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Energy Saving of Cleanrooms in Electronic Industries

Energy Saving of Cleanrooms in Electronic Industries. Xu Han Tianjin University, China 2013 .01.11. Outline. Characteristics of cleanrooms Energy consumption of cleanrooms Identification of energy saving opportunities Commissioning. Characteristics .

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Energy Saving of Cleanrooms in Electronic Industries

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  1. Energy Saving of Cleanrooms in Electronic Industries Xu Han Tianjin University, China 2013.01.11

  2. Outline • Characteristics of cleanrooms • Energy consumption of cleanrooms • Identification of energy saving opportunities • Commissioning

  3. Characteristics • Design or control ranges of key parameters for semiconductor cleanrooms Source: ISO 14644, R Schrecengost, 2004

  4. Characteristics • Recommended air change rate • Empirical value1 • Wide range • Variation between standards Air change rate (1/hr) • Note: • Unidirectional airflow type is recommended for ISO Class 1-5, and non-unidirectional for ISO Class 6-8; • Average airflow velocity is specified for unidirectional airflow type and air changes per hour for non-unidirectional airflow type. • The average airflow velocity is transformed to air changes per hour related to a room height of 3.0 meter. ISOcleanliness class Source: [1] R Jaisinghani et al., 2003 [2] IEST RP-12.1 [3] ISO 14644 [4] GB 50073

  5. Outline • Characteristics of cleanrooms • Energy consumption of cleanrooms • Comparison among different countries/regions • Comparison among different cleanliness level • Energy end use allocation • Identification of energy saving opportunities • Commissioning

  6. Energy consumption • Power use of different clean classifications • The power uses were estimated based on typical cleanrooms in CA, USA, by LBNL in 1993; +24.3% +94.9% +90.2% +28.9% • Note: • Airflow velocity updates are taken from Chapter 7 (Class 1&10 to 90 fpm, Class 100 to 70 fpm, Class 1,000 to 30 fpm, Class 10,000 to 10 fpm, and Class 100,000 to 5 fpm) Cleanrooms - 1992-2000, Rooms and Components Vol. Three. • Outside air estimates for cleanroom make-up air (5 cfm/sq.ft. for both heating and cooling): Brown, W.K., PE. “Makeup Air Systems Energy-Saving Opportunities.” ASHRAE Transactions V. 96, 1990. Cleanrooms of higher cleanliness level consume much more energy than its lower level especially when the cleanliness level is 100 or 1000 Source: E Mills et. al,LBNL-39061 Report, 1996

  7. Energy consumption • Power use in different countries/regions • High power use in Taiwan and China; • Fabs in US decrease power use by about 27% within last ten years; • Fabs in China consume 15% more than that in US; [1] Power consumption range of 12 fabs in the USA, from LBNL report , 1999 [2] Power consumption range in Japan, from Japan Mechanical Association, 1990 [3] Power consumption average value of 9 fabs in Taiwan, from SC Hu et al., 2003 [4] Power consumption range of 8” fabs in the USA and China, GM Lu and R Wang,2012

  8. Energy end use in cleanrooms Recir and Makeup Fans 17% Process Tools 39% Chillers and Pumps 21% Exhaust Fans 6% Figure 1 Fab energy flow Source: R Schrecengost, P Naughton, 2004

  9. Energy end use allocation Taiwan China HVAC sector: 53.0% Water treatment Lighting Process Compressed air Figure 1 Average power consumption allocation of 9 fabsin Taiwan1 Air condition HVAC sector: 39.9% Chiller Figure 2 Powerconsumption allocation of a fabin China2 Source: [1] SC Hu, 2003 [2] PX Chen, 2003

  10. Energy end use allocation CA, USA v HVAC sector: 58.0% HVAC sector: 64.0% HVAC sector: 36.0% Source: Report of LBNL HIGH TECH BUILDINGS PROGRAM,2001

  11. Energy end use allocation USA HVAC sector: 46.0% Figure 1 Average electricity consumption in 12 example semiconductor fabs Source: LBNL benchmark project, 2001

  12. Energy end use • Observations: • The HVAC systems account for 40-50% of power consumed in the fabs, while the process tools account for 35-40%; • Among HVAC system, chillers consume 20-35% of the total power used, and fans consume 10-26% of total power used; • HVAC efficiency influenced by: • Airflow system: • Air change rate; • Airflow system efficiency; • Water system: • Chiller plant efficiency; • Operation and Control; • Temperature and relative humidity control;

  13. Outline • Characteristics of cleanrooms • Energy consumption of cleanrooms • Identification of energy saving opportunities • Airflow system: • Air change rate; • Airflow system efficiency; • Water system: • Chiller plant efficiency; • Operation and Control; • Temperature and relative humidity control; • Commissioning

  14. Air change rate Figure 1: Measured air change rates for ISO 5 (Class 100)cleanrooms.1 ISO 5 facility could be operated with an air change rate of approximately 200 air changes per hour and still provide the cleanliness classification required Source: [1] LBNL Cleanroom Benchmarking Study

  15. Air change rate Two cleanrooms of ISO Class-4 exceeded the upper limit recommended by IEST, Energy saving opportunities might well exist in the meanwhile Figure 1 Autual recirculation air change rates for ISO 5/4 cleanrooms.1 Source: [1] LBNL Cleanroom Benchmarking Study

  16. Air change rate • Observations: • Air change rates vary significantly among different cleanrooms having the same cleanliness classification; • The ACR needed depends largely on the mount of contamination, which is not necessarily well understood at design; thus the cleanroom may be designed/operating with more ACR than needed; • Air change rate can be optimized by: • Use mini-environment to reduce area of clean zone; • Measure actual ACR and compare with benchmark and Standard; • Use CFD to model air flows, effects of convention from heat sources to identify minimum downward velocity needed to overcome heat convection, movement of people; • Use distributed particle counters to monitor cleanroom conditions in the real time; • Demand controlled filtration, Automatic set-back, and Occupancy sensors were demonstrated

