Christian Heerup, Danish Technological Institute

1. Operation costs for heat recovery from
supermarkets to district heating grids
Christian Heerup, Danish Technological Institute

2. District heating supply and temperatures for a
supermarket building over a year.
2/16

3. LT
MT
M
M
M
M
M
HXR 3P
District Heating Supply
District Heating Return
Shop
A B C
A
Cooling only,
no heat recovery.
3/16
LT
MT
M
M
M
M
M
HXR 3P
District Heating Supply
District Heating Return
Shop
A B C
LT
MT
M
M
M
M
M
HXR 3P
District Heating Supply
District Heating Return
Shop
A B C
LT
MT
District Heating Supply
District Heating Return
Shop
M
M
M
M
M
HXR 3P
A B C
C
Heat recovery,
no load on outdoor
heat exchanger.
B
Heat recovery,
partial load on outdoor
heat exchanger.
D
Heat recovery,
auxiliary refrigeration
load.

4. Operating mode B. Floating or minimum head
pressure. In this case 50 bar (tsat = 15 °C)
4/16

5. Operating mode B. Increased head pressure 90 bar.
Water temperature 35/ 60 °C
5/16

6. Operating mode C. Increased head pressure, 97,3 bar.
Water temperature 35/ 70 °C.
6/16

7. Typical winter day, mean load 20.9 % swept volume, no HR
7/16

8. Heating load and HR profile for the day in 2018 with
the highest demand.
• Design capacity MT compressor 109 kW (including LT load)
• Engaged swept volume 25% (day) and 13% (night)
8/16

9. Winter worst case Supply - Return 85 °C - 45 °C
Unit Night Day Totals
Number of hours h 1.75 1.25 3.75 0.25 3.75 9.75 3.5 24
Cooling demand kW 25 25 25 25 49 49 49
Heating demand kW 28 37 56 111 37 56 111 (1417)
HR kW 28 37 45 45 37 56 111
Ptot kW 13.8 17.7 23 23 20.9 27.1 56.6
Pref kW 5.4 5.4 5.4 5.4 10.4 10.4 10.4
Pnet = Ptot-Pref kW 8.4 12.3 17.6 17.6 10.5 16.7 46.2
COPHR = HR/Pnet 3.3 3.0 2.6 2.6 3.5 3.4 2.4 (2.9)
Tax 0.15 DKK/kWh DKK/h 2.07 2.66 3.45 3.45 3.14 4.07 8.49
Power 0.63 DKK/kWh DKK/h 5.29 7.75 11.09 11.09 6.62 10.52 29.11
Total Cost DKK/h 7.36 10.40 14.54 14.54 9.75 14.59 37.60
Specific cost HR DKK/kWh 0.26 0.28 0.32 0.32 0.26 0.26 0.34
Energy Recovered kWh 49 46 169 11 139 546 389 1349
Cost DKK 12.88 13.01 54.52 3.63 36.56 142.21 131.59 394.40
DH cost 0.37 DKK/kWh DKK 18.13 17.11 62.58 4.17 51.34 202.02 143.75 499.09
Savings DKK 5,25 4,10 8,06 0,54 14,78 59,81 12,16 104.69
Cost:
DH 0.37 DKK/kWh (W)
DH 0.45 DKK/kWh (S)
HR 0.29 DKK/kWh
(80% 0.26 DKK/kWh)
Sale to DH:
0.25 DKK/kWh (W)
0.15 DKK/kWh (S)
9/16

10. 10/16
Prelim
inarydata!
Prelim
inarydata!

