PROCEEDINGS, 45th Workshop on Geothermal Reservoir Engineering

Stanford University, Stanford, California, February 10-12, 2020

SGP-TR-216

1

Evaluation of Geothermal Wellhead Generation Using Well BN-06D in Province of Biliran,

Philippines 1Maria Zhahata Geraldinne Malana,

1Aylmer Marbello,

1Ariel Fronda,

2Saied Jalilinasrabady

1Department of Energy, Energy Center, Rizal Drive cor. 34th Street, Bonifacio Global City, Taguig City, Philippines, 1632

2Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan

zhahatamalana@doe.gov.ph

Keywords: geothermal energy wellhead, energy, Biliran Island, Philippines

ABSTRACT

Biliran I Geothermal Project is one of the promising yet undeveloped intermediate-enthalpy geothermal resources in the Philippines. It

was initially explored but later abandoned due to high corrosive brine from the wells. Years later, scientists and engineers created Fluid

Management System (FMS) and chose Well BN-06D for the well testing procedure. The FMS was eventually completed and has been

successful. Due to wellhead power plants are currently being used worldwide, this study will use Well BN-06D for determining its

power generation. By using the parameters from FMS bore output measurements and Engineers Equation Solver (EES) codes, this study

evaluated the potential generation of Well BN-06D through energy analysis as well as the applicable and available conceptual models

suited for the well, including the system optimization.

1. INTRODUCTION

Philippines uses geothermal energy as one of the main of source of electricity. Based on Philippine Department of Energy (DOE)’s

2018 Power Statistics Report, geothermal energy contributed a total of 10,435 Gwh gross power generation or 10.5% share on total

gross of the country (Department of Energy 2018). However, geothermal development is idle and still for over the last decade. The

future development now relies to the government by further intervening and promoting the utilization on unconventional geothermal

resources such as low-to-intermediate enthalpy and acidic fluids throughout the country.

Geothermal wellhead units have been used for many decades. It is commonly used on remote areas that are isolated from national grid, a

power source during resource development or simply, this technology is applied because it only needs a small area to construct and have

shorter steam transmission lines compared to central power plants. Biliran Island has a 5 MW baseline demand, while the peak demand

is eight (8) MW. Installing geothermal wellhead units would contribute and eventually a solution to island’s frequent power outage.

Energy analysis is based on the first and second law of thermodynamics. The first law of thermodynamics states the heat is a form of

energy that can be neither created nor destroyed. However, it can be transferred from one place to another and can be converted to other

forms of energy. It means that the work of internal energy of a system has to be equal that is being done on the system.

First law of thermodynamics on a system can be expressed as

)()(2/1)(Q121212

zzgvvhhmW

[1]

By disregarding the enthalpy resulted from kinetic and potential energy, it can be expressed as

)(Q12

hhmW

[2]

The second law of thermodynamics states that when energy increases, entropy also increases. The entropy is equal to the heat

transferred into a closed system divided with temperature.

oTQssmO /)(

12

[3]

For an ideal reversible operation, entropy assumes it is zero. From above, the maximum work can be expressed as

)]()[(1212max

ssThhmWo

[4]

1.1 Geothermal Power Plant Classifications

1.1.1 Single Flash Geothermal Power Plant

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Single Flash Geothermal Power Plant (SFGPP) represents the geothermal power production because of its simple design and low cost

(Clarke 2014). In a single flash geothermal power plant, the geothermal fluid has undergone a single flashing process in which a

process of transitioning from a pressurized liquid to a mixture of liquid and vapor by lowering the pressure.

1.1.2 Back Pressure Geothermal Power Plant

Back Pressure Geothermal Power Plant (BPGPP) are the simplest on all system since it is the cheapest but have the lowest thermal

efficiency. It is usually used for temporary power generation or where energy efficiency is not a priority.

