Every year, Americans flush an estimated 350 billion kilowatt-hours of energy into the sewers. This comes from warm and hot water waste, a forgotten yet powerful source of energy that may soon be tapped into through sewage heat recovery systems.
The technology is pretty simple for what sounds like a complex procedure. Wastewater is a combination of hot water from showers, dishwashers, washing machines, and other appliances that actually maintains a consistent temperature of about 60 degrees Fahrenheit as it travels through sewers to treatment plants. With sewage recovery, a heat pump captures the warmth of wastewater and transfers it to the clean water entering homes and businesses. It is a closed-loop system, so the water sources never come in contact with each other. This warmth heats the clean water, which is used in showers, dishwashers, washing machines, and radiators to heat homes and buildings.
The key to this is that it takes much less energy to heat 60 degree water than it does to heat cold water. In the summer, buildings with a sewage heat recovery system can reverse the pump and use the sewage to dissipate excess building heat, reducing air conditioning costs. It’s a pretty neat way to reduce both heating and cooling costs by tapping into a waste that is already there.
There is already a system like this in place in Vancouver, British Columbia, that provides 70% of energy to the Olympic Village community. The site was previously an industrial waterfront, and is now a residential and mixed-use enclave on track to becoming one of the greenest communities on the planet. The exhaust stacks are displayed as public artwork, topped with LED lighting that glow blue or red, depending on the current energy demands.
There are also sewage heat recovery systems in Tokyo and Oslo, Norway, so it’s about time the United States gets in on the action. Chicago put one up in May in the Metropolitan Water Reclamation District, an area in desperate need of cutting costs. According to district engineer Catherine O’Connor energy costs for heating and cooling in the facility have been cut by 50%.
Of course, additional research still needs to be done in order to determine how this technology will work in varying climates and environments. It may also be difficult convincing some people that dirty water is a great source of clean energy, but if it proves to cut costs and work well for some places, there’s no reason why it wouldn’t catch on over time.
Do you think this will catch on around the world?
Image courtesy Ausenco Sandwell, City of Vancouver