This document discusses the energy benefits of integrating air conditioning, medium temperature, and low temperature refrigeration systems in supermarkets using water-cooled two-stage transcritical CO2 systems. Key points include: 1) Such systems can reduce energy consumption for refrigeration, AC, and heating by 45% on average in US supermarkets, representing a 29% reduction in total store energy use. 2) There would be a 67% reduction in total emissions and a 33.5% reduction in annual operating costs, saving around $80,000 per year for the average US supermarket. 3) Evaporative gas coolers allow subcritical CO2 operation in most climates worldwide and achieve high performance with

1. “Energy Benefits of Integrating
AC, MT and LT Refrigeration
in Supermarkets with Water Cooled
2 Stage Transcritical CO2 Systems”
Klaas Visser
Principal
KAV CONSULTING Pty. Ltd.
Dip.Mar.Eng. (NL)
Hon.M.IIR, F. Inst R, M.IIAR, M. ARA, M.KNVvK, Meurammon.
PO. Box 1146, KANGAROO FLAT, VIC, 3555 AUSTRALIA
Tel: +61 3 54 479 436 Email: kavconsult@bigpond.com

2. Slide 2 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Profile of an Average U.S. Supermarket’s
Direct Greenhouse Gas Emissions from Refrigerant
Leaks Compared to Indirect Electrical Emissions
U.S. Supermarket Store Size Average 46,000 ft2
Annual Electricity Consumption Intensity for U.S.
Supermarkets
Annual Electricity Consumed (Annual Consumption
Intensity x Store Size)
Electricity Use Emission Factor (U.S. Average)
Annual CO2 Emissions from Electricity Consumption
Typical Commercial Refrigerant Used
Global Warming Potential (AR4 standard) 3,921.6
Commercial Refrigeration Charge Size
Annual Commercial Refrigeration Leak Rate 25% per year
Annual Volume of Commercial Refrigerant Leaked
51 kWh/ft2
2,346,000 kWh/year
1.30 lbs of CO2 per kWh
3,049,800 lbs of CO2 per year
Annual CO2 eq of R404A Leaked
R404A
3,500 lbs
875 lbs per year
3,431,400 lbs CO2 eq per year

3. Slide 3 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
A few sacred cows are slaughtered based on personal experience
with CO2, NH3, R22 & R12 since 1959.
The benefits of evaporative CO2 Condensers are;
1. In Melbourne Supermarkets: 43 – 56% reduction in
specific electrical energy consumption if AC on CO2
parallel compression. 32 – 42% overall reduction.
2. In the average USA Supermarket the following benefits
per square foot of floor area are to be had;
a. 45% reduction in energy consumption for
Refrigeration, AC and Heating. This represents a 29%
reduction in the total store specific energy
consumption.
b. A 67% reduction in total emissions – 29% reduction
in indirect electrical emissions; 75% reduction in
direct gas heating emissions and 99.98% reduction in
direct R404A emissions.

4. Slide 4 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
c. 33.5% reduction in annual operating costs for energy and
refrigerant replacement amounting to US$1.94/square
foot/annum equalling to US$80,000 annually at 90%
realisation.
3. 100% Subcritical CO2 possible in Sydney, Melbourne, Adelaide,
Perth and Hobart; Brisbane 98%, Darwin 75%.
4. Evaporative Gas Coolers for Transcritical CO2 produce high COP
performance.
5. This makes CO2 the future ubiquitous refrigerant for all
standard refrigeration applications from -50 to +15°C from very
small to very large – if compressors become available.
6. Efficient CO2 refrigeration may be applied all over the world
when using CO2 evaporative condensers and gas coolers.
7. Gadgets like ejectors and expanders are completely obviated.

5. Slide 5 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Refrigeration Condensing Methods and
Advantages/Disadvantages in
Melbourne at 35°C Dry Bulb, 22°C Wet Bulb
Parameter Refrigerant Condensing Method
No. Description Air Cooling Cooling Towers
Evaporative
Condensers
1 Refrigeration Application
Commercial and
Small Scale AC
Large Scale AC & Low
ChargeIndustrial
Industrial
2
Coolant Temperature Worldwide
Maximum
Ambient Air Dry Bulb
Temperature
Temperature + 3 to
Ambient Air Wet Bulb
10K
Air Entry to Leaving
Water Approach
Ambient Air Wet Bulb
Temperature
3
CO2 Condensing Temperature/Gas
Cooler Exit in Melbourne Ambient
+35°CDB, + 22°C
+40-45°C +30-37°C +28-30°C
4 CO2 Critical Temperature,°C +31°C +31°C +31°C
5 CO2 Type of Operation Transcritical
Mostly Transcritical,
but Subcritical with a
Low Air WB Entry
Approach
Subcritical
All the Time
6 Advantages Low Costs
Moderate Energy
Consumption
Low Energy
Consumption
7 Disadvantages
High Energy
Consumption
Consumes Water and
Chemicals, Legionella
Consumes Water and
Chemicals, Legionella
8 Max 1% Design Wet Bulb in New Zealand + 20°C in Christchurch

6. Slide 6 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Performance of a Commercially Available
Transcritical CO2 Compressor
at 50HZ. 30 kW/27.2m3/h
RawCOP=Q÷BkW
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
16 18 20 22 24 26 28 30
Saturated Condensing Temp.,°C
+10°C SST, 5K SSH, 3K Liq. Subc. +5°C SST, 5K SSH, 3K Liq. Subc.
-5°C SST, 5K SSH, +5°C gc out -5°C SST, 5K SSH +10°C gc out
-5°C SST, 5K SSH, 5K Liq. Subc.
2
5
4
3

