Implementing thermal energy networks (TENs) in neighborhoods, including commercial buildings, convention centers, and hotels, can significantly reduce water usage, as outlined in a new report by the Building Decarbonization Coalition.
Analyzing eight sites that utilize TENs for heating and cooling, the study found that building operators saved a combined 337 million gallons of fresh water annually. This volume equates to the average yearly water use of 3,000 U.S. households or enough to fill 511 Olympic-sized swimming pools.
“Decarbonization and water conservation are defining sustainability issues of the next decade, but too often, they are handled separately,” stated Ashley Besic, Senior Associate of Thermal Energy Networks at the Building Decarbonization Coalition and author of the report. “This makes a clear case that TENs should be seen as a water conservation tool, not just an emissions reduction or energy savings tool. Collecting more data to understand their full water-savings potential is critical as temperatures rise, drought persists, and more buildings must decarbonize while keeping occupants cool.”
Commercial buildings consume between 5 and 15 billion gallons of water daily, comparable to the daily water use of approximately 50 million Americans. This high water consumption is primarily due to cooling systems that use chillers and cooling towers to dissipate excess heat via evaporation. In contrast, TENs use a network of underground water pipes to recycle heat, providing efficient heating and cooling to multiple buildings. For instance, Miami University reduced its water usage by 43% by installing a district energy system using geothermal energy, serving a network of 39 buildings.
“Cooling towers are the second-largest consumer of potable water in our built environment,” explained Jay Egg, President of Egg Geothermal. “By converting buildings to geothermal exchange, we can reduce water consumption as well as our cooling load and electrical demand in the summer, a double benefit across the nation.”
Thermal energy networks have proven effective in various climates and geographies. Colorado Mesa University reduced its water use by 60% per square foot of conditioned space after installing a thermal energy network in 2008. Microsoft saves 8 million gallons of water annually at its Redmond campus due to its district energy system utilizing chilled and hot water tanks. Additionally, Nashville International Airport and Cornell University save approximately 30 million and 4 million gallons of water annually, respectively, using lake source cooling systems.
“So far, building owners or organizations have generally installed TENs to reduce emissions, increase efficiency, and save on energy costs; water savings have been seen as a nice bonus,” said Ania Camargo, Thermal Energy Networks Senior Manager at the Building Decarbonization Coalition. “With utilities launching TENs pilots across the country and seven states passing TENs-enabling legislation, this is an opportunity to save water at scale. Instead of evaporating heat away from buildings, we can harness it to heat buildings or water down the street.”
The report underscores the importance of consistent and rigorous data collection to maximize water savings potential. This includes assessing existing heating and cooling infrastructure and standardizing water data reporting. With the number of heat waves in the U.S. tripling over the past 60 years, efficient cooling remains a health and safety necessity. The report calls on researchers, system designers, facilities managers, policymakers, and advocates to prioritize these steps to optimize the adoption of TENs in their specific contexts.