1.1.3 Binary Cycle Geothermal Power Plant

Binary Geothermal Power Plant (BGPP) can operate with geothermal brine temperatures ranging from 85 ˚C to 170 ˚C. It also uses a

secondary fluid or commonly known as Working Fluid (WF) that undergoes to a closed cycle. The chosen working fluid absorbs heat

from a geothermal brine, will reach to its boiling point in which would eventually evaporates and expands through a turbine. Then it

condenses and complete the cycle to the evaporator through the feed pump. Majority of the binary geothermal power plants use the

Organic Rankine Cycle (ORC). ORC is similar to Rankine Cycle of a thermal power plant except the heat source came from geothermal

brine instead of boilers (Saeid Jalilinasrabady, Ryuichi Itoi, Hiroki Gotoh 2010). Selection of working fluid are decided between its

thermodynamic properties, health, safety and environmental impacts (Di Pippo and DiPippo 2012).

1.1.4 Combined Single Flash System with Binary Cycle

In this system, single flash system is combined with binary cycle and thus, increases the power output of the plant and improves the

ratio of geothermal resource utilization. From the wellhead the geothermal brine will enter to the separator and the steam will be

separated from the geothermal brine. The single flash generates electricity through steam while the separated hot geothermal brine,

binary cycle uses an organic fluid to exchange the thermal energy and then, generates additional electricity (Gong et al. 2010).

2. BILIRAN I GEOTHERMAL POWER PROJECT

Biliran I Geothermal Project is located in the Eastern Visayas region just beneath Tongonan Geothermal Field (see Figure 1) and

positioned on the Philippine Fault Zone, resulted to active volcanism and tectonism since the Miocene (Lawless and Gonzalez 1982).

Biliran Island has an optimistic geothermal resources in the country hence it is estimated to produce 93 to 371 MW power potential

(FEDCO 2009). PNOC-EDC who was responsible for the successful exploration and development of Tongonan geothermal power

plant, continue their geoscientific exploration in Biliran Island on 1979. The preliminary results were promising and together with

Kingston, Reynolds, Thom and Allardice Ltd., which part of New Zealand Government Energy Co-operation Programme, initially

drilled three (3) standard vertical wells (BN1 to 3). They discovered that the resource is extremely acidic hence one of the three wells

discharged high enthalpy and acidic fluids. It damaged the wellhead and years later, PNOC-EDC management decided to abandon the

project. On the year 2008, Biliran Geothermal Inc. (BGI) which consists of Icelandic and Philippine companies, continued the

geoscientific studies and eventually drilled another five (5) production wells (BN4 to 8) wells targeting the location of the neutral zone

of the resource (see Figure 2). The result was, all the wells are also acidic. Not losing hopes, Emerging Power Incorporated (EPI) took

over the project and continue the FMS using the Well BN-06D due to lowest acid concentration among others. They injected diluted

caustic soda inside the well thru a 2/8” capillary tube and placed above the estimated flash point. Then, they conducted discharge testing

for three (3) months (see Figure 3) and the pH level results were acceptable (see Figure 4), in spite of the chemical misbehavior of the

well. Further, iron (Fe) and magnesium (Mg) concentrations also decreased since no thinning above the ground piping. Using the multi-

finger caliper survey, it also proved minimum thickness reduction of the production casing. Aftermath, the FMS has been successful and

Well BN-06 may now utilized for power generation (Marbello et al. 2020).

Figure 1: Location of Biliran I Geothermal Project Figure 2: Location of the wells in Biliran I

Geothermal Project

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Figure 3: Bore output measurements for BN-06D during the FMS test (WHP, MF, Enthalpy) on 2016, November 15 to

December 07

Figure 4: pH trend on 2016, November 15 to December 29 as it maintained a stable range of 4.5 to 5.5

3. METHODOLOGY

There are different classifications of geothermal power plants that are currently used worldwide. All geothermal power plants convert

from thermal energy (e.g. steam, geothermal brine), to mechanical energy (e.g. turbine) and finally to electrical energy (e.g. electricity).

