The Water-Energy Nexus in Large Cities

Abstract

To fully understand water and energy use within a city, both the individual use of these resources and their interactions must be observed. An understanding of this water-energy nexus (WEN) can inform decisions about reducing the use of either resource and the implications that changes in one resource have on the other. These decisions can help a city respond to climate change, demand increases from urbanization, greenhouse gas emission reduction goals, infrastructure sustainability, and economic cost. This thesis uses data from various reports on New York City (NYC) to build a quantitative understanding of the WEN in large cities. The overall flows of water and energy and their interactions are mapped, and quantitative relationships of embeddedness are developed. The most significant interaction of water and energy found was a surface water withdrawal demand for electricity generation of 7.5 billion gallons needed for every trillion Btu of electricity generated. The most significant energy demand in water systems in NYC is electricity demand for wastewater treatment plants, although this would be overshadowed by municipal water treatment if filtration were required for all of NYC’s water, as is likely in other cities. The heating and cooling demand met by the NYC steam system impacts both impacts energy demand and creates an embedded water demand. However, the use of steam that is created as a byproduct from electricity generation instead of petroleum-produced steam or another energy source can lower the city’s overall energy demand.