  17. Airflow efficiency • Air flow efficiency was analyzed separately for the recirculation units (RCU), make-up air units (MAU) • Wide variation in air system performance • Similar average results with International Sematech study Average 1.06 from International Sematech study Average 0.51 from International Sematech study Average 0.49 Average 0.91 Airflow efficiency (W/cfm) Airflow efficiency (W/cfm) Cleanroom ID Cleanroom ID Figure 1 MAU airflow efficiency Figure 2 RCU airflow efficiency Source: LBNL benchmark database and International Sematech study

  18. Airflow efficiency • Relationship between recirculation system efficiency (W/cfm) and ceiling filter exit velocity Source: LBNL benchmark database

  19. Airflow efficiency • Relationship between recirculation system efficiency (W/cfm) and filter coverage Average FFU:0.63 Ducted HPEA:0.58 Pressurized plenum:0.43 Source: LBNL benchmark database

  20. Airflow efficiency • Relationship between recirculation system efficiency (W/cfm) and filter pressure drop Source: LBNL benchmark database

  21. Airflow efficiency • Observations: • Benchmarking results showed wide variation in air system performance; • No necessarily strong correlation between airflow efficiency and ceiling filter exit air velocity/ceiling filter coverage; • Filter pressure drop shows more critical influence on airflow efficiency, which varies with type of airflow system; • Airflow efficiency influenced by: • System pressure drop; • Fan and motor efficiency; • Filter design; • Other system design characteristics.

  22. Water system efficiency • Chilled water system comparison Chiller plant efficiency (kW/Ton) Facility ID Source: LBNL benchmark database

  23. Water system efficiency • Observations: • The Chilled water system efficiency varied, and was similar between water cooled and air cooled systems, but the water system generated chilled water with lower temperature; • The Chilled water system generating 36℉ chilled water consumed 2.67 times energy than that generating 43 ℉ to generated one ton chilled water; • Water system efficiency can be improved by: • Temperature reset may provide substantial savings opportunities; For centrifugal-compressor-based chillers, a 1 ℉ change in chilled-water-supply temperature can increase efficiency by 1-2%. • Medium-temperature (55-70 ℉)chilled water, which potential for “free cooling”; • Optimizing Exhaust; • VSD technologies;

  24. Operation and Control • Temperature and relative humidity control 70 60 50 40 30 20 10 0 22.2 21.1 20.0 18.9 17.8 16.7 15.6 RH (%) Temperature (℃) 3 10 11 12 13 14 18 23 17 24 Temperatures and humidity were not as tightly controlled as specified 3 10 11 12 13 14 18 23 17 24 Cleanroom ID Cleanroom ID Figure 2 Design and Measured Space Temperature Figure 1 Design and Measured Space Relative Humidity Source: LBNL benchmark database

  25. Operation and Control • Observations: • Cleanroom reheat energy usage can be significant when the required space temperature and relative humidity requirements are very stringent； • The temperature and RH measured were not as tightly controlled as specified; • Owners were unaware of actual conditions; • Processes may not need tight control? • Commissioning and monitoring are important; • Energy efficiency opportunities abound

  26. Outline • Characteristics of cleanrooms • Energy consumption of cleanrooms • Identification of energy saving opportunities • Commissioning • Verification • Cleanroom performance • HEPA filters • Other parameters • Commissioning • HVAC air system • HVAC water system

  27. Verification • Cleanroom performance: • Space Particulate level • Room Recovery • Space Pressurization • Space Temperature • Space Humidity • Lighting • Noise

  28. Verification • HEPA filters performance: • Efficiency; • Air leakage; • Air flow; • Air velocity,

  29. Verification • Other parameters: • Cleanroom enclosure • Enclosure Leak Testing to Verify no contamination entering and air leakage is not excessive; • Process equipment • Exhaust air flow

  30. Commissioning • Verification of HVAC air system performance: • Total supply air flow • Total return air flow • MAU operating data

  31. Commissioning • Optimization of HVAC air system : • Optimizing Air-Change Rates • Actual measurement or CFD technology; • A 30% reduction in air-change rate may reduce power consumption by 66%1, and also improve cleanliness by minimizing turbulence • Optimizing make-up air unit and exhaust • Makeup air requirements vary correspondingly, with an added amount for leakage and pressurization; • Heat recovery in process exhaust/condensation; • Optimizing operating and control strategies. [1] Source: a report of Industrial Energy Efficiency Workshop, 2007

  32. Commissioning • Verification of HVAC water system performance: • Design scheme and control strategies of chillers; • History operation data • Chiller-water-supply temperature; • Operating parameters;

  33. Commissioning • Optimization of HVAC water system : • Feasibility study of optimization of operation and control strategy of chillers • through history operation data or simulation to avoid long term part-load operation of chillers with low energy efficiency; • Feasibility study of application of variable frequency technology, dual-temperature, cooling tower, free cooling, heat recovery; • For example, In a pilot project for a multiple-cleanroom-building campus, the implementation of a dual-temperature chilled-water system was analyzed. The site had 2,370 tons of makeup-air cooling and 1,530 tons of sensible and process cooling. With 42-F (5.7C) water for low-temperature use and 55-F (12.8C) water for medium-temperature use, approximately $1 million was saved per year, with a payback of two years1. [1] Source: a report of Industrial Energy Efficiency Workshop, 2007

  34. Thank you!

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