In this study, Well BN-06D will be used and the gathered FMS results and parameters will be used on the following geothermal power

plant classifications: single flash, back pressure, binary cycle (Organic Rankine Cycle), and combined single flash system with binary

cycle. It will evaluate of the said well through energy analysis including the system optimization. By using the Engineering Equation

Solver (EES), it would calculate and estimate the potential generation from the view point of thermodynamic aspect. Further, plant

optimization maximizes the work output and efficiency. It can estimate the precise parameters to have an optimum work. However, one

of the main constraints of optimizing the work output is the re-injection temperature. The lower the temperature, the higher the work

output. Below are the following wellhead parameters of Well BN-06 that it will be used in this study:

Table 2. Well BN-06 Wellhead Parameters

Pressure 669 kPa

Temperature 165°C

Mass flow rate 33.7 kg/s (brine flow:26.3 kg/s; steam flow: 7.4 kg/s)

Enthalpy 1,159 kJ/kg

Further, the following are the processes on analyzing geothermal power plants;

1. The isentropic process in which the entropy (s) is constant. It applies to turbines, compressors, and pumps. No loss of energy to

environment or fluid when work is ideally delivered or consumed.

2. The isenthalpic process in which the enthalpy (h) is constant and no work or heat is delivered or consumed from the environment.

Thus, the energy of the fluid remains constant.

3. The isobaric process in which the pressure (p) is constant

4. Heat exchange, wherein only heat is transferred from or to the fluid. This affects both enthalpy and entropy while the pressure is

mostly constant.

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3.1 Single Flash Geothermal Power Plant

3.1.1 Wellhead to Steam Separators

From the wellhead to separator, it is assumed the geothermal fluid have an isenthalpic process. The fluid will flow to the separator.

Separator are shaped a cylindrical and as the two-phase geothermal fluid will enter, the steam will rise up and to be collected to the

steam pipe while the brine will be dropped and re-injected back to the resource. Flashing process occurs at the separator, steam and

brine will be separated at a specific pressure of 669 kPa (P[1]). Dryness fraction was solved using the equation below:

1

2

1

m

mx [5]

After the separator the steam will enter to demistifier. It is assumed that it is constant and the steam will enter the turbine. The steam

quality was set to 1 (x[2]=1) hence only the steam enters to turbine and the pressure remains constant. On the other hand, the brine

steam quality was set to 0 (x[12]=0) since it is in saturated liquid state, can be calculated using the equation below:

2112,

mmm b [6]

3.1.2 Turbine Entry

The mass flowrate of the steam to turbine is equal to the mass flowrate after the demistifier assuming a negligible loss. In an ideal

turbine, as the steam expands there is a consideration of isenthalpic. However, ideal conditions are not achievable hence an efficiency

factor t is set as 0.85 (85%).

Further, work done by the turbine can be calculated by:

tThshmW *)(

433

[7]

3.1.3 Condenser

Instead of steam is discharged to the atmosphere, condenser are designed to optimize the work output by maximizing the pressure drop

from the outlet of turbine. It condensed the exhausted steam from the turbine by a banks of spray nozzles in which the cooling water

came from the cooling tower. Non-Condensable Gas (NCG)s is negligible in this system. Mass balance is required in order to solve the

mass flow rate of cooling water.

584

mmm [8]

558844 *** hmhmhm

[9]

The condenser was assumed to have a 3°C temperature drop between inlet and outlet. The density of the condensate, ρ can be found in

the steam tables and the volume flux Q can be calculated by:

600,3*

5

5

5

mQ

[10]

While work done by the condenser can be calculated by:

000,1*

54

5

hhmDuty

cond

[11]

3.1.4Condenser Pump Work

The condensate fluid will be pumped to the cooling water and the assumptions for pump efficiency and pump motor efficiency are 0.80

(80%) and 0.95 (95%) respectively. Also, the assumption for the pump head height is 43m.

