NIU receives grant for campus cooling system

by Joe King

The Illinois Clean Energy Community Foundation has awarded a $24,900 grant to NIU to aid in the creation of a more energy-efficient and environmentally-friendly cooling system on campus.

Specifically, the money will be used to study the feasibility of building "thermal energy storage" units on campus. The units would store chilled water or ice, which would be used to help meet air conditioning needs across campus.

The thermal storage units would be an integral part of the campus-wide "district cooling" system that is currently in the design phase. That system will allow the university to eliminate the individual air conditioning units that serve most buildings across campus. Instead, chilled water will be created in large centralized plants and piped around campus for use as needed.

Such systems can be operated much more efficiently than a series of stand-alone air conditioning units, said Jim Bryant, director of the university's Architectural and Engineering Services. "In simplified terms, it is like removing a bunch of window air conditioners from a home and replacing them with central air," he said.

Thermal storage units make such a system even more efficient, explained Ron Beldon, a mechanical engineer in Architectural and Engineering Services, because they would allow the university to create chilled water for use in the system at night when electricity is cheaper, store it, then use it during the day when demand for electricity is high and the energy is expensive.

The storage units would likely take one of two forms. The first option would be a set of heavily insulated water tanks (in ground or above ground) where the chilled water would be stored until needed. The other option, ice storage, would require one or more buildings where the water would be frozen at night, then melted during the day so that the runoff can be piped around campus. In either case, the system would be a closed, continuous loop and the water would be recycled for use again and again.

District cooling is becoming increasingly common around the country and has been used extensively in Chicago's Loop for nearly a decade. In fact, some west and central portions of campus already operate on small-scale versions of such a system.

The new campus system is badly needed, as about 75 percent of chillers in use on campus are near, at or beyond their anticipated life expectancy, the university estimates. Those units are inefficient to operate, expensive to repair and would be extremely expensive to replace one by one.

District cooling systems have a longer lifespan than stand-alone air conditioning units and are more reliable and easier to maintain, Beldon said. The new system, whether it incorporates thermal storage or not, also will be more environmentally friendly because unlike most chillers currently in use on campus, it will not use ozone-depleting refrigerants in the cooling process.

The university has about $17.5 million in funding from Illinois First, the Illinois Capital Development Board and the university already earmarked for construction of two new chiller plant on campus. That budget does not allow for thermal storage units, but they can be added at a later date, Beldon said.

The Clean Energy Community Foundation praised NIU's grant application, saying that it was one of only a few requests approved out of many. They were particularly impressed with those aspects of the project that seek to minimize the environmental impact of the university's energy use.