International Geothermal Development World Geothermal ... · International Geothermal Development. be considered as part of installed capac-ity, but may be accounted for separately

GRC BULLETIN88 MAY / JUNE 2006 89

International Geothermal Development

Editor's Note: The following article is published in the GRC Bulletin by special permission of Geothermics, the International Journal of Geothermal Research and its Applications (Elsevier), Vol. 34, No. 6, December 2005, pp. 651-690. This rendition of the article underwent minor editing to GRC Bulletin style.

A review has been made of all the country update papers submitted to the World Geothermal Congress

2005 (WGC2005) from countries in which geothermal electricity is currently being generated. The most significant data to emerge from these papers, and from follow-up contacts with representatives of these countries, are:• A total of 24 countries now generate

electricity from geothermal resources;• Total installed capacity worldwide is

approximately 8,930 megawatts-elec-tric (MWe), corresponding to about

World Geothermal Power Generation 2001 – 2005

By Ruggero Bertani – Enel, Generation and Energy Management -Renewable Energy - Geothermal Production

8,030 MWe running capacity and electric energy production of nearly 57,000 giga-watt-hours (GWh) (early 2005 data);

• Costa Rica, France (Guadeloupe), Ice-land, Indonesia, Italy, Kenya, Mexico, Nicaragua, Russia, and the United States have increased the capacity of their geo-thermal power plant installations by more than 10 percent with respect to the year 2000;

• New members of the geothermal electric-ity generating community include Aus-tria, Germany and Papua New Guinea;

• Installed capacity in Argentina and Greece is now null since their geother-mal power plants have been dismantled; and

• 19 countries have carried out significant geothermal drilling operations since 2000, with 307 new wells.

Introduction This paper discusses the latest develop-ments in geothermal electricity generation worldwide. It focuses on changes with respect to previous similar reports (Hut-trer 1995, 2000, 2001). For each country producing electricity from geothermal re-sources, information from relevant Coun-try Update Reports presented at the World Geothermal Congress 2005 (WGC2005, convened on April 24-29, 2005 in Antalya, Turkey) has been integrated with first-hand data provided by members of the Interna-tional Geothermal Association (IGA). De-tailed information is not provided here, but can be readily obtained from papers listed under References. The primary objective of this paper is to identify geothermal fields currently under exploitation to generate electricity, their characteristics (e.g. reservoir depth, and fluid temperatures and pressures), and the status of operating geothermal power plants. Limited emphasis is given to data on geothermal field potential. A summary of data is provided in Table 1, including geothermal capacities in early 2005; annual energy production; number of geothermal units installed; percentage of national power capacity that is contributed by geothermal; and the percentage of en-ergy produced nationally from geothermal resources. Changes in installed geothermal power generating capacity worldwide over the last 10 years are presented in Table 2. Before proceeding further, two terms frequently used in this paper should be de-fined. Installed capacity (in MWe) is the reference value for power plants, set by the manufacturer as its target output when the facility is operating under design con-ditions. Possible reserve units should not

Figure 1. Installed geothermal capacity and electricity generation 1995-2005.



be considered as part of installed capac-ity, but may be accounted for separately. Running capacity (in MWe) is the highest average value over a one-hour period of output from a power plant, measured at the generator transformer supply volt-age terminals, while operating at stated design conditions or corrected to design point conditions (Spielberg-Planer et al., 2001). Running capacity can be correlated directly with energy produced and with relevant reservoir characteristics (Table 3). The main characteristics of geothermal fields worldwide are presented in Table 3. The table includes only fields providing at least a few MW running capacity and fields for which at least some relevant data were available. It is worth recalling the final part of the message delivered during the World Geothermal Congress 2000 by Dr. Phillip

Country Installed Running Annual Energy Number Percent of Percent of Source Capacity Capacity Produced of Units National National of Data (MWe) (MWe) (GWh/y)1 Capacity Energy

Australia 0.2 0.1 0.5 1 negligible negligible WGC05Austria 1.2 1.1 3.2 2 negligible negligible WGC05China 28 19 96 13 30% of Tibet 30% of Tibet WGC05Costa Rica 163 163 1,145 5 8.4 15 WGC05El Salvador 151 119 967 5 14 22 WGC05Ethiopia 7.3 7.3 0 2 1 n/a WGC05France (Guadeloupe) 15 15 102 2 9 9 WGC05Germany 0.2 0.2 1.5 1 negligible negligible WGC05Guatemala 33 29 212 8 1.7 3 WGC05Iceland 202 202 14,838 19 13.7 17.2 WGC05Indonesia 797 838 6,085 15 2.2 6.7 WGC05Italy 791 699 5,340 32 1.0 1.9 WGC05Japan 535 530 3,467 19 0.2 0.3 WGC05Kenya 129 129 1,088 9 11.2 19.2 WGC05Mexico 953 953 6,282 36 2.2 3.1 WGC05New Zealand 435 403 2,774 33 5.5 7.1 WGC05Nicaragua 77 38 271 3 11.2 9.8 WGC05Papua New Guinea (Lihir island) 6 6 17 1 10.9 n/a WGC05Philippines 1,930 1,838 9,253 57 12.7 19.1 WGC05Portugal (Sao Miguel island) 16 13 90 5 25 n/a WGC05Russia 79 79 85 11 negligible negligible WGC05Thailand 0.3 0.3 1.8 1 negligible negligible WGC05Turkey 20 18 105 1 negligible negligible WGC05United States 2,564 1,935 17,917 209 0.3 0.5 WGC05

Total 8,933 8,035 56,786 490

Table 1. Worldwide geothermal power generation in early 2005

Wright, IGA President at that time: “At the 1975 United Nations Conference on Geo-thermal Energy, held in San Francisco, Cali-fornia, Dr. Patrick Muffler (USGS, retired) reported that some 1300 MW of geothermal electrical power generation capacity were installed in 10 countries. At this meeting, WGC2000, Mr. Gerry Huttrer (Geothermal Mgmt. Co., Inc. – Frisco, CO) reported that installed geothermal generation capacity has reached 7,974 MW in 21 countries. In 25 years, we have added 6,700 MW of installed capacity around the world. This amounts to an average of only 270 MW of new geother-mal generating capacity per year since Dr. Muffler’s report in 1975, and an average of only 240 MW of new geothermal genera-tion capacity per year since WGC1995 in Florence, Italy. Mr. Huttrer also reported that the worldwide electrical energy pro-duction from geothermal power plants has

reached 49,000 GWh per year. Energy production is a much better measure of our contribution than installed capacity, because geothermal power plants usually operate at a higher capacity factor than other types of power plants. But how are we to understand this figure of 49,000 GWh/y of energy pro-duction? To help form a perspective, let us note that the International Energy Agency reports that total electricity consumed worldwide in 1996 was 13,700,000 GWh. In other words, geothermal energy accounts for less than 0.4 percent of the world’s total electricity consumption.” The trend has not improved since 2000. Installed geothermal capacity has increased by approximately 960 MWe (Fig. 1 and Table 2), or only about 190 MWe per year added during the 2000-2005 period. World-wide, the contribution of geothermal to total electricity generated is less than half of one



percent. World net electricity generation for 2003 was 15.8 million GWh/y (U.S. Department of Energy, www.eia.doe.gov/pub/international/iealf/table63.xls), while geothermal generation was only 0.057 million GWh per year. Figure 2 is a world map showing coun-tries that generate electricity using geother-mal resources, and their installed capacity in early 2005. Changes in installed capacity during the last 30 years, as well as changes in electricity generation between 1995 and 2005, are reported in Table 4. Recent increases in oil prices and pre-dicted decline in oil reserves during the coming years could lead to a boost in the amount of geothermal electricity produced. However, this will be affordable only with appropriate government policies and regu-lations, and with some sort of incentives to attract investors. The acceptance of the Kyoto Climate Change Protocol by many countries might also help the geothermal electricity market achieve a one-percent share in world electricity production by 2010. This is still a long way from fulfilling the world’s renewable energy target, but for the next five years it is a reasonable objec-tive with geothermal technologies currently available.

