VARIABLE SPEED COMPRESSOR TECHNOLOGY AND APPLICATIONS

Jay EldridgeBusiness Development Manager – Applied Air SystemsSpring 2016

AGENDA

• Why Variable Speed• Enabling Technologies - Variable Speed

Motors • VRV/VRF Systems • Rooftop Products • Magnetic Bearing Chiller Technology

2

WHY VARIABLE SPEED

• Energy Savings• BHP at Fan• BHP at Pump• BHP at Compressor• Meet or exceed ever more challenging energy

codes• LEED• Sustainable• Acoustics

3

FULL RANGE ENERGY PERFORMANCE

• Full range performance is almost always far more important than full load performance

• Best designs take into account reduced load and reduced condensing pressure (dry bulb or wet bulb relief) on refrigeration systems

• Emerging technologies include;– Full range compressors– Permanent magnet synchronous motors– Magnetic bearings– Integrated controls

Vs.

Full Range Full Load

4

NEW TECHNOLOGY

• Motors: ECM, Reluctance DC, PMSM• Inverter Scroll Compressor• High Speed VFD with PMSM

5

BETTER THAN PREMIUM EFFICIENCY

84858687888990919293

2 3 5 7.5

Efficiency

Motor HP

NEMAECM

6

RELUCTANCE DIGITALLY COMMUTATEDADVANTAGES OF THE RELUCTANCE DC MOTOR

CurvedIron

NeodymiumMagnet

Rotating stator field Electrical field is in the stator

not the rotor; no need for brushes

Based on the principles of a direct current motor Uses neodymium magnets Benefits from an additional

reluctance torque when loaded Extreme high performance in low and medium RPM

7

DC COMPRESSOR MOTOR TECHNOLOGY

Digitally Commutated (DC) Motor The rotor uses neodymium magnets – 7 times the

magnetism of a common magnet Increased power with decreased electrical requirement

8

COMPRESSOR MOTOR TECHNOLOGY

N

N

N

N

S

S

S

S

Core

Rare Earth MagnetInterior

Permanent Magnetic

6065707580859095

100

1800 3600 5400

Efficiency (%

)

RPM 

InductionMotorDaikin InverterMotor

18 %30%

9

PMSM MOTOR TECHNOLOGY

10

Ferrite Magnet

N

N

N

N

S

SS

S

Core

Rare Earth Magnet

1800 3600 5400 72000

60

70

80

90

Induction Motor

SPM Motor

PMSM Motor

Speed（rpm）

Effic

ienc

y（

%）

Interior Permanent MagneticSurface Permanent Magnetic

10

TRADITIONAL NON-INVERTER SYSTEMCONTROLS TEMPERATURE WITH ON-OFF OPERATION ANDMINIMAL CAPACITY CONTROL

• 60 Hz AC input power drives the compressor

• The compressor must operate at full RPM under all load conditions

• Very limited efficiency under part load conditions

T(sec)

+V

-VFrequency (Hz)

11

INVERTER DRIVE SYSTEM

• The inverter control converts the incoming ac voltage to dc voltage

• The inverter then smooths the sine wave to insure smooth motor rotation

• Reconverts dc to 3 phase ac voltage to the compressor

• Vary the frequency applied to the compressor motor to modulate the rotational speed which increases or decreases system capacity

T(sec)

+V

-VFrequency (Hz)

T(sec)

+V

-VFrequency (Hz)

InverterCircuit

12

INVERTER TECHNOLOGY

T(sec)

+V

-VFrequency (Hz)

T(sec)

+V

-V Frequency (Hz)

13

COMFORTABLE COOLING OPERATION

Set temp.

Temp.

Time.

Inverter Cools a room quickly

Inverter:Small temp.difference

Non-Inverter:Large temp.difference

14

WHAT’S OUT THERE? COMPRESSOR OVERVIEW

Two stage scroll• 2 thru 6 tons

Digital scroll VCC• 3 thru 15 tons• Load/unload

20sec time step

Variable Speed IPM• Variable Speed

Interior Permanent Magnet Motor

Fixed scroll• On/Off Control

15

2 STAGE SCROLL

Fixed Scroll Sub-Assembly

SolenoidCoil Assembly

Modulation RingAndBy Pass Seals

Locating & HoldDown Pins

Unloads to about 67%

16

DIGITAL SCROLL

Loaded OperationUnloaded Operation

• Operates as loaded or unloaded• Compressor pulses between

conditions–100% loaded and 0% loaded

17

HOW DIGITAL SCROLLS WORK

• Digital sounds better than “OFF/ON”

