Refrigeration Playbook
Optimizing Heat Rejection and
Refrigeration Heat Reclaim for
Supermarket Energy Conservation
Learning Objectives
• Understand basic refrigeration heat reclaim systems and
apply this knowledge to create accurate energy models and
effective design strategies.
• Calculate the energy impacts associated with reclaiming
heat from commercial refrigeration systems in order to
confidently guide building owners and designers in
optimizing building performance.
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.
Acknowledgments
Refrigeration Playbook: Heat Reclaim
Optimizing Heat Rejection and Refrigeration Heat Reclaim
for Supermarket Energy Conservation
August 15, 2014 — December 31, 2014
Chuck Reis, Eric Nelson, James Armer, and Tim Johnson
CTA Architects Engineers
Boise, Idaho
Adam Hirsch and Ian Doebber
National Renewable Energy Laboratory
Golden, Colorado
NREL Technical Monitor: Adam Hirsch
Prepared under Subcontract No. LEA-0-40383-01
Agenda
• Why Use Heat Reclaim?
• Why Model Heat Reclaim?
• Project Background
• Refrigeration Cycle Basics
• Common Heat Reclaim Methods
• Tools Available
Why Heat Reclaim?
• What is Heat Reclaim?
• Food Sales: 2nd Highest EUI – 200 kbtu/sf
• Refrigeration: Largest Energy End-Use
• Space Heating: 2nd or 3rd Largest End-Use
• Code Requirements
Energy Intensity by Sector (2003 CBECS)
Site EUI (kbtu/sf-yr)
250
200
150
100
50
0
Why Model Heat Reclaim?
• Optimize Investment
• Inform Design
• Code Compliance
• 3rd Party Certifications
• Energy Savings from “Process Loads”
• Baseline Model Resources
• AHRI Standards 540, 1200
• EISA 2007
• DOE 2012 Standards for Commercial
Refrigeration
Background
• Create Guide for Designers / Owners /
Contractors
• Identify Common Heat Reclaim Methods
• De-mystify Heat Reclaim
• Transparent Calculation Methods
• Rule of Thumb: Don’t model unless you can write
sequence
• Adapt Methods into EnergyPlus code
• Add a tool to your tool belt
• 17 Locations – All ASHRAE U.S. Climate
Zones
• E+ Model with Spreadsheet Tools
Refrigeration Basics
Refrigeration Basics
Refrigeration Basics
THR
Refrigeration Basics
THR
Condensing
Superheat
THR = Q̇cond + Q̇DSH
Q̇DSH = ṁ(hD – hE)
Q̇cond = ṁ(hE - hA)
System Selection
• Look at Big Picture
• Practical Considerations
•
•
•
•
•
•
•
•
Budget
Design Constraints
Climate
New or Existing Construction
Life Cycle Cost
Initial Cost
Energy Savings
Maintenance Costs
General Considerations
• Lower Refrigeration Loads First
• Find Consistent Heating Demand
• Space Heat
• OA Preheat
• Domestic Hot Water
• Desuperheat or Full Condensing?
• DSH: Higher Temperature, Lower
Quantity
• Condensing: Lower Temperature,
Higher Quantity
General Considerations
• DX Reclaim Coil vs. Water Reclaim Coil
• DX: More Efficient, More Considerations
• Water: Less Efficient, More Control
• Low Temp vs. High Temp Refrigeration
• LT: Higher Discharge Temperature, Lower
Capacity
• MT: Lower Discharge Temperature, Higher
Capacity
• Active Maintenance Program
Reclaim Methods
• Service Hot Water (Desuperheat)
• Mixed Air Heating (DSH / Cond.)
• Outdoor Air Preheat (DSH / Cond.)
• Water Loop Heat Pump (Full Condensing)
• Boiler / Cooling Tower
• Ground Loop Heat Exchanger
Service Water Heating
• Usually Desuperheat, DX Coil
• Hourly Tank Temp Calculation:
• Weighted Avg. of Tank Temp, Makeup Water Temp
• Reclaim Calculation:
• Q = min(Qref, QSHW)
• When Tref > Ttank
• Approach = f(Coil Effectiveness)
Mixed Air Heating
• Desuperheat or Full Condensing
• Q = min(Qref, QHVAC)
• Unless MAT > Tcond
• Approach = f(Coil Effectiveness)
Outdoor Air Preheat
• Simplest Calculation Method
• Condensing Temp > OA Temp
• Q̇ideal = min(Q̇air, Q̇ref)
• Q̇actual = Q̇ideal × Coil Effectiveness
Water Source Heat Pump
• More Complicated Calculation
• Simulation may be required
• Efficiency = f(Loop Temperature)
• Loop Temp = f(QHP, THR)
• Heat Pump Performance Curves
• Loop Temp Control Strategy
• Balance Loads
Other Considerations
• Heat Reclaim Is Not Free Heat!
