Flash steam geothermal l t power plants

Flash steam geothermall tpower plants

f dMain features and issues

Fabio Sabatelli

Enel Green Power Pisa Oct 9th 2013Enel Green Power Pisa, Oct. 9 , 2013

Presentation overviewPresentation overview

illi d d llh d i ll i• Drilling pad and wellhead installations• Gathering systemg y• Flash steam power plant• Main components• Main components• Mercury and Hydrogen Sulfide abatement• Operation and maintenance• Remote controlRemote control• Operation problems

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Power generation technologyPower generation technology

3

Geothermal generation in ItalyGeothermal generation in ItalyLarderello/Lago (250 km2) Larderello/Lago (250 km2) 

Since 1913 – superheated steam Installed capacity: 478 MW

Travale Radicondoli (30 km2)

Since 1913 – superheated steam Installed capacity: 478 MW

Travale Radicondoli (30 km2)Pisa FIRENZE

Travale‐Radicondoli (30 km2)  Since 1950 – saturated steam Installed capacity: 175 MW

Travale‐Radicondoli (30 km2)  Since 1950 – saturated steam Installed capacity: 175 MW

SienaPisa FIRENZE

Piancastagnaio/Bagnore(Mt Amiata – 50 km2)Piancastagnaio/Bagnore(Mt Amiata – 50 km2)

GrossetoROMA

VITERBO

(Mt. Amiata 50 km ) Since 1955 – water‐dominated Installed capacity: 69 MW

(Mt. Amiata 50 km ) Since 1955 – water‐dominated Installed capacity: 69 MW

ROMA

722 MW gross generating capacity

4

g g g p y

Drilling pad layoutDrilling pad layout

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Drilling pad featuresDrilling pad features

• Underground piping in well pad area (avoids interference with rig for well work‐over)g )

• Separator with dedicated line for well start‐up and initial dischargeand initial discharge

• Water pit• Water‐steam separation (at wellhead)

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Typical wellheadTypical wellhead

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Gathering system: layoutsGathering system: layouts

• Separation at wellhead– Separate steam andp

(saturated) water flows

• Separation at satellite stations• Separation at satellite stations– Two‐phase flow + separate flows

• Separation at the power plant– Two‐phase flowTwo phase flow

Source: DiPippo

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Two Phase flowTwo‐Phase flow

• Higher pressure drop• Flow regimeFlow regimeconsiderations(slug to be avoided)(slug to be avoided)

• Transient analysishard to implement

• Downhill strongly• Downhill stronglypreferred

Mandhane flow map

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Typical production curvesTypical production curves

40

50)

30

40

sure (b

ar)

Bagnore 22CP 1

20

head

 pres

10Wellh

00 100 200 300 400

Total flow rate (t/h)

10

Total flow rate (t/h)

Pipeline optimizationPipeline optimization

• CapEx increases with diameter (approx. linear) and thermal insulation thickness

• Thermal loss increases with external diameter and decreases with insulation thicknessand decreases with insulation thickness

• Pressure drop (power loss) decreases with diameter (5th power: Δp = 4fLρu2/d)

• Optimum at the lowest total lifecycle cost• Optimum at the lowest total lifecycle cost (strongly dependent on electricity FIT)

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Pipeline optimizationPipeline optimization

INT. RATE 10%TAXES 30%GENERATION 1 kWGEN. HRS. 8400 hr/yrENERGY VALUE 170 €/MWh

1,2

4

ENERGY VALUE 170 €/MWhACTUAL. 15 YRS. 7603 €/kW

100 t/h 27,78 kg/s18 bar2% NCG

0,8Cape

x (M

€)2

Total (M€)

2% NCG206,7 °C (saturated)

1 km length80 mm insulation

u hIN Q pOUT hOUT Tout Xout Win Wout ΔW LOSS CAPEX TOTALID

0,4300 500 700 900

ID (mm)

0300 500 700 900

ID (mm)

u hIN Q pOUT hOUT Tout Xout Win Wout ΔW LOSS CAPEX TOTAL(mm) (in) (m/s) (kJ/kg) (kW) (bar) (kJ/kg) (°C) (%) (kW) (kW) (kW) (M€) (M€) (M€)

300 12 49,2 2742,6 143 12,86 2737,5 192,5 100,00% 15598 14640 958 7,28 0,49 7,77350 14 35,3 2742,6 160 15,92 2736,9 200,7 99,87% 15598 15220 377 2,87 0,53 3,40450 18 20,9 2742,6 195 17,45 2735,6 205,2 99,67% 15598 15455 142 1,08 0,64 1,72600 24 11 5 2742 6 247 17 87 2733 7 206 3 99 54% 15598 15502 95 0 72 0 87 1 59

