Performance Evaluation of Cleanroom Environmental Systems

Abstract

This paper presents in-situ measurement results for energy and environmental performance of thirteen cleanroom systems located in the USA, including key metrics for evaluating cleanroom air system performance and overall electric power intensity. Comparisons with the IEST Recommended Practice (IEST-RP-CC012.1) are made to examine the performance of cleanroom air systems. Based upon the results, the paper discusses likely opportunities for improving cleanroom energy efficiency while maintaining effective contamination control. The paper concludes that there are wide variations in energy performance of cleanroom environmental systems, and that performance benchmarking can serve as a vehicle to identify energy efficient cleanroom design practices and to highlight important issues in cleanroom operation and maintenance.

Opportunities for sustainable design and operation of cleanspaces: A case study on minienvironment system performance

“…If we convert the airflows into actual air change rates for the minienvironment studied, the actual air change rates ranged from 480 to 800 air changes per hour corresponding to the airflow speeds ranging from 60 fpm to 100 fpm. The air change rate range of the minienvironment was higher than the range observed from those of ISO Cleanliness Class 4 cleanrooms, which were in the range of 385 to 680 air changes per hour corresponding to airflow speeds ranging from approximately 60 fpm to 120 fpm [13].…”

“…Figure 4 shows the results in air system's energy performance index, with the EPI ranging from 0.20 W/cfm to 0.42 W/cfm corresponding to the range of airflow speeds from approximately 60 fpm to 110 fpm. This was within or lower than the overall benchmarked range observed in many large cleanrooms (ISO Class 4 or Class 5) [13]. The re-circulation air system efficiency for ISO Class 4 and 5 cleanrooms ranged from approximately 1,100 cfm/kW to 10,500 cfm/kW, corresponding to the approximate range of EPI values of 0.10 W/cfm to 0.90 W/cfm for all recirculation air systems.…”

“…Cleanliness Class 4 cleanrooms that was in the range of 16 W/ft 2 to 38 W/ft 2 [13,14]. Given a same airflow speed in general, the power density of the minienvironment tended to be slightly higher than those of cleanrooms of similar cleanliness requirements, especially when the cleanrooms were not fully covered by HEPA filters.…”

Considerations for Efficient Airflow Design in Cleanrooms

“…To avoid ambiguity, we define cleanroom air velocity as the total circulation airflow rate divided by primary cleanroom floor area (meters per second or feet per minute); and cleanroom air change rate as the total circulation airflow rate divided by primary cleanroom volume (per hour). A prior study by Xu et al 3 of relevant publications found various industry recommendations 7,8 for airflow ranges; however, in-situ measurements showed actual airflow rates (average air velocity or air change rate) were often much lower than the recommended ranges. Recent discussions on an update to IEST-RP-CC-012.…”

“…In particular, cleanroom cleanliness requirements specified by cleanliness class 1,2 have an impact on overall energy use. A previous study 3 covering Europe and the US reveals annual cleanroom electricity usage for cooling and fan energy varies significantly depending on cleanliness class, and may account for up to three-quarters of total annual operating costs. A study on a semiconductor cleanroom in Japan 4 found air delivery systems account for more than 30% of total power consumption.…”