000,1**

**5

cmcp

p

CP

hgmW

[12]

3.1.5 Cooling Tower

In this study, the mechanically forced draft (cooling fans) will be used. The supplied water came from the condenser which it was

collected and cooled and recycled again to condenser. The efficiency will be depending on the atmospheric wet bulb temperature. Mass

balance are required which are from the turbine that needs cooling. Mass evaporated in the cooling tower can be calculated by:

10107996 *

mmmm [13]

Further, fluid enthalpy in the cooling tower and air enthalpy was assumed from the EES property tables and the energy balance can be

obtained by:

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1010779966 *** hmhmhmhm

[14]

Mass evaporated from the cooling tower can be calculated by:

76, mmm evaploss

[15] Ratio of inlet steam mass flow evaporated from the cooling tower can be calculated by:

100*

3

,

m

mMER

evaploss

[16]

Table 3. Conditions and assumptions of the cooling tower

Cooling tower efficiency , ctf

0.7

Cooling tower fan motor

efficiency ctm

0.80

Pressure change on the cooling

fan , CTF

P

328 kPa

Work done by the Cooling Tower is calculated by:

000,1**

**9

ctmctf

ctctf

ctf

VPmW

[17]

3.1.6 Power losses due to other equipment

The value of Non-Condensable Gas extraction system is ideal and assumed where, Non-Condensable Gas extraction system (Wloss.NCG)

is equal to 75W. The net power produced and parasitic load can be calculated by:

NCGlossctfcpTnetWWWWW

,

[18]

NCGlossctfcpparasloadWWWW

,

[19]

3.1.7 Plant Optimization

This system shall apply the plant optimization by lowering the turbine outlet pressure for maximum power output.

3.2 Back Pressure Geothermal Power Plant

In this study, the process will be the same comparing it with single flash but there is no existence of condenser and cooling tower. The

turbine exhausted steam will be discharged in the atmosphere at 1 atmospheric pressure (101.325 kPa).

3.3 Binary Cycle Geothermal Power Plant

3.3.1 System Description of the Proposed Binary Power Plant for BN-06

On Figure 4, shows the schematic diagram of the proposed ORC binary power plant for BN-06. From the wellhead (Stream 0), the

steam and brine will be separated from the separator. The separated hot brine will act a heat source as it enters to evaporator (Stream 12)

pass through to pre-heater (Stream 13) and will be re-injected back to the reservoir (Stream 14). Because of the hot brine, the WF will

became vapor after it passes to the evaporator (Stream 1). The saturated vapor of working fluid expands inside the turbine from high

pressure (P1) to low pressure (P2) generating the electricity (Streams 1 and 2). The exhausted vapor condenses as it passes through the

wet cooled condenser and will change into liquid (Streams 3). The WF enters to a feed pump with a high pressure (Stream 4), passes

through to the pre-heater to reach its boiling point (Stream 5) and finally enters again to evaporator, completing the closed cycle.

Thermodynamic analysis are shown in Figure 4 and 5.

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Figure 5. ORC Binary Schematic Diagram Figure 6. Temperature-Entropy Diagram showing the

working fluid flow

Assumptions for the proposed ORC binary power plant are the following:

Frictional losses are not considered

Pressure drops in the evaporator, condenser as well as along the pipelines are neglected

Working fluid after the condenser is considered saturated liquid

75% and 85% in isentropic efficiencies of pump ( p) and turbine ( t), respectively

3.3.2 Turbine Analysis

The vapor undergoes isentropic expansion inside the ideal turbine (See Figure 5).