• Refrigeration Impacts
• Condenser Fan Energy (Reduction)
• Piping Configurations
• Pressure Drop (Compressor Energy)
• HVAC Impacts
• Coil Airside Pressure Drop
• Coil Waterside Pressure Drop (if applicable)
• Increase Head Pressure to Maximize
Heating?
• Increased Heating Capacity
• Decreased Refrigeration Efficiency
• Cost of Refrigeration Heat vs. HVAC Heating
SHW Results(DSH, LT)
No.
ASHRAE
Climate
Zone
1
2
3
4
6
5
7
8
9
10
12
11
13
14
15
16
17
1A
2A
2B
3A
3B
3B
3C
4A
4B
4C
5A
5A
5B
6A
6B
7
8
DHW
Representative City Desuperheating F
Savings (kbtu)
Miami, FL
Houston, TX
Phoenix, AZ
Atlanta, GA
Los Angeles, CA
Las Vegas, NV
San Francisco, CA
Baltimore, MD
Albuquerque, NM
Seattle, WA
Chicago, IL
Boston, MA
Denver, CO
Minneapolis, MN
Helena, MT
Duluth, MN
Fairbanks, AK
265,761
264,778
284,859
256,082
228,388
275,570
223,711
251,461
254,925
230,693
252,309
244,659
255,031
254,703
247,772
246,398
249,030
Mixed Air Results(Cond, LT)
No.
1
2
3
4
6
5
7
8
9
10
12
11
13
14
15
16
17
ASHRAE
ASHRAE
DHW
Space
DHW
Heating
Space Heating VS
Climate No.
Representative
Climate City
Representative
Desuperheating
City Desuperheating
Full Condensing Full
Desuperheating
Condensing De
Zone
Zone
Savings (kbtu)
Savings (kbtu)
Savings (kbtu)
S
1A
2A
2B
3A
3B
3B
3C
4A
4B
4C
5A
5A
5B
6A
6B
7
8
1Miami, FL1A
Miami, FL 265,761
2Houston, 2A
TX
Houston, TX 264,778
3Phoenix, 2B
AZ
Phoenix, AZ 284,859
4Atlanta, GA
3A
Atlanta, GA 256,082
6Los Angeles,
3B CA Los Angeles, CA
228,388
5Las Vegas,3BNV
Las Vegas, NV275,570
7San Francisco,
3C CA San Francisco,223,711
CA
8Baltimore,
4AMD Baltimore, MD
251,461
9Albuquerque,
4B NMAlbuquerque,254,925
NM
10
Seattle, WA
4C
Seattle, WA 230,693
12
Chicago, IL
5A
Chicago, IL 252,309
11
Boston, MA
5A
Boston, MA 244,659
13
Denver, CO
5B
Denver, CO 255,031
14
Minneapolis,
6A MN Minneapolis, 254,703
MN
15
Helena, MT
6B
Helena, MT 247,772
16
Duluth, MN
7
Duluth, MN 246,398
17
Fairbanks,8AK
Fairbanks, AK249,030
265,761
512,782
264,778
782,508
284,859
676,161
256,082
942,543
1,176,558
228,388
275,570
898,983
1,317,392
223,711
1,013,205
251,461
254,925
974,207
1,271,816
230,693
1,005,135
252,309
1,102,669
244,659
255,031
976,418
1,001,394
254,703
1,063,681
247,772
1,103,733
246,398
1,133,295
249,030
512,782
189,195
782,508
231,934
676,161
204,035
942,543
262,520
1,176,558
334,633
898,983
246,113
1,317,392
330,268
1,013,205
278,475
974,207
270,468
1,271,816
315,505
1,005,135
288,159
1,102,669
299,485
976,418
281,565
1,001,394
292,792
1,063,681
301,019
1,103,733
311,989
1,133,295
317,776
OA Preheat (Cond, LT)
No.
