design of geothermal power plants holistic approach...

ENGINE Final Conference

Vilnius, Lithuania

12-15 February 2008

Stephanie Frick, Ali Saadat, Stefan Kranz GeoForschungsZentrum Potsdam

DESIGN OF GEOTHERMAL POWER PLANTS

holistic approach considering auxiliary power

ENGINE Final Conference, 12-15 February 2008

� Power plants serve for net power production

� Net power = gross power - auxiliary power

� Auxiliary power

Introduction

conversion cycle

1


source: http://www.erdwaerme-kraft.de/ source: http://www.refplus.com/



� Auxiliary power

Introduction

conversion cycle

cooling cycle

1




� Auxiliary power

Introduction

conversion cycle

cooling cycle

thermal water cycle

1




� Auxiliary power

� For geothermal power plants, a maximum net power

output can‘t be reached by maximising the gross power

� Geothermal power plant design needs a holistic approach

Introduction

conversion cycle

cooling cycle

thermal water cycle

1


Overview

� Methodical approach to power plant design

� Gross power characteristics

� Auxiliary power characteristics

� Practical approach to power plant design

� Conclusions & Outlook

2


Methodical approach

� site-specific reservoir characteristics and ambient

conditions(→ boundary conditions)

PI = II = 30 m3/(h MPa)

TTW = 150 °C ρTW = 1,147 kg/m3

cp = 3,5 kJ/(kg K) depth = 4.500 m

Ta = 20 °Cφa = 65 %

3


Methodical approach

� site-specific reservoir

characteristics and ambient

conditions (→ boundary conditions)

� plant-specific parameters (→ component quality)

∆T = 5 K∆p = 0,1 bar

∆T = 5 K∆p = 0,1 bar

ηi = 0,75ηm = 0,95

η = 0,8

Isobutane

η = 0,6

∆T, ∆p, η, …

3





� plant-specific parameters

(→ component quality)

� design parameters:

condensation temp. TKond

injection temperature TTW,in

thermal water mass flow mTW

Methodical approach

TKond

TTW,inmTW

.

3





� plant-specific parameters

(→ component quality)

� design parameters:

condensation temp. TKond

injection temperature TTW,in

thermal water mass flow mTW

Methodical approach

TKond

TTW,inmTW

.

3

What influence have the

design parameters on

power plant performance?


Methodical approach

TKond

TTW,inmTW

3

Exemplary power plant in the North German Basin:

TTW = 150 °C

PI = 30 m3/(h MPa)

...

other parameters see slide 13


Gross power characteristics

4

0

1000

2000

3000

4000

20 40 60 80 100

thermal water mass flow in kg/s

gro

ss p

ow

er

in k

W...

T_cond=30 °C : T_TWin=60°C


Plant-specific parameters, reservoir and ambient conditions = const. (see slide 13)


Gross power characteristics

gross power = ƒ (Tcond, TTW,in) • mTW

.

0

1000

2000

3000

4000

20 40 60 80 100


gro

ss p

ow

er

in k

W...



400

500

600

700

800

60 65 70 75 80

thermal water injection temperature in °C

T_cond=30 °C

T_cond=40 °C

thermal water mass flow 20 kg/s


4


Auxiliary power characteristics

Conversion cycle


0

100

200

300

400

20 40 60 80 100




po

we

r d

em

an

d c

on

ve

rsio

n c

ycle

in

kW.

..

5



Conversion cycle

Power demand conversion cycle = ƒ (Tcond, TTW,in) • mTW

.

0

100

200

300

400

20 40 60 80 100




po

we

r d

em

an

d c

on

ve

rsio

n c

ycle

in

kW.

..

20

40

60

80

60 65 70 75 80

thermal water injection temperature in °C

T_cond=30 °C

T_cond=40 °C



5



Cooling cycle (wet cooling tower)

0

400

800

1200

1600

20 40 60 80 100


po

we

r d

em

an

d w

et co

olin

g in

kW

...

T_cond=30°C : T_TWin=60°C


100

150

200

250

300


6



Cooling cycle (wet cooling tower)

Power demand cooling cycle = ƒ (Tcond) • TTW,in • mTW

.

0

400

800

1200

1600

20 40 60 80 100


po

we

r d

em

an

d w

et co

olin

g in

kW

...



0

50

100

150

200

250

300

30 35 40 45

condensation temperature in °C

T_TWin=60°C

T_TWin=70°C

T_TWin=80°C



6



Thermal water cycle

Power demand thermal water cycle = ƒ (mTW ).


7

0

1000

2000

3000

4000

20 40 60 80 100

themal water mass flow in kg/s

po

we

r d

em

an

d th

erm

al w

ate

r cycle

in

kW.

..


Practical approach

site-specific reservoir and ambient conditions

plant-specificparameters

designparameters

power plant

design

net power output

gross power output

8


Exemplary power plant design

TTW = 150 °C, PI = 30 m3/(h MPa), depthreservoir = 4,500 mreservoir conditions

1,8 MWgross power

maximum net power

(wet cooling)

30 °Ccondensation temp.

460 kWnet power

66 °Cth. water injection temp.

