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Power generation from geothermal resources in Turkey

Niyazi Aksoy*

Dokuz Eylül University, Torbali Technical Vocational School of Higher Education, 35120 Izmir, Turkey

a r t i c l e i n f o

Article history:Received 17 September 2013Accepted 27 February 2014Available online 20 March 2014

Keywords:Geothermal energyPower generationCO2 emissionTurkey

a b s t r a c t

This study provides information on power generation via geothermal resources and sector development.The first instance of power generation from geothermal resources was performed by a state-ownedpower plant at Kızıldere-Denizli, whereas the first private sector investment was the Dora-I powerplant, commissioned in 2006. Legislation regulating rights ownership and certification laws was issued in2007. The installed capacity of the geothermal resources is 311.871 MW for 16 power plants, and powergeneration licenses were issued for 713.541 MWat the end of 2012. The total potential geothermal powerthat can be generated in Turkey is estimated to be approximately 2000 MW. The geothermal fields inTurkey produce high levels of greenhouse gases, which have been deemed highly responsible for globalwarming. Due to high CO2 emissions, the geothermal energy sector risks a carbon tax in the near future.For certain geothermal resources, multiple investors produce electricity from the same resource. Thesector will inevitably experience severe damage unless permanent solutions are devised for problemsrelated to sustainably managing geothermal resources and environmental problems.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Turkey’s geological features offer geothermal energy opportu-nities. Turkey is in the central part of the Alpine-HimalayanMountain Belt, which began to form due to closing/shrinking ofthe Tethys Ocean in the Late Mesozoic. High mountain ridges wereformed along the northern and southern sides of Anatolia, whilecertain pre-CambrianePaleozoic metamorphic shields (i.e., theMenderes and Central Anatolian Massifs) remain at its center. Thetectonic plate convergence and subduction history of the MenderesMetamorphic Massif (MMM) was developed based on data for themajor flyschoidal basin and ophyolithic fields of the Izmir-Ankararange at its western and northwestern boundaries. Recent tec-tonics associated with westward movement of the Anatolian sub-plate and related NeS extension, particularly in southeasternAnatolia, caused by the Afro-Arabian Plate’s northward pushcreated several major EeW oriented grabens (Fig. 1). The faultsbounding these structures created suitable conditions for the deepcirculation of infiltrating meteoric waters and heating at certaindepths. The tectonic forces and resulting structures are thought tobe responsible for the current high heat flow in the MMM, themedium to high enthalpy geothermal systems in Western Anatolia

and the many low- to medium-enthalpy systems throughout themassif, especially in the Aegean Coastal Belt (Fig. 1). The regionalheat flow is approximately 100e120 mW/m2 [1] in the MMM,which is the largest (in size and output) in Turkey. Several recentgrabens have developed in the MMM, where all of the geothermalfields have medium to high enthalpy with reservoir temperaturesof 120e287 �C. BüyükMenderes Graben (BMG), Gediz Graben (GG),and Simav Graben (SG) contain many medium and high enthalpygeothermal resources. The thermal fluids are composed of alkaline-bicarbonate, have high CO2 levels and show evidence of watererock interactions and mixing with shallow waters. The geothermalsystem at Tuzla is at the SW border of the young (Lower Tertiary)Kazda�g Metamorphic Massif (KMM) (Fig. 1), where Miocenevolcanism shaped the Biga Peninsula following two intersecting,approximately NeS and NWeSE trending regional fracture sys-tems. During the Pliocene, several dacitic-rhyolitic lava domeswereplaced along an NeS line in and north of the geothermal field. TheTuzla system is thermally recharged through an ascension of deepwaters through this NeS structural discontinuity, which also ex-plains the Pliocene lava domes in the area [2].

The power potential of 11 fields in Turkey with medium andhigh enthalpy is probabilistically 570 MW (P10, proven), 905 MW(P50; probable), and 1389 MW (P90, possible) [2]. Ten more fieldsare not studied herein but are suitable for power generation.Therefore, Turkey’s total power potential can be estimated at2000 MW.

* Tel.: þ90 232 8531828; fax: þ90 232 8531820.E-mail addresses: [email protected], [email protected].

