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Energy-Water-Air Conditioning Nexus
Henry W. Johnstone, PE, President of GLHN Architects and Engineers, Inc.
Photo: Wikimedia Commons
The dynamic relationship between water and energy has become a national topic in recent years and is of particular interest to those in Arizona, where projections of water scarcity and changes in electrical generation are frequently reported in the media. This presentation will provide a brief overview of the sources and sinks of energy and water in Arizona then focus on their interaction at campus or municipal district scale. Relative per capita magnitudes of water consumption for both domestic use and use in cooling the built environment will be reviewed. As air conditioning is often the primary consumer of both electric power and water within campus boundaries, we will explore the trade-offs between energy and water efficiency in building cooling. A summary will suggest concepts in policy, planning, and design that address this element of sustainability in the built environment.
The presentation, which involves extensive use of the Sankey diagram - a graphical tool to compare and contrast relative magnitudes of energy and water flow - has been refined over a number of years through talks to various audiences, including the International District Energy Association 2017 annual conference and International Cooling Conference in Dubai, UAE, Tucson Metropolitan Pima Alliance, and Tucson Mayor’s Energy Conference. While past versions were aimed at engineers, and planners, this discussion focuses on management and policy, attempting to provide an understanding of the water-energy relationship and its role in satisfying one of the principal requirements of the built environment.
Henry Johnstone moved to Arizona in the late 1970s to pursue an interest in active solar energy systems at the UArizona which culminated in study of salt gradient solar thermal ponds at the Solar Energy Research Institute in Golden, Colorado. His 33-year career in mechanical engineering began at GLHN, a Tucson based architectural engineering consulting firm. He was Principal-in-Charge and Mechanical Engineer-of-Record for the award winning UArizona Environmental and Natural Resources Building (ENR 2).