TRANSCRITICAL CO2 IN AUSTRALIAN SUPERMARKETS

Mike Baker

Baker Refrigeration

M. IE Aust, C P ENG, M. AIRAH

TRANSITION TO TRANSCRITICAL

• Drakes Angle Vale, SA

– First Generation

• Coles Coburg North, Vic

– Second Generation, Parallel

• AJ Baker & Sons

– 10 sites completed

TRANSCRITICAL BOOSTER SCHEMATIC

MT

LT

Ref Component1 Low stage (LT) comp2 High stage (MT) comp3 Oil Separator & oil return system4 Gas cooler5 High pressure regulating valve6 Liquid receiver7 Receiver pressure reg (flash gas) v/v8 Expansion device9 System evaporators

HIGH AMBIENT INSTALLATIONS

• Has been found problematical

• Mid 2010’s seen as a ground-breaking for Transcritical CO2:– COP21 & 2015 F-Gas Reg & 2016 Kigali Amend.

– ATMO 2016 Europe

– Site trials in GCOT reduction technologies to reduce energy consumption

– First Australian transcritical CO2 supermarket installations

HIGH AMBIENT INSTALLATIONS• AJ Baker Australian installations

x6

x2

x1

x1

HIGH AMBIENT INSTALLATIONS• AJ Baker Australian installations

Store Ref

LT / MT loads & Qty of compressors Location GCOT Control Method

A 26kW (3) /111kW (3) Northern Perth R134A DX PHE desuperheater

B 4kW (1) / 77kW (3) Western Melbourne R290/Chilled water PHE & adiabatic spray

C 19kW (2) / 77kW (3) Western Perth R134A DX PHE & adiabatic spray

D 29kW (3) / 118kW (4) Southern Perth R513A (XP10) DX PHE & adiabatic spray

E 29kW (3) / 121kW (4) Northern Perth R513A (XP10) DX PHE & adiabatic spray

F 4kW (1) / 81kW (3) Western Sydney R290/Chilled water PHE & adiabatic spray

G 4kW (1) / 81kW (3) Eastern Perth Evaporative cooling on gas cooler intake

H 4kW (1) / 79kW (3) Western Brisbane R134A DX PHE & adiabatic spray

I 20kW (3) /148kW (5) Southern Perth R513A (XP10) DX PHE & adiabatic spray

J 4kW (1) / 81kW (3) Western Melbourne Evaporative cooling on gas cooler intake** Parallel compression** 60bar liquid system

GAS COOLER OUTLET TEMPERATURE CONTROL

• Sites utilising PHE for high pressure desuperheating

• Secondary system of adiabatic water sprays

• Two sites trialling evaporative pre-cooler system on gas cooler inlet

GAS COOLER OUTLET TEMPERATURE CONTROL

• High Pressure Desuperheating

– Increases overall efficiency when Tamb>20°C

– Controls compressor discharge temp & pressure

– Trials in service with a number of refrigerant options and designsHFC, HFC replacement, HC ; DX / water

– A simple & effective solution in warm climates

GAS COOLER OUTLET TEMPERATURE CONTROL

• Adiabatic Sprays

– Effective for secondary GCOT control after desuperheater

– Can reduce GCOT by 3°C.

– Both proprietary and local manufactured units on trial.

– Water quality can be an issue, plus overspray

GAS COOLER OUTLET TEMPERATURE CONTROL

• Adiabatic Sprays

Spray initiation

GAS COOLER OUTLET TEMPERATURE CONTROL

• Evaporative Pre-cooling

– Results have shown can be used without high pressure desuperheating

– Water usage is minimal

– Ideal where water quality is poor (no direct water contact with gas cooler coil)

– Only suitable in low RH climates

OTHER ENERGY SAVING INITIATIVES

• Suction temperature optimisation

– Installing high performance display case evaporators

– Medium temp suction temperature floated up to -2.8°C.

– Coil diff temp reduced to 2K.

– Still achieving M1 (even M0) case conditions

OTHER ENERGY SAVING INITIATIVES

• Defrost on Demand

– Utilising the intelligent control system

– LT case defrost intervals of up to 14 days experienced.

– No degradation of product quality

– Case TEC reduced by 3%

OTHER ENERGY SAVING INITIATIVES• Defrost on Demand

FUTURE INITIATIVES

• Parallel Compression

– Uses additional MT comp for flash gas removal

• Complex

• Only works when flash gas is produced (in TC).

• MT comp discharge remains high

FUTURE INITIATIVES

• Ejectors

– Liquid

– Gas

• Complex

• Requires parallel compressor

• Only suitable when system running in transcritical mode

• Savings only seen when Tamb is high

• Oil return issues

• Not commercially available

FUTURE INITIATIVES

• Ejectors

FUTURE INITIATIVES

• FTE (Full Transcritical Efficiency)

- Uses liquid overfeed on MT cases to thenfeed LT cases

- Has the benefit of reducing liquid temp to MT cases, and then MT comp discharge T.

- LT cases also aided by cooler liquid temp

- Oil return is uninterrupted in entire circuit

- Works both in sub & trans critical states.

- Europe studies → 10% gain; Australia → 7%

F.T.E. / LOW PRESSURE TANKIT Patent Pending: IT 102016000049985AU Patent Issued: AU2016101310

CLO

SE

SH

F.T.E. / LOW PRESSURE TANKIT Patent Pending: IT 102016000049985AU Patent Issued: AU2016101310

FUTURE INITIATIVES• FTE (Full Transcritical Efficiency)

• 13 units in operation: ITA, GER & AUS

CONCLUSIONS

• TC CO2 is being designed to allow operation in high ambient climates

• The number of installations in Australia is growing

• No major penalty in system efficiency or complexity

• Simple plant designs making the technology to be understood by mechanics

• It should definitely be the system design of choice for supermarkets and other commercial installations.

Thank you