Country 1995 2000 Early 2005 2000-2005 Percent (MWe) (MWe) (MWe) Increase (MWe) Increase

Australia 0.2 0.2 0.2 0 unchangedAustria 0 0 1.2 1.2 new plantChina 29 29 28 -1 unchangedCosta Rica 55 143 163 20 14%El Salvador 105 161 151 -10 -6%Ethiopia 0 7.3 7.3 0 unchangedFrance 4.2 4.2 15 10.8 250%Germany 0 0 0.2 0.2 new plantGuatemala 0 33 33 0 unchangedIceland 50 170 202 32 19%Indonesia 310 589 797 208 35%Italy 632 785 791 6 1%Japan 414 547 535 -12 -2%Kenya 45 45 129 84 186%Mexico 753 755 953 198 26%New Zealand 286 437 435 -2 unchangedNicaragua 70 70 77 7 11%Papua New Guinea 0 0 6 6 new plantPhilippines 1,227 1,909 1,930 21 1%Portugal 5 16 16 0 unchangedRussia 11 23 79 56 243%Thailand 0.3 0.3 0.3 0 unchangedTurkey 20 20 20 0 unchangedUnited States 2,817 2,228 2,564 336 15%

Total 6,833 7,972 8,933 961 13%

Table 2. Variation in installed geothermal generating capacity worldwide between 1995 and early 2005.

Figure 2. Geothermoelectric installed capacity worldwide in early 2005.


Country Field Drilled Area Type of Reservoir Reservoir Production Reinjection Capacity (km2) Reservoir Depth (m) Temperature (°C) Wells Wells (MWe)

China Yangbajain 4 Liquid 200 140-160 12 6 15Costa Rica Miravalles 30-35 Liquid 1000-2000 240 32 20 163El Salvador Ahuachapán 3-4 Liquid /Steam 600-1500 230-240 19 5 63El Salvador Berlín 2-3 Liquid 2000-2500 300 9 15 56France Guadeloupe 4 Liquid 300-1100 250 6 n/a 15Guatemala Amatitlán 6-9 Liquid /Steam 1000-2000 300 4 n/a 5Guatemala Zunil I 4 Liquid 1500-2300 300 6 2 24Guatemala Zunil II 8-10 Liquid /Steam 800-1200 240 2 n/a 5Iceland Krafla 5-6 Liquid 300-1200 190-210 20 2 60 1000-2000 240-340Iceland Nesjavellir 6-8 Liquid 1000-2000 270-320 15 n/a 90Iceland Svartsengi 6-8 Liquid /Steam 1000-2000 240 10 1 46Indonesia Darajat 10 Steam 2000 245 17 n/a 135Indonesia Dieng 12 Liquid 1000-2000 280-330 25 n/a 60Indonesia Kamojang 15-20 Steam 1400-1600 245 29 n/a 140Indonesia Lahendong 4 Liquid 1000-2000 260-330 15 n/a 20Indonesia Salak 20-25 Liquid 1000-2000 240-310 30 15 371Indonesia Wayang Windu 30 Liquid 1000-2000 250-270 18 n/a 110Italy Bagnore 5 Liquid 1000-3000 200-330 7 4 19Italy Larderello 250 Steam 1000-4000 150-270 180 23 473 350Italy Piancastagnaio 25 Liquid 1000-3000 200-300 19 11 60Italy Travale 50 Steam 1000-4000 190-250 22 0 147 Radicondoli 350Japan Kakkonda 6 Liquid/Steam 500 1000 230-260 29 29 80 2500-3000 350-360Japan Matsukawa 4 Steam 1000-1500 260 10 1 24Japan Mori 6 Liquid 500-1500 230-250 10 9 50 2000-2500Japan Ogiri 8 Liquid 1000-2000 260 11 6 30Japan Onikobe 8 Liquid 500 1000 250 7 7 12Japan Otake 8-10 Liquid 1000-2500 240-300 20 13 122 Hatchobaru Japan Sumikawa 5 Liquid 1500-2500 250 8 12 50Japan Takigami 5 Liquid 2000 160-260 5 9 25Japan Uenotai 9-10 Liquid 1000-2000 300-320 9 3 29Japan Yanauzu 10 Liquid 1000-2600 270-320 19 2 65 NishiyamaKenya Olkaria E 5 Liquid 500-2000 250-300 26 0 45Kenya Olkaria NE 9 Liquid 1800-2700 250-300 9 n/a 12Kenya Olkaria W 12 Liquid 1000-2000 250-300 1 n/a 70Mexico Cerro Prieto 150-200 Liquid 2800 300-340 149 9 720Mexico Las Tres Vírgenes 30 Liquid 2100 280 4 2 10Mexico Los Azufres 35 Liquid/Steam 1600 150-200 29 6 188 2000-3000 280-300Mexico Los Humeros 20 Liquid 1000-2000 290-320 17 2 35New Zealand Kawerau 2 Liquid 1000-2000 240-300 6 2 14New Zealand Mokai 12 Liquid 2000 270-320 4 3 51New Zealand Ngawha 25 Liquid 600-2800 220-240 2 2 9New Zealand Ohaaki 5-8 Liquid 1500-2500 230-280 24 n/a 96New Zealand Rotokawa 25 Liquid 2000-2500 270-330 2 3 29

Table 3. Main characteristics of geothermal fields worldwide (early 2005).



Geothermal Power GenerationActivities During 2001-2005 This section highlights new geothermal projects worldwide that were initiated and completed between 2000 and 2005. Power plants that started up after the year 2000, but related to activities that began earlier, have not been included. New installed ca-pacities are reported in Table 5. Facilities currently under construction, for a total of 551 MWe, are listed in Table 6. It is also possible to estimate short-term prospects for additional installed capacity, as there are some geothermal projects needing only financing and final approval for plant construction. It is real-

istic to expect an increase of at least 1,300 MWe in installed capacity worldwide before 2010. These projects (or areas) are: Deep Yangbajain field (China); Miravalles, Rincón de la Vieja, Las Pailas, Borinquen (Costa Rica); San Vincente, Chinameca, Obrajuelo, Cuyanausul (El Salvador); Langano (Ethiopia); Bouillante III (France, Guadeloupe); Amatitlán, Zunil (Guate-mala); Hellisheidi, Reykjanes (Iceland); Darajat, Lahendong, Kamojang (Indone-sia); Larderello, Travale, Bagnore (Italy); Olkaria (Kenya); Los Humeros, La Prima-vera (Mexico); Wairakei (New Zealand); San Jacinto-Tizate (Nicaragua); Northern Negros (Philippines); Terceira (Azores,

Portugal); Kamchatka-Mutnovsky, Kuril Islands (Russia); Glass Mountain, Salton Sea (California), Steamboat, Desert Peak (Nevada), and Cove Fort-Sulphurdale (Utah). Considering these short-term prospects (at least 1,300 MWe more) and power plants already under construction or likely to be installed (additional 551 MWe), the forecast for world installed capacity by 2010 is ap-proximately 10,800 MWe (Fig. 3).

Country Reports onGeothermal Power Generation The situation in each country currently producing electric energy from geothermal

New Zealand Wairakei 15 Liquid/Steam 1000-2000 160-260 60 n/a 204Nicaragua Momotombo 4 Liquid 300-800 180-200 12 4 38 800-1700 200-240Papua 1700-3000 240-300New Guinea Lihir 3-5 Liquid/Steam 300-1000 250-300 3 n/a 6Philippines Bac-Man 25-30 Liquid 1000-2000 260-280 24 12 150Philippines Mak-Ban 14 Liquid 900 345 72 21 402 3400Philippines Mt. Apo 8 Liquid 500 240-280 16 4 108 1500Philippines Palinpinon 15-20 Liquid 2000-3000 280-320 43 26 192Philippines Tiwi 13 Liquid 900 320 43 16 263 2800Philippines Tongonan 120-150 Liquid 1000-2000 260-300 75 26 723 2000-3000 300-320Russia Mutnovsky 12-15 Liquid/Steam 700-2500 240-300 17 4 62Russia Pahuzhetka 1-2 Steam 300-800 180-210 7 n/a 11Turkey Kizildere 4 Liquid 500-1000 240 15 2 17USA-CA Casa Diablo 12 Liquid 200 160 8 5 27USA-CA Coso 20 Liquid 500-3500 200-330 90 20 230USA-CA East Mesa 24 Liquid 1500-2500 150-190 35 44 98USA-CA Heber 5 Liquid 1200-1800 160-180 21 23 65USA-CA Salton Sea 16 Liquid 1000- 2500 290-310 31 26 336USA-CA The Geysers 100 Steam 600-3000 300 424 43 888USA-HI Puna 1-2 Liquid 2000 200-300 3 4 27USA-NV Brady 10 Liquid 300-700 180 6 9 21USA-NV Beowawe 3 Liquid 1000-2500 215 3 1 16USA-NV Dixie Valley 5 Liquid 1800-2500 230 7 10 68USA-NV Soda Lake 8 Liquid 500-1500 180 5 5 17USA-NV Steamboat 5 Liquid 200-800 160 11 5 66USA-NV Stillwater 16 Liquid 1000-1500 160 4 3 13USA-UT Roosevelt 3 Liquid 500-2000 240-270 4 3 20

n/a: data not available; this table includes only fields providing at least a few MW running capacity and for which some relevant data were available.


