1

Automatic Commercial Ice 

Maker Energy Conservation 

Standards – Energy Modeling

Appliance Standards

Department of Energy

Building Technologies Program

EERE-2010-BT-STD-0037

ACIM-2010-STD-0037@ee.doe.gov

June 19, 2014
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Welcome

• Introductions (around the room)

• Role of the Facilitator

• Ground Rules

– Speak one at a time.

– Say your name for the record – there will be a complete transcript of this 

meeting.

– Be concise – share the “air-time.”

– Keep the focus here – cell phones on silent; limit sidebar conversations.

– Webinar participants turn phone on mute; “raise your hand” to be recognized 

to speak.

• Housekeeping Items

• Agenda Review

• Opening Remarks
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Agenda

• 9:00 – 9:20 am Welcome, Introductions

• 9:20 – 9:50 am Opening Remarks

• 9:50 – 10:45 am Background and Energy Model Overview

• 10:45 – 11:00 am Break

• 11:00 am – 12:15 pm Use of the Energy Model in DOE Analysis

• 12:15 – 1:15 pm Lunch

• 1:15 – 3:30 pm Energy Model Demonstration(s)

• 3:30 – 4:00 pm Next Steps and Closing Remarks
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Public Meeting Topics

1 Introduction and Opening Remarks

2 Background

3 Energy Model Description

4 Use of the Energy Model in DOE’s Engineering Analysis

5 Additional Energy Modeling

6 Discussion
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Listening Via the Webcast

• The Department is broadcasting this meeting live over the 

Internet.

• DOE is providing the webcast to accommodate stakeholders who 

are unable to attend the public meeting in person.

• The webcast allows stakeholders to listen in and view the slides.
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Purpose of the Public Meeting

• Present the analytical approaches for the energy modeling used to 

evaluate energy conservation standards for automatic commercial 

ice makers (ACIM).

• Invite participants to provide summary comments or statements 

and raise additional issues for discussion. 

• Discuss next steps in the rulemaking, particularly response to 

comments regarding the engineering analysis.
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Opening Remarks

Meeting participants are invited to provide opening 

remarks or statements at this time.
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Public Meeting Topics

1 Introduction and Opening Remarks

2 Background

3 Energy Model Description

4 Use of the Energy Model in DOE’s Engineering Analysis

5 Additional Energy Modeling

6 Discussion
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Background

• Energy Policy Act of 2005 (EPACT) P.L. 109-58

– Amended EPCA to add coverage for cube type automatic commercial ice makers 

between 50 and 2,500 pounds of ice per 24 hours.

– Granted DOE authority to set standards for additional types of ACIM equipment 

that are not covered in EPCA (includes flake and nugget ice makers and batch 

type ice makers not included in the original EPCA definition).

– Required DOE to complete one rulemaking cycle to determine whether to 

further amend ACIM standards.

– Final rule required no later than January 1, 2015.

• NOPR published March 17, 2014.

– The NOPR proposed standards for batch and continuous ice makers with harvest 

capacity 50 to 4,000 lb/24 hours. 79 FR 14846. 

• NOPR Public Meeting held April 14, 2014.

• Energy Model Meeting today, June 19, 2014.
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Rulemaking Stages

Market & 

Technology

Screening

Analysis

Engineering

Analysis

Energy Use & 

End Use Load

Characterization

Shipments

Analysis

National

Impact

Analysis

Markups for

Equipment

Price

Determination

Life-Cycle

Cost and

Payback 

Period Analysis

Manufacturer 

Impact 

Analysis

Regulatory

Impact

Analysis

Employment

Impact

Analysis

Utility

Impact

Analysis

Emissions

Impact

Analysis

Manufacturer Production Cost–

Efficiency Relationship

Manufacturer 

Production Cost

Efficiency Level

(kWh/100 lb ice)

Purpose of Engineering Analysis: 

Characterize manufacturer production cost 

versus efficiency for higher-efficiency ACIM 

equipment.

The energy model was used to characterize equipment efficiency in the 

rulemaking’s engineering analysis. 
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Public Meeting Topics

1 Introduction and Opening Remarks

2 Background

3 Energy Model Description

4 Use of the Energy Model in DOE’s Engineering Analysis

5 Additional Energy Modeling

6 Discussion
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Development of the Energy Model

• FREEZE Model developed by Anthony Varone in 

1995.