]1[]2[ sSs [20]

After the turbine with the fixed P2 and entropy S1, the enthalpy of the WF is calculated using EES code. The turbine power output (Wt)

can be calculated as:

twfturbinemhhW **)(

21

[21] 3.3.3 Heat Exchangers

In heat exchangers, thermal energy is transferred from one fluid to another. Evaporator, pre-heater, and condenser were identified as

heat exchangers in this paper. All are well insulated in which the entire heat is transferred between the fluids (Di Pippo and DiPippo

2012).

3.3.4 Evaporator

Geothermal hot brine transfers the energy Qin, to the WF in the evaporator. Considering it is a steady flow, the following are the

equations:

)(**131212 TbTbmcQ

pevaporator

[22]

)(**)(*13121251

TbTbmchhmpwf

[23]

wfturbinemhhW

*)(21 [24]

Area of the evaporator and pre-heater can be calculated by:

LMTDevevaporatorevaporatorTAUQ

** [25]

terLMTDpreheapreheaterpreheaterTAUQ

**[26]

3.3.5 Condenser and cooling tower

A water-cooled condenser is used to condense the saturated vapor coming from the turbine.

[27]

ercoolingwatpcoolingcoolingTCmQ

** [28]

3.3.6 Pump analysis

The feed pump transmits power to WF (Streams 3 and 4). The equation is given by:

32EnEnQ

cooling

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wfpumpmhhW

*)(34 [29]

While the cooling water pump transmits power to water (Streams 6 and 7). The equation is given by:

000,1*

**

pump

ercoolingwat

pumpcw

hgmW

[30]

3.3.7 Choosing a Working Fluid

In selecting a working fluid, it has great indication for maximizing the binary power plant performance. There are plenty of working

fluids to choose from, but there are many constraints related to fluid thermodynamic properties, health, safety, and environmental

impact (Uhorakeye 2008). In terms of the resource, reinjection temperature is one of the constraints in the binary cycle. Below are the

working fluid candidates for the proposed binary cycle geothermal power plant.

Table 4. Thermodynamic Properties for Binary power plant’s working fluid

Working Fluid Formula Boiling Point, ˚C Critical Temp, Tc, ˚C Critical Pressure, Pc, kPa

Ammonia NH3 - 33.33 132.25 11,280

n-Butane C4H10 - 0.49 151.97 3,796

1-Butene C4H8 -6.31 146.35 4,020

Isobutane C4H10 -11.75 134.66 3,640

Isobutene C4H8 -7 144.75 4,000

Isopentane C5H12 27.83 187.75 3.380

Further, the scaling problem from the reinjection temperature is not yet fully determined and will consider not below 90 ˚C as the

reinjection temperature.

3.4 Combined Single Flash System with Binary Cycle (Hybrid System) Geothermal Power Plant

In this study, the power output of the hybrid system is the total amount of the power output produced from the steam and on the power

output produced from brine.

4. RESULTS AND DISCUSSIONS:

The energy analysis on each system using the parameters from Well BN-06D were analyzed by the EES. In the single flash system, this

study applied the power plant optimization by decreasing the turbine outlet pressure by 12.22 kPa. The power plant optimization was

not applied in back pressure geothermal power plant since the turbine outlet pressure must be controlled at 1 atmospheric pressure

(101.325 kPa). In the binary system, i-butene with chemical properties of critical temperature of 146.35 ˚C and critical pressure of 4,020

kPa was chosen to be the working fluid. To meet the maximum the power output, this study uses the plant optimization and had an

output of turbine inlet and outlet pressures of 2,650 kPa and 305 kPa respectively. Further, since the resource has a high chance of silica

scaling, the re-injection temperature is 90.54˚C.

