A Novel District Heating System Coupled with Reclaimed Water Source Heat Pump: Energy, Economic, Environmental, and Application Analysis

The large amount of low-grade thermal energy from reclaimed water is not fully utilized. It can be used as a good heat supplement for district heating. A novel district heating system coupled with a reclaimed water source heat pump (RWSHP) is proposed in this article. The models of energy efficiency, economic feasibility, environmental benefits, and application suitability are established to analyze three typical systems including the traditional district heating system (TDHS), the direct heating system using RWSHP (D-RWSHP), and the traditional district heating system coupled with RWSHP (T-RWSHP). The results show that the energy consumption and operating costs of T-RWSHP are lower than those of TDHS. T-RWSHP can achieve longer distance heating than D-RWSHP. Under design conditions, the annual energy consumption of T-RWSHP can be reduced by 11.36% and the annual operating costs can be reduced by 5.8 CNY m(-2) compared with TDHS. Taking the Yanqing wastewater treatment plant as an example, the heating area of D-RWSHP is only 2% of that of T-RWSHP. According to the sensitivity analysis, the energy consumption, operating costs, and CO2 emissions of the system decrease greatly with the increase of temperature difference between the influent and effluent reclaimed water of RWSHP.