Texas Lutheran University
TEXAS UNIVERSITY ENJOYS GROWTH THANKS TO A HYBRID PLANT
TRANE HELPS TAKE THE HEAT OFF A THRIVING COLLEGE WITH AN INNOVATIVE SOLUTION
Despite a thriving student body and a beautiful campus 20 miles east of San Antonio, it was apparent Texas Lutheran University had a problem. “We had only 950 tons of usable chiller capacity and on hot days we were sending out water at up to 58 degrees Fahrenheit. We could only barely meet sensible load,” according to Thomas Dodgen, Texas Lutheran University Physical Plant Director. The university, founded in 1891, had a student population of 1,300 and 19 buildings, was planning to expand. But expansion wouldn’t be possible as long as their chiller plant, consisting of two older chillers, couldn’t even support the existing campus. It was time to deal with the present problem and lay the groundwork for a brighter, and cooler, future.
The University hired BMW Engineering and Trane San Antonio to analyze their situation and offer them options. Because the University was looking for growth in the future and it was located in a part of the country where gas and electric prices were frequently competitive, BMW and Trane recommended a hybrid chiller plant. This type of chiller plant employs both electric centrifugal and gas-fired absorption chillers. A TRANE CenTraVac™ centrifugal chiller is the primary unit. These model CVHF units are high efficiency two-stage machines with hermetic compressors that use low-pressure, ecofriendly R-123 refrigerant and offer exceptional efficiency. The gas-powered chiller selected was a TRANE Horizon™ absorption chiller with an integrated gas-fired steam generator. The final piece to the puzzle was a Trane direct-fired Horizon chiller to balance the University’s use of natural gas during the cooling season.
The three chiller plants can operate in any combination, providing chilled water at a much more refreshing 44ºF with water returning at 54ºF. The system is designed as a primary-secondary loop with a plate-and-frame heat exchanger at the mechanical plant, and plant operations are optimized by a Tracer Summit control system. There are many ways to judge the success of this system. One, as Dodgen says, is its flawless operation: “We hear nothing from the students or staff about the comfort system [so] we know we are doing a great job.” Another might be how quickly it helped the university realize energy savings. The university has already begun heavy summer use of natural gas that puts it in a very attractive rate bracket, and as Dodgen says, “Having a good solid load in the summer helps us negotiate a better year-round price.” But in the long run the most telling example of this system’s success is that, since its installation, the University has added a 53,000 sq. ft. residence hall, a 13,00 sq. ft. fitness center and a 12,000 sq. ft. field house—without having to add to their chiller plant. Dodgen says their success has piqued the interest of other many other school districts: “We tell them we really like the hybrid approach. We feel we made the right decision.”
BMW Engineering, Corpus Christi, Texas
Trane, San Antonio, Texas
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