GEOELEC -Binary-Plant Pisa Bombarda

8/20/2019 GEOELEC -Binary-Plant Pisa Bombarda

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Binary geothermal power plants

Main features and issues

Paola Bombarda

Gecos Group, Dipartimento di Energia

Politecnico di Milano Pisa, October 9th, 2013


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Presentation overview

• Geothermal fluid loop

• Thermodynamic cycles

• Plant power balance• Case study: Soultz plant

• High enthalpy and hybrid plant schemes

• Main components• Operation and maintenance


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Binary technology

Main features:

• Power generation by means of closed thermodynamic

cycle

• Geothermal fluid loop and power cycle are completely

separated

• Nearly zero emission plant (for all-liquid geofluid)

• Suitable for integration with other energy sources(solar, biomass, waste....)


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The geothermal fluid loop

Power plant


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Geothermal fluid gathering

• Doublet: (1 production well, 1 injection well)

is the typical layout

• Triplet is also used

• Multi-well, with several modules is being

discussed


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The downhole pump:lineshaft (LSP), submersible (ESP), hydraulically driven (HTP)

Main issues: depth, pumping head, temperature,reliability and availability

Source: TP-Geoelec) “Strategic Research Priorities for Geothermal Electricity»


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Power cycle: the reference ideal cyclefor all liquid heat source, with constant heat capacity

Entropy

L IN

QP η ⋅= Geothermal fluid

reinjection

temperature

Ambient

temperature

T

Geothermal

fluid inlet

temperature

OUT Q

IN Q

Lorenz cycle

REMIND: the cycle

efficiency depends only

on the geothermal

source and ambient

temperatures

L


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Power cycle: the real cycleORC, pure fluid

Turb.

Reg.

Pump

Eva.

Eco.

Sh.

Air Cond.

4

3

2 1

6

7

8

9

10

5

11

2

ΔTap,Cond

3

45 6

7 8

9

1011

P H E

Tin,Geo

Treinj,Geo

ΔT*pp,Cond

ΔTap,PHE

ΔTpp,PHE

ΔTpp,Reg

1


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Concepts for binary cycle design

• Objectives:

- high efficiency

- => second law analisys: minimize second law

losses

- low cost, €/kW

- => optimize component design

- Critical choice: the cycle working fluid


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Concepts for binary cycle design

The heat introduction process


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ORC working fluid selection

• The fluid must be suitable for the selectedgeothermal source and plant size (Fluidcritical temperature and pressure, molecular

complexity and mass are relevant )• Hydrocarbons

• Refrigerants

• OthersImportant issues: environmental, toxicity, flammability,

material and lubricant compatibility, cost


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ORC simple cycle optimization

• Introduced thermal

power decreases with

evaporation temperature

• Cycle efficiency increaseswith evaporation

temperature

=> Maximum cycle powerfor the optimum

evaporation temperature


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Cycle selection: simple or recuperativesubcritical or supercritical


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Kalina cycle

working fluid: ammonia-water mixture


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Cost & component sizing

• Turbine sizing

• Selection of ∆Tpinch point for the heat exchangers:

the smaller the ∆T pinch point

, the higher the

efficiency but also the heat exchanger cost


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Component sizing and performance

Source: C. Pietra et al. 2010

Example for heat recovery case (Diesel engine)


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Binary plant performance


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ORC preliminary evaluation

• online ORC calculator

http://www.turboden.eu/en/rankine/rankine-

calculator.php

http://www.turboden.eu/en/rankine/rankine-calculator.phphttp://www.turboden.eu/en/rankine/rankine-calculator.phphttp://www.turboden.eu/en/rankine/rankine-calculator.phphttp://www.turboden.eu/en/rankine/rankine-calculator.php


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The plant power balanceNet plant power = (turbine power – pump power) -auxiliaries power consumption


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Case study: Soultz, ideal cycleNominal conditions: ambient 10°C;

geothermal fluid salt content 100 g/linlet temperature 175 °C, reinjection 70 °C

• Thermal power: ̇ = ̇ ∙ ∙ ∆

̇ = 33.57 ∙ 3. 7

∙ 175 79.1 = 13

• η = 1 28.5

7 −70,

7+7,

70.+7.

