Demonstration Projects - Cleanrooms

Demand-controlled Filtration in Cleanrooms

LBNL has developed a methodology for controlling cleanroom airflow based upon contamination levels in the room. Using commercially available particle counters, fan speeds are directly controlled by sensing particle counts in real time (rather than full-time, full-speed ventilation based on little more than rules of thumb.) Since fan energy varies with the cube of fan speed, small changes in fan speed will lead to large changes in fan energy. In a pilot study, LBNL implemented the strategy in a 300 ft2 ISO class 5 cleanroom, measuring particle concentrations using multiple particle counting instruments while changing recirculation system fan speeds. The results validated our expectation that DCF can save energy, i.e. higher fan speeds (step curve to left) do not necessarily mean lower particle counts (jagged curve to left). There may be an optimum recirculation fan speed that is unique to each facility and/or processes occurring in each facility. Following the pilot study, the strategy was demonstrated in an industrial cleanroom where again, large energy savings were realized through lower air flow when contamination levels were low. Other control strategies using timers and occupancy sensors were also demonstrated and similarly showed the potential for energy savings. In a previous study we estimated that implementing DCF had a payback time of 1 to 4 years. [more information]

Characterizing Cleanroom Minienvironments

Cleanrooms have extraordinarily high rates of energy use in part because they are traditionally configured to maintain ultra clean conditions over very large areas. However, sensitive processes requiring high cleanliness levels are only carried out in relatively small areas within the larger cleanroom. “Minienvironment” technologies—essentially a cleanroom within a cleanroom—can be used to isolate these sensitive processes, thereby reducing the risk of contamination. LBNL field tests have shown that—if cleanliness conditions are appropriately relaxed in the main cleanroom through the use of minienvironments--significant energy savings can also result. In addition, we found that the efficiency of minienvironments varies widely, depending largely on the quality of the fan filter unit used to provide filtered air to the minienvironment. Simply installing a minienvironment does not guaranty energy savings. [more information]