LBNL Report Number
The HVAC systems in cleanrooms may use 50 percent or more of the total cleanroom energy use. Fan energy use accounts for a significant portion (e.g., over 50%) of the HVAC energy use in cleanrooms such as ISO Classes 3, 4, or 5. Three types of air-handling systems for recirculating airflows are commonly used in cleanrooms: 1) fan-tower systems with pressurized plenum, 2) ducted HEPA systems with distributed-fans, and 3) systems with fan-filter units. Because energy efficiency of the recirculation systems could vary significantly from system type to system type, optimizing aerodynamic performance in air recirculation systems appears to be a useful approach to improve energy efficiency in cleanrooms.
Providing optimal airflows through careful planning, design and operation, including air change rate, airflow uniformity, and airflow speed, is important for controlling particle contamination in cleanrooms. In practice, the use of fan-filter units (FFUs) in the air-handling system is becoming more and more popular because of this type of system may offer a number of advantages. Often modular and portable than traditional recirculation airflow systems, FFUs are easier to install, and can be easily controlled and monitored to maintain filtration performance. Energy efficiency of air handling systems using fan-filter units can, however, be lower than their counterparts and may vary significantly from system to system because of the difference in energy performance, airflow paths, and the operating conditions of FFUs.