Empirical TITP correlation for geothermal ORC

KIT – University of the Baden-Württemberg State andNational Research Center in the Helmholtz Association

Institute for Nuclear and Energy Engineering, Energy and Process Engineering Group

www.kit.edu

Empirical Correlation for Optimal Turbine Inlet Temperature and Pressure for Geothermal Organic Rankine Cycles (ORC)Yodha Y. Nusiaputra, Fitratul Qadri, Dietmar Kuhn, Halim Abdurrachim

Institute for Nuclear and Energy Engineering2 28.04.23 Yodha Y. Nusiaputra

IntroductionOrganic Rankine Cycles (ORCs) is well suited for renewable energy, low-grade heat utilization (Quoilin, 2013)Medium temperature geothermal resources

Combined (flash-binary) cycle for high-enthalpy geothermal reservoirMid-enthalpy geothermal reservoir

(Gabbrielli, 2012)(Yari, 2010)

Institute for Nuclear and Energy Engineering3 28.04.23 Yodha Y. Nusiaputra

ORC configurationSimple Organic Rankine Cycle (ORC) without recuperatorSub- and Supercritical ORC

(Quoilin, 2013)

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Simulation results example

Yodha Y. Nusiaputra

(Vetter, 2013)

TIT : 104 ºC TIP : 4.6 MPa

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Simulation data collection5 hydrocarbon working fluids as samples

PentaneIsopentaneButaneIsobutanePropane

Two site-specific boundary constraints:Geothermal (brine) temperatureInjection temperature due to mineral scaling / reservoir temperature-breakthrough

Simulation range: geothermal (brine) temperature of 120 – 180 with injection temperature of 70 – 160 174 simulation data pointsCorrelate the optimal Turbine Inlet Temperature and Pressure (TITP) to geothermal (brine) temperature and injection temperature

Yodha Y. Nusiaputra

Institute for Nuclear and Energy Engineering6 28.04.23

Simulation data collection

Yodha Y. Nusiaputra

ORC - ProcessCondensation temperaturePump efficiencyTurbine efficiencyPinch-pointPressure drop in HEX

40°C0.750.85 K-

Geothermal brineMass flowPressureBrine temperature Tgeo

Injection temperature Tinj

1 kg/s1.4 MPa120 - 180 °C70 - 160 °C

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2-D Empirical correlation

0.91

1.11.2

360380

400420

0.7

0.8

0.9

1

1.1

1.2

1.3

Tg/TcritTinj [K]

T1,o

pt/T

crit

0.91

1.11.2

360380

400420

0

0.5

1

1.5

2

2.5

Tg/TcritTinj [K]

p1,o

pt/p

crit

2,10,

2

9,8

3,7

2,6,5

3

4

2

321,

ninjncrit

gninj

ncrit

gninj

ncrit

g

ninjninjninjncrit

g

ncrit

g

ncrit

ginj

crit

g

TTT

aTTT

aTTT

a

TaTaTaTT

aTT

aTT

aaTTT

f

Yodha Y. Nusiaputra

210263.9006.1

crit

g

ncrit

g

TT

TT

01.221.372, injninj TT

Polynomial constants refer to Nusiaputra et.,al. (2015)

R-squared: 0.98 RSME: 0.017 R-squared: 0.98 RSME: 0.076

, with

TIT TIP

101a

Institute for Nuclear and Energy Engineering8 28.04.23

2-D Empirical correlationGeothermal brine temperature has a strong influence to the optimal TITPCorrelation for TIT is better fitted the data

Tg/Tcrit

Tinj

[K]

0.85 0.9 0.95 1 1.05 1.1 1.15 1.2

360

380

400

420

0.8

0.9

1

1.1

Tg/Tcrit

Tinj

[K]

0.85 0.9 0.95 1 1.05 1.1 1.15 1.2

360

380

400

420

0.5

1

1.5

2

Yodha Y. Nusiaputra

0.85 0.9 0.95 1 1.05 1.1 1.15 1.2-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

Tg/Tcrit

T1,o

pt/T

crit

TIT - residualsTIT - validation residuals

0.85 0.9 0.95 1 1.05 1.1 1.15 1.2

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

Tg/Tcrit

p1,o

pt/p

crit

TIP - residualsTIP - validation residuals

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Validation to simulation results15 different working fluids (excluding 5 HCs from previous simulation) at randomly chosen geothermal (brine) temperature – injection temperature

Yodha Y. Nusiaputra

+ 5%

- 5%

+ 2%

- 2%

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Study cases20 different working fluids (15 + 5 WFs) at Tgeo-Tinj of 180-140 (combined-cycle) and 140 – 80 (mid-enthalpy)

Yodha Y. Nusiaputra

Institute for Nuclear and Energy Engineering11 28.04.23

ConclusionsA new empirical correlation for TITP has been devised for geothermal (brine) temperature of 120 – 180 ºC and injection temperature of 70 – 160 ºCIt was obtained that all the optimum point spread around correlation line with relative error for optimum TIT, TIP, and specific net power output within 2.5%, 26%, and 2%Within typical value ranges, it is valid regardless of pinch-point, condensation temperature, and recuperation effect. However, multi-dimensional fitting which includes these parameters is foreseen to predict optimal TITP more accurately

Yodha Y. Nusiaputra

Institute for Nuclear and Energy Engineering12 28.04.23

Thank you for your attention !

Yodha Y. Nusiaputra