options for energy reduction in data centres

BYRNE DIXON HAS BRIGHT IDEAS

Controlling the energy use in IT server rooms

How to reduce energy usage in the Server Room.

1 Define Data Centre Efficiency.

Energy Efficiency Metrics

2 Analysis of our current environment.

Data Centre power usage in Europe

Guidelines for future power reduction.

3 Server Room Efficiency Strategy.

Cooling System Overview

IT Server Efficiency

Server Room Efficiency

Mechanical Plant Efficiency

Free Cooling

Electrical Distribution

4 10+ Easy Steps

Measures which can easily be implemented without effecting business continuity.

ASSOCIATESBYRNE DIXON

1 Define Data Centre Energy Efficiency

The Green Grid, an industry based consortium dedicated to developing and promoting efficiency for data centres and information services, has adapted the terms power usage effectiveness (PUE) and data centre efficiency (DCE).

PUE (power usage effectiveness) = Total Facility Power (Green Grid 2007)

IT Equipment Power

The reciprocal of the PUE is the term data centre efficiency (DCE) which takes the following form:

DCE ( data centre efficiency) = IT Equipment Power (Green Grid 2007)

Total Facility Power



2 Analysis of our current environment

At the time of the Efficient Servers survey (2006). Data Centre power usage in Europe (EU15 + Switzerland) was 39.6TWh. Server power usage was at 14.7TWh for 6.77 million installed servers.

This number increased by 37% between 2003 and 2006. (See www.efficient-server.eu)

Current PUE is = Total Facility Power = 39.6TWh = 2.69

IT Equipment Power 14.7TWh

For every 1Kw of IT equipment we require 1.6Kw of electrical power to facilitate it.


In Practice: In 2000 the average electrical load was 1kw per rack, by 2004 it had risen to 3kw and in 2008 it has risen to 6kw per rack with an average design load of 10-12kw. We predict that this trend will continue. By 2010 the average rack load shall rise to 8kw and the average design load to 16kw.



The two most significant areas are HVAC and the UPS and these are the areas which we shall consider.


3.3 Server Room Efficiency

Temperature and humidity

CRAH coefficient of performance COP

Effective air distribution

CRAH electrical efficiency

3.4 Mechanical Plant Efficiency

CRAH Vs CRAC units.

CRAH system efficiency

Chiller efficiency (COP)

CRAC system efficiency

Electronic expansion valves

3.5 Free Cooling

CRAH System

Evaporative pre-cooling

CRAC system

Additional CRAC free cooling options

Kyoto Cooling

3.1 Cooling System Overview

Data centre cooling process

Target areas for increased efficiency

3.6 Electrical Distribution

UPS Systems

3 Data Centre Efficiency Strategy.

3.2 IT Server Efficiency

Technology refresh

Utilisation/Virtualisation.


3.1 Cooling system overview.

WATER

WaterCHILLER

EVAPORATORCHILLER

CONDENSER

REFRIGERANT

OUTDOORCONDENSER

WATER

AIRCRACAIR

COLD WATER

HOT WATER

COLD LIQUID REFRIG

HOT GAS REFRIG

COLD WATER

WARM WATERWARM AIR

COLD AIR

WARM AIR

COLD AIR

DATA CENTRE COOLING PROCESS


CHILLEREVAPORATOR

CHILLERCONDENSER

OUTDOORCONDENSER CRAC

CRACCOP

CHILLERCOP

CONDENSERCOP

FREECOOLING

TARGET AREAS FOR INCREASED EFFICIENCY

AirLoss

SERVER ROOMPLANT ROOMEXTERNAL


3.1 Cooling system overview.


3.2 IT Server Efficiency

Technology Refresh

The latest energy efficient servers have reduced power consumption and improved performance. Upgrade of a server can reduce energy consumption by 15%

Utilisation/VirtualisationThe industry average for server utilisation is 20% (LBNI). Through the implementation of the

latest virtualisation techniques the utilisation factor can rise to 80%.

3.3 Server Room Efficiency

3.3.1 Efficiency Basics – Coefficiency of performance

3.3.2 Temperature and Humidity Requirements

3.3.3 Effective Air Distribution

Under-floor Air Balancing and Direction

Rack Air Distribution

Room Air Distribution

3.3.4 CRAH/CRAC Electrical Efficiency

3.3.5 EMBS vs Punker

3.3.6 EC Motors

3.3.7 N+1 Redundancy Operation


3.3.1 Efficiency Basics - Coefficient of Performance

Coefficient of Performance (COP) = Cooling Output = Qi

Work input Wnet

Increase COP = Reduce area Wnet = Decrease Condensing temp and increasing evaporator temp.