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Renewable Energy 68 (2014) 595e601


According to the 2012 statistics, the total power generated inTurkey is 239 billion kWh, and the total installed capacity is57.058 MW. The distribution for power generation is 73% thermal,24.2% hydraulic, 2.4% wind, and 0.4% geothermal power plants. Thedemand for power increases approximately 6.5e7.5% each year [3].The Turkish energy market was liberated in 2001; the EMRA wasestablished to perform a regulatory and supervisory role in theenergy market. Investors must have a production license from theEMRA.

The Law of Geothermal Resources and Mineral Waters was is-sued in 2007 and enacted one year later in 2008, which led to animmediate issuance of approximately 3200 licenses. Almost allwell-known, high enthalpy geothermal fields in Turkey werelicensed by a governmental institution, namely the General Direc-torate of Mineral Research and Exploration (MTA). Later, theselicenses and operation rights were sold by the MTA throughtendering, which created approximately 600 million US dollars ofincome for the government. Law 6094 was enacted in 2011 andissued tariff subsidies as well as purchasing guarantees for powergeneration via renewable energy resources. The governmentannounced a 10.5 ¢/kWh subsidized tariff and 10 year purchasingguarantee from the date the plants are commissioned for powergeneration via geothermal resources until 2020. There is alsoadditional local product support applicable for generators, turbines,power electronics, and injectors manufactured in Turkey, which is

also valid for 10 years and amounts to 2.7 ¢/kWh; thus, the subsi-dized tariff was increased to 13.2 ¢/kWh. The tariff and purchasingguarantee subsidies have undoubtedly eased project financing forinvestors. A value-added tax (VAT) and customs duty exemption forpower generation investments in Turkey are also available. Due tocomplete liberalization of the energy market by Law 4628 in 2001,electricity can be sold and purchased on the free market.

2. Power generation development by geothermal resources inTurkey

Turkey is rich in geothermal resources. The geothermal re-sources are used for indoor heating, spa centers, food drying andpower generation. Turkey includes 20 geothermal-based districtheating systems. Nearly 80,000 residential buildings and over 2million m2 greenhouses are heated by geothermal energy. Directusing capacity is nearly of 800 MWt [2]. The heating time isapproximately 2000 h of operation per year.

A pilot power plant was constructed in 1975 at the Kızılderegeothermal field and provided free electricity to the surroundingvillages for years with a 0.5 MW capacity. The first commercialgeothermal power plant in Turkey was installed in the Kızılderegeothermal field by the former Turkish Electric Authority (TEK)with the gross capacity 15MW. No other plants were constructed inTurkey until 2006. However, the MTA continued its studies and

Fig. 1. Distribution of locations with geothermal resources suitable for electricity generation and current power plants in Turkey.

N. Aksoy / Renewable Energy 68 (2014) 595e601596


explored the potential for geothermal energy production anddiscoveredmany other high-capacity fields. Table 1 includes a list ofgeothermal power plants in operation and under construction. Thetotal installed capacity of geothermal power plants was 165.8 MWin 2012. By adding new plants, the installed capacity rose to311.031 MW in 2013. It is expected to reach 444.6 MW in 2014according to EMRA records [4]. When the licenses issued by EMRAare considered, the installed capacity is predicted to be 713 MW by2015 and 1000 MW by 2020 assuming that all projects underconsideration are approved (Fig. 2). Today, 20 different drilling rigsare used to develop geothermal fields with drilling capacitiesgreater than 3000 m. Twice as many drilling rigs are used forgeothermal drilling as for the oil and gas industries. Since 2007,over 200 wells have been drilled for power generation. The deepestdrill is in Yılmazköy (Fig. 1) with a 4.250 m depth at 278 �C andyields a 150 t/h capacity. The maximum temperature in GG isapproximately >287 �C, while it is approximately >260 �C in BMG.Oil has also been observed in sedimentary units overlying meta-morphic series in the deep wells (>2500 m) drilled in the Salihli-Alasehir region in GG. While 15 of 16 installed power plants are inthe BMG region, the other plant is located in the Tuzla regiongeothermal fields. The geothermal waters of Tuzla-Çanakkale fieldconsist of NaeCl compounds with a very high salt content(>60.000 ppm). The geothermal fields in Turkey that were issuedlicenses for power production and with completed and ongoingprojects are presented below.

