As in life, so it is in energy storage: maturity is often not considered very sexy. With all the attention lately being showered on lithium-ion battery energy storage systems, we might forget to consider an effective storage technology that has been around awhile. However, the facilities systems team at the University of Nebraska–Lincoln (UNL) is showing its appreciation for maturity by planning a new chilled-water thermal energy storage (TES) cooling system at its City Campus.
Shaving the peak
Like many satisfied TES cooling system owners, including the California State University system with 19 TES installations on 14 campuses, UNL is a repeat customer. The university’s first experience with the technology was a 2.4 million-gallon system installed at its East Campus location in 2009.
As the largest load served by Lincoln Electric System, UNL was looking for a way to lower its high demand charges. TES uses off-peak electricity to chill water for cooling a building or a group of buildings during the hottest time of day when electricity is most expensive. “Electricity rates are not usually the driver for installing TES, especially in a state like Nebraska where electricity is very inexpensive,” explained Lalit Agarwal, interim director of utility and energy management for UNL’s facilities systems.
The City Campus TES will save UNL between $800,000 and $900,000 annually in demand savings by shifting chilled water production from peak to off-peak hours. Agarwal suspects that there are additional savings because chillers run more efficiently at night when it is cooler. “But we are not hanging our hat on those figures,” he added.
Right technology for right place
Before finalizing the decision to build a second TES cooling system on the City Campus, the facilities team weighed other options. Cool Solutions, a thermal energy storage consulting company, performed a scoping study for UNL.
In addition to being extremely cost effective, TES leads the other technologies in such areas as safety, ease of permitting and life expectancy. Siting flexibility is another advantage TES offers that was particularly important for UNL, as the City Campus is “landlocked,” observed Agarwal. “There is a certain amount of NIMBY-ism [not in my backyard] involved with other types of systems and only so many places we can build,” he acknowledged.
Related to the siting issue is the ease with which TES can be expanded. The system will be located on the edge of the campus and have oversized piping so it can be expanded in the future. Stefan Newbold, director of UNL Engineering Services, pointed out that the ideal time to look at installing TES is when a chilled water plant is already close to reaching its capacity. “It grows chilled water capacity significantly,” he explained. “TES is economical anyway, but it becomes more so when you throw in not having to expand a chilled water plant.”
Findings from the Cool Solutions study made up the basis of an article in District Energy’s quarterly newsletter. The story also included a comparison of TES with a hypothetical battery system.
Tried and true pays off
The new TES system, which has four times the capacity of the East Campus plant, will be commissioned over the winter and spring, and be ready for the 2018 cooling season. The system controls will be centralized to eliminate the need for additional staff and to minimize new demands on existing staff. Using existing infrastructure and operators who already have chiller experience is another way the technology keeps costs down.
As the grid and the power supply continue to evolve, large facilities and municipalities will have to look at new solutions for managing their energy use. And while every end-user faces different circumstances, UNL’s story is a reminder that sometimes the best answer to a new challenge is an “old” idea.
Source: District Energy, 2nd Quarter 2017