Like many universities across America, The University of Cincinnati had a major challenge having to operate aging central utility plants with older technology, reduced efficiencies and capacities, with chilled water equipment at the end of its service life. Even so, UC needed to maintain plant operations under diverse load conditions, including critical hospital utility demands that are currently expanding and in daily periods subject to energy tariff.

Free cooling can take two different forms: air-side economizers that directly exchange cool outdoor air with the building or water-side economizers that use outdoor air to cool the chilled water used to cool the building. This article focuses on water-side economization in particular using two different methods: stand-alone dry coolers and air-cooled chillers with integrated free cooling coils. 

A technology called, “cool storage” offers a reliable, cost-effective means of managing electricity costs while ultimately helping to limit greenhouse gas emissions. The technology allows facilities to take advantage of less costly electricity available at night and functionally save that energy for use at a later time. Cool storage achieves this performance by using ice or chilled water as a medium for storing and deploying energy.

Water-cooled chiller plants have three major components that consume electricity: the chiller, the condenser and evaporator pumps, and the cooling tower fan. The chiller consumes the highest amount of total plant room energy. In certain applications, the energy consumption of a chiller is very significant.