Country Field Drilled Area Type of Reservoir Reservoir Production Reinjection Capacity (km2) Reservoir Depth (m) Temperature (°C) Wells Wells (MWe)


resources, along with relevant data, is de-scribed in the following pages. Tables and figures are provided only for countries, but in the case of the United States, information is provided for states with more than 200 MWe installed capacity.

Australia. At the moment, only one unit is generating electric power from geo-thermal resources, the 150-kilowatt (kW) binary cycle plant at Birdsville, southwest Queensland (Chopra, 2005). Electricity demand for the small town of Birdsville follows a familiar seasonal pattern, with highest demand in the hot summer months when air-conditioning is used extensively (250 kW) and relatively low demand in winter (120 kW). The geothermal power plant, with a nominal power rating of 150 kWe, supplies the baseload, using 98°C fluid from a 1,200 m well. The power plant, installed in 1992, was upgraded and refurbished in 1999, and is currently in operation. Australia has also conducted research on Hot Dry Rock (HDR) technol-ogy. The most advanced project is in the Cooper Basin region of northeastern South Australia, where two wells have already been completed, for a total drilled depth of 6 km. A third is scheduled to reach 4 km. So far, downhole measured temperatures are 248°C, but stabilized conditions have not yet been reached. The government's Mandatory Renewable Electricity Target (MRET) Scheme introduced in 2001 re-quires that by 2010 approximately 2 percent of Australia’s annual electricity needs be supplied by renewable energy resources. Geothermal energy, and in particular, HDR technology, are expected to contribute to these goals.

Austria. Geothermal research is fairly active in Austria, but focused mainly on tapping low-temperature geothermal waters for use in balneology. Two small binary power plants have been installed, at Altheim (in the northwest) and Blumau (in the southeast) (Goldbrunner, 2005). Altheim is an excellent example of a successful geothermal exploration and exploitation project by a small community (5,000 inhabitants). A production/injection doublet with bottomhole at 2,500 m pro-duces fluid at a wellhead temperature of

Year Installed Capacity (MWe) Electricity Generation (GWh/y)

1975 1,300 n/a1980 3,887 n/a1985 4,764 n/a1990 5,832 n/a1995 6,832 38,0352000 7,972 49,2612005 8,933 56,786

Table 4. Variation in geothermal installed capacity over the last 30 years, and in geothermal electricity generation over the last 10 years.

Figure 3. Predicted increase in installed geothermal power generation capacity worldwide to 2010.

Table 5. Geothermal power plants that came on line during the 2000-2005 period.

Country New Project Completed in 2000-2005 MWe

Costa Rica Miravalles V 18France Guadeloupe-La Bouillante II 10Iceland Nesjavellir 30Indonesia Sulawesi-Lahendong 20Italy Larderello, Travale, Bagnore 250Kenya Olkaria II & III and Oserian 86Mexico Los Azufres and Las Tres Vírgenes 110Nicaragua Momotombo 7Papua-New Guinea Lihir 6Philippines Leyte-Tongonan 22Russia Kamchatka - Mutnovsky 50United States Salton Sea V 60

Total 669

Editor's note: For the United States, the table does not include new geothermal projects brought online during 2005 at Heber (10 MW) in Imperial Valley, CA, and the Steamboat Geothermal Complex (20 MW) at Reno, NV. Personal communication, Dan Schochet, ORMAT 6/9/06.



105°C. The fluid is utilized both for district heating and for electricity generation, in an Organic Rankine Cycle (ORC) power plant. Net output is 500 kWe, after accounting for a 350-kWe parasitic load, mainly for a sub-mersible pump. The Blumau project taps the hottest geothermal water in Austria found so far: 110°C at 2,000-3,000 m depth. It is used to heat a spa facility and to generate electric-ity in a 180-kWe net output ORC plant that has been in service since 2001.

China. Geothermal exploration effectively began in China in the early 1970s. During the socialist economy, geothermal explora-tion was managed by government entities using public funds. Productive wells were transferred free-of-charge to the final user. Since the mid-1980s, as a result of priva-tization and liberalization of the economy, there has been a steady decrease in national investment in geothermal exploration. No new geothermal power plants were commis-sioned in the period 2000-2005 (Battocletti and Zheng, 2000; Zheng et al., 2005). The only fields used for electricity generation are those in Tibet. The most important of the Tibetan fields is Yangbajain, with eight double-flash units for a total capacity of 24 MWe. Eighteen wells with an average depth of 200 m tap a shallow, water-domi-nated 140-160°C reservoir. The field covers an area of only 4 km2, although there are clear indications that the thermal anomaly is spread over 15 km2. Annual energy pro-duction is approximately 95 GWh, about 30 percent of the needs of the Tibetan capital, Lhasa. A deeper, high-temperature reservoir has been discovered at Yangbajain, but has not yet been exploited. A 2,500 m deep well was drilled in 2004, reaching the deep reservoir at 1,000-1,300 m. Temperatures in the 250-330°C range have been measured at 1,500-1,800 m depth. Geothermal potential for Yangbajain is estimated at about 50-90 MWe. A total of 80 geothermal wells have been drilled in Tibet for electric-ity production, to an accumulated depth of 20 km. Additional plants have been installed in Langju, western Tibet (two 1-MWe dou-ble-flash units) and a 1-MWe binary power station (using brine at inlet temperature of 110°C) in Nagqu. Two small 300-kWe plants are operating in Guangdong and Hu-nan. In Taiwan, a 3-MWe single-flash unit

Figure 4. Location of geothermal fields, power plants and volcanoes in El Salvador(from Rodriguez et al., 2005).

Country Geothermal Field/Power Plant Installed Capacity (MWe)

El Salvador Berlín III 40Guatemala Amatitlán Hybrid Plant 20Iceland Nesjavellir, Hellisheidi and Reykjanes 210Italy Larderello 60Mexico La Primavera 50New Zealand Wairakei, Rotokawa and Mokai 55Nicaragua San Jacinto-Tizate 10Papua New Guinea Lihir 30Philippines Palinpinon 20Portugal Azores-Pico Vermelho 16Russia Kamchatka, Mutnovsky and Pauzhetka 40

Total 551

Table 6. Geothermal power plants under construction in early 2005.

went online in the Qingshui field in 1981 (the reservoir is shallow, less than 500 m depth, with 150-220°C temperatures). A 300-kWe binary unit (Tu Chang) was installed in the same field, exploiting fluid with a maximum temperature of 170°C. In 1994, both power plants stopped operations.

Costa Rica. The only operational field in Costa Rica is Miravalles, which extends over a 20-km2 area. The reservoir, at 1,000-2,000 m depth, is water-dominated with a temperature of 240°C (Mainieri and Robles, 1995). The first power plant (single-flash,

55 MWe) came online in 1994, followed by a small 5-MWe wellhead back-pressure unit and a second single-flash 55-MWe unit (Miravalles II) in 1998. In 2000, Miravalles III (single-flash 29.5 MWe), and in 2003 the binary Miravalles V (18 MWe), brought to-tal installed generating capacity in the field to 162.5 MWe. Total electricity generated in 2003 was 1145 GWh/yr (Mainieri, 2003; Mainieri, 2005). The project uses 52 deep wells (32 for production and the remainder for gravity injection). The binary Miravalles V has been the major improvement since 2000. This power plant exploits heat from



separated brine on the injection streamline. At present, geothermal installed capacity represents 8.4 percent of the country’s total, and 15.1 percent of electricity produced. To date, 131 geothermal wells have been drilled in Costa Rica, to a total depth of 124 km. There are plans to extend the Mi-ravalles field further eastward. Recently, well PGM-55, drilled to 1.5 km, identified a new high-permeability productive zone, hydraulically connected with the reservoir presently under exploitation. The potential of this well is estimated at 4 MWe. Since it is located near a protected natural area (virgin rain forest), directional drilling will be required for environmental reasons. This will be the first time in Costa Rica that mul-tiple wells are drilled from the same pad. Geothermal energy is the second most im-portant contributor to electricity generation in Costa Rica. It is of strategic economic importance, because of the country’s strong dependence on imported oil for its thermal power plants. Although these facilities represent 17 percent of total installed ca-pacity, they contribute only 2 percent of

electricity produced annually. With such important geothermal (and hydropower) resources available, it is possible to oper-ate the oil-burning plants as reserve units. In the northern part of the country near the Nicaraguan border, a second geothermal area near the Rincón de la Vieja volcano will be exploited in the near future. On the southern slope of the volcano, in the Las Pailas field, five exploration wells were drilled in 2001-2002. A proven resource associated with the 250°C reservoir is es-timated at 18 MWe, with possible expan-sion to 35 MWe. On the northwestern slope of the Rincón de la Vieja volcano, in the Borinquen field, the first of four planned exploratory wells is being drilled. Prelimi-nary results have confirmed the presence of an important thermal anomaly.