4.1 Single Flash Geothermal Power Plant (SFGPP)

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Figure 7. Schematic diagram of the SFGPP

Table 5. Parameters of SFGPP from using EES

Figure 8. Optimization of Turbine Outlet Pressure

4.2 Back Pressure Geothermal Power Plant (BPGPP)

Figure 9. Schematic Diagram of BPGPP

Table 6. Parameters of BPGPP from using EES

Parameters Value

Turbine Inlet Temperature (T3) 163.1 ˚C

Turbine Inlet Pressure (P3) 669 kPa

Turbine Outlet Temperature (T4) 51.8˚C

Turbine Outlet Pressure (P4) 12.22 kPa

Turbine Outlet Steam Quality (x4) 1

Condenser Pressure (P5) 988.5 kPa

Condenser Temperature (T5) 48.8˚C

Re-injection Temperature (T6) 163.1˚C

Re-injection Pressure (P6) 669 kPa

Power Output (Wnet) 3,188 kW

Efficiency 8.2%

Parameters Value

Turbine Inlet Temperature (T3) 163.1 ˚C

Turbine Inlet Pressure (P3) 669 kPa

Turbine Outlet Temperature (T4) 99.97˚C

Turbine Outlet Pressure (P4) 101.325 kPa

Turbine Outlet Steam Quality (x4) 1

Condenser Pressure (P5) 988.5 kPa

Re-injection Temperature (T6) 163.1 ˚C

Re-injection Pressure (P6) 669 kPa

Power Output (Wnet) 1,945

Efficiency 5.0%

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4.3 Binary Cycle Geothermal Power Plant (BCGPP)

Table 7. Parameters of the selected Working Fluid in the BCGPP

Working Fluid Turbine Inlet

Pressure, P1, kPa Turbine Outlet

Pressure, P2, kPa

Power Output WNet,

kW Re-Injection

Temperature, ˚C

Ammonia 7,600 1,250 1,120 90.38

n-Butane 2,100 350 1,060 90.64

1-Butene 2,650 305 1,241 90.54

Isobutane 3,500 1,400 547.5 91.27

Isobutene 2,800 330 1,218 90.27

Isopentane 1,000 105 1,134 93.26

Figure 10. Schematic Diagram of BCGPP

Tables 8. Parameters of BGPP from using EES

Parameters Value

Working Fluid Butene

Turbine Inlet Temperature (T1) 121.7 ˚C

Turbine Inlet Pressure (P1) 2,650 kPa

Turbine Outlet Temperature (T2) 26 ˚C

Turbine Outlet Pressure (P2) 305 kPa

Re-injection Temperature (Tb14) 163.0 ˚C

Power Output (Wnet) 1,241

Efficiency 7.1%

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4.4 Combined Single Flash System with Binary Cycle Geothermal Power Plant

Figure 11. Schematic Diagram of Combined Single Flash System with Binary Cycle (Hybrid System) Geothermal Power Plant

Table 9. Comparison of each system with Power Output and Energy Efficiency Conceptual Model Power Output, kW Energy Efficiency

Single Flash 3,188 8.2%

Back Pressure 2,019.83 5.2%

Binary Cycle 1,241 7.1%

Combined Single Flash and Binary 4,429

11.3%

5. CONCLUSION

This study is only to discuss the possibility of power production from the view point of thermodynamic and

comprehensive feasibility study is needed to determine the viability of the project. In terms of the binary cycle,

Butene is the most suitable working fluid. Combined single flash and binary with the re-injection temperature of

90.54 ˚C has the highest power output and would utilize the resource. Estimation of 4,429 kW is maximum power

output that Well-BN06 can contribute and provide to the host community.

6. ACKNOWLEDGEMENTS I would like to thank the Japan International Cooperation Agency (JICA) for giving this opportunity to participate on

the 2019 “Intensive Training Program for Geothermal Resource Engineers” held in Kyushu University and to the

Philippine Department of Energy for nominating me on the training course. Moreover, want to express my sincere

gratitude to my supervisors, Prof. Ryuichi Itoi and Prof. Saied Jalilinasrabady as well as to the personnel and

students in the Earth Resources Engineering (ERE) laboratory, for sharing their boundless knowledge, endless

patience and continuous efforts for my project study.

