Optimized geothermal Optimized geothermal binary power cycles - - PowerPoint PPT Presentation

EN ENhanced hanced G Geothermal eothermal I Innovative nnovative N Network for etwork for E Europe ( urope (ENGINE ENGINE) )

Optimized geothermal Optimized geothermal binary power cycles binary power cycles

Kontoleontos E., Mendrinos D., Karytsas C. Kontoleontos E., Mendrinos D., Karytsas C.

Centre for Renewable Energy Sources

19th km Marathonos ave., 19009 Pikermi Attikis, Greece

LOW LOW-

• BIN project

BIN project

• ORC power plant

ORC power plant for for 65 65-

• 90

90° °C C geothermal water geothermal water

• ORC heat & power

ORC heat & power cogeneration plant cogeneration plant for for 120 120-

• 150

150° °C C geo geo-

• water

water and and 60/80 60/80° °C C district heating district heating Industrial partner: TURBODEN Industrial partner: TURBODEN Supported by DG-TREN (FP6)

Isobutane (R600a) and R134a Isobutane (R600a) and R134a as working fluids as working fluids

• widely used with excellent results in the heat

widely used with excellent results in the heat pumps and cooling/refrigeration industry pumps and cooling/refrigeration industry

• available in the market

available in the market

• The necessary parts for a Rankine cycle machine

The necessary parts for a Rankine cycle machine are available in the market are available in the market

• CARRIER, lately developed low cost 200 kWe

CARRIER, lately developed low cost 200 kWe ORC units using R134a. Two units commenced ORC units using R134a. Two units commenced

• peration in August
• peration in August-
• December 2006

December 2006 in “Chena”, in “Chena”, Alaska, USA, utilizing 74°C water Alaska, USA, utilizing 74°C water

Shell & tubes condenser Shell & tubes condenser

( )

• i
• i

i

• h

kL r r A h A A U 1 2 / ln 1 1 + + = π

Overall heat transfer: Overall heat transfer:

( )

( )

25 . 3

725 . ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ − − =

w g f f fg v

• T

T d k gh h µ ρ ρ ρ

Laminar condensation Laminar condensation

• n tubes surface:
• n tubes surface:

µ ρ ⋅ ⋅ = = = D u Nu D Nuk hi Re Pr Re 023 .

4 . 8 .

Turbulent flow in tubes: Turbulent flow in tubes:

Plate H.E. as evaporator Plate H.E. as evaporator

g sp tp l sp total

U U U U

/ /

1 1 1 1 + + =

gw g sp g sp gw tp tp gw l sp l sp

h ktit x h U h ktit x h U h ktit x h U 1 1 1 , 1 1 1 , 1 1 1

/ / / /

+ ∆ + = + ∆ + = + ∆ + =

35 . 12 . 4124 . 2

65 Re ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = β

cr P fg l e l tp

p p L h D k C h

L k Nu h St Nu c St c L u

g l sp f f

⋅ = ⋅ ⋅ = ⋅ = − = ⋅ ⋅ =

, / 3 2 2 .

Pr Re Pr 1 2 Re 1050 Re 074 . Re µ ρ

One side: Geothermal water One side: Geothermal water Second side: working fluid Second side: working fluid Liquid Liquid ⇒ ⇒ Two Phase Two Phase ⇒ ⇒ Vapor Vapor

__________________________________________________________________

Evaporation heat transfer Evaporation heat transfer Single phase heat transfer Single phase heat transfer

Rankine cycle Rankine cycle optimisation

• ptimisation

Objectives: Objectives:

• Maximize

Maximize overall net conversion efficiency conversion efficiency of the plant

• Minimize

Minimize the cost cost of the plant → Minimize both Heat Exchangers surface → Minimize both Heat Exchangers surface

( ) ( )

wf pump wf heatexch pump turbine cycle

m h h N m h h Q N W ⋅ − − ⋅ − = − =

2 3 5 4

η

using the EASY software code (Evolutionary Algorithm System) by National Technical University of Athens, ref. http://velos0.ltt.mech.ntua.gr/EASY