ID

600 24 11,5 2742,6 247 17,87 2733,7 206,3 99,54% 15598 15502 95 0,72 0,87 1,59800 32 6,4 2742,6 315 17,97 2731,3 206,6 99,40% 15598 15496 101 0,77 1,07 1,841000 40 4,1 2742,6 384 17,99 2728,8 206,7 99,26% 15598 15478 120 0,91 1,32 2,22

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Pipeline designPipeline design

• Loads/stresses– Weight (even steam pipes as if filled with water)g ( p p )– Internal pressureWind snow seismic– Wind, snow, seismic

– Dynamic loads (esp.h fl )two‐phase flow)

– Thermal expansion– Friction on supports

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Pipeline routePipeline route

• Safety• EnvironmentEnvironment• Land availability• Cost

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Gathering systemGathering system

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Typical gathering systemTypical gathering system

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Power generationPower generation

l h l• Flash steam cycle– Backpressure (single stage)– 1 to 3 flash stages (2 stages most common)– Rule of thumb for flash pressure optimizationp p– Lower pressure limit 1.2 to 2 bar

• Binary cycle• Binary cycle• Combinations thereof

– Flash + binary (bottoming cycle)– Backpressure turbine + binary

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Flash steam power plantFlash steam power plant

• By far the most common technology, developed in New Zealand in the 1950sp

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Single flash power plantSingle flash power plant

• Hot water from the reservoir flashes into the well, as a consequence of the pressure dropq p p

• Steam is fed to the turbine from a surface separatorseparator

• The power plant is quite similar to a dry‐steam facility

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Single flash power plantSingle flash power plant

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Single flash power plantSingle flash power plant

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Double flash power plantDouble flash power plant

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Flash optimizationFlash optimization

• Steam flow decreases with flash pressure• Power generation per unit mass flow of steamPower generation per unit mass flow of steam increases with flash pressure i f ifiMaximum of specific power output

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Flash optimizationFlash optimization

• Thermodynamic calculations• Rule of thumb (equal temperature split)Rule of thumb (equal temperature split)

– Tflash opt = (Tres – Tcond)/2 (single flash)T T (T T )/3– Tflash 1 opt = Tres – (Tres – Tcond)/3

– Tflash 2 opt = Tres – 2(Tres – Tcond)/3 (double flash)p

• Bottoming binary cycle using flashed water

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Flash optimizationFlash optimizationTres 245 °C NCG 0,10% hbrine 1061,6 kJ/kg Gbrine 682 t/h Hbrine 201,1 MWt

p 7,92 barTflash1 170 0 °C WATER NCG 0 00% pflash 7 92 bar hLsat 719 12 kJ/kgTflash1 170,0 C WATER NCG 0,00% pflash 7,92 bar hLsat 719,12 kJ/kgWturb 16708 kW hVsat 2767,1 kJ/kg

STEAM NCG 0,60% hV 2766,90 kJ/kg r 2047,94 kJ/kgTcond 41,5 °C NCG 0,0068 t/h Xflash 16,72%Tsplit(singleflash) 143,2 °C Gliq 568,0 t/h 113,5 MWtTsplit(doubleflash) 177,2 °C Gvap 114,0 t/h 87,7 MWt

682,0 t/h 201,1 MWtTflash2 170,0 °C WATER NCG 0,00% pflash 7,92 bar hL 719,11 kJ/kgWturb 0 kW hV 2767,1 kJ/kgTsplit(doubleflash) 109 3 °C STEAM NCG 0 00% hV 2767 06 kJ/kg r 2047 94 kJ/kgTsplit(doubleflash) 109,3 C STEAM NCG 0,00% hV 2767,06 kJ/kg r 2047,94 kJ/kg

Xflash 0,00%Gliq 567,9 t/h 113,4 MWtGvap 0,0 t/h 0,0 MWt

113,5 MWt18,0

18,4

19,0

17,2

17,6

Power (M

W)

13,0

15,0

17,0

wer (M

W)

CONDENSING

16,4

16,8

120 130 140 150 160 170T flash (°C)

7,0

9,0

11,0

120 130 140 150 160 170 180 190

Pow

BACKPRESSURE

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T flash ( C)T flash (°C)

Flash optimization constraintsFlash optimization constraints

h l l• Technical issues: minimum pressure, silica scaling (for high Tres)res

• CapEx issue (increase at lower pressures)

Source: DiPippo

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Resource utilization efficiencyResource utilization efficiency

cy*

fficien

ergy

ef

TR 230°C ƞT 0.75 TA 45°C

Exe

Flash stages* 2nd principle eff.

