Eco-Mode: Benefits and Risks of Energy Saving Modes of UPS Operation

Eco-Mode: Benefits and Risks of E S i M d f UPSEnergy Saving Modes of UPS Operationp

Schneider Electric Data Center Science Center White Paper #157

Introduction

This paper shows that eco-mode typically provides a reduction of about 2% in datareduction of about 2% in data center energy consumption and explains the various limitations and concerns that

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arise from eco-mode use.

Eco-mode Introduction

•Overall system architecture•Right-sized system design•Individual devices•Operational decisions

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Simple diagram of power flow of a double-conversion, online UPS…online UPS…

STATIC BYPASS

Bypass Path

SWITCH

Online Path

DCAC

DCAC

RECTIFIER INVERTER

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BATTERY

Online and Eco-Mode Operationp

Online mode Eco-mode Comment

NormalEco-mode exposes theNormal

operation Rectifier/Inverter Bypass exposes the load to raw mainsO li d

During a power disturbance Inverter Inverter

Online mode requires no path change during powerduring power disturbances

During a fault Bypass Bypass Extremely rare

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condition Bypass Bypass event

Output waveforms of 275 kVA UPS in eco-mode responding to a power failure…responding to a power failure…

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Upper waveform is output voltage, lower is output current

Advanced eco-mode

●Result of recent advances in firmware control schemes and electrical design

●Primary power path during normal operation is the same as standard or “classical” eco-mode: through the bypass path

●But, the inverter remains “ON”, operating in parallel with the input w/o actually handling the load current

●Since the inverter is already “ON”, it can more seamlessly take over the y , ysupply to the output when there is a mains failure

Schneider Electric Galaxy VM UPS with ECOnversionTM

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Standard vs. advanced eco-mode

UPS operating in standard eco-mode

UPS operating in advanced eco-mode

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Additional advantage of advanced eco-modemode…

I d filt i f ti●Improved filtering function ●Reduces harmonic injection back into Utility mains or standby generators●In principle filtering function works at●In principle, filtering function works at nearly the same level and quality as a double conversion UPS not operating indouble conversion UPS not operating in eco-mode

© 2014 Schneider Electric All Rights Reserved – Eco-mode: Benefits and Risks of Energy Saving Modes of UPS Operation – June 2014 9

Advantages come with a tradeoff…

Overall efficiency of the UPS is less●Overall efficiency of the UPS is less●It’s a small difference, however…●0.5% - 1.0% range●Efficiency less than standard, but better thanEfficiency less than standard, but better than traditional online mode

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Efficiency Improvements: PUE of Typical Data CentersData Centers

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Efficiency Improvements: PUE ImprovementImprovement

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Efficiency Improvements: Eco-mode

Eco-mode corresponds to a savings of 3.3% of total energy use and US $20 000 per year

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$20,000 per year.

Efficiency Improvements: Eco-mode (1/2)

Considerations of eco-mode include:•Loss of electrical protection

Energy saved depends on:•Specific equipment•Loading of data center p

•Reliability impacts•Operations issues

Loading of data center•Cost of electricity

These factors often cause operators to decide against eco-mode.

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Loss of Protection: UPS Systems

Virtually all equipment sold today is immune to mains frequency variations and designed to accommodate any variations of mains voltage within a specified

ioperating range.

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Lost of Protection: Response to Power ProblemsProblems

1 • Power problem is detected1 p

• UPS determines how to respond2 • UPS determines how to respond

3 • UPS inverter is energized*

4 • Transfer switch is actuated

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*NOTE: in advanced eco-mode, inverter is already energized

Loss of Protection: Power Problem SituationsSituations

Power problems:Power problems:● Transformers may trip breakers● Loss of power leads to overloads

and dropped loadsand dropped loads●Protective devices on pumps and

fans may operate●Non-server IT devices are not●Non server IT devices are not

robust in handling dips and sags●Static switches cannot protect

loads from overvoltage

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Harmonics & eco-mode…

Harmonic issues will not be a factor in most data centers, but the use of eco-mode may require that

they be studied or mitigated.

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Reliability Impacts: Thermal Shock and CyclingCycling

Eco-mode:•Primary cause of failure of electronic power systemspower systems•Applied when UPS is needed the most

Normal UPS operation:p•No shock when power fails•UPS will go into bypass

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Reliability Impacts: Battery Life

Battery Operating Temperature•Strongly affected by UPS

Battery Wear•Eco-mode requires transfer more often Strongly affected by UPS

design

•May operate at higher t t i d

transfer more often

•Wear depends on implementation of eco temperatures in eco-modeimplementation of eco-mode

© 2014 Schneider Electric All Rights Reserved – Eco-mode: Benefits and Risks of Energy Saving Modes of UPS Operation – June 2014 20

Reliability Impact: Fault Clearing

When the UPS is in eco mode it can beWhen the UPS is in eco-mode, it can be very difficult to distinguish an output fault from a loss of input power: an additional factor that should be considered.

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Effect on Operations: Consequences

AdjustingTesting for capability

Adjusting sensitivities or delaysor delays

UtilizingEstablishing procedures

Utilizing power

forensicsp forensics

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Conclusion

As data center designs become more standardized, IT equipment continues to improve and real worldcontinues to improve, and real world experience using eco-mode accumulates, predictability and confidence in eco-mode will improve

d it li ti b i tand its application may begin to expand, especially in data centers with lower availability requirements.

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Resources ListThe Different types of UPS SystemsAPC White Paper 1

Making Large UPS Systems More EfficientAPC White Paper 108

An Improved Architecture for High-Efficiency, High-Density Data CentersAPC White Paper 126

Browse all APC white papers http://whitepapers apc comhttp://whitepapers.apc.com

Browse all APC TradeOff Tools™htt //t l

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http://tools.apc.com

Thank You

Questions?Questions?

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