Variables: Variables: P P2

2, m

, mgr

gr, m

, mwf

wf,

, ∆Τ ∆ΤΗ

Η,

, ∆Τ ∆ΤC

C

Constraints: Constraints: Net Power Output 200 kW 200 kWe

e±

±5kW 5kWe

e

ORC machine for 65 ORC machine for 65° °C: R134a C: R134a

8.4 8.6 8.8 9 9.2 9.4 9.6 9.8 10 0.066 0.067 0.068 0.069 0.07 0.071 0.072 0.073 0.074 exchangers' surface binary plant's overall efficiency

• ptim

al solutions - R134a

ORC machine for 65 ORC machine for 65° °C: R600a C: R600a

10 11 12 13 14 15 16 0.06 0.062 0.064 0.066 0.068 0.07 0.072 exchangers' surface binary plant's overall efficiency

• ptim

al solutions - isobutan

ORC machine for 65 ORC machine for 65° °C: C: R134a vs Isobutane R134a vs Isobutane

8 10 12 14 16 18 0.06 0.062 0.064 0.066 0.068 0.07 0.072 0.074 exchangers' surface binary plant's overall efficiency Com parison R134a - isobutan isobutan R134a

ORC machine for 65 ORC machine for 65° °C: C: R134a vs Isobutane R134a vs Isobutane

Variable Variable Isobutane Isobutane R134a R134a P P2

2 (bar)

(bar) 6.19 6.19 11.99 11.99 m mgeothermal water

geothermal water (kg/sec)

(kg/sec) 4 46 6 51.2 51.2 m mworking

working fluid fluid (kg/sec)

(kg/sec) 10.2 10.2 17.5 17.5 ∆Τ ∆ΤH

H (

(° °C) C) 2 21.8 1.8 18.6 18.6 ∆Τ ∆ΤC

C (

(° °C) C) 7.5 7.5 7.5 7.5 pump power pump power ( ( kW kW) ) 3 3. .9 9 13.4 13.4 cooling cooling water flow water flow (kg/sec) (kg/sec) 119 119 116 116 surface of the condenser (m surface of the condenser (m2

2)

) 7.0 7.0 5.5 5.5 surface of the heat exchanger (m surface of the heat exchanger (m2

2)

) 5.7 5.7 4.0 4.0 total H.E. surface (m total H.E. surface (m2

2)

) 12.7 12.7 9.5 9.5 net conversion efficiency net conversion efficiency 7.04 7.04 7.16 7.16

ORC heat & power cogeneration ORC heat & power cogeneration source: 120 source: 120° °C, cooling: 60/80 C, cooling: 60/80° °C C

15 20 25 30 35 40 0.048 0.05 0.052 0.054 0.056 0.058 0.06 0.062 exchangers' surface binary plant's overall efficiency

• ptim

al solutions - R134a

R134a ORC plants R134a ORC plants

5 10 15 20 25 30 35 40 45 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08 0.085 surface of the exchangers

• verall efficiency of the binary

plant R134a - tem perature threshold at 65,100,120 65 100 120

Cogeneration 120°C-60/80°C Low temperature 65°C Standard 100°C

R134a ORC plants R134a ORC plants

Variable Heat & power cogeneration 120οC Power generation 65oC Standard binary power plant, 100οC P2 (bar) 34.99 11.99 15.52 mgeothermal (kg/sec) 52 51.2 45 mR134a (kg/sec) 35 17.5 17.8 ∆ΤH (°C) 26 18.6 20.0 ∆ΤC (°C) 20 7.5 7.5 Cooling Temp (°C) 60 10 10 Condensing Temp (°C) 80 30 27 R134a pump power (kW) 58 13.4 18.5 cooling water flow (kg/sec) 66 116 110 Condenser surface (m²) 22.0 5.5 4.6 Surface of the PHE (m²) 2.0 4.0 5.4 Total H.E. surface (m²) 24.0 9.5 10 Net conversion efficiency 5.93 7.16 7.7 Net electrical Power (kW) 207 202 204