56 kg/sthermal water mass flow

maximum gross power

(wet cooling)

Plant-specific parameters, ambient conditions = const. (see slide 13) 9


plant-specifcparameters

designparameters

power plant

design

net power

outputmaximum

gross power




1,3 MW1,8 MWgross power

600 kW

33 °C

71 °C

41 kg/s

maximum net power

(wet cooling)

30 °Ccondensation temp.

460 kWnet power

66 °Cth. water injection temp.

56 kg/sthermal water mass flow

maximum gross power

(wet cooling)

Plant-specific parameters, ambient conditions = const. (see slide 13) 9


plant-specifcparameters

designparameters

power plant

design

maximumnet power

gross power

output


0

400

800

1200

1600

2000

0 200 400 600 800

net power in kW

gro

ss p

ow

er

in k

W…

.

Conclusions

► Choice of mTW, TTW,in and Tcond has a decisive impact

on power plant performance

► A maximum net power

output can‘t be reached by

maximising the gross power!

► Geothermal power plant

design needs a holisticapproach

maximum

gross power

maximum

net power

.

10


Outlook

� Successful geothermal project development needs a

detailed and site-specific analysis

� Further technical constraints need to be considered

� Possible combination with other energy carriers to hybrid-

plants (…please have a look at the poster “The combined use of geothermal

and biomass for power generation - drawbacks and opportunities –“)

11


turbine

feed pump

condensator

heat transfer

thermal water

waste heat

(Biogas CHP)

heat

recuperation

turbine

feed pump

condensatorheat transfer

thermal water

waste heat I (Biogas CHP)

heatrecuperation

waste heat II (Biogas CHP)

BMKW

ORC

Kalina I

Kalina II

A B A B C A B CAreference cases

0

200

400

600

800

1000

1200

1400

1600

1800

0

200

400

600

800

1000

1200

1400

1600

1800

Ele

ctr

ic p

ow

er

in k

W

The combined use of geothermal and biomass for power generation- drawbacks and opportunities -

Jan Wrobel a, Martin Kaltschmitt a,b

a Institute for Environmental Technology and EnergyEconomics, Hamburg University of Technology

b Institute for Energy and Environment

IUEIUEIUEIUEIUEIUEIUEIUE

ENGINE Final Conference poster session


Outlook

� Successful geothermal project development needs a

detailed and site-specific analysis

� Further technical constraints need to be considered

� Possible combination with other energy carriers to hybrid-

plants (…please have a look at the poster “The combined use of geothermal

and biomass for power generation - drawbacks and opportunities –“)

� Non-technical aspects can be further limiting factors

� Successful geothermal development needs integrating, holistic planning tools

11


Thank you very much for your attention!

Contact: Stephanie Frick

GeoForschungsZentrum Potsdam

Telegrafenberg

14473 Potsdam

e-mail: [email protected]

http://www.gfz-potsdam.de/pb52

12


Plant-specific parameters & site-specifc conditions

thermal water temperature 150°Creservoir depth 4,500 mthermal water heat capacity 3,5 kJ/(kg K)thermal water density 1,147 kg/m3

productivity-/injectivity index 30 m3/(h MPa)

ambient temperature 20°Crelative humidity 60%

reservoir and ambient conditions

down-hole pump efficiency 60%misc. parameter see [Legarth, 2005]

thermal water

cycle

wet cooling:water-sided pressure losses 1 barair-sided pressure losses 0,002 barcooling range 6Kapproach 3Kcooling tower constant 0,8cooling pump efficiency 80%fan efficiency 80%dry cooling: air-sided pressure losses 0,002 barfan efficiency 80%

cooling cycle

turbine isentropic efficiency 75%turbine mechanical efficiency 95%heat exchanger temp. gradients 5Kheat exchanger pressure losses 0,1 barworking fluid Isobutane

conversion cycle

plant-specific parameters

13


Exemplary run of power output against

thermal water injection temperature

50 60 70 80 90 100

thermal water injection temperature

conversion efficiency

transferred heat

power output

Power output = transferred heat x conversion efficiency

14



Cooling cycle (dry condensation)

0

400

800

1200

1600

20 40 60 80 100


po

we

r d

em

an

d d

ry c

oo

lin

g in

kW

... T_cond=30°C : T_TWin=60°C




0

50

100

150

200

250

300

30 35 40 45

condensation temperature in °C

T_TWin=60°C

T_TWin=70°C

T_TWin=80°C


air-sided pressure loss 0,002 bar;

fan efficiency 80 %

Plant-specific parameter, reservoir and ambient conditions = const. (see slide 13)

15

Power demand cooling cycle = ƒ (Tcond) • TTW,in • mTW

.




485 kW

1,1 MW

36 °C

73 °C

37 kg/s

maximum

net power

(dry cooling)

100 kW

1,8 MW

30 °C

66 °C

56 kg/s

maximum

gross power

(dry cooling)

600 kW

1,3 MW

33 °C

71 °C

41 kg/s

maximum

net power

(wet cooling)

460 kW

1,8 MW

30 °C

66 °C

56 kg/s

maximum

gross power

(wet cooling)

gross power

condensation temp.

net power

th. water injection temp.

thermal water mass flow

16

design of geothermal power plants holistic approach...

Documents