2.1. Kızıldere-Denizli field

In 1983, the first government-initiated power plant had a15 MW net installed capacity in six wells and was operated at a5 MW capacity for several years after its commissioning due toCaCO3 precipitationwithin thewells. Three morewells were drilledin 1987, and the average capacity increased to 9 MW. A liquid CO2production facility was installed in 1986 and has been operatingwith the plant. The plant is operated at 147�C, and its waste heat is

used for residential heating (2500 houses) in the Sarayköy district,which is near the plant. The company operating the district heatingsystem, Bereket Energy, installed a binary power plant with a7.06 MW capacity using the Kızıldere-I power plant’s waste heat in2007. The field and power plant were taken over by Zorlu Energy in2008 due to privatization. After improvements, the plant beganoperating at a 15MW capacity, and 20more wells were later drilledin the field. The wells were 2900 m deep, and the highest tem-perature is 245 �C. A triple flash-steam turbine with a 60 MW ca-pacity plus two binary units with a 20 MW capacity werecommissioned in 2013. The electricity production capacity of thefield rose to 95 MW. A new 80 MW plant is planned with 20 newwells that have been drilled to extend the capacity.

2.2. Salavatlı-Aydın field

The Dora-I geothermal power plant installed in the Aydın prov-ince Salavatlı district is a milestone for Turkey’s geothermal history

Table 1Data on geothermal-based power plants in Turkey.

Place Licence holder Unit name Capacity,MW

Type-workingfluids

Mean sourcetemperature,�C

NCG content,kg NGC/kgbrine

CO2

emissiong/kWh

Start date Manufacturer

Kizildere-Denizli Zorlu Energy Kizildere e I 15 Single flash 230 0.02e0.044 900 (xx) 1984 AnsaldoKızıldere e II 60

(10 þ 10)Triple flashþ B-R-134

[22e24] 1300 2013 Fuji-TASEnergy

Bereket E. 7.06 B-pentane 150 n/a n/a 2008 Ormat

Salavatlı-Aydın Mege Dora-I 7.95 B-pentane 170 0.015 1120 (xx) 2006 OrmatDora-II 9.5 B-pentane 172 900 (xx) 2010 OrmatDora-IIIa 17 B-pentane 165 2013 OrmatDora-IIIb 17 B-pentane 170 2014 (x) Ormat

Germencik-Hıdırbeyli-Gümüsköy Aydın

Gürmat-Burç 47.4 Double flashsteam

220 0.02 [24] 1100 2009 Mitsubishi

22.5 B-pentane 220 2014 (x) Ormat47.4 Double flash

steam230 2015 (x) Mitsubishi

BM 6.6 B-R 134 160 n/a n/a 2013 TAS Energy6.6 B-R 134 n/a n/a 2014 (x) TAS Energy

Maren Energy Irem 22 B-pentane 170 900 2011 OrmatSinem 22 B-pentane 180 0.015e0.02 900 2012 OrmatDeniz 24 B-pentane 180 900 2012 OrmatKerem 24 B-pentane 175 2014 (x) Ormat

Yılmazköy KenKipas Energy 24 B-pentane 175 0.02 2014 (x) OrmatTuzla-Çanakkale Enda Energy Enda 7.5 B-pentane 165 0.005 400 2010 OrmatSarayköy-Denizli Jeoden Energy Jeoden 0.84 B-isobutane 101 n/a ? 2012 TurbodenPamukören-Aydın Çelikler Energy Çelikler 45.02 B-isobutane 170 0.02 2013 Atlas CopcoAlasehir-Manisa Türkerler Energy Türkerler 24 B-pentane 190 0.034 [24] 2014 (x) Ormat

NCG: Non-condensable gases; B: binary type-working fluid. (x) under construction; (xx) CO2 is used in commercial gas production.

Fig. 2. Development of electricity generation by geothermal resources in Turkey. Theworld’s figures derived from Ref. [5].