El Salvador. Electricity has been gen-erated from geothermal resources in El Salvador since 1975 (Rodriguez and Herrera, 2005). In the competitive energy market adopted in this country, geothermal electricity supplies 22 percent of national

requirements, with production in 2003 of 967 GWh. There are two major geothermal fields, Ahuachapán and Berlín (Fig. 4). The Ahuachapán field has been exploited since 1975, with three condensing units (two 30-MWe single-flash, and one 35-MWe dou-ble-flash). Because of reservoir decline, only two of the three units are currently in operation. A project for reaching the units’ full capacity (Ahuachapán optimization) is underway. The 230-240°C reservoir is at shallow depth (600-1,500 m). There are 19 production and five reinjection wells over a 3-4 km2 area. In 2004, total injection of all produced fluid was achieved at Chipilapa, 6 km from the Ahuachapán area. A former policy of sending cooled geothermal flu-ids to the ocean through a canal has been abandoned. The possibility of utilizing residual heat through a 3.5-MWe binary power plant is being investigated, with plans to begin operations in 2006. The Berlín geothermal field was explored in the 1970s, but because of civil unrest commercial operation did not begin until 1992, when two 5-MWe wellhead units came online. They were decommissioned in 1999, and two 28-MWe single-flash units were installed. The 300°C reservoir is at approximately 2,000-2,500 m depth. There are nine production and 15 reinjec-tion wells in the field. An extensive upgrad-ing, aimed at installation of an additional 40-MWe, is currently scheduled. The first four wells for this project have already been drilled near the southern border of the reservoir. The presently exploited area is quite small, only 2-3 km2. An additional 6.5-MWe binary unit is under evaluation. Projects are ongoing in other geothermal areas of the country. In Cuyanausul, near the Chipilapa injection field, an explorato-ry well is being drilled. Should estimates of field potential be confirmed, one or two 5-MWe back-pressure units might be installed. Further concessions have been released for exploration in San Vincente, Chinameca and Obrajuelo. The overall potential of these fields could be around 100 MWe. In 2002, the Salvadoran and Honduran electricity grids were intercon-nected via a 230-kilovolt (kV) transmission line. This is the final link of the Central America grid. Now power can be traded from Panama to Guatemala within the

Figure 5. First regional electricity grid: the SIEPAC (Sistema Eléctrico para América Central) line (from Lippmann, 2003).



Regional Electricity Market (MER) (de la Torre, 2002; Lippmann, 2003). The new regional SIEPAC (Sistema Eléctrico para América Central) transmission line with a transfer capacity of 300 MW (Fig. 5) is expected to be online during the first half of 2008.

Ethiopia. Aluto-Langano is the only geo-thermal area currently exploited for elec-tricity production in Ethiopia. It is located on the floor of the Ethiopian Rift Valley, about 200 km southeast of Addis Ababa. Eight deep wells (maximum depth of about 2,500 m) have been drilled in the field, four of them productive (Teklemariam and Beyene, 2005). Maximum reservoir temperature is about 350ºC. The potential of the field has been evaluated at up to 30 MWe for 30 years. A 7.3-MWe binary geothermal plant was installed in 1999. It is not fully functional because operational experience is lacking. The government's five-year plan includes rehabilitation of the power plant, and possible installation of an additional 20-MWe unit if financial support becomes available. In the Ten-daho field, in the Northern Afar, three deep (2,100 m) wells found temperatures above 270ºC.

France. At present, the only geothermal power production by France is under the French Overseas Department, at La Bouillante on the Caribbean Island of Guadeloupe. The old Bouillante-1 double-flash power plant is still operating after its rehabilitation in 1995-1996. An 11-MWe power plant (Bouillante-2) came online in 2004, bringing total capacity of the field to 15 MWe (Laplaige et al., 2005), with production in 2004 of 102 GWh. Three new production wells were drilled for Bouillante-2 (single-flash, 10-MWe plant). The Bouillante-3 project is currently in its pre-feasibility phase. After installation of the third unit, geothermal electricity should provide nearly 20 percent of the island's electricity needs. Geothermal exploration programs are planned for the near future on the islands of Martinique and La Réunion, in the French Antilles. The HDR project at Soultz-sous-Forêts, in Alsace, is now in the scientific pilot plant stage, with mod-ule construction underway. The enhanced

geothermal project, based on a three-well system in granite at a depth of 5,000 m, is expected to go online during 2006.

Germany. The first geothermal power plant in Germany, at Neustadt-Glewe, has been online since 2003 (Schellschmidt et al., 2005). It has an installed capacity of about 230 kWe using an ORC. In addi-tion, 10.7 MWt are used for district and space heating. Energy production of 1.5 GWh/y will provide 500 households with electric power. The plant uses a flow rate of 100 m³/h at a temperature of 98°C; at the end of the cycle the water is cooled to 72°C. Currently, six new installations for power generation are being planned at

Groß Schönebeck, Bad Urach, Offenbach, Speyer, Bruchsal and Unterhaching.

Guatemala. Geothermal exploration began in Guatemala in 1972, but commercial ex-ploitation started in 1998 at Zunil. This area has two geothermal fields located close together, Zunil I and II. Despite their proximity, they have separate reser-voirs with different heat and fluid sources. Zunil I, located on the border of the Quet-zaltenango caldera west of Guatemala City, has temperatures of 300°C at 1,500-2,300 m depth. There are seven binary units with a total installed capacity of 28 MWe (24 MWe running capacity). A research and development project for Zunil I was

Figure 6. Location of geothermal fields in Iceland (from Ragnarsson, 2005)

Field Installed Capacity Number Annual Electricity (MWe) a of Units a Production (GWh/yr) b

Nesjavellir 90 3 692Krafla 60 2 401Svartsengi 46 11 368Namafjall 3.2 1 12Husavik 2 1 9Reykjanes 0.5 1 1

Total 202 19 1,483

Note: a: Early 2005 data; b: 2004 data

Table 7. Geothermal fields in Iceland.



completed recently with installation of an injection facility. There are nine producing and four injection wells in this field, with six production and two injection wells cur-rently operative. At Zunil II, a small steam cap linked to a deep hot aquifer has been discovered at shallow depth. Its potential has been estimated at up to 50 MWe. A development project was launched in 2003, with the drilling of two production wells and one for injection. In the near future, a long-term test will be performed to evaluate the reservoir and its possible decline with fluid production. The other Guatemalan field, at Amatitlán, also came online in 1998. An old 5-MWe back-pressure unit

is still in operation. Following the first four deep exploratory wells (two of which produce steam), two new wells have been successfully drilled to define the extension of the geothermal anomaly. As a result of a positive field assessment, a five-year proj-ect has been initiated to gradually increase installed capacity with modular binary units totaling up to 50 MWe. A 20.5-MWe hy-brid power plant at Amatitlán was expected to go online in 2005 (Lima Lobato et al., 2003; Roldán Manzo, 2005). In 2003, total geothermal power production in Guatemala was 212 GWh/yr. Developments at Zunil and Amatitlán are supported by a new re-newable energy law (2004), that provides

tax exemptions for renewable energy projects. The government’s commitment to renewables has also been confirmed in a four-year geothermal development program, signed in 2003. Geothermal exploration is under way in other parts of the country at Tecaumburro, San Marcos, Moyuta, and Totonicapán, but drilling has not been carried out.

