This presentation summarized an engineering assessment of the refrigeration system at Stonyfield Farm Yogurt to optimize efficiency. The assessment analyzed the existing compressor sequencing strategy and developed two proposed optimized strategies estimated to save 27,471 kWh annually and 18,322 kWh annually, respectively. Additional opportunities for further study were also identified, such as floating head pressure controls, condenser and evaporator fan upgrades, and refrigerant cycling for evaporators.

1. Main Headquarters: 120 Water Street, Suite 350, North Andover, MA 01845 With offices in: NY, ME, TX, CA, OR www.ers-inc.com
OPTIMIZATION OF INDUSTRIAL REFRIGERATION PLANTS:
INCLUDING A CASE STUDY AT STONYFIELD FARM YOGURT
Prepared and presented by
Mark D’Antonio: Energy & Resource Solutions, Inc. (ERS)
Satyen Moray: Energy & Resource Solutions, Inc. (ERS)
Lisa Drake: Stonyfield Farm Yogurt
Randy Dixon: Public Service of Ne Hampshire

2. PRESENTATION OVERVIEW
 Introductions
 The US Industrial Refrigeration Market
 Overview of Industrial Ammonia
Refrigeration Systems
 Primary Refrigeration Components
 Compressors
 Condensers
 Evaporators
 Energy Savings Strategies
 Case Study

3. INTRODUCTIONS
Public Service of New Hampshire
(PSNH)
 Funded Technical Assistance – Engineering
Assessment
 Incentives
 Stonyfield Farm Yogurt
 Supported the Engineering Assessment
 ERS
 Conducted the Engineering Assessment ers
energy&resource
solutions

4. OVERVIEW - US INDUSTRIAL
REFRIGERATION MARKET
 Food & Beverage Sectors have high PC&R %
 Food & Chemicals comprise a high % of consumption in the
industry (55%)
Process Cooling &
Refrigeration
(PC&R) (A)
Total
(B)
Food 311 17,679 67,390 26.2% 28.6%
Beverage and Tobacco Products 312 2,349 8,242 28.5% 3.8%
Chemicals 325 16,109 215,008 7.5% 26.1%
All Manufacturing Industries 311-339 61,763 (D) 1,025,149 6.0% 100.0%
% of Total
US PC&R (A/D)
Energy Consumption (Millions of kWh)
Industries
PC&R %
of Total (A/B)
NAICS Code
Source: EIA
PC & R = Process Cooling & Refrigeration

5. INDUSTRIAL REFRIGERATION SYSTEMS -
OVERVIEW
 Refrigerant – typically Ammonia
 Compression
 Single Stage
 Multi-Stage
 Economizer
 Evaporators
 Direct Expansion
 Flooded (Shell)
 Liquid Overfeed
 Hybrid
 Controls

6. INDUSTRIAL REFRIGERATION SYSTEMS -
OVERVIEW
45-50 F
Cooling Loads
High
Pressure
Receiver
(Liquid)
135-165 psia
Liquid
Ammonia
(NH3) Gas
Liquid +Gas
Thermal
Expansion Valve
Backpressure
Valve
Intermediate
Pressure
Receiver
(Liquid+Gas)
Throttle Valve
25-30 F
Cooling Loads
Pump
Throttle
Valve
Low Pressure
Receiver
(Liquid+Gas)
-10 to -15 F
Cooling Loads
Pump
Gas
Liquid +Gas
Gas
Gas
Compressor #1
Compressor #2
Condenser
Hybrid Liquid Overfeed & DX

7. REFRIGERANT - AMMONIA
 Refrigerant - Ammonia (R-717) is typical for
industrial systems
 Less expensive
 3-10% > efficiency than HCFC-22 and HCFC134a
 More tolerant of moisture than other refrigerants
 Lubricants are easily separated out
 High latent heat capacity results in smaller
equipment
 Strong odor - leaks are easily detected

8. COMPRESSORS
 Consume a large % of system energy
 Should be optimized for load profile
 Predominant Types
 Reciprocating
• Single Stage
• Internally compounded
• Typically < 100 HP
• Good efficiency at part load
 Screw
• Fixed Volume Index - slide valve or bypass ports
• Variable Volume Index - slide valve or VFD
• Part load efficiency dependent on controls
• Output capacity control from 10%-100%
• Typically > 100 HP

9. COMPRESSORS – PERFORMANCE
FACTORS
 Suction Pressure
 Lower suction pressure = increased energy
consumption
 Condensing Pressure
 Dependent on condenser capacity & ambient
conditions
 Lower condensing pressure = lower temp = lower
compressor energy (likely higher fan energy)
 Efficiency
 Design Selection
 Sequencing to Match Load Profile

