Transcritical CO2 SystemsA Case Study into the latest evolution

John Austin-DaviesSamuele da Ros

Who is Epta?

Transcritical – WHY?

• It is a true solution – no additional cooling required– “Pumped CO2” requires an additional circuit to cool

the CO2, using what refrigerant?– “Cascade CO2” requires an additional circuit to cool

the CO2, using what refrigerant?• Additional circuit can be

– HFC (we want to eliminate)– HC (good refrigerant but limitations)– Ammonia (good refrigerant in limited application)

• Lowest cost when industrialised

• 1999 – First complete natural refrigerant solution … Iceland Harlesden

• 2002 – First Supermarket CO2 transcritical system … Coop Lestans Italy

• Installations in Italy, Sweden, Denmark, Norway Switzerland, Luxemburg, UK, Germany …

Our Knowledge

• 2006 – First CO2 transcritcal in UK … Tesco Swansea (inc design, build, install, maintenance)

Our Knowledge

Energy ModellingSINGLE STAGE

CHILLED FOOD SYSTEM

INTERNAL COMPOUND TWO-STAGE

FROZEN-FOOD SYSTEM

MT COP

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

jan

feb

mar ap

rm

ay jun jul

aug

sep

oct

nov

dec

CO

P

0.02.04.06.08.010.012.014.016.018.020.0

ambi

ent t

empe

ratu

re [°

C]

MT COP R404A

MT COPCO2

ambient temp

Lt COP

0.0

0.5

1.0

1.5

2.0

2.5

jan

feb

mar ap

rm

ay jun jul

aug

sep oct

nov

dec

CO

P0.02.04.06.08.010.012.014.016.018.020.0

ambi

ente

tem

pera

ture

[°C

]

LT COP R404A

LT COP CO2

ambient

£ € COST € £

0

20

40

60

80

100

R404A R744

Commercial

MaterialSpecification

Benchmark

• CO2 systems have smaller compressors and pipework• Pressures are higher, and specification has be

appropriate• Components are purchased in low volumes and without

the commercial benefits of competitive negotiation

Practical requirements for a Supermarket Transcritical CO2 System

• Systems conform to Pressure Equipment Directivethrough use of specifically designed components

• Understanding of Power Off situations, will pressure relief valve settings be experienced?

• High quality required over the whole design, component, manufacture, installation and commissioning project

• Supply chain support for manufacture, installation, maintenance

• Training of ALL PERSONNEL involved• Clear Labelling on site

• Objectives– Prove to a customer “new to CO2” that this is

a practical and reliable concept– Provide a single pack to meet this market

sector needs with MT & LT load– Prove benefits of improved control of

transcritical / sub-critical change-over– Reduce liquid pipe pressures– Prove benefit of variable speed drive– Prove benefit of wet-cooled gas-cooler

Aldi Sud Jüchen – July 2006

ALDI Jüchen – July 2006

Epta Display cabinetsWurm controls

Dorin compressorsIntegrated installation

Aldi Sud Jüchen – Principle of System

Aldi Sud Jüchen – Detail of System

Modeled efficiency of Aldi Sud Jüchen

• COP CO2 in winter conditions (Tamb: 6-13°C)

– MT : from 6.2 to 4 (R404A 4)– LT : from 1.9 to 2.5 (R404A 1.9)

• There is room for further improvements of the controlling parameters

Aldi Sud JüchenPerformances update: March 2007

Aldi Sud Jüchen – July 2006

The Customer has ordered new systems … now in build!

Transcritical CO2 SystemsA Case Study into the latest evolution

Grazie … Thank-You … Danke … Merci … Diolch yn Fawr