N. Aksoy / Renewable Energy 68 (2014) 595e601 597


because it is the first geothermal power plant investment by theprivate sector. The work began in 2003 and was finalized bycommissioning a binary power plant with a 7.35 MW capacity in2006. The CaCO3 scaling problem, whichwas previouslymanaged bymechanical cleaning, was solved for the first time by applying aninhibitor; it serves as a model for other fields in Turkey. In addition,the first 100% re-injection application was used in this plant and hasbeen successfully sustained. The CO2 discharged from the Dora-I andDora-II units is processed in commercial dry-ice and gaseous CO2facilities near the plant; therefore, these units have been operatedwith zero emissions. A 40,000-m2 greenhouse was constructed onthe field and is heated by geothermal water. The technical and eco-nomic success of the Dora-I/II projects increased interest in Turkey’sgeothermal resources and finally resulted in issuance of the law thatregulates rights to operate and license geothermal fields in 2007. TheDora-II power plant was first operated in 2010 with a 9.5 MWinstalled capacity; Dora-IIIa has a 17 MW capacity and wascommissioned in August 2013. The Dora-IIIb units with a 17 MWinstalled capacity is planned for commissioning at the beginning2014,whereas theDora-IV unit is planned for commissioning in 2015with a 1 � 17 MW installed capacity. Based on the modular growthmethod, which is preferred for the field, Dora-I is operated with twoproduction wells and one re-injection well, and Dora-II is operatedwith two production and two re-injection wells. Dora-IIIa is alsooperated with four production and three re-injectionwells. Twenty-five total wells were drilled in the field with depths ranging between1300 and 3250 m. Although the highest temperature is 212 �C, thetemperature range feeding the power plant is between 165 and185 �C. The capacities of each well range between 5 and 9 MW. Thecirculation of the re-injected fluid is monitored using a micro-seismic grid [6] and tracer tests. All of the installed power plantsare Organic Rankine cycles (ORCs).

2.3. ÖmerbeylieHıdırbeylieGümüsköy fields

The westernmost part of BMG, where the graben changes di-rection from west to southwest, includes three geothermal re-sources: Ömerbeyli, Hıdırbeyli, and Gümüsköy. Three companies(Gürmat, Maren and BM Gümüsköy Inc.) share these resources.Gürmat produces electricity using a double flash turbine, which isthe first in Turkey with a 47.4 MW capacity. On the other hand,Maren Geothermal Energy Inc. installed 3 units with a 68 MW totalcapacity in the Germencik-Hıdırbeyli region, and 24 MW of addi-tional capacity is under construction with 24 MW more planned.Gürmat Geothermal Inc., which shares the southern part of the fieldwithMaren, has continued drilling in the field; however, the licensefor a 165.5 MW capacity plant has already been granted, and a47.4 MW double flash and a 22.5 MW binary plant is also underconstruction.

BM Gümüsköy Geothermal Energy Inc. is located on the west-ernmost edge of the graben and has obtained a license for 13.2 MW,6.6 MW of which was commissioned in 2013. The power plant willrun two productionwells and one re-injectionwell. The productionwells will have the 181 and 165 �C temperatures. The investor isplanning a concentrating solar thermal (CSP) system to improveproduction during ambient temperature extremes because air-cooled Rankine Cycle plants lose up to 40% of their peak produc-tion capacity during summer days. A commercial CO2 facility willpurify and liquefy exhausted NCG for zero emissions [7]. Anotherunit with a 6.6 MW capacity has been constructed.

2.4. Tuzla-Çanakkale field

This field contains a binary power plant, which was the firstplant constructed in KMM with a 7.5 MW installed capacity.

However, mineral precipitation due to high salt levels plugs heatexchangers, and cleaning this system leads to production loss. Thedeepest well in this field is at 1100 m, and the highest temperatureis 170 �C.

