Energy Efficiency Strategies for Cleanrooms without Compromising Environmental Conditions

Traditional cleanroom filtration design and operation relies upon high recirculation air change rates as a means of maintaning acceptable contamination control. Cleanroom professionals accept recommended air-change rates that were established somewhat arbitrarily as rules of thumb. The guidelines were based upon historically adequate cleanroom conditions, but they were not optimized. Disadvantages of this practice include paying a high cost for excessive airflow, as is usually the case, but also production or other work in the cleanroom could be adversely affected by too much or too little airflow. This paper describes research and several case study projects that suggest that control of recirculation airflow by monitoring cleanliness, or other control strategies, is a viable means to improve energy efficiency. One strategy being researched by Lawrence Berkeley National Laboratory and Cornell University in separate projects involves use of particle encounters to continuously measure particle counts to automatically control recirculation air handlers using the building control system. Given that people are the number one source of contamination in cleanrooms, other less sophisticated strategies, such as timed setback or use of occupancy sensors to reduce airflow, have also been studied. This paper discusses the energy-saving potential for routine use of these methods and provides case study results where setbacks strategies were successfully in use.