• 15‐20 second cycle times

• Compressor pulses between conditions• 100% loaded and 0% loaded

• Head pressure rises quickly when compressor is ON

18

INVERTER SCROLL PERFORMANCE

• 60% savings @ 50% load

0%10%20%30%40%50%60%70%80%90%

100%25

%

35%

45%

55%

65%

75%

85%

95%

% Com

pressor P

ower

% Cooling Capacity

DigitalScrollDPSVariableSpeed

19

VFD COMPRESSOR AND EFFICIENCY

20

Source: 50% Advanced Energy Design Guide, K-12, ASHRAE

• VFD compressors take advantage of low lift

• Far better efficiency at part load

• Minimize temp swings • More efficiency gain

with fewer compressors• One is biggest gain• Two is a little less• Four is still less

• Lots of low load hours give best payback

20

INVERTER BENEFITS

• Capacity control• Very low startup amperage• Quiet compressor startup• No compressor locked rotor amps• Less stress on windings • Longer run cycles• Better dehumidification in cooling• Fewer start/stop cycles• System pressures increase gradually reducing noise and stress on piping• As room temperature nears set point,

capacity is automatically “throttled down”

Capacity is adjusted as the load changes to maximize temperature control

21

ADDITIONAL INVERTER BENEFITS

Electronic control of compressor speed for comfort and energy savings– System capacity modulates up and down

• Capacity matches load conditions as they change• Very high comfort levels

– High quality heating performance• Compressor increases speed during cold outdoor ambient conditions• Generates higher head pressure, which increases hot gas temperatures and discharge air

temperatures• Produces approximately 20% more heat than a standard non-inverter compressor system

– Significant increased energy savings during part-load conditions Heat & Cool loads change

• During a 12 month period, 75% of the total HVAC run time hours is at less than 70% of full load. (Energy Star building simulation)

• Energy efficiency can increase from 40% to 60% during part-loadconditions with Inverter driven compressor at low to medium speeds.

22

SYSTEMS - PUTTING IT ALL TOGETHER

–VRF –RTUs–CHILLERS T(sec)

+V

-VFrequency (Hz)

23

VRF: VARIABLE REFRIGERANT FLOW

• Inverter Scroll• ECM Fan Motor• Over speed

Inverter

24 24

WHAT IS VRF?

Main features:– Energy Saving / Inverter technology– Low Noise Levels– Individual control / Zoning– PPD: tenant billing– Long refrigerant piping runs– Wide range of indoor units– Applied systems w/ 20 year life cycle– Small installed footprint

Outdoor Unit

Indoor Units

25

VRF - OVERVIEW

Water CooledBoiler/Tower

Geothermal

Air CooledOutdoor / Indoor

26

VRF HEAT PUMP SYSTEM COMPONENTS

27

VRF HEAT RECOVERY SYSTEM COMPONENTS

28

INCREASE ENERGY SAVINGS DURING HEAT RECOVERY

Indoor temp : 67oFWB(Cooling)70oFDB(Heating)

Outdoor temp : 95oFWB(Cooling)47oFDB(Heating)

Heat Pump

Heat recovery

Cooling Cooling Heating Heating

6 Ton

6 Ton Cooling5.39kW

Heating6.08kW(22519 btu)

Power input

Cooling Cooling Heating Heating12 Ton

Simultaneous cooling & heating 4.8kW

Power input

Approx.

58% Down

29

INVERTER CONTROL

30

NONINV NONNONINV

(16 Tons)

NON7%

100%

C a

p a

c i t

y C

o n

t r

o l

LoadHigh

Low

Smooth control

Multi unit VRF capacity control

30

31

COMFORTABLE COOLING OPERATION

Set temp.

Temp.

Time.

Inverter Cools a room quickly

Inverter:Small temp.difference

Non-Inverter:Large temp.difference

31

VRF PERFORMANCE

Complete SYSTEM IEER range: 16 ~20!