2.5. Babadag-Denizli field

The Jeoden Babada�g-Denizli geothermal power plant is oper-ated at a 101 �C minimum temperature and a 0.84 MW installedcapacity generated by 3 � 280 kW units; the plant has planned anexpansion in capacity to 2.52 MW with 9 units. The plant canproduce 600 kW gross with a 480 kW net capacity, and a 60 kg/swater flow for the ambient temperature is 24 �C. The plant isoperated with only one production well and currently lacks a re-injection well; thus, it cannot be operated full-time. If this projectis successful, small plants will be a model for low enthalpy(approximately 100 �C) and partially used fields.

2.6. Pamukören-Aydın field

A binary power plant in the Pamukören-Aydın field with a45 MW capacity was completed and commissioned end of 2013.The 2 � 22.5 MW power plant operates using 150e191 �C 2800 t/hfluid from 8wells. The average inlet and outlet temperatures for thefluid are 161 �C and 80 �C. The field investor announced that a new2 � 22.5 MW will be erected soon.

2.7. Piyadeler-Alasehir field

A 17 MW binary power plant will be commissioned in 2014 forthis field by Türkerler Geothermal Inc. Although, drilling the pro-duction and re-injection wells is in progress. This power plantoperates at 190 �C and will be the first plant constructed within GG.Zorlu Energy Inc. is located with and shares the same geothermalfield as Türkerler and announced that they will begin installing a30 MW flash-steam generation and 10 MW binary cycle powerfacility in October-2014.

2.8. Additional ongoing projects

Several fields with medium and high enthalpies suitable forpower generation development are currently being drilled,including the Karadeniz Geothermal Energy (Umurlu-Aydın),KenKipas Geothermal Energy (Yılmazköy-Aydın), ÇeliklerGeothermal Energy (Sultanhisar-Aydın), Alres Geothermal Energy(Atça-Aydın), and Kiper Energy (Nazilli- Aydın) fields in BMG aswell as the Mis Energy (Kemaliye-Alasehir-Manisa) and MaspoEnergy (Kavaklıdere-Alasehir-Manisa) fields in GG. The total ca-pacity of the above project is estimated at 200 MW.

3. Problems faced during geothermal projects

3.1. Resource risks

Low temperature and low permeability are the highest risks indeveloping geothermal resources. Exploration risks are high, and tomitigate them, the best exploration surveying practices should beimplemented, and the funds should be optimized. In addition, theoperating strategy also affects energy production. For instance, apower plant with a 50 MW capacity and 230 �C resource temper-ature requires that approximately 20 million tons of fluid are pro-duced per year and re-injected into the reservoir. The locations ofthe production and re-injection wells should be designed such thatthe re-injected fluid can regain heat energy and reach the



production wells. There is a risk that the field temperatures willdecrease due to poor re-injection design.

While problems with power generation, such as a decrease in ageothermal resource’s temperature and/or pressure, can be causedby the operator’s activities, they can also be related to activities inneighboring fields. Due to the rapid increase in geothermal-basedpower generation in Turkey and the resulting division ofgeothermal anomalies under the operation by different investors,certain fields are likely to have serious resource problems in thenear future.

Determining the potential for a geothermal field is a difficult andlife-long issue involving many uncertainties at the initial stage. Thestored heat method is a common method for determining suchpotentials at the initial stage [8e11]. Many parameters are inferredby assessing geophysical, geological, and geochemical data. Themajor weakness of this method is estimating the recovery factor.The recovery factor is a ratio between the extractable and potentialenergy of the field. It depends onmany factors, such as the porosity,permeability, temperature, pressure, and productionere-injectionstrategy. Thus, it is difficult to estimate howmuch of the calculatedpotential can be extracted in the future. However, other studiesdiscuss the stored heat method and claim that it produces several-fold overestimation [12e15]. Similar problems are also frequentlyobserved in Turkey’s district heating system projects. For instance,the Gönen Geothermal field resource, which is used for residentialheating (2500 houses), has cooled [16], and an LNG peak loadsystem had to be installed on the Balçova-Narlıdere geothermalfield, which is also used for residential heating (38,000 houses).

