1. Technology for a better society 1

2. Technology for a better society 2
SINTEF - A contract research organization based in
Trondheim, Oslo, Bergen, Stavanger and Tromsø
• SINTEF is one of the largest independent research organisations in Europe.
Social perspective
SINTEF wishes to contribute to the creation of value
and to a society in healthy sustainable
development.
Business concept
SINTEF sell research-based knowledge and related
services to Norwegian and international clients.
Fundamental values
Honesty, Generosity, Courage and Unity
SINTEF has 2145 employees,
1600 situated in Trondheim and 430 in
Oslo.
SINTEF receives only 3% basic grants
Norway

3. Technology for a better society
CO2 applications, status transcritical
• Already developed and
commercialised
– Heat pump water heaters –
domestic, commercial and
industrial sized
– Commercial refrigeration
systems, supermarkets
– Beverage coolers
– Ice cream chest freezers
– Water chillers for moderate
climates, air conditioning and
industrial
– Transport refrigeration (bus, train)
• Already developed – not yet
commercialised
– Mobile air conditioning systems
• Under development
– Mobile heat pumps
– Transport refrigeration systems
(containers, truck, marine)
• Under development, contd
– Residential heat pumps (space heating
and reversible)
– Vending machines for combined hot
and cold beverages
– Combined heating and cooling of non-
residential and residential buildings
– Heat pumps for space heating and
combined space and water heating
– Heat pump dryers of residential and
commercial size, e.g. laundry
applications
– Rankine power cycles for utilisation of
low temperature surplus heat
• Early development
– Residential air-conditioning systems
– Water chillers for hot climates, air
conditioning and industrial
– Industrial refrigeration and heat pumps

4. Technology for a better society
Commercial refrigeration
Largest refrigerant GHG emissions of the refrigeration sector, more than 40% of the CO2-eq emissions
• General scepticism to
CO2
– pressure
– efficiency
• However
– Reduced pumping
power LT
– Retrofit R22
• Rolfsmann 1995?
High pressure
compressorCondenser
Intermediate
pressure
vessel
Low pressure
compressor
NH evaporator
CO condenser
CO liquid
separator
Brine cooler.
3
2
2
CO AS SECONDARY REFRIGERANT2
Condenser
NH compressor
CO compressor
Brine cooler.
3
2
Evaporators
Low pressure
reciever
Cascade
cooler
CO IN LOW TEMPERATURE CASCADE STAGE2
High pressure
compressorGas
Intermediate
pressure
vessel
Low pressure
compressor
Brine cooler.
reciever
Low pressure
Evaporators
cooler
TWO STAGE CO SYSTEM.2
CO2 as heat transfer fluid CO2 transcritical /(subcritical)CO2 in low temp cascade stage
• Good arguments for
CO2 LT stage
– No pump
– Reduced swept vol
– Standard pressure
level
• And
– Very efficient
compression
• Norild 1993
• Why not all-CO2?
• Benefits
– One refrigerant
– Small dimensions
– Less costly?
• Status
– Several supermarket
chains and
manufacturers has
decided for CO2

5. Technology for a better society
CO2 is ideally for heat recovery concepts in
moderate and colder climates (Kroppanmarka)
Energy Well
Accumulation
Tanks Floor Heating
DCV
II
DCV I
ECV
LT
Evaporator
Heat pump mode
Gascooler/condenser II
Gascooler/
Condenser I
MT
Normal Cooling
Freezing
HP-Compressors
LP-Com-
pressors
EV
Gaskjøler FH
DCV III
HPV
T LT
T MT
P M
P H
P M
P L
T EV
T GCI
T GCII
T GCIII
E HPC
E LPC
E Pump
E Fans
MP
V
LPV
CO2 refrigeration system superior to HFC systems in moderate and cold climates

6. Technology for a better society
Status CO2 commercial,
centralised system
Field test system in Belluno, Italy 1999
Centralised system
Nominal cooling capacity 11 kW
Medium temperature (-10oC)
Heat rejected to liquid loop
Dry cooler on the roof
Preliminary COP 2.4 at 30oC amb
• More than 1500
supermarkets in Europe
with transcritical CO2
• 10 kW to 1 MW
• Systems have been
installed also outside
Europe
• What about hot climates?
– Too low efficiency with CO2
or ….?

7. Technology for a better society 7
Typical efficiency at varying condenser/gas cooler
air inlet temperature
More than 90% of operation
COP is important
Less than 10% of operation
Capacity is important
Condenser/gas cooler air inlet temperature
COP
R-744
R-404A

8. Technology for a better society
One possible way:
Transcritical R744 refrigeration cycle
Using a two-phase ejector for expansion work recovery and the
corresponding pressure-specific enthalpy diagram

9. Technology for a better society
Proposal for next generation of
R744 commercial refrigeration system
Advantages
- pressure drop in the evaporator, simple valves
- good refrigerant distribution and slightly overfed evaporator
- robust and reliable arrangement
- lubricant management in separator © SINTEF 2012

10. Technology for a better society
More efficient components, a key for improved efficiency
Joint development project between SINTEF and OE
18-90m3/h R744 compressor [2012]
technische Daten
Höhe x Breite x Länge [mm] 500 x 440 x 830
Gewicht [kg] 286
Volumenstrom [m³/h] 18 - 90
Hubraum [cm³] 380
Max. el. Leistungsaufnahme [kW] 100
Drehzahl [min
-1
] 800 – 4 000
Frequenzbereich [Hz] 53 - 267

11. Technology for a better society
1500 rpm
discharge pressure: 80 bar
superheat at the compressor inlet: 10 K
18-90m3/h R744 compressor [2012]
[%]

12. Technology for a better society 12
55
60
65
70
75
80
85
500 1000 1500 2000 2500 3000 3500
OverallEfficiency[%]
Revolution [rpm]
75bar
90bar
100bar
18-90m3/h R744 compressor [2013]
Overall efficiency at varying speed, p0=35 bara

13. Technology for a better society
R744 Compressor and Component
Test Facility @ SINTEF

14. Technology for a better society
Conclusions
14
We need to reduce
and GHG
emissions
• CO2 systems has been
developed and
commercialised for a lot of
applications
• Development of more
efficient components and
work recovery concepts will
enable competitive
performance also at hot
ambient conditions
• CO2 will together with the
other natural refrigerants
give a long term solution to
the refrigerant transition

15. Technology for a better society 15
Thank you for your attention &
Questions are welcome!
Petter.Neksa@sintef.no
This publication forms a part of the SINTEF – NTNU CREATIV
project, performed under the strategic Norwegian
research program RENERGI (195182/S60). The CREATIV is
financially supported by the Research Council of Norway
and several industry partners