7. REFERENCES

C Clemente, V, E H Alcober, Richard de Guzman, and L F Bayrante. 2016. “Country Update on Geothermal Utilization

and Barriers Affecting Its Growth - Philippines.” (November): 18–20.

Clarke, Joshua Geiger. 2014. “Optimal Design of Geothermal Power Plants By.” : 1–204.

Department of Energy. 2018. “2018 Power Statistics.” (March): 2019.

Di Pippo, Ronald, and Ronald DiPippo. 2012. Geothermal Power Plants Geothermal Power Plants.

http://books.google.com/books?hl=fr&lr=&id=Ea2osquPZwUC&pgis=1%0Ahttp://linkinghub.elsevier.com/retrieve/pii/B

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9780080982069000245.

Filtech Energy Drilling Corporation: Resource Assessment: The Biliran Geothermal Field, Philippines, BGI-

Technical Report, Manila, Philippines, (2009).

Gong, Yu-lie, Chao Luo, Wei-bin Ma, and Zhi-jian Wu. 2010. “Thermodynamic Analysis of Geothermal Power

Generation Combined Flash System With.” 1(April): 25–29.

Lawless, J. V., and R. C. Gonzalez. 1982. “Geothermal Geology and Review of Exploration Biliran Island.” Proceedings

of the New Zealand Geothermal Workshop (Espiritu): 161–66.

Marbello, Aylmer, Ariel Fronda, Nilo Apuada, and Dennard Llennarizas. 2020. “Fluid Management System – Acid Well

Neutralization Experience for the Biliran Geothermal Field , Province of Biliran , Philippines.”

Saeid Jalilinasrabady, Ryuichi Itoi, Hiroki Gotoh, and Hiroyuki Kamenosono. 2010. “Energy and Exergy Analysis of

Sabalan Geothermal Power Plant, IRAN.” GRC Transactions 34(418): 25–29.

Uhorakeye, Théoneste. 2008. “Feasibility Design of an Integrated Single-Flash Binary Pilot Power Plant in Nw-Rwanda.”

Training (27).

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Nomenclature

A Area (m2)

ALT Atmospheric Lifetime

BP Boiling Point (℃)

Cp specific heat capacity of water (kJ/kg K)

EES Engineering Equation Solver

g gravity

GWP global warming potential

h enthalpy (kJ/kg)

h1 stage 1 Enthalpy

h2 stage 2 Enthalpy

𝐿𝑀𝑇𝐷𝑒𝑣 Logarithmic Mean Temperature Difference at evaporator

𝐿𝑀𝑇𝐷𝑝ℎ Logarithmic Mean Temperature Difference at preheater

m mass flowrate

m1 total mass flow rate (kg/s)

m2 steam mass flow rate (kg/s)

mbrine brine mass flow rate (kg/s)

mwf working fluid mass flow rate (kg/s)

O change in entropy

ODP Ozone depletion potential

ORC Organic Rankine Cycle

P pressure (kPa)

Pc critical pressure (kPa)

Ps saturation pressure (kPa)

Q amount of heat transferred

Q5 heat transfer in the SFGPP condenser (kW)

Qcooling heat transfer in the BCGPP condenser (kW)

QEV heat transfer in evaporator (kW)

QPH heat transfer in preheater (kW)

rho density

s entropy (kJ/kg K)

s1 state 1 entropy

s2 state 2 entropy

To ambient temperature

T temperature (℃)

Tc critical temperature (℃)

v velocity

W power

Wmax maximum work

Wnet net power output (kW)

Wp work of the SFGPP feed pump (kW)

Wpump work of the BCGPP feed pump (kW)

Wt power of the turbine (kW)

z elevation

ηplant overall plant effiency

ηt isentropic efficiency of turbine

ηPlant overall plant efficiency

ηpump efficiency of the pump

Δp pressure head (kPa)

ρ water density of water (kg/m3)

wet bulb temperature (℃)