• EPA Refrigerator Analysis (ERA) program 

developed by Richard Merriam, used for the 1997 

refrigerator rulemaking and updated in 2009 for 

use in the 2011 refrigerator rulemaking.

• In 2011, Varone and Merriam developed a 

Windows version of FREEZE, incorporating model 

features developed for the ERA program.

• Navigant has permission to use the software. 
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Energy Model

The model calculates energy input of the power-using components and 

ice production for a full icemaking cycle including freeze and harvest.

• Constant Power input P (in watts) for 

constant-power components: condenser 

fan, pump, controls.

• Heat removed from incoming water (or 

circulating sump water) and heat of fusion 

removed to make ice represents the 

thermal load of the evaporator.

• Compressor power input during freeze 

cycle based on refrigeration 

circuit/compressor balance.

• Harvest: 

– Heat added to the evaporator and water 

system during harvest cycle sets the freeze 

cycle start temperatures.

– Harvest duration and energy input are model 

inputs that can be changed based on 

knowledge of trends for these parameters.

Condenser

Evaporator

Compressor

TXV

Ppump

Water In

Drain 

Water Out

Ice Out

Pcomp

Pfan Controls

PCtrl
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Energy Model

For a batch ice maker, the freeze-cycle calculation is conducted numerous times, 

representing the progression of sump water cooling and ice formation.

• At each time step, balance of 

refrigeration system and 

water/evaporator system 

determines rate of heat removal 

from the water and the ice 

formation.

• Water temperature and ice 

thickness for the next time step 

are calculated based on the 

previous step’s heat removal.

• Time steps run till the calculated 

ice quantity equals the pre-harvest 

ice weight.
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Energy Model

The full-cycle energy use and ice production are calculated. 

• Per-Cycle Energy Use:

– Condenser fan: Power × cycle time

– Pump: Power × cycle time.

– Controls: Power × cycle time.

– Compressor: Summation for all time steps of power × duration of time step.

– Harvest: Input harvest energy use. This includes operation of all components 

during harvest, including the fan (if running), pump, controls, and solenoid valve.

• Per-Cycle Ice Production: pre-harvest ice weight minus harvest ice 

loss.

• Energy Use: Per-cycle Energy Use divided by Per-cycle ice production.
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Energy Model

Compressor power input and mass flow are based on compressor 

performance data obtained from compressor vendors.

• Performance based on evaporating, 

condensing, superheat, and subcooling 

conditions.

• FREEZE adjusts for non-standard 

superheat and subcooling.

• Condensing and evaporating conditions 

based on balance of refrigeration 

system: compressor, evaporator, 

condenser. 

• For batch ice makers, obtaining good 

model/test match involves derating 

compressor map capacity.
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Energy Model

Refrigeration cycle balance requires that the evaporator and condenser transfer 

an amount of heat consistent with their sizing and the operating temperature 

differences.

• Heat transfer rate (Btu/hr) equal to surface 

area times heat transfer coefficient times 

temperature difference ∆T.

• Heat transfer rate also equal to refrigerant 

mass flow times refrigerant enthalpy change.

• For condenser or continuous ice maker 

evaporator, heat transfer rate also equal to 

fluid mass flow (water or air) times enthalpy 

change.

• For batch ice maker evaporator, heat transfer 

rate determines water/ice system start 

conditions in next time step.

∆T

T refrigerant

T air

Air-cooled condenser
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Energy Model

Air-cooled condenser modeling and refrigerant-side modeling for the 

evaporator as developed for the ERA refrigerator model.

• See details in Appendix 5-B of the 2011 Refrigerator Final Rule TSD:

http://www.regulations.gov/#!documentDetail;D=EERE-2008-BT-STD0012-0128

• For example, for air-cooled condensers with plain fin, herringbone fin, 

and slit fin, airside heat transfer was modeled according to the Wang 

correlations:

– Wang, Chi-Chuan, “Recent Progress on the Air-side Performance of Fin-and-Tube 

Heat Exchangers,” International Journal of Heat Exchangers 1524-5608 (Vol 1 

(2000), pp. 49-76. 
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Energy Model

Water-side modeling for the evaporator using basic calculations for the 

conduction heat transfer correlated with a polynomial curve fit.

• High thermal conductance at 

start of cycle—lower 

conductance as ice layer 

builds up.