ASHRAE
Climate
Zone
1
2
3
4
6
5
7
8
9
10
12
11
13
14
15
16
17
1A
2A
2B
3A
3B
3B
3C
4A
4B
4C
5A
5A
5B
6A
6B
7
8
DHW
Representative City Desuperheating F
Savings (kbtu)
Miami, FL
Houston, TX
Phoenix, AZ
Atlanta, GA
Los Angeles, CA
Las Vegas, NV
San Francisco, CA
Baltimore, MD
Albuquerque, NM
Seattle, WA
Chicago, IL
Boston, MA
Denver, CO
Minneapolis, MN
Helena, MT
Duluth, MN
Fairbanks, AK
265,761
264,778
284,859
256,082
228,388
275,570
223,711
251,461
254,925
230,693
252,309
244,659
255,031
254,703
247,772
246,398
249,030
Tools Available – E+
• EnergyPlus Capabilities
• Service hot water reclaim
• Desuperheat coil
• EnergyPlus Limitations
• Mass flow estimation
• No compressor discharge temp
• Superheat ratio – Constant fraction
of THR
• No OA preheat coil
• Limited to desuperheat, no full
condensing coil
Tools Available – E+
• EnergyPlus Notes:
• Microclimates in store / case
credits
• Refrigeration Zones
• Room air models
• Compressor coefficients are
different from AHRI
• Offset defrost schedules
Refrigeration Front End
Spreadsheet
• Refrigeration System Energy
120
R404A Low-Temp Condensing Temperature to
Outdoor Dry-Bulb Temperature (°F)
Model
100
• Refrigerant Property Tables
• Compressor Curves
• TMY3 Weather Data
• Condensing Methods
• Air cooled
• Water cooled
• Evaporative
Temperature (°F)
80
60
40
20
Condensing Temperature (°F)
0
Vapor Temperature (°F)
Outdoor Wet-Bulb Temperature (°F)
-20
-10
0
10
20
30
40
50
60
70
Outdoor Dry-Bulb Temperature (°F)
80
90
100 110
Tools Available Spreadsheets
DOE Commercial Buildings Resource Database
• Refrigeration Playbook: Heat Reclaim:
http://www.nrel.gov/docs/fy15osti/63786.pdf
• Space Heating Reclaim Module:
https://buildingdata.energy.gov/cbrd/download/1690
• Outdoor Air Preheat Reclaim Module:
https://buildingdata.energy.gov/cbrd/download/1687
• Space Heating / Cooling Module:
https://buildingdata.energy.gov/cbrd/download/1689
• Refrigeration System Front-End Spreadsheet:
https://buildingdata.energy.gov/cbrd/download/1748
• Domestic Hot Water – Hot Water Recovery Calculator:
https://buildingdata.energy.gov/cbrd/download/1685
Conclusions
• Why Use/Model Heat Reclaim?
• Common Heat Reclaim
Methods
•
•
•
•
Domestic Hot Water
Mixed Air Heating
OA Preheat
Heat Pumps
• Calculation Methods
• Tools Available
• EnergyPlus
• Spreadsheets
Resources
1. ASHRAE Handbook – Fundamentals. Atlanta, GA: ASHRAE, 2013; pp. 30.30.
2. “1991-2005 Update: Typical Meteorological Year 3.” National Solar Radiation Data Base, 2015.
http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/
3. “ANSI/AHRI Standard 1200 (I-P)-2013: Performance Rating of Commercial Refrigerated Display Merchandisers and
Storage Cabinets.” Air-Conditioning, Heating, & Refrigeration Institute, 2013. http://www.ahrinet.org/
4. “ANSI/AHRI Standard 540-2004 Standard for Performance Rating of Positive Displacement Refrigerant Compressors and
Compressor Units.” Air-Conditioning, Heating, & Refrigeration Institute, 2004. http://www.ahrinet.org/.
5. 2013 Nonresidential Compliance Manual, California Energy Commission, 10.5.5, June 2014.
6. 2012 Washington State Energy Code, Commercial Provisions, C403.2.6.3, July 2013.
7. “EnergyPlus Engineering Reference.” (2013). The Board of Trustees of the University of Illinois and the Regents of the
University of California through the Ernest Orlando Lawrence Berkeley National Laboratory.
8. “EnergyPlus Input Output Reference.” The Board of Trustees of the University of Illinois and the Regents of the University
of California through the Ernest Orlando Lawrence Berkeley National Laboratory, 2013.
9. Energy Conservation Program: Energy Conservation Standards for Walk-in Coolers and Freezers. 10 CFR Part 431. Office
of Energy Efficiency and Renewable Energy, Department of Energy (2010): RIN 1904-AB86.
10. Energy Conservation Program: Test Procedure for Commercial Refrigeration Equipment; Final Rule. 10 CFR Parts 429 and
431. Office of Energy Efficiency and Renewable Energy, Department of Energy (April 21, 2014): RIN 1904-AC99.
Questions?
Tim Johnson
TimJ@ctagroup.com