3.2. Risks for power generation investments

In the latest tender held by MTA, the prices dramaticallyincreased. Certain fields with only one exploration well have beenobtained for approximately 110 million USD þ VAT. Therefore, in-vestors are forced to invest in field capacities for a return of theirinvestment in a reasonable period of time. Ever-rising drilling costsfor greater depths (up to 4000 m) and subsequently greater drillingproblems as well as costs have inflated the investment costs and,consequently, risks; more highly sophisticated and expensiveexploration methods applied to deep discoveries have encounteredsimilar problems. Certain geothermal investors are already feelingthe effects from such risks and have temporarily shut down oper-ations; some are looking for partners to share the risks, whileothers are considering selling their licenses. On the other hand,certain financial institutions refrain from giving loans forgeothermal operations in times of crisis and/or have consideredcalling back loans already given. These risks also disturb the in-vestment environment. Integrated Resource Management (IRM)[17,18] can be defined as a group of processes that add value to aresource through its characteristic and proposed method for sus-tainable production and conserving natural resources and theenvironment. The IRM approach could be a solution for reducingcosts and generating savings through optimizing operations,thereby mitigating the risks involved with these investments.

3.3. Problems related to the environment

CO2 is a colorless and odorless gas that is generally released inthe atmosphere fromburning. Experts state that the CO2 increase inthe atmosphere might lead to glacier melting, global warming,floods, forest fires, elevated sea levels, and lower bio-diversity. It isaccepted that renewable energy resources, such as solar, wind,ocean waves and geothermal heating, can contribute greatly toreducing greenhouse gas emissions. Gases such as CO2, H2S, NH3,N2, H2, and CH4 are generally found in steam and are invariably

present in geothermal discharges from both natural features andwells. These gases are often collectively referred to as the ‘non-condensable gases’ (NCG) because they do not condense (becomeliquid) at the pressure used in electricity-generating cycles andmust, therefore, be extracted from the condenser. They are usuallyexhausted to the atmosphere if the H2S levels do not exceedenvironmental standards [19]. The vast majority of NCG (95e99%)is CO2, while the remainder is H2S and CH4. H2S emissions (up to 3%of all NCG) encountered during drilling, workover or productionhave caused severe danger to workers’ lives and disturbed thepeople living in the near area due to the noxious fumes. Bloomfieldet al. [20] compared resources used for electricity generation in theUSA and reported that geothermal resources produce the lowestCO2 emissions. Bertani and Thain [21] stated that 2% of geothermal-based power plants have CO2 emissions of at least 0.5 kg/kWh,whereas 50% have 0.1 kg/kWh or fewer emissions. On the otherhand, the geothermal power plant CO2 emissions in Turkey differ.While new-generation thermal power plants running on coalrelease 0.6e0.8 kg/kWh CO2 into the atmosphere, emissions fromthe geothermal power plant located in BMG vary between 900 and1150 g/kWh (Table 1). The power plants to be constructed in Ala-sehir in GG will emit NCG up to 1400 g/kWh; combined with thehigh CO2 levels in geothermal fluid have created unique conditionsin Turkey (Fig. 3). A d13C isotope analysis can provide informationon the origin of the CO2. The d13C values are 0.07e0.17 for theKizildere [25] field and 0.86 per mill for Hidirbeyli, which indicatesthat CO2 is released due to thermal decomposition of marine-carbonated rocks [26]. The sources within BMG and GG areformed from carbonate rocks, such as marble, limestone, andcalcschist, the thermal decomposition of which releases CO2. TheCO2 released from geothermal power plants is typically 98e99%pure; thus, it can be used as industrial CO2 and for dry-ice pro-duction. A facility on the Kızıldere field processes the CO2 releasedfrom the 15 MW geothermal power plant. It is used for dry-iceproduction, with a capacity of 40,000 tons/year after CO2 purifica-tion. CO2 production factories are also near the Dora-I and Dora-IIplants with the total capacities 40,000 and 80,000 tons/year,respectively. Forty percent of the Turkish CO2 market demand isprovided by geothermal sources. Because the production is alreadygreater than the demand for CO2 production in the region, the newplants no longer demand CO2.

