Flash steam geothermal l t power plants
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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
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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
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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)
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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
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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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Thank You!VISIT GEOELEC.EU
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