Performance Analysis and Optimization of Hybrid Wastewater Heat Pump Systems Using Numerical Simulation

Wastewater heat pump (WWHP) systems utilize raw wastewater flowing through a sewer pipe to serve as an energy source/sink and provide space conditioning to buildings. These systems can be hybridized by coupling them with conventional heat addition and rejection equipment such as natural gas fired boilers and cooling towers. Numerical simulation is used to analyze and optimize the performance of a WWHP system and its hybrid variant for three distinct climate zones. An optimization algorithm is used to determine ideal temperature setpoints for each major component of the hybrid WWHP system. The results of the WWHP system are compared against a conventional water loop heat pump (WLHP) system in terms of energy consumption, financial viability, and CO2emissions. It is concluded that WWHP systems are an excellent alternative to WLHP systems, both in terms of financial performance and environment impact, for mild and heating dominated climates.