10. COMPRESSORS – LOAD SHARING
STRATEGIES
 Multiple Screw Compressors of Same Size
 Loads between 50%- 65%: split equally between compressors
 Loads greater > 65%: Base Load one, trim with other
 Multiple Reciprocating Compressors of Same Size
 Loads between 50%- 65%: split equally between compressors
 Loads greater > 65%: Base Load one, trim with other
 Multiple Compressors of Varying Types & Sizes
 Optimize to Load Profile
 Base Load Screws, trim with Recips or VFD controlled units
 Part Load Operation of Screw Compressors should be avoided
(except w/VFD control)

11. CONDENSERS
 Rejection of heat from the system
 Consume approx. 15%-20% of system energy
 Air Cooled
 Function of Ambient Conditions
 Less Capacity, Lower efficiency
 Water Cooled
 Operate at Lower Condensing Pressures
 Greater Capacity, Higher efficiency

12. CONDENSERS - CONTROL
 Evaporative Condensers
 Capacity Control
• Head Pressure Control (altered by airflow rate)
• Shutting off spray water (winter)
 Fan Flowrate Control
• On/Off
• Two Speed
• VFD
Source: Energy Center of Wisconsin

13. CONDENSERS – EFFICIENCY
STRATEGIES
 Use High Efficiency Motors on Fans & Pumps
 Use VFDs on Fans & Pumps where appropriate
 VFD control can result in considerable reduction over ON/OFF
strategy
 Greater Surface Area = Improved Efficiency
 Oversized Condenser
 Optimization of Condenser Systems
 Staging of Multiple Condensers
 VFDs & Floating Head Pressure Control
 Keep Surfaces Clean for Optimal Heat Transfer
 Water Treatment – free of mineral and bacterial buildup

14. EVAPORATORS
 Properly Sized for Design Loads
 Types
 Pumped Liquid Overfeed – higher efficiency,
lower temperatures and more uniform liquid
 Flooded Shell & Tube – indirect or secondary
cooling through water/brine
 Direct Expansion – not typically used with
Ammonia Systems (low efficiencies and higher
refrigerant temperatures)
 Hybrid – a combination of evaporator types

15. EVAPORATORS - CONTROL
 At Design Conditions only a small % of the time
 Fan Control Strategies
 Fan Cycling –maintain space setpoint temperature
 Refrigerant Cycling – refrigerant delivery is controlled, fan operates continually
 Fan Speed Control – speed is varied to maintain space setpoint temperature using
VFD or Two-Speed Fan
 Shell & Tube Capacity
 Control the Return Liquid Temperature
 Defrost
 Hot Gas Bypass – preferred, when needed vs. timed
 Hot Water
 Electric
 Warm Air

16. EVAPORATORS - PERFORMANCE
 Optimized Operations can save 10-15%
in System Energy Consumption
Source: Energy Center of Wisconsin

17. OVERALL ENERGY SAVINGS STRATEGIES
 Reduce Heat Loads – low cost
 Turn Off Lights, Increase Insulation,Reduce Infiltration, Maintain Clean Heat Exchanger Surfaces
 Reduce Temperature Lift in the Refrigeration Plant
 Optimize Compressor Plant Efficiency (lowest BHP/Ton)
 Equipment Selection
 Controls
 Aux Pumping Efficiency
 Optimize Defrost Control Strategy
 Optimize Evaporator/Condenser Relation
 Lowest Condensing Temperature and Highest Evaporator Temperature
 Optimize Fan Usage (condenser, evaporator)
 Staging or VFD
 Automated Real-time Central Controls
 Heat Recovery

18.  Founded 1983
 All Natural and Organic Dairy Products
 Yogurts
 Smoothies
 Ice Cream
 100,000 Square Foot Facility
 24/7 Operation
 $90 Million in Annual Sales
 Produces 45,000 cases of yogurt/day
 Primary Focus was to verify Sequencing Strategy
 1+ MW, 6 Million kWh
CASE STUDY – STONYFIELD FARM YOGURT

19.  Ammonia – Pumped Liquid Overfeed
 Peak Summer Load = 570 Tons
 Multiple Screw Compressors w/Slide Valve Capacity Controls
 350 HP, 250 HP, 125 HP, 50 HP
 Central Sequencer Controls
 The 50HP was not on the system
 Set to maintain 25 psig suction pressure
 Process & Space Cooling Loads
 High Temp Short Time Pasteurizers
 Pasteurization & Culture Vats
 Silos & Cream Tanks
 Chill Cells
 Warehouse
 Space Conditioning
 Refrigeration = 35% of Facility Electrical Usage(~2 million kwh)
CASE STUDY – STONYFIELD FARM YOGURT
SYSTEM DETAILS

