Energy-Saving Potential of Seawater-Source Heat Pump District Heating System over Boiler-House District Heating System

The seawater-source heat pump district heating system (SSHPDHS) is a renewable energy utilization system. However, under what conditions can the system achieve its energy-saving effect and how to evaluate its energy-saving potential are not very clear in practice, yet they are of vital importance for the popularization of the system in the cold coastal area. The paper derived an expression of the critical COP value of the heat pump unit for energy-saving (COP_h,c) through the comparison of the SSHPDHS and the conventional boiler-house district heating system (BHDHS) in energy consumption aspect. At the same time, the actual COP values of a heat pump unit (COP_h,a) under different evaporator water temperatures are calculated out by an experiment data regression model on the basis of the manufacturer´s dataset. Then the comparison of COP_h,c and COP_h,a under several typical scenarios are presented, which make the energy-saving judgement of an SSHPDHS and its energy-saving potential readily available. It concludes that the utilization of renewable energy of the SSHPDHS cannot guarantee its energy-saving effect due to the restriction of the actual COP value of a heat pump unit. It is also found that both the natural conditions of the seawater and the heating district radius (R_H) are the most important factors that affect the energy-saving potential of the SSHPDHS.