DATA CENTER EFFICIENCY: Data Center Temperature Set-point Impact on Cooling Efficiency

Transcription

1 DATA CENTER EFFICIENCY: Data Center Temperature Set-point Impact on Cooling Efficiency September 27 th, 2013 Tejas Desai, PE CEM CEA LEED AP Sameer Behere, PE CEM LEED AP

2 Agenda Problem: Quick fixes can prevent long-term data center energy savings Overview of typical data center energy use 1. Identifying energy usage 2. ASHRAE TC 9.9 Changes 3. Overview of refrigeration cycle Impact of Raising Set-points 1. Efficiency Improvement 2. Capacity Increase 3. Economizer effectiveness 4. Air Flow Reduction 5. Case Study 6. Q&A

3 Problem: Quick fixes can prevent long-term data center energy savings Non-uniform temperature in the Data Centers leads to Hot/Cold Spots Hot spots increase risk of IT equipment failures Quick Fix : set average data center temperature lower than ASHRAE TC9.9 Guidelines (65-80 F) Disadvantages to quick fix : 1. Increase PUE 2. Increase energy consumption 3. Increase operating costs

4 Power Utilization Effectiveness (PUE) PUE = Total Power / IT Power Total Power = IT power, PDU/UPS losses, Lighting Power and HVAC Power IT Power = Servers, Storage and computing support equipment HVAC Power = Fan power, cooling power, pumps, heat rejection PUE is yardstick to compare data centers energy efficiency performance Average data center today operates with PUE of 1.4 to 2.2 based on Willdan s observation Very efficient data center operate at a PUE of 1.1 or better

5 Average Data Center Energy Use Cooling energy accounts for 20-50% of total energy usage Strategy to Improve Cooling energy efficiency: 1. Lower PUE of whole data center 2. Save operational costs

6 ASHRAE TC Environmental Guidelines for Datacom Equipment Temperature and Humidity Settings Recommended by ASHRAE TC 9.9 Ranges Temperature Moisture 2004 Version 2008 Version Low End 20 C (68 F) 18 C (64.4 F) High End 25 C (77 F) 27 C (80.6 F) Low End 40% RH 5.5 C DP (41.9 F) 60% RH & 15 C DP High End 55% RH (59 F DP) Raised temperature set points on high end from 77 F to 80.6 F Relative Humidity limits were also raised Significant testing determined for any class of server equipment this temperature range are safe and minimal failure due to temperature and humidity

7 Data Center Cooling Equipment WATER COOLED CHILLERS CRAC OR CRAH AIR COOLED CHILLERS

8 Refrigeration Vapor Compression Cycle Four main components: 1. Compressor (1-2) 2. Condenser (2-5) 3. Expansion Device (5-6) 4. Evaporator (6-1)

9 Raising Evaporator Stpt Reduces Compressor work Vapor compression cycle with temperature rise for R-22

10 Refrigerants and Compressor Efficiency Refrigerant Case Set Point ( F) Evap in/out ( F) COP Efficiency (kw/ton) % Improvement COP kw/ton R-22 Baseline % 1.63% Proposed R-134a Baseline % 1.56% Proposed R-123 Baseline % 1.87% Proposed R-407a Baseline % 1.33% Proposed R-410a Baseline % 2.06% Proposed Percent improvements of compressor Coefficient of Performance (COP) and kw/ton for refrigerants per every F

11 Impacts of raising evaporator supply temperature (Example R-22 Refrigerant) Refrigeration Effect BTU/lb or Capacity in Tons Ref. Heat Capacity Ton/CFM Raising evaporator supply temperature: 1. Increases cooling capacity 2. Improves efficiency 3. Increases heat capacity of the refrigerant Evaporator Supply Temp F 0 Ref. Effect BTU/lb Capacity in Tons Ref. Heat Capacity Ton/CFM

12 60-ton MultiStack chiller with 20-ton modules EER and Capacity in Tons Efficiency (kw/ton) Raising evaporator temperature: 1. Increases capacity 2. Improves Energy Efficiency Ratio (EER) 3. Improves kw/ton efficiency CHWS F Capacity in Tons EER Eff. kw/ton 0.60

