heat pump system. In summer, the sewage temperature is approx. 22 °C, the cold-water supply temperature is approx. 5.5 °C, the average COP of the unit is 4.45, and the average COP of the system is 3.25. The cooling energy consumption of the heat pump system is 79.39% of the energy consumption of the traditional chiller and 61.56% of the cooling energy consumption of the air source heat pump system. This shows that the sewage source heat pump system has a remarkable energy-saving effect.

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