• Additional thermal resistance 

for the water film layer.

ice film thickness 

back film thickness twice the side-film thickness

bridge

solder fin

one dimensional conduction

Example for a 126-

cube evaporator
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Energy Model

Other model details.

• Continuous ice maker evaporator

– Constant UA value (Btu/hr-F) to represent heat transfer from water/ice to 

refrigerant.

– Constant power input P (Watts).

– Ice exit enthalpy based on input for exit ice hardness.

• Water-cooled condenser

– Constant condensing temperature.

• Refrigerant-flow limit for TXV at start of freeze cycle for batch ice 

makers.

• Refrigerant properties using REFPROP 8.0
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Energy Model

DOE has adopted procedures to modify model inputs to improve match 

to test data. 

• Compressor capacity derating for batch ice makers.

• Adjustment of harvest cycle inputs for condenser temperature 

reduction in batch ice makers, based on observed trends in test 

data. 

• Addition of a refrigerant mass-flow limit to limit the maximum 

evaporating temperature, based on evaporator conditions 

measured during testing. 
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Energy Model

DOE used physical testing and teardown data for 41 ice makers in its work 

on model calibration. Preliminary Phase: 

Type Equipment Class Harvest 

Capacity

lb/24 

hours

Energy Use 

kWh/

100 lb

Potable 

Water Use 

gal/100 lb

Energy 

Test

Reverse 

Engineering

Energy 

Use 

Model

Batch

IMH-A-Small-B 270 7.70 20.0   

IMH-A-Small-B 324 5.80 22.6   

IMH-A-Large-B 780 5.70 20.5  

IMH-A-Large-B 844 5.00 18.4  

IMH-A-Large-B 1,460 4.95 20.0  

IMH-A-Large-B 1,560 4.10 18.8   

IMH-W-Large-B 851 4.40 19.7  

IMH-W-Large-B 2,820 3.60 19.7   

RCU-A-Large-B 1,510 4.59 20.0  

RCU-A-Large-B 1,694 3.80 18.1   

RCU-A-Large-B 2,350 4.64 19.7  

SCU-A-Small-B 121 8.40 17.8   

SCU-A-Small-B 112 11.80 34.0  

SCU-W-Large-B 285 5.50 18.0   

Continuous

IMH-A-Small-C 310 6.31 12.0  

IMH-A-Small-C 822 5.51 13.6  

IMH-A-Small-C 845 3.40 12.0   

RCU-A-Large-C 1,780 3.40 12.0   

SCU-A-Large-C 280 6.00 19.0   
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Energy Model

DOE considered physical testing and teardown data for 41 ice makers in 

its work on model calibration. NOPR Phase: 

Type Equipment Class Harvest 

Capacity

lb/24 hours

Energy 

Use kWh/

100 lb

Potable 

Water Use 

gal/100 lb

Energy 

Test

Inspecti

on

Energy 

Use 

Model

Batch

IMH-A-Small-B 335 6.0 20.0  

IMH-A-Large-B 528 6.0 19.1  

IMH-W-Small-B 360 4.7 20.0  

IMH-W-Small-B 270 6.19 23.9  

IMH-W-Small-B 275 6.1 39.0   

IMH-W-Medium-B 650 4.1 18.6  

IMH-W-Medium-B 832 4.0 18.9  

RCU-NRC-Small-B 780 4.7 18.4  

RCU-NRC-Small-B 843 5.6 22.8  

RCU-NRC-Large-B 2,256 4.34 17.0  

SCU-A-Small-B 143 8.48 32.7  

SCU-A-Large-B 204 9.5 32.4  

SCU-A-Large-B 228 8.6 32.9   

Continuous

IMH-A-Large-C 921 6.6 12.0  

IMH-A-Large-C 1,100 5.5 12.0  

IMH-W-Small-C 560 5.9 12.0  

RCU-NRC-Small-C 610 6.9 12.0  

RCU-NRC-Small-C 835 5.0 12.0  

SCU-A-Small-C 250 9.1 12.0   

SCU-W-Small-C 455 5.0 12.0  
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Energy Model Demonstration

Energy Model
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Public Meeting Topics

1 Introduction and Opening Remarks

2 Background

3 Energy Model Description

4 Use of the Energy Model in DOE’s Engineering Analysis

5 Additional Energy Modeling

6 Discussion
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Use of the Energy Model in the Engineering Analysis

DOE used the energy model to predict energy use reductions. 

