Have you wondered what happens to all the hot water that you use in your homes for showers or washing dishes? This water goes into our city's sewage system.
Now imagine tapping into this wasted heat and using the recovered energy to heat and cool buildings. Known as sewer energy, this unconventional source of energy may very well be at the forefront of the future clean energy revolution.
Cities are realizing that wastewater is a valuable resource of heat energy that can be harnessed and processed in treatment plants to power homes. One estimate measures that American cities lose about 350 billion kilowatt-hours of waste energy -- enough to power 30 million homes!
As the U.S city of Denver in Colorado begins to take the lead in the project of utilizing sewer energy, many cities are following and employing this eco-friendly source of energy.
A Unique Proposal
Mining sewer energy may be a simpler process than you think. In Denver, Colorado, work has already started on the construction of a wastewater energy retrieval plant.
A large pit in the new facility contains the main sewer line, through which the wastewater flows at a constant 55ºF to 75ºF. A large heat pump will transfer heat from the wastewater to a clean-water loop that is pumped to buildings around the city. This recovered energy can be used to heat water, heat indoor spaces in buildings, as well as power air conditioning units.
The wastewater system operates similarly to geothermal energy. Since the sewage is always kept at a fairly constant temperature, much like the energy from the Earth used by geothermal systems, it takes much less energy to heat this water up than cold water. This eco-friendly method also makes use of wastewater that would otherwise cause harm to local wildlife if it were released directly into river systems.
However, there are some roadblocks to using sewer energy. Such a system functions best when used in districts that have central heating and cooling systems. Experts say careful planning is necessary when deciding how to implement the sewer recovery system.
Sewer Energy in Action!
Denver is one of the first U.S cities to begin a major project of wastewater recovery. The harvested energy will be used to heat and cool a newly designed center to be used for art, education, and agriculture.
Cities worldwide such as Tokyo, Oslo, and Chicago have already begun to harness sewage using major wastewater recovery systems. In fact, in Vancouver, Canada, sewage energy provides 70% of the energy to the Olympic Village community.
Using energy from wastewater is certainly a unique method of powering your home, but in just a few years, it may just prove to be one of the key players in the energy industry.
Sources: NPR, WRI, National Geographic