Wastewater Heat Extraction for Commercial HVAC Applications: A U.S. Pilot Project

Abstract

NovaThermal Energy's wastewater heat pump technology combines a geothermal heat pump with a patented filtration device to transfer heat energy directly from wastewater for commercial HVAC applications. By tapping directly into the pre-existing pipe system provided by the sewer infrastructure, the technology delivers geothermal savings to large urban buildings (> 100,000 sq ft) where traditional geothermal is often infeasible. Heat pumps move heat from one location to another, drawing heat from environmental sources (air, groundwater, and wastewater) and transferring that heat into buildings. Wastewater follows a highly predictable temperature curve relative to outside air, and is warm in the winter and cool in the summer. In the heating cycle, warm wastewater is transported to the wastewater heat pump which absorbs this heat. The heat pump then transfers heat to the building's clean water circulation loop, which provides heating to the building. The wastewater is then returned to the sewer main, whereupon the 6~20 o F degree temperature differential is dissipated. NovaThermal Energy's filtration device makes direct use of wastewater feasible without creating blockage in the heat pump system. The high efficiency heat pump has a coefficient of performance (COP) of up to 6.26 in the cooling mode. The system is being installed and tested at the 20,000 sq ft (1,858 m 2 ) Philadelphia Water Department (PWD) Compressor Building in the Southeast Wastewater Treatment plant in the City of Philadelphia.