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By Terrence Morris & Steve Blaine PE, CH2M HILL, Oregon, USA

ABSTRACT

Outside of the process tools themselves, the chilled water plant is typically the single largest consumer of electrical energy in a semiconductor facility. This load includes not just chillers but also cooling tower fans, primary pumps, secondary pumps and condenser pumps. In order to meet the cooling requirements for any particular heat load, many different combinations of this equipment can be run. However, electricity consumption varies considerably depending on the combination of equipment used and the operating levels of the individual components. Selecting the optimal mix of equipment and operating levels presents a substantial challenge for an automatic control system and plant operators. Typically, no method is available to predict the effect of interactions and variations in load demand and outside air. This makes it challenging, if not impossible, to find an equipment mix that achieves optimal energy use. In response to this challenge, we set out to create a model/tool that would allow operators to automatically determine the optimal equipment mix to satisfy cooling requirements and minimize energy use. This paper describes how this model was created and how it works.