7. Slide 7 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
COP variation with gas cooler CO2 leaving temperature at
Transcritical CO2 Compressor: BOCK, 50 Hz MODEL: HGX
46/345-4SHCO2T; 30.2m3/h, 37 kW 75-100 bar discharge
pressure, +10°C SST, 5K SSH CO2 Compressor performance
for DX/LR direct CO2 for AC
Source – Bock VAP10 Software
7.52
7.12
6.7
6.23
5.69
5
2.73
6.23
5.91
5.57
5.21
4.8
4.34
3.71
5.32
5.05
4.77
4.47
4.15
3.8
3.38
COP @ 75 bar discharge pressure
COP @ 80 bar discharge pressure
COP @ 90 bar discharge pressure
COP @ 100 bar discharge pressure
8.4
7.94
7.45
6.91
6.27
5.3
2
3
4
5
6
7
8
9
5 10 15 20 25 30 35
Gas Cooler CO2 Exit Temperature, °C
Ambient Wet Bulb Temperature, °C
2 7 12 17 22 27 28 30
COP
Approx. 98% of world climates
Approx. 2% of world climates

8. Slide 8 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
COP variation with gas cooler CO2 leaving temperature
at Transcritical Compressor: BOCK, 50Hz
MODEL: HGX 46/345-4SHCO2T; 30.2m3/h, 37 kW
75-100 bar discharge pressure, +5°C SST, 5K SSH CO2
Compressor performance for chilled water AC & Retrofit.
3
3.5
4
4.5
5
5.5
6
6.5
7
5 10 15 20 25 30 35
Gas Cooler CO2 Exit Temperature, °C
2 7 12 17 22 27 28 30
Ambient Wet Bulb Temperature, °C
COP
Source – Bock VAP10 Software
COP @ 75 bar discharge pressure
COP @ 80 bar discharge pressure
COP @ 90 bar discharge pressure
COP @ 100 bar discharge pressure
6.66
6.31
5.92
5.5
5
4.24
6.05
5.73
5.39
5.02
4.6
4.04
5.11
4.85
4.58
4.28
3.96
3.58
4.43
4.21
3.98
3.73
3.47
3.18
Approx. 98% of world climates Approx. 2%
of world climates

9. Slide 9 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
The variation in COPs of R717, R22, R507A, R290
and R134a with Saturated Condensing
Temperature compared to subcritical CO2 from
16 to 30°C Saturated Condensing Temperature
Compressor Make & Model for R717, R22, R507A, R290 & R134a: Mycom 8 WB, 1,000 rpm
Saturated Suction Temp: -8°C, Suction Superheat: 5 K, Liquid Subcooling: 3 K
Compressor Make & Model for CO2: Bock HGX 46/345-4S CO2 T @ 50Hz
-5°C SST, 5K SSH, +5°C gc out
-5°C SST, 5K SSH +10°C gc out
-5°C SST, 5K SSH, 5K Liq. Subc.
2
3
4
5
6
7
8
16 18 20 22 24 26 28 30 32 34 36 38 40
Saturated Condensing Temp., °C
COP
R717 R22 R507AR290 R134a.
Source – Bock VAP10 Software

10. Slide 10 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Australian climate zones: % of a year
when subcritical CO2 can be
condensed
Geraldton
Alice Springs
Ballina
Kingaroy
90% of Australian Population

11. Slide 11 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Virtually all of Continental Europe
can enjoy subcritical CO2 condensing

12. Slide 12 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
USA climate zones: % of a year
when subcritical CO2 can be condensed

13. Slide 13 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Asian climate zones: % of a year
when subcritical CO2 can be condensed

14. Slide 14 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Latin American climate zones: %
of a year when subcritical CO2
can be condensed

15. Slide 15 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
Conclusions
• Evaporative Cooling units, either condensing subcritical CO2 or cooling
supercritical CO2, enable the efficient application of CO2 refrigeration
anywhere in the world.
• At 28°C ambient wet bulb temperature, 31°C supercritical CO2 exit
temperature is easily achieved.
• Ambient design wet bulb temperatures above 28°C are experienced in only
about 2% of the world.
• Suction heat exchangers are obviated in virtually all applications.
• Energy recovery by expanding the supercritical fluid no longer has any merit
with the high COPs resulting from evaporative condensers. At 31°C gas cooler
exit the 1st stage expansion takes place at virtually constant entropy. If excess
energy is not used during the compression phase like happens with air
cooled gas coolers, there is no need to try to recover any during the 1st
expansion stage.
• Suitable for conversion of existing HFC/CO2 cascade systems to highly
efficient two-stage sub- or trans-critical CO2 systems as the HFC phase-out
starts to bite.

16. Slide 16 Energy Benefits of Integrating AC, MT and LT Refrigeration in
Supermarkets with Water Cooled 2 Stage Transcritical CO2 Systems.
2nd Annual HVACR Energy Efficiency Seminar - Sydney, 5th April 2016
• Large scale application of CO2 to all refrigeration and air conditioning
awaits the availability of larger compressors.
• California has mandated that at least 25% of the heat from the
refrigeration systems in grocery stores be used for store heating under
Section 120.6(b)4 of California’s Title 24 Heat Recovery Requirements.
• Using evaporative condensers and gas coolers requires water
consumption. It is recommended that rain water collected from the roof
and car parks be stored and used as condenser cooling water when
required.
• The special designs required for multifunction CO2 systems result in higher
cost refrigeration systems compared to CO2/HFC cascade systems, but it is
expected that the simple payback period will not exceed 4-5 years.
• In summary, both business and the community benefit with reduced
energy costs and emissions respectively.
Conclusions