Iceland. The locations of geothermal ar-eas in Iceland are shown in Figure 6, and listed in Table 7. Geothermal electricity generation has increased significantly in Iceland since 1999, with installation of new power plants at Nesjavellir and Husavik. Total installed capacity in Iceland is now 202 MWe. An additional 30-MWe single-flash unit at Nesjavellir is at an advanced stage of construction (Gunnlaugsson, 2002; Ragnarsson, 2005). Two other geothermal power plants are currently under construc-tion, at Hellisheidi and Reykjanes. Their combined installed capacity will be about 180 MWe, which will almost double Iceland’s total. At Krafla, in the northern part of the country, there are two 30-MWe double-flash power plants. The geothermal projects at Svartsengi and Nesjavellir in-clude power plants with an installed capac-ity of 46 and 90 MWe, respectively, and transmission of hot water to the Reykjavik and Hitaveita Sudurnesja district heating systems. Hellisheidi, a new field that is part of the large Hengill geothermal area in the southwestern part of the country, is currently under exploration, with plans to install 80 MWe and increase the amount of hot water supplied to the City of Reykja-vik. There has been a great deal of drilling activity in Iceland over the last five years, with 39 new wells that reach a total depth of 55 km.

Indonesia. Despite the huge geothermal potential of Indonesia, there has been relatively little development during the 2000-2005 period, mainly because of a severe economic crisis that has adversely affected power demand and growth (Ibra-him et al., 2005). Currently, the 797 MWe of installed geothermal capacity from the fields listed in Table 8 and shown in Fig. 7 are being fully utilized. Note that total run-ning capacity for the country is 838 MWe. A

Field Location Installed Number Annual Electricity Capacity (MWe) of Units Production (GWh/yr) a

Gunung Salak Java 330 6 n/aKamojang Java 140 3 n/aDarajat Java 135 2 n/aWayang Windu Java 110 1 n/aDieng Java 60 1 n/aLahendong Sulawesi 20 1 n/aSibayak Sumatra 2 1 n/a

Total 797 15 6,085 a The only data available are for total production referred to late 2004 (Ibrahim et al., 2005)

Table 8. Geothermal fields in Indonesia (early 2005 data).

Figure 7. Location of the geothermal fields in Indonesia (from Sudarman et al., 2000, modified).



20-MWe geothermal unit at Lahendong is the only installation in Indonesia after 2000 (it came online in 2002), but the situation may change in the future. An investment plan for a new 100-MWe power plant at Darajat was approved in 2004. A tender has been launched for an additional 20 MWe at Lahendong. There are also plans to expand Kamojang by 60 MWe, but the project has not yet started.

Italy. A major event during 2000-2005 was the centennial celebration of the first suc-cessful experiment in producing geothermal electricity, which took place at Larderello in 1904. The first commercial power plant in that field went online in 1913 (250 kWe). Since then, geothermal power generation in Italy has increased steadily to the current 791-MWe installed capacity (699-MWe running capacity). Electricity generation reached a historical maximum of 5,340 GWh in 2003, as shown in Figure 8 (Cap-petti et al., 2000; Cappetti and Ceppatelli, 2005). Geothermal fields in Italy are listed in Table 9 and their locations shown in Fig-ure 9. The two major fields are Larderello-Travale/Radicondoli and Mt. Amiata. Ten new power plants (254-MWe installed ca-pacity) have been commissioned and gone online at Larderello-Travale/Radicondoli during the last five years, to replace old and obsolete units and to de-velop a deeper reservoir found in old, shallow fields. A deep exploration program has also been launched, which includes a 3D seismic survey and 11 deep (3,000-4,000 m) wells. Twenty-one wells with a total depth of 64 km were drilled between 2000 and 2005. The adjacent Larderello and Travale/Radicondoli areas are part of the same deep field that extends over a large (approximately 400 km2) area. The deep, super-heated steam reservoir has the same temperature (300-350°C) and pressure (4-7 MPa) throughout the field (Bertani et al., 2005). The exploited area at Larderello covers 250 km2, with 180 wells and 21 power units totaling 543-MWe installed capacity.

Location Installed Capacity Number Annual Electricity (MWe ) a of Units a Production (GWh/yr) b

Larderello 543 21 3,606Travale-Radicondoli 160 6 1,109Mt. Amiata 88 5 625(Bagnore and Piancastagnaio)

Total 791 32 5,340

Note: a Early 2005 data; b 2003 data

Table 9. Geothermal fields in Italy.

Figure 8. A century of electric power production in Italy (from Cappetti et al., 2005).

Figure 9. Location of geothermal regions and power plants in Italy (from Cappetti et al., 2005).



The Travale/Radicondoli area (50 km2) has 22 wells, which send steam to six units totaling 160 MWe installed capacity. Condensed water from Travale is carried

through a 20-km pipeline to the center of the Larderello field, where it is injected. An additional 60 MWe are under construc-tion (Nuova Larderello 3 and Nuova San

Martino). The Mt. Amiata area comprises two water-dominated geothermal fields, Piancastagnaio and Bagnore. In the 1980s, a deep reservoir was discovered in both fields, under the shallow geothermal reservoir exploited at that time. The deep resource is characterized by 20 MPa, 300-350°C water (at 3,000 m). Objections by lo-cal communities have delayed development of this high-potential deep system. At pres-ent, there are five units totaling 88 MWe installed capacity at Mt. Amiata, one in Bagnore and four in Piancastagnaio. A 20-MWe unit online since 1987 was decom-missioned in 2000. In 2003, the 40-MWe power plant at Latera was closed because of environmental and technical problems. This field is no longer under exploitation. Liberalization of the electricity market has been completed in Italy, with an incentive scheme for renewables (Green Certificates)

that should lead to further ex-ploration and development of deep geothermal resources. On the basis of positive re-sults achieved so far, some 100 MWe are expected to be installed in Italy within the next five years.

Japan. Seventeen geothermal power plants are in operation in Japan, most of which are located in the Tohoku and Kyushu districts (Fig. 10) with total installed capacity of 535 MWe (Kawazoe and Combs, 2004; Kawazoe and Shirakura, 2005). Geo-thermal locations in Japan are listed in Table 10. Because financial support and favorable regulations are lacking, there have been no major geothermal developments in recent years. Only a small, 2-MWe binary unit was set up at the Hatchobaru geothermal power station in February 2004. This is the first binary-cycle geothermal power plant in Japan. On the other hand, there has been significant drilling activity

Location Installed Capacity Number Annual Electricity(Prefecture) (MWe) a of Units a Production (GWh/yr) b

Oita 153 7 1,108Iwate 104 3 643Akita 88 3 619Fukushima 65 1 400Kagoshima 60 2 416Hokkaido 50 1 185Miyagi 12 1 81Tokyo 3.3 1 15

Total 535 19 3,467


Table 10. Geothermal fields in Japan.

Figure 10. Location of geothermal plants in Japan ( Kawazoe et al., 2005, modified, see Table 10).



during 2000-2005, with 41 geothermal wells (totaling 74 km depth) equally distributed for exploration, production and injection. Deregulation of the Japanese power generation market started in 2000. As a consequence, electric power companies changed their investment policies regarding new power plants. This process, in addition to a drastic reduction in commitment to geothermal by the New Energy and Industrial Technology Development Organization (NEDO), was responsible for the decline in recent Japanese geothermal development. A recent Renewable Portfolio Standard (RPS) law promulgated in 2003 may be a useful tool for attracting private investment in geothermal energy development. It should be noted that only binary-cycle geothermal power plants are covered by the RPS, encouraging a trend in development of small-scale geothermal fields. In 2004, NEDO launched its Geothermal Development Promotion Surveys, based on the concept of “local energy for local areas.” Three new target areas were carefully selected, based on economic and social factors, and on estimated potential for installing binary power plants of 10 MWe or less. Though these units may be relatively small, the program may lead to further utilization of geothermal energy. Results of the surveys will be evaluated by the end of March 2006. A strategy has recently been proposed by the Ministry for Education, Culture, Sports, Science and Technology (MEXT) for developing Japanese geothermal resources in ways consistent with global environmental expectations for the 21st Century, the so-called EIMY, or “Energy in My Yard.” The idea is that local energy requirements should be met by an optimum combination of local renewable sources. Shortfalls and surpluses would be accommodated through interface with the national electricity grid (Niitsuma and Nakata, 2003). These integrated renewable energy systems offer a considerable advantage over independent utilization of renewable resources. In rural areas of Japan, such systems could reduce CO

2 emissions and

energy costs. Geothermal energy will play a key role in these EIMY systems. Heat pumps are of primary importance, together

with other geothermal technologies such as injection, HDR, “Hot Wet Rock”(HWR), and binary systems. This innovative concept is expected to give a welcome boost to geothermal power generation, as it will obviate many problems with local permits and encourage local acceptance of small-scale installations.

