How to determine the efficiency of Chillers at part loads and the factors that affect the NPLV / IPLV for water cooled chillers.
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EFFICIENCY VERMONT Successful Cooling System Energy Optimization
Topics for Discussion
C om mercia merciall E nerg er gy Co nsumption nsumption
Equipm Equipm ent Eva Ev aluation
Full-lo Full-lo ad ef ficiency ficiency
Integrated part-load values
E lectr ec tric ic utility tility char ha rges ge s
P ow er F acto ct or Help Help you underst understan and d how to evaluate an airair- cool cool ed system wi th regard to bot bot tom-line tom-line implicat implicatiions. ons .
Commerc Commer cial Energy Cons C onsumpt umptiion
U.S. DOE Electrical End-Use Estimates “Com “Com mercial mercial Bu B ui ldings Energy En ergy Co C onsumption nsumption Survey” S urvey”
Electric Utility Charges • Customer Charge • Elec Electr tric ic Fuel Fuel Char Charge ge Adj Adjustm ustmeent – Fuel Fuel Char Charge ge Adju Adjust stme ment nt
• Environmental tal Su Surcharge • Energy Charge • Kilo Kilowa watt tt (kW (kW)) Dem Deman and/ d/De Deli live very ry Char Charge ge • Powe Powerr Fact Factor or Adju Adjust stme ment nt/P /Pen enal alty ty
ASHRAE 90.1-2001 (Mandatory Provisions) • Full Load (FL) – Predicts performance at a single operation point • Doesn’t anticipate how equipment will respond during off-design conditions • Equipment with excellent full-load characteristics may have less than satisfactory part-load characteristics
• Integrated Part Load Value (IPLV) – Predicts performance over a defined range of operating points • Provides a more accurate account of actual equipment operation
Equipment Evaluation Air -Conditioning & Refrigeration Institute • Provides programs to certify manufacturer’s published equipment data – Verified through random testing
• Equipment labeled when in compliance ARI Standard 550/590-98
Standard defining the testing and rating requirements for all chillers
Provides an equal baseline for all manufacturers
Defines testing conditions for real-world,
ARI Standard 550/590-98 • Developed through real-world studies – 1992 U.S. Department of Energy Study • DOE/EIA-0246(92)
• Developed Weighted Average for: – Building types, Buildings with/without economizer, Chiller operational hours, etc.
• Determined 1% of a chiller’s operating hours spent at full load design conditions. – With such few hours spent at FL operation, an analysis comparing FL only would be completely inaccurate.
Equipment Evaluation
ARI Standard 550/590-98 IPLV = .01A + .42B + .45C + .12D A = EER @ 100% load (95°F Ambient) B = EER @ 75% load (80°F Ambient) C = EER @ 50% load (65°F Ambient) D = EER @ 25% load (55°F Ambient)
VAR SPEED Chiller Efficiency Matrix Percent Load Entering Condenser Water Temperature 55 F 65 F 75 F 85 F kW/ton usage 10% 0.520 0.680 1.100 20% 0.320 0.430 0.660 0.900 30% 0.260 0.353 0.527 0.753 40% 0.235 0.320 0.475 0.670 50% 0.220 0.308 0.444 0.612 60% 0.210 0.303 0.420 0.577 70% 0.209 0.311 0.423 0.569 80% 0.233 0.325 0.428 0.558 90% 0.249 0.340 0.442 0.560 100% 0.270 0.360 0.460 0.576
VAR SPEED Chiller Efficiency Curves 1.200 1.100 1.000
Entg Cond Wtr Temp
0.900 0.800 n o t / 0.700 W k 0.600
55 F 65 F 75 F 85 F
0.500 0.400 0.300 0.200 10%
20%
30%
40%
50%
60%
Pct Load
70%
80%
90%
100%
Cooling tower entering condenser water bin hours for Burlington Vt.: • 85F ECWT = 10 hrs • 75F ECWT = 1000 hrs • 65F ECWT = 1450 hrs • 55F ECWT and below = 6300 hrs
Chiller Performance Generalities: • Lower lift = less compressor energy (Compressor lift is the difference between the suction and discharge pressure). • Capacity has less affect on compressor performance than lift. • Different chillers have different minimum lifts due to design differences…
Flooded Evaporator @ 44F leaving chilled water Refrigerant pressure = 6.1 psia Tubes not covered by liquid
Motor cooling and oil loss problems stem from the same phenomenon; low internal differential Flooded pressure for systems which rely on a differential Compressor Evaporator pressure to operate. Condenser @ 55F ECWT Refrigerant pressure= 10.4 psia
@ 44F leaving chilled water Refrigerant pressure = 6.1 psia Tubes not covered by liquid
2B: The Tower: • Raising the tower setpoint will save fan energy but penalize the chiller. • Two- speed fan motors better than single speed. • Variable speed is best for energy and control.
