Field Test Analysis of a Urban Sewage Source Heat Pump System Performance

The sewage flow rate of the urban drainage system is relatively large and generally stable, its sewage temperature range varies relatively lightly and maintains 10~15℃ in winter. The sewage in the drainage system can be the low grade thermal source for building heating and cooling. Sewage source heat pump technology can efficiently extract or discharge the amount of heat from the sewage in the drainage system for building heating or cooling. The field test of the actual operation thermal performance of the sewage source heat pump were carried out and investigated. The sewage source heat pump system were continuously measured for 72 hours. Based on the test datum, the average COP of the heat pump was 4.5. The relationship between energy consumption of system and energy consumption of transportation are analyzed. The analysis shows that the pump of this system cannot match the load change well and the use of variable frequency pump can improve the energy efficiency of the system. Before the use of the sewage source heat pump system, the traditional coal-fired boiler and air-cooled chiller are the heating and cooling system of this building. Compared with the traditional coal-fired boiler and air-cooled chiller, the advantages of sewage source heat pump system in energy saving, economy and environmental protection are analyzed. The results show that: Compared with the original system, direct heat exchange type sewage source heat pump system can save 53% of the primary energy consumption, reduce the annual operating cost by 11%, increase the initial investment by a factor of 14.3%, and the payback period of incremental investment is about 4.7 years. This method not only has better energy saving, saving capital benefit, but also can reduce the local pollutant emission, and has better environmental emission reduction benefits.