Kenya. Geothermal electricity genera-tion capacity in Kenya has increased by 84 MWe since 2000. Olkaria is the only geothermal field developed to date. Ex-ploitation has grown from 45 MWe in 1999 to 129 MWe in 2004, a 186-percent increase (Mwangi, 2005). Production in 2003 was 1,088 GWh. The Olkaria

geothermal system is located in the East Africa Rift valley about 120 km north-west of Nairobi. The greater geothermal anomaly covers 80 km2; only three sec-tors (east, west and northeast) are being exploited at this time. In the Olkaria East field, three 15-MWe turbo-generating units at Olkaria I have been online for 23 years. The first of 33 drilled wells were shallow (<1,200 m); subsequent deeper wells as-sessed resources down to 2,500 m. Five percent of waste brine is injected hot, and 20 percent cold, back into the reservoir; the rest evaporates in an open-air pond. In the Olkaria North-East field, two 35-MWe units at Olkaria II were commissioned in 2003. This new facility has lower specific

Figure 11. Location of geothermal fields in Mexico (from Gutiérrez-Negrín et al., 2005).

Location Installed Capacity Number Annual Electricity (MWe) a of Units a Production (GWh/yr) b

Cerro Prieto 720 13 5,112Los Azufres 188 14 852Los Humeros 35 7 285Las Tres Vírgenes 10 2 33

Total 953 36 6,282


Table 11. Geothermal fields in Mexico.



steam consumption (7.5 t/h/MW) than Ol-karia I (9.2 t/h/MW). A private geothermal company is developing the Olkaria West area (Olkaria III). It drilled nine wells to

Figure 12. Location of geothermal fields in New Zealand (from www.eeca.govt.nz/programmes/renewable/, modified).


Wairakei-Poihipi 220 11 1,505Ohaaki 105 4 300Mokai 55 7 470Rotokawa 31 5 290Kawerau 14 4 130Ngawha 10 2 79

Total 435 33 2,774


Table 12. Geothermal fields in New Zealand.

depths of 1,800-2,800 m. Currently, some of the geothermal fluids are being utilized in three 4-MWe binary units. In 2005, the Olkaria IV project received financial sup-

port for appraisal drilling. A minor project, with a 1.8 MWe binary plant, was com-missioned for North-West Olkaria by a flower-growing company in September 2004. The overall geothermal potential of Kenya is large and has been evaluated at as much as 2,000 MWe. Many projects have already been defined and funding is being sought. The Kenyan government has proposed creation of a special geothermal development company, with a mandate to explore and sell geothermal energy for electric generation and other uses. Risks associated with geothermal exploration will be covered by the Kenyan govern-ment. These policies may lead to private investments in the development of Kenyan geothermal resources.

Mexico. Currently, there are four geother-mal fields in production in Mexico: Cerro Prieto, Los Azufres, Los Humeros and Las Tres Vírgenes (Gutiérrez-Negrín and Qui-jano-León, 2005) Total installed geother-mal capacity in the country is 953 MWe (Fig. 11 and Table 11). Mexico is one of the leading countries in geothermal devel-opment for electricity production. Since 2000, eight new single-flash units went online: four at Cerro Prieto (100 MWe); four at Los Azufres (100 MWe); and 10 MWe at Las Tres Virgines, a new field that recently started production. Further installations are planned at Los Humeros (50 MWe) and La Primavera (75 MWe). The Cerro Prieto field is located near the Mexico-U.S. (California) border. Cur-rently, commercial exploitation (started in 1973) has reached an installed capacity of 720 MWe (four 110-MWe units; four 37.5-MWe units; four 25-MWe units; and one 30-MWe unit). All power plants are the condensing type. There are 149 pro-duction wells in operation. Waste brine is primarily discharged into a 14 km2 solar evaporation pond, and a portion returned underground through nine injection wells. The four 25-MWe units at the Cerro Prieto IV went online in 2000. The Los Azufres geothermal field is located in the central part of Mexico, 250 km west of Mexico City, with 14 power units of diverse types (condensing, back-pressure, binary cycle), and capacities varying from 1.5 to 50 MWe. Present total installed capacity



is 188 MWe, with 29 production and six injection wells. In 2003, four 25-MWe units went online. Los Humeros, located in east-central Mexico, has an installed capacity of 35 MWe (seven 5-MWe back-pressure units) and 17 production wells. All separated brine is injected back into the reservoir through two wells. Two new units for an additional 50 MWe are sched-uled to be installed in 2008. The Las Tres Vírgenes geothermal field is in the middle of the Baja California Peninsula. Two pro-duction wells feed two 5-MWe condensing units. At La Primavera, near Guadalajara, there are plans to install 50 MWe in 2008 and another 25 MWe in 2009. Fifty-nine geothermal wells were drilled in Mexico between 2000 and 2003, for a total depth of 150 km.

New Zealand. In the 2000-2004 period, three new geothermal power plants were under construction or completed, including start of construction for a 15-MWe binary plant at Wairakei, commissioning of an additional 6 MWe at Rotokawa, and start of construction for an additional 30 MWe at Mokai. The status of the New Zealand geothermal fields is summarized in Table 12. All but one (Ngawha) are located in the Lake Taupo area, as shown in Figure 12 (Dunstall, 2005). The Wairakei-Poihipi field has been in continuous operation for nearly 50 years, with a stabilized decline. The most recent installation of the 55-MWe Poihipi power plant is exploiting a steam cap that formed as a consequence of ex-ploitation of a liquid-dominated reservoir beneath. The Mokai field, which started commercial fluid production in 2000, is a unique example of a geothermal resource wholely owned by a local community, the Maori Trust, and operated via a state-owned enterprise. This is a key element for local acceptance of geothermal energy develop-ment. Another 40 MWe of capacity are currently under construction at Mokai. Total installed capacity in New Zealand in early 2005 was 435 MWe, with a running capacity of 403 MWe. Nicaragua. Despite Nicaragua’s very large geothermal potential (1,000 MWe), the only exploited area by the end of 2004 was the Momotombo field, which has been

Figure 13. Location of the geothermal fields in Philippines (from Benito et al., 2005, modified).

Field Location Installed Capacity Number Annual Electricity (MWe) a of Units a Produced (GWh/yr) b

Tongonan Leyte 723 21 4,746Mak-Ban Luzon 426 16 1,538Tiwi Luzon 330 6 442Palinpinon Negros 192 7 1,257Bac-Man Luzon 151 5 457Mt. Apo Mindanao 108 2 813

Total 1,930 57 9,253

Note: *Early 2005 data; #2003 data

Table 13 Geothermal fields in the Philippines.

in operation since 1983. Recently, the proj-ect has been rehabilitated, including instal-lation of a 7.5-MWe binary power plant. Running capacity increased from 12 MWe in 1999 to the present 38 MWe. Total in-stalled capacity at the field is 77.5 MWe (Zuniga, 2005), with 2004 production of 271 GWh. Four injection wells have been

drilled at Momotombo, stabilizing produc-tion from 12 producing wells. The shallow production zone is affected by lake water infiltration, with consequent severe cool-ing effects. In response, there are plans to achieve full production by drilling new deep wells and expanding exploitation of the deep part of the reservoir (1,700-3,000



m). Two 5-MWe back-pressure units are currently being installed at the nearby San Jacinto-Tizate field, where seven explora-tion wells (between 700 and 2,200 m) en-countered temperatures from 264 to 289ºC. These units are expected to be operational in early 2006, with planned expansion to a total of 66 MWe over the next few years. Ratification of a new geothermal law and energy policies should help to attract local and foreign private investment in geother-mal projects. Economic development of the entire Central American region should also improve when the SIEPAC transmission line begins operation.