32

VRF: SUMMARY

FEATURES:– Inverter Scroll– ECM Fan Motor– Over speed VFD

BENEFITS:– Great SYSTEM efficiency– Space comfort– Flexibility– Low sound

33 33

SMALL RTUS CAN BE AN APPLIED PRODUCT

• Constant or variable air flow• Single Zone VAV• Cooling only• Cooling with heating

– Nat. gas, electric, hot water• Heat pump• Heat pump with auxiliary heating• 100% outdoor air

34

RTU VS VARIABLE SPEED CHILLER PLANTS

Chillers have used VFD for quite a while…All variable speed components in a central plant

Why? For the Lowest Total System EnergyNow we have the same type of performance for RTUs

35

EER EQUIVALENT

kW/ton 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

(I)EER 24 20 17 15 13 12 11 10

++ Rooftop IEER includes all energy covered by chiller plant, plus..• Supply fan energy (Coils, filters, etc)• 0.75” Distribution staticRooftops have much lower installed costs

Variable speed RTU IEER range

36

APPLICATIONS FOR VARIABLE SPEED RTUS

• DOAS / 100% outside air• High efficiency RTU

– LEED– Stretch standards

• Small space / tight control• Sound sensitive RTU jobs • Medical

– Medical office buildings– Stand alone urgent care

• Labs• Process / manufacturing

• Better temp control– Cooling– Heating– Humidity

• Dehumidification– Recovered energy reheat

good for 90.1

• Less cycling• Much quieter• Applied options

– Built to order– Customizable

37

ADVANTAGES OF INVERTER CONTROL TECHNOLOGY

38

TEMPERATURE CONTROL

• Fully modulating Single Zone VAV (SZVAV) • Variable speed compressor controls air temperature• Fan varies speed to match the load

39

405060708090100110120

Tempe

rature

Time

Discharge AirOutdoor AirReturn Air

Actual performance: Convenience store, Dallas TX 39

CYCLING EFFECTS

• Reduces latent removal• Re-evaporates coil

moisture• As cycling increases,

latent cooling goes to zero

• As humidity goes up, cycling is more important

40 40

HOW DIGITAL SCROLLS WORK (VARIABLE CAPACITY)

41

• Digital sounds better than “OFF/ON”• 15-20 second cycle times• Compressor pulses between conditions

- 100% loaded and 0% loaded

- Head pressure rises quickly when compressor is ON

41

LEAVING AIR CONTROL – VARIABLE SPEED VS DIGITAL

• VFD vs digital scroll compressor (1 min increments)• VFD gives lower kW, stable leaving air temp• 57-75 LAT = 2.7 lbs/min water difference for 4000 CFM

kW Power

Lvg Air

Room

OA temp

2013- Northwest Energy Efficiency Alliance; NBI: Report #E13-269: Variable Rate Rooftop Unit Test

42

DEFINING SINGLE ZONE VAV (SZVAV)

• What is Single Zone VAV (SZVAV) – Fan speed controlled by zone temp vs VAV box pressure– Compressor controlled by leaving air temp

• Minimum for requirements for SZVAV in 90.1?– DX: 2-Stg supply fan, Min speed<66% and < 40% fan kW– Chilled Water & other: Min capacity <50% and < 30% fan kW– Hot gas bypass not allowed above min loading (66% for RTU)

• Fully modulating SZVAV will perform better– Fan energy savings (2 speed vs VFD)– Compressor savings (stepped vs VFD)– Tighter control

43 43

ENERGY PLUS MODEL

› Energy Plus has a variable speed DX coils— Up to 10 speed curves vs ambient— Big savings at lower loads

› Building models by Pacific Northwest Natl. Labs

› Examples for Rochester— 7000 ft2 retail space

– Lights = 8 W/ft2, 62.1 ventilation — 15 ton RTU vs 90.1 baseline— Rigid schedules

44

ENERGYPLUS

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Compressor Energy (kW) - September, Rochester, NY

Outdoor Air Temp (F) Variable Speed Single Stage Two Stage

45

ENERGYPLUS

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kW

Compressor Energy (kW) - July Day in Rochester, NY

Variable Speed Two Stage

46

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Compressor Energy (kW) - A week July in Rochester, NY

Variable Speed Compressor Two Stage Compressor

47

WHAT TO WATCH OUT FOR…

• Size ranges may not be complete– Offerings from manufacturers may change by capacity

• Consider multiple set points vs stepped changes • Units are more complex than off/on

– Controls are different than stepped control– Often integrated compressors & heat with dampers and

fans– May tie-in to network, BAS, cloud, etc. – Make sure your technicians are trained