2C: The pumps: • Condenser water flow: Reducing the condenser water flow will save on the pump energy but penalize the chiller (similar to holding up the entering condenser water temperature).
Performance Matters
First Cost Advantage of Air Cooled Chillers Easy Installation – 20% less than Water Cooled Equivalent No Cooling Tower, Tower pumps, Tower and Pump Starters No equipment room required for the chillers Multiple Circuits for redundancy – not multiple chillers Mounted starters
Maintenance Advantage of Air Cooled Chillers Easy Maintenance – vs. Water Cooled No on site Systems Engineer required No water treatment or make up water required No leaks on the roof No cooling tower, condenser pumps, associated starters
Performance – The Traditional Trade-off for Air Cooled Chillers Energy Full
Load typically 65% more than Water Cooled system
9.6
EER = 1.25 kW/TR (ASHRAE 90.1 Tier 1 requirement)
10.2 Part
EER = 1.17 kW/TR (ASHRAE 90.1 Tier 2)
Load typically 100% more than Water Cooled system
12.5
EER = .96 kW/TR
Performance – The Traditional Trade-off for Air Cooled Chillers Sound Multiple Typical Lower
Compressors and Condenser fans full load sound levels often 100+ dBA
nighttime sound regulations can be limiting factor
Required Sound Unit
acoustical treatments drive up first cost
blankets (-1 dBA) = 2-3% of first cost
enclosures (-3 to 5 dBA) ~$10 K
How Latitude changes the balance • All the best of today’s air cooled chillers – – – – –
ASHRAE 90.1 energy level compliance up to 10.3 EER R-134a environmentally sound HFC refrigerant Compact single package design (150 – 260 TR) Simple maintenance requirements Dual Circuit design for redundancy
PLUS YOU NO LONGER COMPROMISE ON PERFORMANCE…
New
World class IPLV performance – real world savings during the other 98% of the operating time vs. 90.1 requirements
15.2 EER
Part load sound levels 5-6 dBA lower than competitors
New New
New New
Soft Start Capabilities for increased motor life
Reduced Full load amps for a reduction in wire sizing
load shedding software for noise level management
Performance matters The power of off design on Energy - 98% of operating hours are at off design conditions
Latitude delivers 15-25% Real World kWh Savings
Performance matters Annual Energy Savings due to part load efficiency
180 TR Chiller 180 TR Chiller – ARI IPLV part load points 5000vshours – 5000 12.5 15.2 IPLV hours $7500/year savings – $.0813/kWh $7500/year savings (2003 DOE National Average)
3000 hours $4500/year savings
$14,000 $12,000 s g n i v a S l a u n n A
$10,000 $8,000 $6,000 $4,000 $2,000 $2000
2500
3000
3500
4000
4500
5000
5500
6000
Operating Hours 150 TR
180 TR
200 TR
250 TR
Latitude’s part load performance is tested & ARI certified
Electrical Characteristics • Soft Start • Power factor • First Costs – Electrical installation – Wire and circuit breakers reduced by 1-2 sizes – 5-15% Generator cost savings
• Operating Costs – .95 Power Factor throughout operating range
Performance through Technology • 25 years of real world experience with varying compressor motor speeds • Logical Extension of Variable Speed Drive technology for compressor motor applications • Eliminates Slide valve and associated inefficiencies, and reduces compressor moving parts by 50% • Solid State unit mounted starter
Lowest Total Cost of Ownership
• First Cost savings = 10-15%
Latitude – Electrical Savings can save you 10% of the – Elimination of sound attenuation equipment cost of the chiller…….
• Operating Costs Savings = 1525%
Every year it operates!
– 15 Year equipment life – 5000 hours per year operation – National Average $$/kWh ($0.0813)
Performance that delivers real world savings every year of operation
