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Water-Energy Nexus: What You Need To Know

Water-Energy Nexus: What You Need To Know

From ASHRAE Journal Newsletter, March 14, 2017

By Amy Wilson, Associate Editor

Using water uses energy. Using energy uses water. This water-energy nexus is becoming a hot topic in the industry, so ASHRAE Technical Committee 2.8 sponsored a comprehensive program to raise awareness at the 2017 ASHRAE Winter Conference.

“The program was well-received,” said Fred Betz, Ph.D., Member ASHRAE, Water-Energy Nexus subcommittee co-chair. “Not a lot of people fully grasp the water-energy nexus, so the program was very comprehensive,” he explained. “We had nine seminars with 30 presentations. The rooms were full and we covered a wide range of topics. Some presentations were on a macro level (like power plants) and some were more micro (like domestic hot water), and more in between. We got a critical mass of information out there.”

Proposed ASHRAE Standard 191
In addition to the program, progress was made on creation of ASHRAE Standard 191, Standard for the Efficient Use of Water in Building Mechanical Systems, during the conference. Betz is also chair of the standing project committee.

“We are hoping to get that out for public review shortly,” Betz said. “We have completed the mechanical section and the process equipment section; one of two modeling compliance paths was completed, with a good start to the second path. The standard is meant to be used in conjunction with Standard 90.1 with some overlap. I’m a heavy user of 90.1. Overall, we got a lot of things finalized, including how to regulate water usage in cooling towers, which took more than a year. Half or more of the water usage in cooling intense facilities can be consumed in cooling towers, so getting it right was critical. We want proposed Standard 191 and Standard 90.1 to work well together.”

What’s Significant About the Water-Energy Nexus?
So what do members of the ASHRAE community need to know about the water-energy nexus? According to Betz, “That as you use water you use energy, and as you use energy you use water. That you need to account for both as you make design decisions.”
Betz reports that many engineers often don’t account for the cost of water, and costs vary greatly across the country. “Often by a factor of 30, and not always in obvious or logical ways,” Betz explains. “For example, water-rich climates don’t always have cheap water, and desert climates don’t always have expensive water. People need to be aware and account for this in design—that water is a bigger driver than energy in some places.”

Many unexpected factors go into determining the cost of water. For example, costs in Chicago are about the same as in Phoenix. Why would this be?
• Availability: supply/demand;
• Quality of water/source; municipality, etc.;
• Whether or not water costs are subsidized by property taxes;
• Age of infrastructure; and
• Amount of growth in the area (increase in demand).

Even within the same region, costs can vary greatly. “You can travel 20 miles down the road and the cost of water can be higher by a factor of three times,” Betz said.

Next Steps

Next, TC 2.8 plans to promote information and awareness at the chapter level. And, this summer, the group will reconvene in Long Beach during ASHRAE’s Annual Conference to address attendee comments compiled during the conference. Also, Betz expects more of a research focus moving forward, with an emphasis on gathering more data. “The next push should be analyzing research to see what’s missing and getting a critical mass of data.”