2007 ASHRAE Annual Meeting Conserving Natural Resource Use in Buildings William Tschudi – Tengfang Xu – Lawrence Berkeley National Laboratory ASHRAE Annual Meeting Long Beach, California Fan-Filter Testing - The Results Are In

Overview Background leading to testing fan-filter units Description of test configuration Illustrative results Use of the procedure Possible next steps

Background Previous cleanroom benchmarking illustrated a large variation in air recirculation efficiency Systems with fan-filter units typically were found to be less efficient

Benchmarked Recirculation System Efficiencies

Background, con ’ t In 2000, a Taiwanese Research Institute evaluated fan-filter units – a wide range of performance was noted

Background, con ’ t We then began developing a standard test procedure for fan-filter units to help get “ apples-to-apples ” comparisons The procedure is now available on our website. It was used in the evaluation of 17 2 ’ x4 ’ fan-filter units to “ test ” the procedure and obtain performance information

Test Configuration Layout in test lab

Configuration was dictated by space available

Flow meter An Accurate, Calibrated Flow Nozzle Determined Air Flow

Flow measurement: Accuracy of a flow meter (Nozzle) compared to a flow hood was studied Accuracy of a flow meter (Nozzle) compared to a flow hood was studied Discrepancies were observed across units between the two methods Discrepancies were observed across units between the two methods Flow meter gives consistent, accurate results Flow meter gives consistent, accurate results

Pressure Tap (Pitot Tube) Pressures were determined at various places throughout the system

Electric Power Monitoring Equip. Available From Utility Tool Lending Library

Testing Considerations Air flow rate measurements Pressure measurements Power Device calibration and uncertainties Integrity of the testing system, e.g. leakage Size of testing rig Additional parameters, e.g., space/material cost Ambient conditions

Sample Operating conditions Unit with AC motor tested within its operating range

Operating conditions, cont. Unit with ECM motor tested within its operating range

Total electric power demand of the fan filter unit under selected operable conditions: 20 Pa ≤ Dp ≤ 150 Pa, Q ≥ 9.9 m3/min (or 0.08 iwc ≤ Dp ≤ 0.6 iwc, Q ≥ 350 scfm) Airflow cfm

Total Pressure Efficiency For FFUs with a multi-speed-drive, the total electric power demand may be calculated as: Dp is the pressure differential across the fan filter unit Q is the airflow rate across the unit under standard atmospheric condition. Ci,j (i, j = 0, 1, 2) is a coefficient developed from experimental data through polynomial regressions.

FFU power efficiency FFU power efficiency (Et) is defined as the airflow dynamic power divided by the total electric power input to the FFU unit. The FFU power efficiency includes electrical and mechanical efficiency of the FFU unit taking into account fan motors, fan design, housing, etc. Et = Pt Q / W Pt = FFU pressure rise (Pa) Q = air flow rate (m3/s) W = electric power input to FFU (W)

FFU Total Pressure Efficiency

Total pressure efficiency of the fan filter unit under selected operable conditions: 20 Pa ≤ Dp ≤ 150 Pa, Q ≥ 9.9 m3/min (or 0.08 iwc ≤ Dp ≤ 0.6 iwc, Q ≥ 350 scfm) Airflow cfm

Total pressure efficiency of the fan filter unit under selected operable conditions: 20 Pa ≤ Dp ≤ 150 Pa, Q ≥ 9.9 m3/min (or 0.08 iwc ≤ Dp ≤ 0.6 iwc, Q ≥ 350 scfm) Airflow cfm

Efficiency Comparisons Variations in electric power and efficiency More than a factor of 10 difference for the same unit across different operating conditions Different units varied by 3 to 4 times for the same operating condition Variation patterns not obvious

Efficiency in the Range of Interest

Variation of FFU Efficiency Xu, T (9). Cleanrooms Magazine. Standard Development and Laboratory Testing of Fan Filter Units

Efficiency Comparisons ECM motors tended to be more efficient however overall unit design influences efficiency Simple metrics not sufficient – depends upon pressure and flow

How to Identify Efficient FFUs Implement Standard Lab Testing Standard test protocols to fully characterize performance Standard reporting Determine expected range of operating conditions Review test results in range of expected operation Select unit considering energy performance along with other desired features

Incentive Criteria Development Relative performance ranking system quantify the observed difference identify rebate-criteria. Relative ranking scores examine the robustness of the suggested initial rebate criteria. Once an incentive criteria is set, units that exceed that threshold can be selected

Recommended Practice IEST RP CC036.1 – Testing Fan Filter Units Working draft of RP036.1 is being developed Interested parties are encouraged to participate

Recommendations Owners/designers - define requirements for Air recirculation Air change rate Air flow rate Cleanliness Uniform air flow System design Pressure conditions

Recommendations Procurement of fan-filter units Define range of operating conditions Require testing in accordance with standard test procedure Evaluate performance in the range of interest Select based upon efficiency or perform life cycle cost analysis

Use of the standard test procedure A major semiconductor manufacturer adopted standard, built a test rig, and required bidders to provide units for testing as part of the procurement process An Asian company required FFU manufacturers to provide test results during the procurement process A semiconductor manufacturer investigated replacing aged FFUs with more efficient units as determined by the test procedure

Reaction to the standard test procedure Manufacturers are eager to know the performance of their units - product improvement is expected Recommended Practice (RP) CC036.1 is planning on adopting the procedure A major utility is considering adding fan-filter units to their incentive program

Possible next steps Recommended practice issued for use Optimize test rig (size) Testing of 4 ’ x4 ’ units Utility incentive programs

Questions??