13 400-ton Daikin magnetic bearing water-cooled chiller Chiller Efficiency kw/ton Ton, Water-Cooled Magnetic Bearing Chiller Percentage Part Load 400 ton Water cooled Magnetic Bearing Daikin Chiller Selected % part load efficiencies at variety of CHWS Temp F Efficiency kw/ton Vs % Part Loads CHWS 42 F kw/ton CHWS 45 F kw/ton CHWS 48 F kw/ton CHWS 44 F kw/ton CHWS 46 F kw/ton CHWS 50 F kw/ton

14 170-ton Daikin air-cooled screw chiller Chiller Efficiency kw/ton Ton Air-Cooled Screw Chiller 170-ton air cooled Daikin Screw Pathfinder Chiller Selected % part load efficiencies at variety of CHWS Temp F Efficiency kw/ton Vs % part load Percentage Part Load CHWS 42 F kw/ton CHWS 44 F kw/ton CHWS 46F kw/ton CHWS 48F kw/ton CHWS 50F kw/ton

15 Raising evaporator temperature increases air-side economizer hours Ideal conditions for air-side economizers (Courtesy of U.S. Dept. of Energy and The Green Grid)

16 Raising evaporator temperature increases water-side economizer hours Ideal conditions for water-side economizers (Courtesy of U.S. Dept. of Energy and The Green Grid)

17 Increase economizer hours by increasing set points US Cities with OA Temp 40 F-50 F Chart demonstrates # of hours climate zones 40 F to 50 F, which are equivalent to increased hours for water-side economizers for different cities When space set point rise, SAT or CHWS temp increase linearly Economizer can start at relatively higher temp than standard SAT or chilled water temp for more hours

18 Sensible Cooling Capacity Sensible Cooling Capacity (BTU/Hr) = 1.08 x Airflow (CFM) x (RAT ( F) SAT ( F)) Sensible loads dominate in Data Centers Airflow containment increases RAT temperature Raising space temperature set point enables the supply-fan variable-frequency device (VFD) to operate at reduced speed Increased Delta T (difference between RAT and SAT) reduces air flow requirements, which enables reduced VFD speed or turn off units completely

19 Summary of advantages of raising set points Advantages of raising data center and mission critical temperature set-points 1. Increased cooling equipment capacity 2. Improved cooling equipment efficiency 3. Increased economizer hours for cooling system with economizer capabilities 4. Reduced supply fan speeds for CRAC/CRAHs with VFD supply fans

20 Willdan Case Study Project basics: 124,000 sq.ft. raised floor data center Thirty-four (34) 120-ton rooftop split units with 50 HP supply air fans (VFD), Two (2), 24 ton air cooled DX CRAC units. Cold air is supplied via under-floor plenum and discharged through raised floor diffusers and returned via ceiling plenum Problem: Warmer return air mixes with cold or supply air creating hot and cold spots resulting in a very small delta T and uneven room air distribution

21 List of Energy Efficiency Measures (EEMs) Solution: Install containment solution, increasing return air temperature and allowing SAT to be raised Results: Improved mechanical cooling efficiency Reduced VFD fan speeds Increasing set points allows economizer lock out to be raised which increases economizer hours and reduces mechanical cooling for the data center Approximately 7% electric energy saving, 3.5 million kwh saving, $ 254k saved per year, $ 245k paid out as incentive

22 Pre and post case mechanical load vs. OAT 3,500 3,000 Mechanical Load (kw) vs. OAT ( F) y = x R² = Mechanical Load (kw) 2,500 2,000 1,500 y = x R² = y = x R² = ,000 y = x R² = OAT ( F) Pre-M&V Mechanical Load Post-M&V Mechnaical Load Pre-M&V Mechanical Load (Partial-Econ)

23 Pre and post case compressor amps vs. OAT Compressor Amps vs. OAT ( F) Compressor Amps 2,400 2,200 2,000 1,800 1,600 1,400 1,200 1, OAT ( F) Pre-M&V Compressor Amps Post-M&V Compressor Amps

24 Pre and post case PUE vs. OAT

25 Conclusion 1. Raising the set point in the data center has many advantages. 2. The most important data center temperature: rack/server inlet temperature 3. Increasing the data center space temperature should be carried out in conjunction with air flow management 4. Raising the set point increases the cooling capacity of equipment and provides for load growth. 5. Higher space temperature set points increase available economizer hours for both air-side and waterside economizers. 6. The cooling system design should be carefully evaluated before making changes.

26 Q & A Questions????????