• Batch ice maker analysis based on ice makers with “waffle-plate” 

evaporator making full-cube (7/8-inch) ice. No similar restrictions 

on continuous ice maker analysis.

• Representative baseline ice makers selected for developing costefficiency curves: 

– Models with efficiency-level within a few percent of the defined baseline.

– Representative characteristics based on publicly available information (e.g. 

package size).

Develop 

Baseline 

Model

Model 

Alternative 

Designs

Calibrate at 

Higher 

Efficiency
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Use of the Energy Model in the Engineering Analysis

DOE used the energy model to predict energy use reductions. 

• Calibrate energy model for the representative baseline ice maker, using 

the following inputs and calibration checks.

– Physical measurements based on reverse engineering.

– Third-part laboratory test data at DOE energy test conditions (90  ̊F/70  ̊F): Energy 

use, ice production, refrigerant pressures, temperatures.

– Component power input measurements: fans, pumps, controls, auger motors 

(while making ice)

• Calibration involves adjustment of less certain input parameters within 

reasonable ranges in order to match observed performance parameters:

– Per-cycle ice production.

– Cycle time.

– Per-cycle energy use.

– Refrigerant conditions.

• For representative models more than a few percent better than 

baseline, revise the energy model with less-efficient design features to 

represent baseline.

Develop 

Baseline 

Model

Model 

Alternative 

Designs

Calibrate at 

Higher 

Efficiency
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Use of the Energy Model in the Engineering Analysis

DOE used the energy model to predict energy use reductions. 

• Model energy use for alternative higher-efficiency designs.

• Calibrate at higher efficiency by ensuring efficiency-level 

consistency with max available unit for equivalent design option 

mix.

– If max-available unit was reverse-engineered: direct comparison of design 

details for purchased/reverse-engineered max-available units.

– Otherwise: compare efficiency level of energy model design with highestefficiency compressors, increased-size heat exchangers, and best-efficiency 

PSC motors with max-available level.

Calibrate at 

Higher 

Efficiency

Develop 

Baseline 

Model

Model 

Alternative 

Designs
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Demonstration

Design Option Analysis Walk-Through
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Additional Work

• DOE’s contractor has obtained additional information from ice maker 

manufacturers under non-disclosure agreement (NDA), and has been 

promised more information.

• Some of this information addresses model/test discrepancies associated 

with specific design options—but not all design options cited in 

comments as being improperly represented by the model.

• Some of the information will help calibration of model results at 

intermediate efficiency levels.

• Some information will supplement the modeling results to confirm the 

cost-efficiency curve.

• DOE’s contractor is also in the process of obtaining additional cost 

information under NDA to allow potential revisions of cost projections.

DOE’s analysis approach for the final rule will depend on obtaining data 

to make further model adjustments and allow complementary analysis to 

confirm results.
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Additional Work

• In order to perform further calibration of the energy model, the 

Department requests test data representing implementations of each of 

the following design options:

– Compressor replacements

– Increases in evaporator size

– Increases in condenser size (air-cooled and water-cooled)

– Application of batch potable water controls

– Efficiencies of available PSC and ECM motors for replacement in current units

• Model adjustments may be made as adjustments to input or by 

reducing the improvement associated with the output.
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Public Meeting Topics

1 Introduction and Opening Remarks

2 Background

3 Energy Model Description

4 Use of the Energy Model in DOE’s Engineering Analysis

5 Additional Energy Modeling

6 Discussion
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Additional Energy Modeling

Model Demonstration with Stakeholder Input Data
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Public Meeting Topics

1 Introduction and Opening Remarks

2 Background

3 Energy Model Description

4 Use of the Energy Model in DOE’s Engineering Analysis

5 Additional Energy Modeling

6 Discussion
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Energy Conservation Standards - Rulemaking Timeline

2010

ECS Framework 

Document Public 

Meeting

December 16, 2010

ECS Preliminary 

Analysis

Public Meeting

February 16, 2012

ECS NOPR

Public Meeting

April 14, 2014

2012 2015 2016

Proposed Energy 

Conservation 

Standard Final 

Rule Compliance 

Date 

To Be Determined

TP NOPR 

Public Meeting

April 29, 2011

2011

Energy Model

Public Meeting

June 19, 2014
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Discussion

Open discussion and closing remarks.