Case study: Energy efficiency improvements in a legacy data centre. Robert Tozer Director Opera>onal Intelligence

Transcription

1 Case study: Energy efficiency improvements in a legacy data centre Robert Tozer Director Opera>onal Intelligence

2 Objec>ves First improve air management Air supply temperature to servers Lower temperature Reduce range (also control CRAH on supply air temperature) Then save energy: Increase temperature set points (chilled water, air): Refrigera>on energy (and free cooling) Reduce air flow (to what is required) Fan energy (cube law, VFDs)

3 Air management: improvements Reduce Bypass flow Close cable penetra>ons Locate air grilles in front of IT equipment Reduce Recircula>on flow Use blanking plates, improve rack layout Reduce Nega>ve Pressure flow (< air velocity) Supply air control (not return air control) Physical Containment (cold aisle, hot aisle or rack)

4 Background Built in 2007 in London 2N 1,800 3,500m2 data hall area Incremental changes in a kw Tier 3+ Cooled by 53 CRAH units Current IT load ANNUAL SAVINGS per year (1 site) = $1.7m LIVE ENVIRONMENT

5 Energy op>misa>on programme 1. Energy assessment and data hall air temperature survey 2. Outdoor fresh air AHU dew point control 3. Air management improvements 4. Reduce fan speeds and control on supply air 5. Increase in data hall air set points 6. Increase chilled water set points 7. Free cooling feasibility study 8. Installa>on of free cooling modifica>on 2.3 $4.7m PUE reduc>on 1.49 Annual energy saving $3m

6 Energy assessment/air temperature survey 1 Thermal Performance 1- R Af=4 Af=0.25 BP = 80% R = 20% Af = 4 Server intake: 15 and 27 C (upper limit ASHRAE recommended range) Air management a priority 0 Flow Performance 1 1- BP

7 Scalability 200% 175% 150% PUE = 8 Original Improved 125% Data centre load rela>ve to IT 100% 75% 50% 25% C Ini>al Load IT % 50% 75% 100% IT Load

8 Air management improvements Step 2: Air Performance Blanking plates Mea Revised floor grille loca>ons an Sealing Step 2:floor Airgaps Performance Measurement A o Proof of concept: Hot and cold air stream segrega>on 4C reduc>on 5C reduc>on 1 year payback: deployed throughout data hall i i r h b e s w s R t i t E a

9 CRAH fan speeds and control 100% Original fan speed Op>mised fan speed 60% Work in Progress: 40% with Dynamic Control

10 Fan speed, flow rate and power Fan st at ic pressure, p s Fan shaf t power, P r P r1 P r2 P r3 p s1 p s2 Full speed 75% full speed 75% full speed 50% full speed 2 1 Fan power characteristic at full speed Design operating point Fan output characteristics 50% full speed p s3 3 Fan Applica*on Guide CIBSE TM42: 2006 q v3 q v2 q v1 Volume flow rat e, q v

11 Set points $million savings/yr Cooling unit set points Chilled water temperature set points FROM FROM TO TO 24 C Return Air 22 C Supply Air 15-17/24 C 6/12 C COP chilled water + chiller delta T

12 Ven>la>on & addi>onal chw temp Ven>la>on flow rates ven>la>on extract fan $million savings/yr % RH Opera>ng envelope for humidity control widened in line with ASHRAE recommenda>ons 5.5 C dew point Small number of hours above 15 C dew point

13 Psychrometric chart

14 Key decisions Choice of free cooling system Choice of an evapora>ve system No. of heat transfer processes Area of heat exchangers CAPEX OPEX Q = A. U. LMTD Q = cooling (kw) A = area (m2) U = heat transfer coefficient (kw / K m2) LMTD = log mean temperature difference (K) Given fixed Q and U then LMTD α 1/A

15 Free cooling feasibility study T 31 C Before Heat exchange area T 31 C Arer Heat exchange area BP 27 C BP 23 C Air Data Hall R 23 C 22 C R 23 C 22 C 12 C 21 C Total Appr 27 K 18 C 15 C Total Appr 12K Chilled water 2 C Free cooling Outside air 6 C 11 C - 4 C

16 Primary circuit Buffer tanks Secondary circuit Chillers CRAH units Dry coolers / Cooling towers

17 Free cooling feasibility study best op>on Dry coolers Capacity Approach temperature CRAH cooling coils

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19 Free cooling feasibility study! Predic>on:

20 Installa>on of free cooling with dry coolers $million savings/yr Fiscally posi>ve Year 1 ROI less than 3 years

21 Air performance arer improvements 1 Thermal Performance 1- R Af=4 Af=0.25 ORIGINAL: BP = 80% R = 20% Af = 4 IMPROVED: BP = 42% R = 9% Af = Flow Performance 1 1- BP

22 Conclusions ANNUAL SAVINGS per year = $1.7m % Instantaneous PUE Es>mated annual PUE Overall reduc>on

23 Conclusions Dec 11: KW of Heat RejecLon for 10KW electrical energy. COP of 7.6 degc ambient vs ~COP 3 from Chillers DAC ON Annual PUE Trend YTD Note : DAC Turned on in Dec 13

24 Conclusions Pre Initiative : PUE ~2.29 Initiative to date : PUE ~1.49

25 Further savings UPS Op>misa>on Con>nued increase 26C Data hall supply temperature 21/28C Chilled water temperature 2-3% Free cooling hours

26 Ques>ons? Our workshops are accredited by CIBSE oi.com oi.com intelligence-