Total System Efficiency when Specifying VFD’s for Sustainable … · 2019-12-29 · Total System Efficiency when Specifying VFD’s for Sustainable Buildings. John Conboy. Director

Total System Efficiency when Specifying VFD’s for Sustainable BuildingsJohn ConboyDirector of Sales & Marketing – Drives MENA

The Facts

3 | Danfoss Drives | Energy Efficiency

20%of the world’s energy consumptionis electrical energy

50%of electrical energy is used byelectric motors

100%of electric motors are oversized

75%of electric motors are used on Variable Torque load

50%reduction of energy consumption for a 20% reduction of flow

20%of electric motors use a VFD for control


8%of global electricity consumption by 2040

AC drives have the potential to save

The Science


The Affinity Law

100

70

00 70 100

Flow

, %

Speed, %

N2 N1

Q1

Q2

100

49

00 70 100

Pre

ssu

re, %

Speed, %

N2 N1

P1

P2

100

34

00 70 100

Pow

er, %

Speed, %

N2 N1

HP1

HP2

Affinity Laws of Centrifugal Loads:

FLOW is a proportional to motor speed

PRESSURE is proportional to the motor speed squared

POWER is proportional to the motor speed cubed

N = Speed

Q = Flow

P = Pressure

HP = Horsepower

Q2

Q1

N2

N1=

P2

P1

N2

N1=

2HP2

HP1

N2

N1=

3


Pump control methods

Source of images: https://www.linkedin.com/pulse/comparison-different-flow-control-methods-pumps-mircea-tomescu/

Flow Control Methods

https://www.linkedin.com/pulse/comparison-different-flow-control-methods-pumps-mircea-tomescu/


Fan control methods Flow Control Methods

Outlet Damper Inlet Box Damper Variable Inlet Vane Variable Frequency Drive

% Design Flow%

Des

ign

KW

120

100

80

60

40

20

040 50 60 70 80 9030 100


Why do we do this?

The Standards


Definitions according to IEC61800-9

Extended Product

Motor System

Power Drive System (PDS)

Motor Starter(Contactor, Softstarter,…)

Trans-mission

Driven Equipment

Load-machine

Mains & cabling

Complete Drive Module (CDM)

Often named as VSD (Variable Speed Drive)

Feedingsection

Aux-ilaries

BasicDrive

Module (BDM)


Ecodesign from around the world

• Ecodesign is an approach to designing products with special consideration for the environmental impacts of the product during its whole lifecycle – it includes but is not limited to energy efficiency

• Around the world, various countries implement eco-design policies for motor systems

• The requirements are called MEPS (Minimum Efficiency Performance Standard)


Classification of motors and drives

IEC/EN 60034-30-1

• Fixed speed motors (DOL)• Classes IE1 – IE4

IEC/EN 60034-30-2

• Variable speed operation• Classes IE1 – IE5

IEC/EN 61800-9-2

• Complete Drive Module (CDM)• Classes IE0 – IE2

IEC/EN 61800-9-2

• Power Drive System (PDS)• Classes IES0 – IES2

Motor

Drive

Drive + motor


Part load losses

• Part load losses are defined in the nominal point and in 7 additional part load points for:

• CDM (drive)• PDS (drive + motor)

• Note that the nominal point for drives is 90% of nominal load and 100% for systems

• Part load losses can be determined in any point by interpolating between the 8 standardized points

Relative torque [%]

0%0% 100%

100%

50%

25%

50%

Relative speed [%]

CDM

PDS

Relative torque producing current [%]

0%0% 90%

100%

50%

25%

50%

Relative motorstator frequency

[%]

Arbitrary load point


Extended product approach

• The extended product approach combines the losses or efficiency of the motor system with the losses/efficiency of the driven system (pump, fan, conveyor, etc.)

