Energy benchmarking Continuous process improvement is aided by observing actual energy use in operating cleanrooms. By studying the better performing systems, an engineer can debunk old myths and find innovative new solutions.
Energy benchmarking Building owners can compare performance against similar systems without regard to the process in the room.
Goal setting and benchmarking • Facility and End Use “Energy Budgets” • Efficiency Targets or Design Requirements for Key Systems and Components • Cfm/KW • KW/ton • System resistance – i.e. Pressure drop • Face velocities • Etc.
System efficiency metrics vs. production metrics • Compare HVAC systems regardless of process • Focus on HVAC system’s efficiency • Production metrics can mask inefficient systems
Cleanroom HVAC metrics • Air systems – cfm/kW; cfm/ft2 • Recirculation • Make-up • Exhaust • Cleanroom air changes – ACH/hr • Re-circulated, filtered air • Outside air (Make-up and Exhaust)
Cleanroom HVAC metrics Chilled water efficiency – kW/ton • Chiller • Tower • condenser pump • chilled water pump • total chilled water plant
Recirculation air change rates • Studies confirm that air-change rates are often higher than is needed • Benchmark data confirms that many achieve contamination control with lower air changes • Since fan power is roughly proportional to the cube of the airflow, small reductions yield large energy savings • Use of benchmark data and other studies can be used to set energy efficient air change rates • Right Sizing Air Change Rates can result in lower construction costs and lower energy costs
Recirculation systems • Benchmark data reveals large variations in efficiency • All energy in recirculation path (air movement and conditioning) needs to be included • System pressure drop is key concern • Air flow setback may achieve additional savings • Efficient fans and motors can make a difference
Pressure drop is key Benchmark data illustrated that ducted HEPA filters (high pressure drops) were the worst performers
Make-up Air Opportunities Opportunities when higher than average CFM/kW is observed: • Low face velocity/low pressure drop air handler • Low pressure drop filtration strategy • Run multiple makeup units in parallel • Optimize exhaust air flow
Design Load vs Measured Load Design - Med Temp 39% Annual Average - Med. Temp 66%
Swing Chiller Concept Dual Temperature Chilled Water Plant
Chilled water systems • Potential efficiency measures • High-efficiency variable-speed drive chillers • Low pumping energy schemes such as primary only variable speed pumping • Efficient cooling towers with low approach temperature • Optimized setpoints • Free cooling Optimized setpoints • Dual Temperature Chillers
Chilled water system choices • Free Cooling • Chiller Efficiency • Variable Speed Chiller • System Pressure drop • Primary only or primary/secondary • System controls • Efficient Pumping • Water vs. Air Cooled
DI water opportunity • Variable speed drive RO pump • Lower pressure drop RO membranes • Variable speed drives on DI water recirculation pumps
Benefits of benchmarking • Establish Baseline to Track Performance Over Time • Prioritize Where to Apply Energy Efficiency Improvement Resources • Identify Best Practices • Identify Maintenance and Operational Problems • Operational Cost Savings
Non-energy benefits of benchmarking • Reliability Improvement • Controls • Setpoints • Maintenance needs identified • Leaks • Motors, pumps, Fans • Filters • Chillers, boilers, etc. • Safety issues uncovered • Hazardous air flow
Conclusion • Benchmarking Is Useful to Building Owners, Operators, and Designers • Benchmark results can be used set performance targets and point to efficiency opportunities • More Robust Data is Needed To Identify and Advance Best Practices • “You Can’t Control What You don’t Measure” • If You Have Benchmark Data – Share It!