ASHRAE Recommendation

Temperature 20 – 25 degC

Humidity 40 – 50%Rh

3.3.2 Temperature and Humidity Requirements


3.3.2 Temperature and Humidity Requirement

ASHRAE Recommendation

Temperature 20 – 25 degC

Humidity 40 – 50%Rh

To reduce the air output of a 60kw CRAC unit from 45% to 40% RH 11.5 kw

(Approx €1k/Kw/yr)

To raise the air output of a 60kw CRAC unit from 30% to 40% RH requires 7.5kw

(Approx €1k/Kw/yr)


Dry Bulb = 20 deg C

RH = 40%

DP = 6 deg C

W = 5.8g/kG

Dry Bulb = 26 deg C

RH = 30%

DP = 6 deg C

W = 5.8g/kG

Same level of moisture – different RH


100kw of cooling at 26degC requires 19.6kw of electricity

100kw of cooling at 21degC requires 28.5kw of electricity

8.9kw represents a 31% reduction in CRAC unit power consumption.

8.9kw shall cost us € 9,356.00 over the year.

COP (Coefficient or performance) = Cooling output Kw Electrical Power Input

3.3.2 Temperature and Humidity Requirement

ASHRAE Recommendations 20-25ºC room temperature.

Ignore room temperature because its misleading.

Think cold aisle air temperature and return air temperature

Supply enough segregated cold air at the right temperature and return temperature will be high.

Increase CRAH COP = Increase Return Air temperature = Effective Air Management

3.3.3 Effective Air Management = Step 1 Balance under-floor air pressure

Eddy Currents and Rivers below floor Creates hotspots above floor


Through CFD analysis we can analyse the layout of a room to ensure airflow balance.

Sub floor partitioning can divert the airflow and also reduce the velocity therby balancing the pressure.

More balanced pressure and airflow.


Blanking Plates

Koldlok Airguard

Side Panels

Perforated Doors


3.3.3 Effective Air Management = Step 2 Rack airflow management

With Blanking Plates Without Blanking Plates

WWW.BYRNEDIXON .COMWWW.BYRNEDIXON .COM


3.3.3 Effective Air Management = Step 2 Rack airflow management

Hot Aisle Containment Cold Aisle Containment

WWW.BYRNEDIXON .COM


3.3.3 Effective Air Management = Step 3 Room airflow management

Cold Aisle Containment





Hot Aisle Containment




Hot Aisle Containment

Cold Aisle Containment


Project : Reinsurance Company

Location : Bermuda

Before Optimisation




Project : Reinsurance Company

Location : Bermuda

After Optimisation


CRAH Unit Electrical Efficiency

Centrifugal Fans : Forward Curved Impeller Vs Backward Curved Impeller


3.3.4 CRAH/CRAC Unit Electrical Efficiency

Centrifugal Fans : Forward Curved Impeller Vs Backward Curved Impeller

Forward Curved Fan Backward Curved Fan

High velocity 15m/s

Low pressure

Efficiency 50-60%

Low velocity 6 m/s

High pressure

Efficiency 65-75%



EC (Electronic Commutation) Fans

80% efficient Vs 40% for Ac fans

DC driven, no pf losses

Smaller profile, reduced resistance in flow.

Combined in CRAH unit can reduce power by 50%

Higher efficiency at part load



EC fan motor profile AC fan motor profile




3.3.4 N+1 Redundency Operation.

If we increase the fan speed by 33% we increase the electrical load by 180% (Third fan Law)

3.4 Mechanical Plant Efficiency

3.4.1 CRAH Vs CRAC units.

3.4.2 CRAH System

3.4.3 Chiller efficiency (COP)

3.4.4 CRAC System

3.4.5 Electronic Expansion Valves


CRAH units CRAC units

Water or Glycol cooled by chiller, water tower/dry cooler Refrigerant cooled at external Condenser

Generally used in large facilities. Hybrid water precooling

Chilled water temp may be raised to increase efficiency Generally Used in smaller facilities

(Remove latent cooling) Refrigerant temperature is set.