20. CASE STUDY – STONYFIELD FARM YOGURT
SYSTEM DETAILS
Compressor #1
250 HP, 198 tons
Compressor #2
125 HP, 105 tons
Compressor #4
50 HP, 38 tons
Condenser
Low Pressure Receiver
(Gas & Liquid)
Ice Storage
HTST, Vats,
Silos, Cream
Tanks
15 HP
High
Pressure
Receiver
5 HP
Space Cooling
(20) Chill Cells
(9) Warehouse
Coolers
(1) Plate Freezer
Glycol Loop
HX
Ammonia (NH3) Gas
Ammonia (NH3) Liquid
(NH3)
Liquid
(NH3)
Gas & Liquid
Ammonia
(NH3) Gas
Suct
Press
Manually Controlled
Compressor #3
350 HP, 268 tons
Ammonia (NH3) Gas
Valve

21. CASE STUDY – STONYFIELD FARM YOGURT
ANALYSIS
 Goal for this Assessment:
 Optimize Sequencing of Compressors
 Identify Other Opportunities for Future Study
 Developed Load Profile
 Power Monitoring – FES Control System
 Extracted Data and Developed Load Profile
 Established Performance Data
 Created Analytical Models of Sequencing Strategies
 Combined Load Data & Performance Data

22. Case Study – Stonyfield Farm Yogurt
System Performance
Refrigeration Compressor Performance Curves
1.00
1.20
1.40
1.60
1.80
2.00
2.20
2.40
2.60
2.80
3.00
3.20
3.40
3.60
3.80
4.00
4.20
4.40
4.60
4.80
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
% Capacity
BHP/TTt
350 HP 250 HP 125 HP 50 HP

23. Case Study – Stonyfield Farm Yogurt
System Performance
FES - 350 HP
Slide Valve Position % Tons BHP BHP/Ton kW
10% 26.8 77.7 2.9 58.0
20% 53.6 92.9 1.7 69.3
30% 80.5 114.2 1.4 85.2
40% 107.3 141.4 1.3 105.5
50% 134.1 159.8 1.2 119.2
60% 160.9 187.0 1.2 139.5
70% 187.7 220.4 1.2 164.4
80% 214.6 250.8 1.2 187.1
90% 241.4 278.3 1.2 207.6
100% 268.2 305.7 1.1 228.1

24. CASE STUDY – STONYFIELD FARM YOGURT
ENERGY SAVING STRATEGIES FOR SEQUENCING
EXISTING
Cooling Load,
Tons
250 HP
#1
125 HP
#2
350 HP
#3
Step 1 0 - 30 OFF OFF OFF
Step 2 27 - 105 OFF ON-25% OFF
Step 3 150 - 198 ON-77% Backup OFF
Step 4 209 - 268 Backup OFF ON-78%
Step 5 227 - 303 ON-75% ON-75% Backup
Step 6 269 - 373 Backup ON-65% ON-75%
Step 7 275 - 466 ON-85% Backup ON-40%
Step 8 400 - 571 ON-70% ON-70% ON-70%
Existing Sequencing

25. CASE STUDY – STONYFIELD FARM YOGURT
RECOMMENDATIONS
 Sequencing MeasuresEnergy Demand Annual Simple
Savings Reduction Installed Cost Payback
Energy Efficiency Measure (kWh) (kW) Cost Savings (Years)
EEM-1 Optimization of Refrigeration Sequencer Set Points (Option-1) (Include 50-HP compressor in the sequencer)
Savings Summary 27,471 0.0 $10,000 $1,997 5.0
EEM-2 Optimization of Refrigeration Sequencer Set Points (Option-2) (Optimize existing sequencer set points)
Savings Summary 18,322 0.0 $0 $1,332 0.0
Proposed Sequencing
Option 1
OPTION 2
Cooling Load,
Tons
250 HP
#1
125 HP
#2
350 HP
#3
Step 1 0 - 30 OFF OFF OFF
Step 2 27 - 105 OFF ON-45% OFF
Step 3 110 - 268 OFF OFF ON-40%
Step 4 270 - 373 OFF ON-100% ON-60%
Step 5 374 - 466 ON-100% OFF ON-65%
Step 6 470 - 570 ON-100% ON-100% ON-60%
OPTION 1
Cooling Load,
Tons
250 HP
#1
125 HP
#2
350 HP
#3
50 HP
#4
Step 1 0 - 38 OFF OFF OFF ON-20%
Step 2 50 - 105 OFF ON-47% OFF OFF
Step 3 106 - 268 OFF OFF ON-40% OFF
Step 4 269 - 306 OFF OFF ON-87% ON-100%
Step 5 310 - 373 OFF ON-100% ON-75% OFF
Step 6 374 - 466 ON-100% OFF ON-66% OFF
Step 7 470 - 504 ON-100% OFF ON-85% ON-100%
Step 8 520 - 570 ON-100% ON-100% ON-80% OFF
Proposed Sequencing
Option 2

26. CASE STUDY – STONYFIELD FARM YOGURT
RECOMMENDATIONS
 Additional Opportunities Identified for
Further Study
 Floating head pressure controls (set at a
constant 135-psig)
 Oversized condensers
 No VFDs on condensers, evaporators or
compressors
 Evaporator capacity control (refrigerant
cycling)
 Condenser fans - single speed, ON/OFF