Dirty Water’s Potential For Clean Energy
Wastewater may seem like an unorthodox form of alternative energy, but its potential as a source of clean energy is making city planners and developers take a second look, National Geographic reports.
According to NG, calculations put warm wastewater’s energy potential at 350 billion kilowatt hours for every year in the US alone. This is more or less enough to provide power for 30 million American homes. The warm or hot water flushed down the drain from showers, washing machines, dishwashers and others retains energy in the form of heat and maintains a fairly constant temperature (60 °F/15.6 °C) as it flows through pipes and sewers into treatment plants. Though waste water temperature differs according to season and geography, temperatures are constant enough to be a potentially dependable source of energy.
Sewage heat recovery systems take advantage of this energy source through a closed loop system, where a heat pump captures heat energy from warm wastewater and conducts it to clean water flowing into buildings. Using a sewage heat recovery system saves a building considerable amount of energy. An application in a larger scale can supply the energy needs of a community like the Olympic Village in Vancouver, British Columbia. This community has one of the first large-scale heat recovery system built in North America and gets 70% of its energy needs from the system. The facility’s Challenge series page mentions the only other three sewer heat recovery systems around the world that makes use of heat energy from untreated sewage. Two of these are in operation in Oslo, Norway and one in Tokyo, Japan. The community is proud of its False Creek Energy Center and has made parts of the facility public art to underscore its commitment to green living.
Elsewhere in the US dirty water is gaining an audience from city planners and developers, some of which have ignored or set aside its clean energy potential. NG reports that a $175,000 sewage heat recovery system went online earlier this year in Chicago. The system is able to cut energy costs of the James C. Kirie Water Reclamation Plant by 50%, according to district director of engineering Catherine O’ Connor. Despite initial high costs, the system is expected to pay for itself in energy savings in only three years’ time. Moreover, the system only uses 2 percent of the available potential energy in the outflowing water including those from nearby buildings and not only from the facility.
Heat recovery systems for individual buildings can have a greater energy outputs, as wastewater is warmer while it is insulated by the building. Lynn Mueller, the president of International Wastewater Heat Exchange Systems, designs and installs wastewater heat recovery systems particularly fitted for individual buildings. Thanks to Mueller and his company’s system, a number of Vancouver townhouses saw their energy usage drop by 75%.
Developers in Seattle are looking for ways to utilize the heat energy from the area’s over 400 kilometers of pipes that hold warm wastewater. Though further research is needed to obtain crucial and accurate data regarding temperatures and fluctuations, wastewater heat recovery systems remain promising as a potentially significant source of clean energy.
Though it sounds paradoxical at first, further research and development may one day turn dirty water into a significant amount of clean power for modern cities’ energy needs.
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