More opportunity for efficiency and free cooling


3.3.4 CRAH Vs CRAC Units

1 Chiller 5 Chiller Refrigerant

2 Chilled Water Loop

3 Condenser/Dry Cooler

4 Condenser water loop


3.3.4 CRAH Unit operation

CRAH Unit operation


Chiller efficiency is governed by the difference in temperature between the chilled water and the condenser water. The lower the differential temperature the higher the efficiency. Lowering the condensor temperature is more difficult that raising the chiller temperature which is easier to implement and predict.

Each one degree increase in chilled water temperature increases the efficiency 3-4%. But each 1 degree raised reduces the CRAH capacity by 10% unless the return air temperature is raised as well. By raising the

chilled water temperature above the dew point we will eliminate latent cooling.

3.3.4 Chiller Efficiency

1 Evaporator

2 Compressor

3 Expansion valve

4 Refrigerant Loop


3.3.4 CRAC Unit operation

CRAC Unit operation

Electrical consumption is governed by work carried out by the Compressor.

The work at the compressor is dependent on the system pressure.

A proportional electronic expansion valve can vary the pressure in accordance with the

Cooling load required

Outside air temperature.

By varying the valve position we can minimise the condensing pressure and maximise the

evaporation pressure.

Hence reduce the amount of work performed and energy used.

May be requested as an option from suppliers.


3.3.4 Electronic Expansion Valve

3.5 Free Cooling

3.5.1 Free Cooling Hours

3.5.2 CRAH System

3.5.3 Evaporative precooling

3.5.4 CRAC System

3.5.5 Additional CRAC free cooling options

3.5.6 Kyoto Cooling


Number of hours below 13 deg C

Dublin Airport Shannon Airport

year Month

Mean (1977 to 2006) Number of hours with

temperatures <= 13 deg. C month

Mean (1977 to 2006) Number of hours with

temperatures <= 13 deg. C

2006 1 741 1 742

2006 2 674 2 674

2006 3 730 3 728

2006 4 679 4 649

2006 5 576 5 506

2006 6 352 6 278

2006 7 170 7 105

2006 8 193 8 122

2006 9 330 9 263

2006 10 577 10 534

2006 11 685 11 675

2006 12 735 12 736

6442 6012


3.5.1 Free Cooling Hours

Free cooling chiller which combines a DX condensor and a free cooling coil

Can provide full and partial free cooling

Free cooling available for 75% of the year

Available in stages for part load

Free Cooling Chiller Indirect Free Cooling


3.5.2 CRAH System

Can be installed to existing chillers

Requires additional maintenance

Direct Free CoolingEvaporative Cooling


3.5.3 Evaporative Precooling

CRAC System

Hybrid system combining water and refrigerant loops

Dry cooler provides cold condenser water to the refrigerant condensor

Also precooling the air in the CRAC unit


3.5.4 CRAC System


3.5.5 CRAC System - Additional options for incorporating free cooling to CRAC units

Kyoto is the use of outside air to provide cooling to the server room.

< 21ºC Kyoto cooling only 95%

21-26ºC Kyoto cooling plus compression 5%

> 21ºC Compression cooling only < 1%


3.5.6 Kyoto Cooling System


Contain Cold Aisles

Allow cold aisle air to raise from 16ºC up to 22ºC Increase hours of free cooling

Return temperature at 28-37ºC

No humidity transfer across wheel.


Specify UPS based on efficiency at full and part load

Newer UPS have quoted very high efficiency at 50% load


Passive Stand-by Topology

High efficiency, low cost

Does not condition the mains

3.6 Electrical Efficiency


The two most significant areas are HVAC and the UPS and these are the areas which we shall consider.

Data centre power usage before and after optimisation.

Measures which can be implemented without effecting business continuity.

1 Implement a hot aisle - cold aisle layout.

2 Reduce air loss

3 Install blanking plates, air guards and, perforated doors.

4 Install sub floor partitioning to balance the airflow and pressure

5 Balance the load in the room – match the load to the airflow

6 Check the location of air distributing floor tiles, relocate or provide additional.

7 Replace perforated floor tiles with air grills.

8 Install containment between the hot and cold aisles

9 Widen the temperature and humidity bands

10 Bring all units CRAC units on at lower fan speed.

11 Ensure two free tiles between cabinets in cold aisle – Bring cabinets to edge of floor tiles

12 Maintain filters – Ensure filters with minimum pressure drop are installed.

13 Reset chilled water temperature incrementally after return air temperature has risen.

14 Check for and eliminate free cooling – Is there water coming from the condensate drain


4 10 + Easy Steps

options for energy reduction in data centres

Technology

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