Post on 16-Feb-2018
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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8:00:00 10:00:00 12:00:00 14:00:00 16:00:00 18:00:00 20:00:00
kW
Compressor Energy (kW) - July Day in Rochester, NY
Variable Speed Two Stage
46
ENERGYPLUS
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18
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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.