Spatially-Resolved Analysis of Water Use for Vapor Compression and Evaporative Air Conditioning Systems for Commercial Buildings in the United States.

Abstract

Shifting from electricity-reliant vapor compression (VC) air conditioning systems toward alternatives like evaporative cooling (EC) is one strategy being considered to reduce energy use and electricity demand associated with space cooling in the United States (U.S.). However, little work has been done to understand other environmental consequences of this potential shift. In this work, we assess the consumptive water use of these two technologies for nine commercial building archetypes across the continental U.S. To do so, we modeled on-site water use for EC, electric energy consumed by both VC and EC systems, and water consumed by electricity generation at a regional level. We find that while indirect water use for EC systems is less than that of VC systems by approximately 50%, EC systems consume around 5-8 times as much water overall, owing to their on-site water use. The largest differences occur in the hot, humid climates of the Southeastern U.S. due to the region's large cooling needs and saturated atmosphere. Together, these findings indicate the need to design EC systems that include condensation steps in more closed-loop designs.