The University of Nebraska-Lincoln is constructing a specialized water tank to reduce energy costs and increase efficiency of the City Campus heating and cooling system.
Scheduled to go online in spring 2018, the 8.1 million gallon thermal energy storage tank will work like a battery, holding chilled water in reserve to cool campus buildings during peak demand periods. The system reduces energy costs by chilling the stored water when energy use on campus is low, primarily at night and on weekends.
As a large user of electrical power, the university is billed for both the amount of energy used and a demand charge, which is the rate at which energy is consumed. The demand charge is established during the university’s energy use peak — which is normally established during hot, late August days when demand surges to meet air conditioning needs.
“The thermal energy storage tank allows us to shift the energy used to chill water away from peak-demand periods during the day to lower-demand times at night and on weekends,” said Stefan Newbold, assistant director and engineering manager for facilities planning and construction. “That shift helps flatten the university’s electric load profile, eliminating sharp increases in energy used and resulting in money savings.”
Energy cost savings for the $11.9 million City Campus tank are estimated to be between $850,000 and $900,000 annually. A smaller, 2.1 million gallon tank in use since 2012 on East Campus has recorded yearly energy cost savings of approximately $350,000.
“These tanks are really a very simple concept, but they make big impacts in cost savings,” Newbold said.
Thermal energy storage tanks also provide redundancy to meet the university’s cooling needs and reduce wear and tear on existing chillers. The City Campus tank — which could provide air conditioning to an estimated 1,600 average-sized homes — was also designed to supply chilled water to future university facilities built on the east side of Salt Creek.
“This new tank will allow us to meet campus cooling needs anytime a chiller has to go offline for repairs or maintenance,” Newbold said. “It also extends the lifespan of the chillers by reducing the number of hours they have to operate.”
The tank is being built immediately north of landscape services buildings near 17th and Y streets. Construction started in November and will be substantially completed in fall 2017.
Tank capacity can supply chilled water to City Campus for six to eight hours during peak demand periods. The tank will be full automated and controlled remotely from the City Campus Utility Plant near 14th and W streets.
The tank itself will be made of welded plate steel skinned by a layer of insulation covered by decorative aluminum paneling. A detention pond designed to handle storm water runoff from the top of the tank and support building is also being integrated into the site.
A City Campus chilled water outage planned for Dec. 21 to Jan. 4 will install new 36-inch diameter pipe valves at 16th and W streets. The thermal energy storage tank will connect to the campus’ chilled water system via the new valves.
For more information on Nebraska’s thermal energy storage tanks, click here.