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Power plantsPower plants

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Power plant and gatheringPower plant and gathering

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Power plant featuresPower plant features

• Wet (saturated) steam at turbine inlet– Vane‐type demister to minimize erosion– Efficient water removal system in the turbine– Blade coating/protection (erosion)– Blade materials (corrosion)– Entrained water contains dissolves salts that may yprecipitate after isenthalpic expansion (first stage nozzles, HP shaft labyrinth seals)

– Double steam inlet (inlet valve testing)– Low p & T (no creep, low efficiency)

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Power plant features

NCG i

Power plant features

• NCG in steam– Condenser selection (direct‐contact or surface)G li ti i d– Gas cooling section in condenser

– NCG extraction system• Heat rejection• Heat rejection

– Wet cooling towers (steam condensate as make‐up water)• counter‐flow• counter‐flow• cross‐flow

– Hybrid cooling towers– Dry cooling towers– Air cooled condenser

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Power plant flexibilityPower plant flexibility

Inlet pressure adjustment with 1st stage (impulse) nozzle area and stage #g

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Simplified flow schemeSimplified flow scheme

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P&IDP&ID

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Turbine Condenser configurationTurbine‐Condenser configuration

Toshiba

Source: T

35

Power plant layoutPower plant layout

Travale 4 (40 MW)

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Travale 4 (40 MW)

Powerhouse viewPowerhouse view

Chiusdino 1 (20 MW)Chiusdino 1 (20 MW)

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Power plant 3DPower plant 3D

Bagnore 4

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Power plant layoutPower plant layout

Bagnore 4

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Power plant viewPower plant view

Bagnore 4

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Main machineryMain machinery

S bi• Steam turbine– Single flow/Double flow

• Generator• Condenser

– Direct‐contact/Surface

• Hotwell pump• NCG extraction system

– Ejectors/LRVP/Compressor

• Cooling tower– Wet/Hybrid/Dry

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Single and double flow turbinesSingle and double flow turbines

Source: Mitsubishi

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Double admission turbineDouble admission turbine

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Turbine (20 MW reaction)Turbine (20 MW, reaction)

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Turbine rotor (20 MW reaction)Turbine rotor (20 MW, reaction)

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Turbine (20 MW impulse)Turbine (20 MW, impulse)

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Turbine (20 MW impulse)Turbine (20 MW, impulse)

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Turbine (20 MW impulse)Turbine (20 MW, impulse)

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Turbine (60 MW impulse)Turbine (60 MW, impulse)

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Turbine rotor (60 MW impulse)Turbine rotor (60 MW, impulse)

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Turbine (40 MW reaction)Turbine (40 MW, reaction)

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Turbine (40 MW reaction)Turbine (40 MW, reaction)

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DC Condenser (40 MW)DC Condenser (40 MW)

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CondenserCondenser

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Hotwell pumpHotwell pump

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Cooling towersCooling towers

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NCG extraction from condenserNCG extraction from condenser• Steam ejectors (2 or 3 stages)j ( g )

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NCG extraction from condenserNCG extraction from condenser• (Steam ejector) + LRVP( j )

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NCG extraction from condenserNCG extraction from condenser• Centrifugal compressorg p

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NCG compressorNCG compressor

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NCG extraction from condenserNCG extraction from condenserSelection is based on:• NCG flow (steam flow * NCG content)• Condenser pressure• Availability of vendorsAvailability of vendors• Economic considerations

– Value of electricity/steam– Discount rate

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Abatement of H S and Hg (AMIS)Abatement of H2S and Hg (AMIS)AMIS process, developed by Enel, is suitable for:p , p y ,• Direct‐contact condensers (increased H2S partitioning in the NCG)partitioning in the NCG)

• NCG with low calorific value (over 95% w. CO2) th t t th l id tithat prevents thermal oxidation

• Unattended operation (sulfur sludge filtration, chemistry control)

• Small size units: low O&M requirements,Small size units: low O&M requirements, reliable operation

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AMIS simplified schemeAMIS simplified scheme

MX-1TC

C-1

R-1 TREATED NCGTO CT

TCMX-2

NCG FROM COMPRESSOR

C-2

R-2

P-1

K-1 M

K-2 M

O2CP-1

WATER FROM CT

WATER TO CT

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AMIS plantsAMIS plants

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Operation & MaintenanceOperation & Maintenance

l• Remote control center• Data supervision by O&M employees• Local inspection (visual control, daily maintenance))

