NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Michael Deru

ASHRAE Winter Conference

Las Vegas, Nevada

February 1, 2011

NREL/PR-5500-50409

A Proposed Methodology for LEED 

Baseline Refrigeration Modeling
Learning Objectives for this Session

ASHRAE is a Registered Provider with The American Institute of Architects Continuing Education 

Systems. Credit earned on completion of this program will be reported to ASHRAE Records for AIA 

members. Certificates of Completion for non-AIA members are available on request.

This program is registered with the AIA/ASHRAE for continuing professional education. As such, it does 

not include content that may be deemed or construed to be an approval or endorsement by the AIA of 

any material of construction or any method or manner of handling, using, distributing, or dealing in any 

material or product. Questions related to specific materials, methods, and services will be addressed 

at the conclusion of this presentation.

1. Describe options for improving energy efficiency in commercial refrigeration.

2. Design commercial refrigeration systems for reduced greenhouse gas 

emissions. 

3. Describe problems associated with establishing LEED energy credits for 

buildings with refrigeration loads.

4. Distinguish important parameters for developing models of refrigeration 

equipment. 

5. Clarify cost effective opportunities for reducing refrigeration energy 

consumption.

6. Design a commercial supermarket with a 50% reduction in energy usage. 
Refrigeration Modeling: What’s the 

Big Deal?

• Large energy user

• Not all software have refrigeration models

• State of modeling algorithms is not mature

• Complex interactions with the space and HVAC

• Lots of inputs

• No established baseline

Credit: NREL Michael Deru
Heating

20%

Cooling

3%

Fans

7%

Interior 

Lighting

12%

Exterior 

Lighting

1%

Interior 

Equipment

13%

Refrigeration

44%

Typical Supermarket Energy Use

Credit: Michael Deru

Refrigeration is 

20% to 50% of 

the total Energy!
Measured Refrigeration Energy End Uses

Credit: Michael Deru

Compressor

50%

Condenser

6%

Evap. Fans

17%

Defrost

4%

Lights

13%

A/S Htrs

10%
Getting Started – Take Inventory

• Compressors

• Condensers

• Working Fluid

• Cases

• Operating Schedules

Description Size Length Load SST Fans Defrost

ft ft

1000Btu

/h oF Amps Volt Phase kW Amps Volt Phase kW

Frozen cake 3 doors 7.5 4.0 -14 1.5 115 1 0.17 8.6 208 3 3.10

Seafood Freezer 8x10x10 10 8.9 -10 3.3 208 1 0.69 10.5 208 1 2.18

Frozen seafood 4 doors 10 5.3 -14 2.0 115 1 0.23 11.3 208 3 4.07

Service seafood 12 12 14.4 13 3.6 115 1 0.41 0.00

M/D reach-in freezer 15 doors 37.5 16.5 -14 7.5 115 1 0.86 44.0 208 3 15.85

M/D reach-in freezer 18 doors 45 19.2 -14 9.0 115 1 1.04 38.8 208 3 13.98

M/D reach-in freezer 18 doors 45 19.2 -14 9.0 115 1 1.04 38.8 208 3 13.98

Credit: NREL Jennifer Scheib
Energy Models – What are the Inputs?

Example input fields from a whole building program

Reach-in cases – 35 inputs (3 performance curves)

Walk-ins – 33 inputs

Compressors – 8 inputs (2 performance curves)

Condensers – 11 inputs (1 performance curve)

System – 13 inputs

Where do they come from?

Credits: NREL Jennifer Scheib
Resources

• Energy software example files and libraries

– Compressor curves

– Case libraries

– Working fluids

• Manufacturer data

• ASHRAE handbook, Journal articles, 

technical reports, research reports
Resources (2)

• DOE supermarket reference building model

– 45,000 ft2 fully defined supermarket energy model

– Models and results for 16 climate zones

Sales

Bakery

Deli

Produce

Office

Dry Storage

Credit: Michael Deru
Reference Building Model Cases

Case Area 

(ft2)

Length

(ft)

Cooling 

Capacity 

(Btu/h/ft)

Evaporator

Fan

(W/ft)

Lighting

(W/ft)

Defrost

(W/ft)

AntiSweat

(W/ft)

SST

(°F)

Case

Temp.

(°F)

Compressor 

Rack

Medium Temperature

Multideck meat cases 120 1500 26.7 11.8 135 20 15 36 A

Other multideck 

cases

260 1500 12.5 18.3 0 0 15 36 A

Meat walk-in 400 50 400 50 400 50 0 15 36 C

Other walk-in 2600 325 2600 325 2600 325 0 15 36 C

Low Temperature

Reach-in cases 268 560 20 33 400 71 –25 5 B

Single-level open 

cases 

128 550 10 0 420 24 –25 10 B

Walk-in freezer 1000 125 640 32 8 232 0 –25 –10 D
Baseline Model for Energy Savings 

Calculations – What are your options?

• Make-up your own

• COMNET

• Appendix G style method under development
Baseline Configuration

Liquid Manifold

Condenser

Suction Manifold

Discharge Manifold

Compressors

Receiver

Display Case

Walk-in

Cooler

Display Case

Credit: Michael Deru

• Parallel compressor racks

• Air-cooled condenser
Baseline Model Highlights

Compressor racks Parallel DX reciprocating compressors, 3 – 4 racks

Suction Groups 5

Suction Temperature 3°F below lowest saturated evaporator temp

Refrigerant 404A

Case Fans PSC motors with defined W/ft

Case Lighting T8 lamps with defined W/ft

Anti-Sweat Heaters Modulated control based on dew point

Defrost type

Electric with temperature termination on low temp

Electric with time-off control on medium temp

Condensers

Air-cooled, constant speed fans, cycle to meet 

minimum SCT

Heat Reclaim

Domestic HW preheat. De-superheating of low 

temperature rack discharge gas
Example Savings Calculations

• Create and run baseline model

• Create and run proposed model

– Added doors to medium temperature cases

– LED case lights

– ECM evaporator fan motors

– Variable speed condenser fan

• Always question the results!

Credit: NREL Michael Deru
Results

Heating 

7%

Hot Water

3% Cooling 

1%

Lighting 

6%

Equipment 

(elec)

12%

Equipment 

(gas)

3%

Fans 4%

Refrigeration

23%

Savings

41%

Component Savings

Heating 54%

Hot Water 47%

Cooling 44%

Lighting 57%

Equipment (electric) 20%

Equipment (gas) 20%

Fans 52%

Refrigeration 36%

Total 41%
Thank You

Questions?

michael.deru@nrel.gov