Re-injection, which could control surface pollution created bygeothermal fluids, has not seriously been attempted by either stateinstitutions or the private sector for a long time. Releasing waste-water into rivers, creeks and even sewer systems was a commonpractice by geothermal energy producers. Recent, successful 100%re-injection operations in the Salavatlı, Hıdırbeyli, and Ömerbeylifield created an excellent example for the geothermal industry as a

0 500 1000 1500

Natural Gas

Oil

Coal

Hydropower

GPPs in Turkey

CO2 emissions gr/kWh

Fig. 3. CO2 emission contribution from geothermal power plants (GPP) in Turkey.Except for Turkey, the values were taken and modified from Ref. [22].



whole; these good examples have encouraged the state to bettercontrol wastewater pollution. Encouragingly, the energy ministryno longer provides operation licenses unless a sound re-injectionsystem is included; much work remains for this aspect becauselarge volumes of wastewater continue to be released to the surface.

Serious environmental problems can arise during drilling. At a1011 m depth, a well drilled in Alasehir field incurred a blowout inspring of 2012. The pressure continued to increase after the pre-venter was shut down to control the well, and the formation wasquickly fractured with hot water blowing out through the detach-ment fault and reaching the surface at 100 m in the northewestdirection. Later, three more blowouts occurred and the landcollapsed with holes at 2e8 m in diameter. The drilling rig was alsodismantled and removed from the field because the formationsaround the rig were broken, and some of the containers weredamaged (Fig. 4). Next, the rig location incurred an explosion,which threwmud, stone, and rock pieces around the well. Efforts toreach the well through drilling a relief well and taking control alsofailed. The drilling location is surrounded by vineyards and400,000 m2 of vineyard was damaged due to explosions. Thus, thelocal community fought against continued drilling, citing the risk ofexplosion. Although the flow has decreased, fluid continues to flowfrom this uncontrolled well. Because the waters spreading from thewell contain high pollutant densities (such as Na, B, and As), theregion is at risk for soil and groundwater pollution.

3.4. Inadequate power plant type selection

Flash-type plants are used to produce steam that drives theturbines. Steam is gathered from geothermal brine throughdecreasing its pressure. If the geothermal source has high enthalpyand pressure, the geothermal brine can be flashed in two or threestages. If the geothermal source has a low enthalpy (<600 kJ/kg), itis difficult to construct a flash-steam plant [27]; binary plants arethen used with working fluids, such as pentane, isobutene and R-134, in a closed cycle. The working fluid receives heat from thegeothermal fluid, evaporates, expands through prime mover, con-denses and is returned to the evaporator through feed pumps.Turkey includes several types of geothermal power plants, namelysingle flash, double flash, triple flash and binary Rankine cycles.

Adequate binary cycles could be used according to the resourcetemperatures to increase the cycle efficiencies. To increase the flashprocess efficiencies for high enthalpy resources, double flash pro-cesses were introduced in the 1960s. However, these processes arenot compatible with geothermal resources with high NCG levels,such as in Turkey, which results in high parasitic load losses for NCGelimination in condensers [28]. In addition, supersaturated amor-phous silica precipitation in pipes and re-injection wells is a global,endemic problem for this type of fluid production and double flashprocess coupling. Combined cycles could be a solution for theaforementioned problems.

4. Discussion

Liberalizing the energy market, which comprised creating alegal infrastructure for geothermal resource use and licensing,subsidized tariffs for power generation via renewable resources,and government purchasing guarantees, created a geothermal en-ergy sector in Turkey that is globally relevant. However, this rapiddevelopment also has certain risks; the most significant is over-estimating the resource potential and where more than one oper-ator shares the same reservoir. These risks might jeopardize theresource sustainability if they are not controlled and mitigated. TheUSA has also encountered similar problems. The Geysersgeothermal field was discovered in 1960 in the USA and has been

competitively operated by multiple companies for power genera-tion. As a result, the field’s productivity and reservoir pressuresubstantially decreased in 1987e1988. Production in the fieldbecame uneconomic due to a collapse in oil and gas prices that alsoaffected the geothermal sector during the same years. More than600 wells were drilled between 1960 and 1991, when competitiveproduction dominated the field. The significant decrease in powerdrew the attention of the California Energy Commission in 1992,which re-injected the waste fluid into the reservoir to solve thisproblem. Because the economic burden of this responsibility couldnot be assumed by the operators and the income dramaticallydecreased, certain investors left the field, and the field has beencontinuously unified. Finally, two investor companies remained tooperate the field, and production began to increase. A simultaneous9% decrease in electricity generation, which began in 1988,decreased to 2% in 2003 [29]. In contrast to the Geysers case, theMedicine Lake geothermal field, which is located in California, USA,was discovered by three oil companies in 1980, which identifiedtwo dozen temperature gradient wells through drilling and unifiedas the Glass Mountain Federal Unit beginning in the same year [30].