• Interventions (alarms, shut‐downs)• Scheduled maintenance• Scheduled maintenance• Consumables & spare parts

i i i ( ll )• Reservoir monitoring (well measurements)• Work‐overs, drilling of make‐up wells

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O&M highlightsO&M highlights

• Availability is of paramount importance– O&M best practices (remote control & diagnostics)p ( g )– Scheduled maintenance optimizationSpare parts management (substitution & off line– Spare parts management (substitution & off‐line repair)

• Efficiency– Power plants has to adapt to reservoir changesp p g– Machinery repair & improvement (workshops)

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Remote controlRemote control

• Operation data available on‐line (Internet)– General overview– Synoptic schemesMeasurements– Measurements

• Physical (p, T, flows, …)M h i l ( ib i )• Mechanical (vibrations)

• Electrical

– Alarms

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Remote control OverviewRemote control ‐ Overview

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Remote control SchemesRemote control ‐ Schemes

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Remote control SchemesRemote control ‐ Schemes

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Remote control SchemesRemote control ‐ Schemes

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Remote control SchemesRemote control ‐ Schemes

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Remote control SchemesRemote control ‐ Schemes

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Remote control MeasuresRemote control ‐Measures

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Remote control MeasuresRemote control ‐Measures

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Remote controlRemote controlDiagnost

• Targets:– Quick alert

gics

Q– Summarized info

Plant “signature”

Statistical variations

Video pages

SignalsSignals

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Remote controlRemote control

• Diagnostics alarms:– Statistical trend analysis of data w/o seasonal y /variation (e.g. vibrations, frozen measures, etc.)

i i f i l b h i (“ l i ”)– Deviation from typical behavior (“plant signature”) in the relationship between parameters featuring 

l i i i lseasonal variations, in plant start‐up, etc.– “Rules” defined by operational experience

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“Plant signature”Plant signature

f• Performance control:– CWT vs. WBT– Inlet pressure vs. pinlet flow rate

– kg/kWh vs. condenser vacuum

– NCG suction temperature vs. condenser vacuum

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“Plant signature”Plant signature

• Start‐up: vibrations

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Remote controlRemote control

Summarized info (color coding) for quick alert

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Results (unavailability)Results (unavailability)

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Operation problems: erosionOperation problems: erosion

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Operation problems: cloggingOperation problems: clogging

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Operation problems: washingOperation problems: washing

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Operation problems: corrosionOperation problems: corrosion

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Operation problems: pittingOperation problems: pitting

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Operation problems: creviceOperation problems: crevice

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Operation problems: SCCOperation problems: SCC

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Operation problems: SCCOperation problems: SCC

• 60 MW turbine

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Operation problems: fatigueOperation problems: fatigue

• Turbine shaft failure

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Operation problems: mechanical failureOperation problems: mechanical failure

• Compressor impeller failure

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Operation problems: depositsOperation problems: deposits

• Turbine labyrinth seal area

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Operation problems: depositsOperation problems: deposits

• Turbine labyrinth seal area

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ReferencesReferences• DiPi R Geothermal Energ as a So rce of Electricit• DiPippo, R. Geothermal Energy as a Source of ElectricityDOE/RA/28320‐1. Washington, D.C.: U.S. Dept. of Energy (1980)

• Kestin, J., DiPippo, R. and Khalifa, H.E. (eds.) Sourcebook on the P d ti f El t i it f G th l E DOE/RA/28320 2Production of Electricity from Geothermal Energy DOE/RA/28320‐2 Washington, D.C.: U.S. Dept. of Energy (1980)

• Armstead, H.C.H. Geothermal Energy London/New York: E.&F.N. S (2nd d 1983)Spon. (2nd edn., 1983)

• Palmerini, C.G. Geothermal Energy in “Renewable Energies: Sources for Fuels and Electricity”. T.B. Johansson, H. Kelly, A.K.N. Reddy, R.H. Willi ( d ) 549 591 W hi D C I l d P (1993)Williams (eds.), pp. 549‐591. Washington, D.C.: Island Press (1993)

• Dickson, M.H. e Fanelli, M. (eds.) Geothermal Energy Chichester, J. Wiley & Sons (1995)

• DiPippo, R. Geothermal Power Plants: Principles, Applications, Case Studies and Environmental Impact (3rd edn.) Oxford, Elsevier (2012)

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