• Variable speed RTUs cost more than stepped RTUs– Better efficiency and payback– Tighter air temperature control– Applied equipment type sequences

48

VARIABLE SPEED RTU COMPRESSOR SUMMARY

1. Increase part load efficiency2. Reduce operating costs3. Increase comfort by running the unit longer4. Reduce re-evaporation5. Increase unit capacity6. Remove more moisture to keep DOAS cost down7. Keep unit operating with the envelope8. Monitor refrigerant press./temps to take evasive

action

Unit stays on-line

49

CHILLERS

• Permanent Magnet Synchronous Motor (PMSM)

• High Speed VFD

50

BASIC MAGNETIC BEARING COMPRESSOR DESIGN

High Speed Permanent Magnet Synchronous Motor

Axial Thrust Bearing

Impeller Front Radial Bearing

Rear Radial Bearing

51

MAGNETIC BEARING COMPRESSOR

Magnetic bearingsand sensors

Permanent magnet synchronous motor(refrigerant-cooled)

Suction gas

Discharge Port

Inlet GuideVanes

Single StageImpeller

VFD and controlscontained in external panel

52

50

60

70

80

90

100

110

0 10 20 30 40 50 60 70 80 90 100 110

Percentage Speed

Effic

ienc

y (%

)MOTOR EFFICIENCY

Induction Motor

Permanent Magnet Synchronous Motor

25- 40% Efficiency

Gain3-5%

Efficiency Gain

53

DRIVE TRAIN COMPARISON – FULL LOADHigh Speed Permanent

Magnetic Motor Centrifugal Compressor

Traditional Variable Speed Centrifugal

CompressorBearing Windage 1.5% 5.0%Motor 2.0% 4.7%VFD 2.0% 2.4%Gear -- 1.0%Resulting Compressor Efficiency

94.5% 86.9%

Effic

ienc

y

Loss

7.6 Point Efficiency Gain!

54

ENERGY SAVINGS EXAMPLE

0

100

200

300

400

500

600

700

800

900

0 10 20 30 40 50 60 70 80 90 100

Chiller Percent Load

Ope

ratin

g H

ours

0

0.2

0.4

0.6

0.8

1

1.2

kW /

ton

Fixed Speed ~ $243,287/year

Traditional VFD ~ $164,934/year

High Speed VFD w/ Mag Bearing ~ $131,709/year

Cooling Load Profile

10% energy reduction

55

OIL REDUCES SYSTEM EFFICIENCY

From ASHRAE Research Project 751-RP, “Experimental Determination of the Effect of Oil on Heat Transfer with Refrigerants HCFC-123 and HFC-134a”,

Conclusions and Recommendations:

“The heat transfer ratio drops steadily with oil concentration and reaches a value of 0.65 [from 1.0 normalized] at an oil concentration of 10%.”

35% heat transfer reduction with 10% oil concentration in refrigerant

56

IMPACT OF OIL ON SUSTAINABLE PERFORMANCE

Source: The News, 04/15/04, by Jack Sine

Positive pressure, oil-free design eliminates the performance degradation due to non-condensables and oil contamination of the refrigerant

57

ADVANTAGES OF VFD AND MAGNETIC BEARINGTECHNOLOGY

• Resistant to Power Line Disturbances– Rides through voltage drops– Meets semi conductor industry standard SEMI F47

_____________________________________________

• Regenerative power system keeps bearings powered until shaft stops spinning

• Rides through short duration power loss

58

CHILLERS: SUMMARY

PRO:– Part load efficiency– Oil Free Design– Low Maintenance

CON:– First cost typically higher

59

WRAP-UP

• Variable speed compressors have distinct advantages for temperature control and efficiency

• A number of options are available for size and configuration

• Modeling programs, studies and other resources are being developed to estimate actual performance

60

REVIEW QUESTIONS

61

• What is the difference between a digital scroll and an inverter scroll compressor?

• What are the advantages of modulating refrigerant flow?

• What are the limitations of an AC Induction Motor?• What is more efficient: Surface Permanent Magnetic

Motor or an Interior Permanent Magnetic Motor?• What type of rare earth magnet is being used in

Interior Permanent Magnetic Motors?• What are the benefits of removing oil from the system?• Why are new products designed for full range?

THANK YOU.