Outline

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!