Cleanroom energy benchmarking results Page: 4 of 12
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greatly from cleanroom to cleanroom. Some industries use production metrics relating energy use (in watts) to
number of units of produced. The semiconductor industry, for example, considers watts/cm2 of silicon wafer. These
types of metrics focus on overall production efficiency but overlook, or mask, the efficiency (and opportunities for
improvement) of energy intensive HVAC systems and other facility systems. It is therefore possible to have
seemingly efficient manufacturing and/or continuous improvement through manufacturing process improvements,
while continuing to operate inefficient HVAC systems.
This paper presents the results of a study to benchmark measured energy performance in cleanrooms. The project
developed a benchmarking strategy to obtain the energy end use breakdown for the various industries represented in
the study, and to enable direct performance comparison between cleanrooms regardless of the process. The metrics
used allow comparison of energy performance of key systems and components. This paper describes the metrics
used in this study and discusses some of the results obtained during the course of this work. It also provides
summary benchmarks for the HVAC systems for all of the participating cleanrooms. Preliminary results were
previously reported at the ACEEE Summer Study on Industrial Energy Efficiency (Tschudi et al. 2001).
HVAC systems serving cleanroom facilities are typically energy intensive. They include large central plant heating
and cooling, huge amounts of air recirculation, and make-up and exhaust ventilation. They frequently have
demanding environmental considerations with tightly controlled temperature and humidity for worker comfort,
safety, and/or process requirements. Prior research and industry studies have documented representative energy
intensity and some of the opportunities for efficiency improvement (Mills et al. 1996). Representative breakdowns
of total energy use in a cleanroom highlight the need to focus on the HVAC systems for energy efficiency
Recirculation airflows vary considerably based upon cleanliness class, air change rates recommended by the
Institute of Environmental Sciences and Technology (IEST), and individual operating preferences. Exhaust, and
corresponding make-up air requirements, are primarily governed by building and fire codes, and/or insurance
requirements. Within these recommendations and requirements, there is considerable flexibility for the cleanroom
designer and operator to choose air change rates, overall system configuration, and layout that will affect the HVAC
systems' energy performance. We observed a wide variability in performance.
Office (Lights, Plugs)
14% Chilled Water
13% Hot Water & Steam
Compressed Air &
6% Cleanroom Fans
Figure 2. Energy end-use in production cleanroom.
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Tschudi, William & Xu, Tengfang. Cleanroom energy benchmarking results, article, September 1, 2001; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc784920/m1/4/: accessed December 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.