Papua New Guinea. Geothermal power development is focused on tiny Lihir Island, about 700 km northeast of Port Moresby, where there is the unique combination of a significant geothermal resource, a gold mining operation, and isolated location (Booth and Bixley, 2005). Hot (250°C) water from 1,000 m depth—from large-diameter wells used to dewater the mines and regular geothermal wells—will be used for the geothermal project. A 6-MWe back-pressure power plant was commissioned in 2003, and began generating electricity in 2004. The new power plant is a substitute for diesel generation, with fuel cost savings of US$2,000,000 per annum. An additional 30-MWe geothermal power project was commissioned in 2005.

Philippines. The Philippines is the world’s second largest producer of geothermal energy for power generation, with an installed capacity of 1,930 MWe and a running capacity of 1,838 MWe. The geothermal fields are listed in Table 13 and their locations shown in Figure 13. In the last five years, total installed capacity has increased slightly with 22 MWe at Tongonan. Drilling activity developed 28 wells, totaling 63 km depth (Benito et al., 2005). Running capacity at Tiwi has been de-rated from 330 to 263 MWe because of decommissioning of an old power plant. A minimum value of 232 MWe is expected in 2005. Mak-Ban has been in commercial production since 1979, despite its small surface area (~14 km2). Recharge from the extensive surrounding aquifer has played a key role in its sustainable

Figure 14. Location of geothermal fields in Kamchatka, Russia (from Battocletti, 2000).

development over such a long productive lifetime. Make-up wells have been drilled, and 10 new wells completed into the deep reservoir (2,800 m). Running capacity will reach 402 MWe after rehabilitation activities are completed. Tongonan and adjacent geothermal fields on the Island of Leyte are the most important geothermal projects in The Philippines, with 723 MWe of installed capacity. Drilling of make-up and replacement wells, well workovers, and solving corrosion, erosion and scaling

problems have all contributed to sustaining high levels of power generation, with 4,746 GWh produced in 2003. Palinpinon has a total installed capacity of 192 MWe, and has been in operation since 1983. There is an expansion project for an additional 20 MWe scheduled for completion in 2006. Bac-Man has been in operation since 1993 without substantial modifica-tions or additions. Mechanical problems have affected the operating life of its Unit I (55 MWe). Mt. Apo is the sixth operating



geothermal field in The Philippines, with total installed capacity of 108 MWe. The most recent addition is a second unit in 1999 (Mindanao II, 54 MWe). A project for another 20 MWe is currently under evaluation. New areas are under study, the most promising in Northern Negros, where a feasibility study for 40 MWe has already been performed. Development is expected to begin in 2006.

Portugal. Geothermal resources of the largest and most populous Portuguese is-land of the Azores, São Miguel, are utilized for electric power generation. The high-en-thalpy resource is exploited in the Ribeira Grande power plant, where four binary units were installed in 1998. On the same island, another geothermal project is being developed at Pico Vermelho. A 10-MWe binary unit will replace an old 3-MWe unit. Total geothermal capacity, currently at 16 MWe, will represent 38 percent of the electric energy produced on São Miguel. In addition, a 12-MWe power plant proj-ect is underway on the Island of Terceira. Installed electricity generation capacity in the Azores is expected to double by 2009, with 45 percent coming from geothermal sources (Bicudo da Ponte, 2002; Carvalho et al., 2005).

Russia. High-enthalpy geothermal fields presently under exploitation in Russia are located at Kamchatka and on the Kurili Islands (Kononov and Povarov, 2005). On the Kamchatka Peninsula, several geother-mal power plants are in operation, with in-stalled capacities of 12 MWe and 50 MWe at Mutnovsky, and 11 MWe at Pauzhetsky (Fig. 14). On the Kurili islands of Kunashir and Iturup, two small units (2.6 MWe and 3.4 MWe) are in operation. Present total installed capacity in far eastern Russia is 79 MWe. Increased capacity over the last five years is a result of the installation of a 50-MWe single-flash power plant at Mut-novsky in 2002. At present, a 100-MWe power plant is under consideration, as well as a small binary unit. The high-tempera-ture North Mutnovsky field is the primary target for electric power production at Kamchatka. Eighty-two wells in the 200-2,000 m range have been drilled. A shal-low, vapor-dominated reservoir was found

Figure 15. Injection effects at The Geysers in northern California, United States. (from Lund et al., 2005).

Table 14. Geothermal fields in California, USA.


The Geysers 1,421 23 7,784Salton Sea 336 13 3,146Coso 274 9 2,785East Mesa 109 71 859Heber 85 13 641Mammoth 40 4 315Others 4 5 26

Total 2,269 138 15,556 Note: a Early 2005 data; b 2004 data

Editor's Note: The Mammoth geothermal project in California is often erroniously referred to

as “Casa Diablo.” (Personal communication – Dr. Jim Combs, Geo Hills Associates, 6/9/06).

at 700-900 m, which is underlain by a liq-uid-dominated 250-310°C reservoir. Pres-ently, 17 wells producing 330 kg/s of fluids with an average enthalpy of 1,600 kJ/kg are ready for exploitation. This project was supported by a US$100 million loan from the European Bank of Reconstruction and Development. Another partially explored, promising site is Nizhne-Koshelev, where fluids have an estimated enthalpy of up to 2,800 kJ/kg. Similar sites include the Bol-she-Bannoe and Kireuna fields, as well as the Semyachik field adjacent to the Kro-notsky Natural Park and its famous Geyser Valley. Limited use of the Semyachik field (enough to construct a small 5-MWe power

plant) could help development of tourist facilities in this environmentally protected area. Ingoring geothermal resources at the Kronotsky protected area, geothermal re-sources identified in Kamchatka (Fig. 14) to date could permit installation of several power plants with installed capacity of about 1,000 MWe.

Thailand. A small 300-kWe binary power plant provides electricity to the small village of Fang, using 116°C water (Subtavewung et al., 2005). This water is also used in other, direct applications, such as air-conditioning, cold storage and crop-drying, using the 80°C discharge from the



Table 15. Geothermal fields in Nevada, USA.


Dixie Valley 63 1 489Steamboat Springs 58 13 488Soda Lake 26 9 206Brady Hot Springs 21 3 181Stillwater 21 14 166Beowawe 16 1 131Steamboat Hills 15 1 120Desert Peak 12 2 107Empire 5 4 38Wabuska 2 2 17

Total 239 50 1,943


Figure 16. Location of geothermal fields in California, United States (from Lund et al., 2005).

power plant. The geothermal power plant replaced a diesel unit, saving about US15¢ per kilowatt-hour.

Turkey. The only geothermal field current-ly under exploitation for power production in Turkey is Kizildere, where generation began in 1968. The power plant went online in 1984, with an installed capac-ity of 20 MWe and an average running capacity of 12-15 MWe (Simsek et al., 2005). In 2003, it had stable production of 105 GWh.

United States. In the United States, geo-thermal electrical production is restricted to California, Nevada, Utah and Hawaii. Since 1989, only 110 MWe have been added to the country’s installed capacity. Geothermal activity in the last five years includes two injection projects at The Geysers, in which recycled waste and lake waters are sent from a number of local communities to the geothermal field via lengthy pipelines. The Southeast Geysers Effluent Recycling Project (SEGEP) was the first wastewater-to-electricity system. As a consequence of massive reinjection of fluid, power generation at The Geysers has increased by an estimated 77 MWe (Fig. 15). A second pipeline that carries treated wastewater from the City of Santa Rosa to The Geysers went online in 2004. Its ben-eficial effects are under evaluation, but the water is expected to provide recovery of an additional 85 MWe (Monastero, 2002; Sass and Priest, 2002; Lund, 2003, 2004; Camp-bell et al., 2004; Lund et al., 2005). Present installed gross geothermal power capacity in the United States is 2,564 MWe, with a net running capacity of nearly 2000 MWe, and production in 2004 of 17,917 GWh. The difference between capacity and production derives mainly from The Geysers, where the 21 power plants currently in operation have an installed capacity of 1,421 MWe. Because of overexploitation, however, steam is available to generate only about 900 MWe. Several geothermal power plants are scheduled for installation in the western United States. If all of them succeed, U.S. geothermal electric energy production should grow by 340 MWe by 2010, cor-responding to a 20-percent increase over the 2005-2010 period.



