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1
1. Introduction
2. Organic Rankine Cycle
3. Cascade design technique
4. Case study: geothermal power plant
5. Case study: cement plant
6. Conclusion
Introduction
Binary geothermal power plants Flue gases heat recovery systems
Exhaust gases
Waste heat
recoverysystem
2
▪ Enormous amount of available heat
▪ ORC: attractive system for heat → power
▪ Optimization for specific applications
SH
EV
EC
Turbine
Pump
Condenser
1
5
6
2
3
4
Basic
ORCHea
t ex
chan
ger
s
Heat source
Organic Rankine Cycle
3
Thermodynamic diagram
(temperature vs. entropy)Cycle architecture
T
s
1
2
3 4
5
6
▪ Vapor cycle
▪ Organic fluid
(R134a,
isobutane,…)
▪ 4 basic evolutions
▪ Numerous variations
and possibilities
Cascade design method
4
“Heatsep” method Shifting technique Heat cascade
Black box
TB1
TB2
Th,i
Tc,i
Heat
Exchanger
Network
T
H
1
3
+ ΔT / 2
2Ts,1
Ts,4
Ts,3
Ts,2 4
– ΔT / 2
Cascade design method
4
“Heatsep” method Shifting technique Heat cascade
Black box
TB1
TB2
Th,i
Tc,i
Heat
Exchanger
Network
T
H
Ts,1
Ts,4
Ts,3
Ts,2
...Excess
heat
Passed
down
ΔHnet,1
ΔHnet,2
ΔHnet,3
ΔHnet,n
...
Case study: geothermal power plant
5
▪ Low-T° reservoir: T° hot = 120°C
▪ Northern climate: T° cold = 5°C
▪ Working fluid: R1234ze(E)
T
s
Th,i
Th,o
Tc,o
Tc,i
2 3
5
6
1
7
10
13
8
9
12
11
4
ORC/DP
R1234ze(E)
T-s diagram of optimal results
Particle Swarm
Optimization
40% increase in power using
cascade method
Case study: geothermal power plant
6
T-s diagram of optimal results Optimal equipment architecture
TB2PP1
PP2
SH2
EV2
EC2
TB1
7
6
8
11
9
4 REC
CO
2
35
11' 1
1'
13
EC1EV1
10
SH1
Brine
out
Brine in Cold sourceT
s
Th,i
Th,o
Tc,o
Tc,i
2 3
5
6
1
7
10
13
8
9
12
11
4
ORC/DP
R1234ze(E)
Case study: cement plant
7
T-s diagram of optimal results
T
s
2 3
5
6
ORC/DP
Benzene
1
7
10
13
Th2,i
Th1,o , Th2,o
Tc,o
Tc,i
8
9
12
11
Th1,i
Waste heat: 2 gaseous sources
▪ T° hot #1 = 230°C
▪ T° hot #2 = 350°C
▪ T° cold = 40°C
▪ Working fluid: benzene
▪ Power: 3.3 MW
Complex system that self-
generates with cascade method
Case study: cement plant
8
Optimal equipment architecture 1
PP2
EV1bEC1b
EV1aEC1a
EC2 SH2EV2
TB1
Hot gas #2
TB2
Hot gas
#1
CO
REC
1'2 3
5
6 78
13
11 11'
9
10Cold source
Conclusion
9
▪ Tremendous potential in recovering waste heat
▪ Cascade method: first step towards an automated design method for power cycles
Leaves greater freedom in the optimization
Generates designs with considerable performance increase
Easily handles complex systems
▪ Next steps: other power cycles & economic considerations
Thank you! Vielen Dank!