11. 11/16
LP Ejector cycle with
enhancements
•The basic ejector cycle utilizes the
expansion work
•The cycle compares to parallel compression
because both the flash and the gas from
evaporators is taken from a higher pressure.
•However, at low ambient temperatures there
is not enough expansion work available for
creating a lift high enough to circulate the
refrigerant through the evaporator
Low pressure lift ejector
systems are simple and has
higher efficiency as normal
trans critical systems
-10 °C
-3,4 °C
+34 °C
87,4 bar +87 °C
100 %100%
100%
50%
COP 2,01
50%

12. 12/16
-10 °C
-6 °C
+20,7 °C
60 bar +65 °C
100 %100%
29%
71%
COP 3,55
0%
LP Ejector cycle with
enhancements
•To make the system work in cold ambient a
check valve and a gas bypass valve is
added. This ensures that the system can
operate as a normal booster system in cold
ambient and as ejector system in warm
ambient
•Limitations are that the pressure lift of the
ejector is limited to 3-8 bar typically. Below
3 bar ejector operation does not look too
promising.
LP ejector systems has been
running in Advansor lab for the
past 6 months and is getting
closer to the market

13. SEPR MT only [-] Pay back [years]
Oslo 4,69/4,83 (3%) 8
Warsaw 4,17/4,35 (4%) 4,8
Strasbourg 3,93/4,12 (5%) 3,9
Lisbon 3,25/3,46 (7%) 2,2
Athens 2,93/3,14 (7%) 1,8
Pay back HP ejector system
SEPR MT only [-] Pay back [years]
Oslo 4,69/4,95 (5%) 20
Warsaw 4,17/4,36 (5%) 16
Strasbourg 3,93/4,31 (10%) 9
Lisbon 3,25/3,68 (13%) 5,2
Athens 2,93/3,36 (14%) 4,3
70 kW MT, -10 C evaporation, 2K gas cooler, no HR
SEPR MT only [-] Pay back [years]
Oslo 4,69/4,95 (5%) 7,1
Warsaw 4,17/4,36 (5%) 5,6
Strasbourg 3,93/4,31 (10%) 3,3
Lisbon 3,25/3,68 (13%) 1,8
Athens 2,93/3,36 (14%) 1,5
200 kW MT, -10 C evaporation, 2K gas cooler, no HR
Pay back LP ejector system
70 kW MT, -10 C evaporation, 2K gas cooler, no HR
SEPR MT only [-] Pay back [years]
Oslo 4,69/4,83 (3%) 5,6
Warsaw 4,17/4,35 (4%) 3,3
Strasbourg 3,93/4,12 (5%) 2,7
Lisbon 3,25/3,46 (7%) 1,5
Athens 2,93/3,14 (7%) 1,3
200 kW MT, -10 C evaporation, 2K gas cooler, no HR
13/16

14. Estimated savings over a year
• Total 50,000 DKK (summer 33,000, winter 17,000) substituted DH only.
• Sale of surplus HR? Current in conflict with Danish legislation.
• Increased revenue up to 20,000 DKK at lower supply temperatures,
• plus 10,000 DKK by lower power price (more wind and water).
• Pay back time 3 to 6 years on HR.
• Further savings if HR including auxiliary load replace oil/ gas boiler.
• Further savings with ejector operation
14/16

15. Challenges and further work
• Sizing of HR system (should be smaller than design refrigeration load).
• Reduce system dynamics both on refrigeration and heating systems.
• Improved controls and interconnectivity of systems.
• Dynamic optimization of set points is planed for a new project.
• Test required of HR with (cheap) auxiliary load to replace oil/ gas
boilers.
• LP Ejector Pack lab test at Danfoss Nordborg
• LP Ejector Pack Demonstration in COOP supermarket
15/16

16. Thank you for your attention! J
Questions?
16/16
Thanks to our Partners Super Supermarkets EcoPack Digital Twins
Budget mill € 0,6 0,3 2,5
Status Concluding Midterm Applied
EUDP the Danish Energy Agency Funding agent Funding agent Funding agent
DTI x Project Manager Project Manager
Advansor x
Clean Project Manager
Danfoss x x x
COOP x x Supporting
DFF, The Danish District Heating Association x
AK-Centralen x x
KTH, Royal Institute of Technology x
ILK, DFP, OK, GUES, Fyns Varme x
Super Køl x x
TLK-GmbH x
DTU MEK x
DTU Compute x
TU Braunschweig x
AffaldVarme Aarhus x
HOFOR Supporting