Mmm, warm, flowing sewage. Warm enough, in fact, to extract energy for heating and cooling buildings. Climate control in Philadelphia's Southeast Wastewater Treatment Plant is now powered in part by "wastewater geothermal energy." The plant is part of a pilot project run by Philadelphia-based NovaThermal Energy and is the company's first U.S. installation of its technology, which was originally developed in China. Philadelphia mayor Michael Nutter held a ribbon-cutting ceremony for project April 12. The company expects its system to cut heating costs in half, according to its website.
Wastewater geothermal energy works much like conventional geothermal technology, except it extracts heat from the constant, warm temperatures of sewage instead of the warm core of the Earth. Wastewater is warm because it comes from dishwashers, showers and warm industrial plants, NovaThermal's chief engineer, Jimmy Wang, told the Philadelphia Inquirer. It's also warm, of course, from human "biomatter," he added.
NovaThermal's first U.S. unit sits in the Philadelphia treatment plant's basement, adjacent to a sewage channel. The sewage passes through a geothermal heat pump that extracts and concentrates the heat. The pump then passes the heat into the building in pipes. In the summer, NovaThermal's loop of pipes carry heat away from the building.
The patented portion of NovaThermal's system is an "Anti-Block" machine that removes solid matter from sewage before it enters the heat pump, potentially damaging the pump. So it can use any kind of water, including wastewater, without needing to treat the water.
Though this first installation is in a sewage plant, the technology can be used in any building located near a major sewer main. In China, NovaThermal provides the power for the Southern Beijing Train Station, a "luxury residential apartment" complex called Tianjin Chateau, the municipal building for the province of Shanxi and two hotels, according to NovaThermal. U.S. projects in the works include hotels in Texas, a nursing home in New Jersey and office, retail and apartment buildings in Philadelphia.