This is another in our series of stories identifying new technologies and actions that can slow climate change, reduce its impacts or help communities cope with a rapidly changing world.
Flush a toilet with water that could be used for drinking? With water shortages on the rise, coastal cities may have a better option: seawater. Ocean water also can be used to cool buildings. This second idea could help cities reduce their carbon footprint and slow climate change.
So conclude the authors of a March 9 study in Environmental Science and Technology.
Oceans cover most of the planet. Although plentiful, their water is too salty to drink. But it could serve as an important and still largely untapped resource for many coastal cities. The idea came to Zi Zhang shortly after she moved from Michigan to Hong Kong a few years ago to get a PhD in engineering.
Hong Kong sits on the coast of China. For more than 50 years, seawater has flowed through the city’s toilets. And in 2013, Hong Kong built a system that used seawater to cool part of the city. The system pumps cold seawater into a plant with heat exchangers. The seawater absorbs heat to chill pipes full of circulating water. That chilled water then flows into buildings to cool their rooms. The slightly warmed seawater is pumped back into the ocean. Known as district cooling, this type of system tends to use far less energy than typical air conditioners.
Zhang wondered: How much water and energy had this tactic saved Hong Kong? And why weren’t other coastal cities doing this? Zhang and her team at the Hong Kong University of Science and Technology set out for answers.
Water, power and carbon savings
The group focused on Hong Kong and two other big coastal cities: Jeddah, Saudi Arabia, and Miami, Fla. The idea was to see what it might look like if all three adopted city-wide saltwater systems. The cities’ climates were quite different. But all three were densely populated, which should…
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