Barbier [19] reports that the CO2 geothermal emissions are inthe range 0.01e0.4 kg/kWh and that carbon taxes would impactgeothermal power production with an extra charge at 0.04e1 cent/kWh. Certain geothermal power plants in Turkey also use of carbontrading in the voluntary carbon market, which yield approximately20,000 USD/MW-year in income. Zero emission production isapplicable for projects inwhich released NCG is sold to CO2 facilitiesinstalled near power plants. However, because the commercial CO2market is near the saturation point, new projects may not be able touse this benefit. Currently, the geothermal sector in Turkey faces alarge risk from the Kyoto Protocol of United Nations Climate Change

Fig. 4. Disaster during drilling operation, Alasehir field. Broken formation between rigand vineyard. Damaged containers and the destroyed vineyard can be seen at the back.Photo taken from the rig floor.



Agreement that Turkey signed in 2009. However, Turkey has notmade a commitment regarding decreasing greenhouse gas emis-sions, even if its determination on this issue was expressed bysigning the Kyoto Protocol. Geothermal power plant owners mustmake large-scale investments if Turkey commits to decreasinggreenhouse gases emissions.

NCG also causes production losses in steam turbines and binaryplants. The steam turbine power decreases due to additionalpressure at the turbine outlet from partial pressure of the NCGwhich is removed by injectors or compressors from the steamturbine outlet, leading to huge power losses. In binary plants, due tothe high volume of NCG, the heat exchanger efficiency decreases,thereby causing power loss. The power loss due to the increasedNCG levels is much greater in steam turbines than binary plants[28].

5. Conclusions

As mentioned above, Turkey’s geothermal power capacity willlikely to reach 1000 MW in 2020. Simultaneously, the world’sgeothermal power capacity is also increasing (Fig. 2). Rapid growthcarries certain critical risks. Geothermal resource management is along-term job; it requires time to gather data from the reservoirand to monitor and model the resource. Pressure decrease andcooling are large potential risks for the geothermal reservoirs.Before a decision to extend the capacity, the reservoir’s response toand behavior in current production should be understood. Unfor-tunately, attractive incentives, high profits and competition forcecertain investors to take high risks.

Where different firms share the same geothermal anomalies,the resource and their investments can be harmed. Unfortunately,regulations have not been generated for this issue. In the oil sector,unitization applies when oil reserve licensees pool their individualinterests in return for an interest in overall units; it is then operatedby a single company on behalf of a group, which occurs when a fieldlies under different licenses with different equity interests.Voluntary cooperation by license holders for the same anomaly orobligatory unitization, where necessary, is, therefore, important forsustainable production using geothermal resources; a new regu-lation should be propagated to manage this issue.

Due to high CO2 emissions, such investors must purchase morecarbon certificates than coal-fired thermal power plant investors tobalance their carbon emissions, which would be tragic for thissector in Turkey. Currently, this sector is fortunate because thegases released from geothermal power plants are pure and do notcontain such pollutants as ash and dust. These gases are releasedfrom condenser inlets in steam turbine plants and from heat ex-changers in binary plants. Therefore, the geothermal power plantscan be operate with zero emissions if gas emissions can be dis-solved into hot water (80e125 �C) at the outlet of the plant and re-injected into the reservoir. Although they are less efficient units,binary plants can produce much more net power than steam tur-bines under specific circumstances, which is another factor thatshould be considered by investors in Turkey, where the geothermalfields contain high levels of NCG.

Acknowledgments

The author would like to thank to the reviewers for the manyuseful and constructive comments and suggestions.

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