DATA CENTER FREE COOLING STRATEGIES Charles B. Kensky, PE, LEED AP BD+C, CEA Executive Vice President Bala Consulting Engineers
OVERVIEW Understand the different types of economizers. Learn how free cooling contributes to energy efficiency and acceptable temperatures in Data Centers. See best practices for year-round economizer operation. Weigh the benefits of economizers with the potential drawbacks.
FREE COOLING STRATEGIES Free Cooling Airside Economizer Waterside Economizer Pumped Refrigerant Adiabatic Cooling
FREE COOLING AIR SIDE Direct Air Exchange T RH F I L T E R T RH Data Center Greatest Energy Savings Longer Free Cooling Periods Humidity Control Key Not Ideal for All Climates Sensible & Latent Capacity IT IT
FREE COOLING AIR SIDE Heat Exchanger T RH Data Center T RH Sensible Capacity Only Slightly Less Energy Savings Slightly Shorter Free Cooling Periods Slightly More $$ IT IT
FREE COOLING AIR SIDE Energy Wheel Data Center F I L T E R Sensible & Latent Capacity Slightly Less Energy Savings Slightly Shorter Free Cooling Periods IT More $$ IT
FREE COOLING WATER SIDE Glycol/Dry-Cooler Moderate Free Cooling Periods Slightly More Fan Energy at CRAC Sensible & Latent Capacity Smaller Tonnages
FREE COOLING WATER SIDE Air Cooled Chiller Moderate Free Cooling Periods Less Fan Energy than Glycol/Dry Cooler Sensible & Latent Capacity Larger Tonnages Limited Manufacturers Available CRAC
FREE COOLING WATER SIDE With Heat Exchanger CRAC Better Free Cooling Periods Freezing of CT is Key Sensible & Latent Capacity Less Fan Energy than Glycol/Dry Cooler Larger Tonnages More Water Treatment Required
Adiabatic Cooling FREE COOLING Reduced Refrigerant Usage Combo Mode Great for Dry Climates Extends Free Cooling Period Comparable to Cooling Tower System High Water Treatment $$
ROW BASED COOLING Cooling Unit No Access Floor Required Cascade Effect Reduced Reduced Fan Energy Provides T+RH Control Redundancy Moderate Challenge Free Cooling Available w/ Chilled Water Units More Units Required VFDs Adjust Airflows to IT Loads (energy savings) IT Changes Challenging Hot Aisle Service Required In Every Row Cold Aisle
WHY CONTAINMENT?
CONTAINMENT Comes in All Different Configurations
CONTAINMENT Hot Aisle Provides Room Conditioning Provides Ride-Through Capacity During Failure IT Staff Work in Hot Zone Easier for Free Cooling Applications (hot air is captured) Cold Aisle Room is Hot Limited Ride-Through in Failure
HOT CONTAINMENT Vertical Exhaust Ducts (Chimneys) Easier to Retrofit on Legacy Data Centers Rear Cabinet Doors Must be Sealed Airflow Differential Pressure Should be Studied Same Performance as Hot Aisle Containment
FREE COOLING Pumped Refrigerant Summer Operation Outdoor Ambient 95 F KW @ 70% Load 24.1 Check Valve Condenser Solenoid Valve Refrigerant Pumps OFF Check Valve Electronic expansion valve Evaporator Circuit 2 Circuit 1 Compressors ON Check Valve
PUMPED REFRIGERANT Partial Economization Fall/Spring/Evening Operation Outdoor Ambient 65 F KW @ 70% Load 15.1 Check Valve ON Condenser Solenoid Valve OFF Refrigerant Pump Check Valve ON Electronic expansion valve Evaporator Circuit 2 Circuit 1 Compressor OFF Check Valve
PUMPED REFRIGERANT Full Economization Winter Operation Check Valve ON Condenser Outdoor Ambient 25 F KW @ 70% Load 3.7 ON Solenoid Valve Electronic expansion valve Refrigerant Pump Moderate Free Cooling Periods Less Fan & Pump Energy than Glycol/Dry Cooler & Chiller Options Sensible & Latent Capacity Evaporator Limited Manufacturers Available Circuit 2 Circuit 1 Check Valve OFF Compressor OFF Check Valve
ASHRAE CHART ASHRAE Recommended (2004) 59DP Inlet Server Conditions Allows Longer Free Cooling Hours Reduces Humidification Needs & Water Usage Improves Mechanical Equip. Efficiency ASHRAE Allowable 62.6DP 41.9DP ASHRAE Recommended (2008 TC9.9) 59 68 77 80.6 90
SUMMARY Cooling Efficiency Tips Hot Aisle Containment Free Cooling ( Air, Water, or Refrigerant) Air Delivery (don t over CFM) Chase the Cold Spots Increase Supply Air Temperatures Lower Humidity Set Points Balance Air Flows and Pressure Localized Cooling Reduces Fan Horsepower
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