• Based on the losses or efficiency of the extended product, the energy efficiency index (EEI) can be calculated for a given load-time duty profile

• Knowing the part load losses for the motor-drive system is essential for calculating the EEI, which is the ultimate purpose of the ecodesign standard

The products that will affect Total System Efficiency

The Motor


Comparison of efficienciesVentilation Unit with IE2, IE3 and IE4 motor


The Fan


Comparison test – same installationAir Handling Unit, manufactured by Trubel Luft-und Klimatechnik GmbH

AHU w. Radial Fan (Plug Fan) AHU w. High Efficiency Axial Fan

Radial Fan (Plug fan)High Efficiency Axial Fan


Energy cost saving

Energy SavingHigh Efficiency Axial Fan vs. Radial Fan (Plug Fan)


The DriveInstalled Efficiency

Heat lossHarmonics


Input:kW System

++

+ +

Installed or “wire to air” or “wire to water” efficiency is the trend:

Motor/AC drive CAPEX/OPEX split

Investment

Electricity

Harmonic mitigation

AC unit

Installed energy efficiency is important


110 kW 50 Hz, 4 pole motor:• IE 1 = 93,3 %• IE 2 = 94,5 %• IE 3 = 95,4 %

Energy efficiency difference for a 110 kW IE 2 vs IE 3 motor is 0,9 %, price ~15-20 % - 0,9 % efficiency gain seems important !

Which item of efficiency is most important?


There are many solutions:

• Low Harmonic Drive - AAF based

• Low Harmonic Drive – AFE based

• Central/Sep. solutions – AAF based

• Passive Harmonic solutions

Heatloss/efficiency difference between AAF vs AFE

0

10,000

20,000

30,000

40,000

50,000

AQUA AAF

NXC AFE

Heat loss W

PowerSize

Energy Efficiency harmonic mitigation


Additional benefits for AAF:

• AAF sleep mode saves energy

• If the AAF fails, the drive will continue

• The AAF creates lower boost voltage and less motor stress than the AFE

Power Heat Loss W AAF/AFE Size kW AAF AFE Difference conv. to efficiency

160 8.725 11.356 2.631 1,6%200 9.831 13.731 3.900 2,0%250 11.371 18.753 7.382 3,0%355 15.320 23.610 8.290 2,3%400 17.180 26.166 8.986 2,2%450 18.447 29.986 11.539 2,6%500 21.909 33.768 11.859 2,4%560 24.592 38.241 13.649 2,4%630 26.640 40.574 13.934 2,2%710 30.519 46.524 16.005 2,3%

Comparison of heat loss at <5% THD


Typically 0.4W of energy needed to remove 1W of heat.

The energy saving for a 160 kW drive will be about 15 % of investment made in standard AC drive

90%

160 kW AC drive standard: Heatloss 3770 W. AC saving ~ 3770 * 0,9 * 0,4 AC * 0,1 € * 0,6 load * 24 h * 365 d = 713 € ~ 15 % of AC drive purchase price

Intelligent heat managementPart of installed efficiency

90%Reduction in energy use

for air condition


0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

160 200 250 355 400 450 500 560 630 710

conv. to eff.

AC Eff saving

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

45.0%

160 200 250 355 400 450 500 560 630 710

Total

Heat loss AAF/AFE

AC saving

Efficiency % gain

Power size

Power size

Basis for calculations: LHD AC Drive, 0,1 €/kWh, 60 % load, 24/7 operation, 0,4 W AC/W removed

Options Efficiency gained

IE 2 to IE 3 motor 0,9 %

Backchannel cooling ~ 2,5 %

AAF vs AFE 1,6 – 3,0 %

Options Savings % of Inv.

Backchannel cooling 12 – 20 %

AAF vs AFE 7 – 23 %

Total 20 – 43 %

% Savings per year/Inv. in AC drive

Which item of efficiency is most important?

The Summary


Summary

• Consider Energy Efficiency in all parts of your HVAC Systems

• Specify high efficient Drive and Motor Systems to meet IEC/EN 61800-9-2 Class IES2 and capability for more motor technologies with same drive (future proof)

• Specify highest efficiency fans, pumps and compressors

• Apply an Extended Product Approach and Specify Energy Efficiency Index• Utilize intelligent Heat Management e.g. Back-Channel Cooling.

• There are no regulations, which require THDi ≤ 5% at drive mains terminals.

• Apply IEEE-519 recommended limits at the PCC only and not to individual pieces of equipment.

• Do not use harmonics mitigation equipment, if it is not needed.

THANK YOUFOR ATTENDING THE PRESENTATION

Please don´t forget to collect your CPD certificate during the event from the CPD collection area

Total System Efficiency when Specifying VFD’s for Sustainable … · 2019-12-29 · Total System Efficiency when Specifying VFD’s for Sustainable Buildings. John Conboy. Director

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