=0.28

• = ̇ ∙ η = 13 ∙ 0.28 = 3.64

L

L

70.1 )K


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Case study: Soultz , real cyclerecuperative cycle, isobutane (Tcr 134.9 °C, pcr 36.48 bar)

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0 0.5 1 1.5 2

T[°C]

s [kJ/kgK]

T-s Diagram


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Case study Soultz : the plant power balancenominal data

Turbine power, kW 1892

ORC feed pump, kW 242

Condenser fans & other auxiliaries, kW 169

ORC Net power, kW 1481

Downhole pump, kW 150

Plant net power , kW 1331

Thermal power from geoth. source, kW 13022

Cycle efficiency 11.38%

Plant efficiency 10,22%

Ideal power, kW 3646

ORC second law efficiency

(real power/ideal power)

40.6%


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Binary power plant schemes and

main features• The plant comprises two separate section: the geothermal

fluid loop and the power cycle

• NCG and dissolved minerals are confined in geofluid loop

• Power cycle arrangement depends on thermodynamiccycle selected

• Conventional heat rejection (water/ air cooled condenseror hybrid system)

• Cogeneration application and/or hybrid configuration iseligible

• Plant scheme tailored on the geofluid also possible


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Mixed steam-binary plant


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High enthalpy geofluid binary plant

scheme

G

cooling system

separator

evaporator

preheater

pump

turbine-generator

production well reinjection well

STEAM

LIQUID

NONCONDENSABLES


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Hybrid plant scheme

geothermal – waste heat or biomass plant

ORC power

unitFurnace

Air condenser

Productionwell ReinjectionwellDistrictheating


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Main machinery

• Heat exchangers (pre-heater, evaporator,

condenser, recuperator)

• Turbine

• Generator

• Feed pump

•Down-hole pump


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Power plant view


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Turbine

Turbine requirements:

• Work extraction

• Suitability to accomodate increasing volumetric

flow rate

• High efficiency

• Low cost (=> reduced stage number)

Remark: dry vapour expansion, no erosion of blades


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Binary power plant – turbine

• Axial, possibly multistage

most common

• Radial, inflow, usually single stage

sometimes used

• Radial, outflow, multistage

recently proposed again


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Turbine, axial, single stage

By courtesy ofTurboden

Low rotationalspeed

Low peripheral

speed, low

mechanical stress

No reduction gear


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Turbine, radial inflow - Soultz case study:

single stage, rotational speed 12400 rpmHigh rotational speed

with reduction gear

High work extraction

per stage

(centrifugal force

potential increases

work extraction)

Adapt to

accommodate variable

inlet nozzles


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Turbine, radial inflow - Soultz case study


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Binary power plant – turbineradial, outflow, multistage

Fluid passage area naturally increases

along the expansion process

Low work extraction per stage (centrifugal

force potential acts against workextraction)

High number of stages required

Low rotational speed, no reduction gear


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Binary plant – power cycle pump

• Centrifugal,

multistage pump

• Operated at variable

speed


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Power Plant - Heat Exchangersshell and tube or plate – possibly with phenolic coating

Soultz heat

exchangers


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Heat Exchangers – Soultz case study

Soultz T-Q

diagram


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Operation & Maintenance

• Plant remote control

• Monitoring of measured values

• - Physical (p, T, flows, …)

• - Mechanical (vibrations)

• - Electrical

• Check of power plant pump and turbine sealing

• Heat exchanger cleaning

• Check of down hole pump and periodic pump substitution

• brine acidification, scale inhibitors• Operation supplies (chemical for cooling water, inhibitors,

lubricating oil, filters )


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Bibliography

• Di Pippo, Ronald: Geothermal Power Plants: Principles, Applications, CaseStudies and Environmental Impact, Elsevier Science, Dartmouth,Massachusetts, (2007).

• Technology Platform on Geothermal Electricity (TP-Geoelec) “StrategicResearch Priorities for Geothermal Electricity» available on the Internet at:

www.egec.org • Technology Roadmap “Geothermal Heat and Power”, © OECD/IEA, 2011

International Energy Agency, www.iea.org

• Bombarda, P., Invernizzi, C., Pietra C., “Heat recovery from Diesel engines:A thermodynamic comparison between Kalina and ORC cycles” AppliedThermal Engineering 30 (2010) 212–219

• Di Pippo, R.: Second Law assessment of binary plants generating powerfrom low-temperature geothermal fluids, Geothermics, 33, (2004), 565-586.

http://www.egec.org/http://www.iea.org/http://www.iea.org/http://www.egec.org/


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Bibliography

• Bombarda, P., Gaia, M., Pietra, C., “Integration of Geothermal Liquid

Dominated Sources and Waste Heat Sources for Electricity Production”,

Proceedings of the “World Geothermal Congress 2010, Bali, Indonesia

• Pini, M., Persico, G., Casati, E., Dossena, V., “Preliminary design of a

centrifugal turbine for ORC applications”, Journal of Engineering for Gas

Turbines and power, vol. 135, n°4, april 2013

• Invernizzi, C., “Closed power cycles. Thermodynamic Fundamentals and

Applications. Series: Lecture Notes in Energy, Vol. 11, Springer

http://www.springer.com/series/8874http://www.springer.com/series/8874


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GEOELEC -Binary-Plant Pisa Bombarda

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