Alaska. By October 2005, a 400-kW binary power plant is scheduled for installation at Chena Hot Springs, northeast of Fairbanks. The power will be used at a large tourist facility that includes bathing pools, an ice palace, a greenhouse, and more than a dozen geothermally heated buildings.

California. Geothermal power plants in California are listed in Table 14 and shown in Fig. 16. The steam field at The Geysers, with 21 units, after dismantling old units and adding the reinjection proj-ects, reached a total running capacity of 888 MWe (net) in 2004. Electricity genera-tion reached a peak of over 1,600 MWe

Figure 17. Location of geothermal fields in Nevada, USA (from Lund et al., 2005).

in 1987 (Sass and Priest, 2002). At the Salton Sea field in the Imperial Valley, the operator installed a new 50-MWe unit in 1999, followed by a second 10-MWe unit, aimed at a zinc-recovery project from spent geothermal brine. The project was aban-doned recently for financial and technical reasons. Installation of a new 185-MWe power plant has been approved. At present, a single operator is in charge of the Heber and East Mesa plants, both in the Imperial Valley. Projects for optimizing old units and increasing generating capacity at the two fields are underway. Future develop-ments are planned at Glass Mountain in northern California. Permits for 50 MWe

have been approved for the Fourmile Hill area, but were denied for a proposed 50-MWe project at Telephone Flat.

Nevada. Geothermal power plants in Ne-vada are listed in Table 15 and shown in Fig. 17. New plants are scheduled to be in-stalled at Steamboat (42 MWe) and Desert Peak (30 MWe). Additional capacity was installed in the state in 2005 at Steamboat (Ed.). Nevada is the state where most future geothermal activity (exploration, develop-ment and exploitation) will take place in the United States.

Utah. There have been no significant geo-thermal developments in the other states during 2000-2005, a 26-MWe power plant at Roosevelt Hot Spring came online in 2001. This plant generated 200 GWh in 2004. There are plans to install a 25-MWe unit at Cove Fort-Sulphurdale.

Hawaii. At Puna, on the Big Island of Hawaii, there are 20 new small binary and single-flash units totaling 30 MWe for 218 GWh of annual production. The project was affected by well casing failure from heat and corrosion in 2002. After months of workover, it is now operating at its rated capacity.

Conclusions Based on information shown in Table 2, the countries generating electricity using geothermal resources in early 2005 can be classified into three groups:

• Countries that began geothermal gen-eration after 2000. Austria, Germany and Papua New Guinea belong to this group. In two European countries, power plants are small binary units (less than one MWe). In Papua New Guinea, a 6-MWe back-pressure unit can be consid-ered the first stage of a project that will soon add another 30 MWe.

• Countries that began geothermal genera-tion before 2000 but have not increased their installed capacity since 2000, or only slightly include Australia, China, El Salvador (but with an important 50-MWe project at Berlín), Ethiopia, Gua-temala, Japan (with some prospects for



Table 16. Worldwide geothermal drilling activity for power projects, 2000-early 2005.

Country Number of Wells Total Drilled Depth (km)

Australia 2 6China 1 2Costa Rica 6 12 El Salvador 5 10France 3 5Germany 4 12Guatemala 5 8Iceland 39 55Italy 21 64Japan 41 74Kenya 9 22Mexico 59 150New Zealand 9 25Papua New Guinea 7 4Philippines 28 63Portugal 6 4Russia 4 10Turkey 4 3United States 54 42

Total 307 571

Table 17. Power plant distribution by plant type (early 2005 data).

Plant type Installed Percent Installed Capacity Percent Capacity (MWe) (number of units)

Dry steam 2,545 28 58 12Single flash 3,294 37 128 26Double flash 2,293 26 67 14Binary/combined cycle/hybrid 682 8 208 42Back-pressure 119 1 29 6

Total 8,933 100 490 100

Figure 18. Plant categories: percent of installed capacity.

EIMY projects), New Zealand (projects for the coming years for Wairakei and Mokai), Portugal, Thailand, and Tur-key.

• Four other countries can be added to this group:

Indonesia. No new units have been installed since a number of power plants came online around the year 2000 (80 MWe at Darajat, 60 MWe at Dieng, and 110 MWe at Way-ang Windu). This increased the country’s installed capacity by 35 percent.

Italy. There was only a modest increase in capacity; although 10 new units have been placed online for a total of 254 MWe, they were replacing old or obsolete units;

Philippines. There has been only a mod-est increase (i.e. 1%) in capacity with the commissioning of the 22 MWe unit at Tongonan; and

United States. The country’s installed capacity grew by only 3 percent with the new 60 MWe Salton Sea Unit V.

Countries that began geothermal generation before 2000 and have signifi-cantly increased (percentage) geothermal power generation over the last five years include:

• Costa Rica, with a 14-percent increase in installed capacity (18-MWe Miravalles V power plant);

• France, with a 250-percent increase at Guadeloupe (10-MWe Bouillante II plant);

• Iceland, with a 19-percent increase (30-MWe power plant at Nesjavellir and a 2-MWe binary plant at Husavik);

• Kenya, where the installed capacity has almost tripled (two new units at Olkaria II and III for a total of 92 MWe);

• Mexico, with a 26-percent increase in installed capacity (new units at Cerro Prieto, Los Azufres and Las Tres Vír-genes, for a total of 198 MWe);



Figure 19. Geothermal power plant categories: percentage of number of units.

Figure 20. Power density distribution of developed geothermal fields. The vertical axis shows the number of geothermal fields in each category, as a percentage of all analyzed reservoirs.

• Nicaragua, with a 11-percent increase in running capacity (due to the rehabilita-tion of Momotombo and the installation of new binary unit); and

• Russia with a 243-percent increase in installed capacity (50-MWe unit at Mutnovsky).

Drilling Activity Drilling data for 19 countries that use geothermal resources in the generation of electric power are presented in Table 16 (data for Costa Rica, Russia and New Zea-land are estimates). More than 300 wells have been drilled to obtain hot fluids for electricity production (and/or reinjection of spent brines) over the last five years, for a total of 571 km. Average well depth is about 1.9 km. Mexico, the United States, Japan, Ice-land, and The Philippines were the most active countries for geothermal drilling.

Power Plant Classifications Total installed geothermal capacity worldwide has been classified under the following plant categories: dry steam; single flash; double flash; binary/combined cycle/hybrid; back-pressure (Table 17 and Fig. 18). The largest installed capacities correspond to dry steam and single-flash units, with 2/3 of the total. Binary units, despite their low position in this ranking because of their smaller capacity rat-ings, are becoming increas-ingly more common. There were a total of 490 geothermal units oper-ating in early 2005 (Table 17). The distribution of units over the different categories are shown in Figure 19. The maximum corresponds to 205 bi-nary units (42%), with a total installed capacity of 682 MWe (i.e. 3.3 MWe per unit). The average size of single-flash units is 26.2 MWe, followed by the 34.2 MWe for double-flash units, and 43.9 MWe for dry steam plants.


Table 18. Effect of reservoir temperature on production indexes. (Hotter: > 250°C; Cooler

<250°C).

Index Hotter Cooler

Power density (MWe/km2) 7.8±6.4 6.5±5.2Well density (Wells/km2) 1.9±1.4 1.9±1.6Well productivity (MWe/well) 4.7±3.3 4.2±2.2

Note: Values in the second and third columns are mean and standard deviations


Geothermal Production Indicesand Other Statistics Data presented in Table 3 should be considered preliminary, and an indicator of work-in-progress. For many fields, it was not possible to obtain all requested information. However, power density (i.e., MW/km2) was calculated using informa-tion from 70 geothermal fields chosen at random, for which reservoir data were

Figure 21. Well density distribution of developed geothermal fields. The vertical axis shows the number of geothermal fields in each category, as a percentage of all analyzed reservoirs.

Figure 22. Distribution of well productivity in developed geothermal fields. The vertical axis shows the number of geothermal fields in each category, as a percentage of all analyzed reservoirs.

available, by dividing running capacity by estimated reservoir surface (inferred from drilling area). Results are shown in Fig. 20. The average value is 7.4 ± 6.0 MW/km2, but it is clear from the shape of the distribution that smaller power densi-ties are more common, in the range 2-6 MW/km2. It is also interesting to analyze the number of productive wells per square

kilometer (Fig. 21). The aver-age value is 1.9 ± 1.5 well/km2. On the other hand, average well productivity is 4.6 ± 2.9 MW/well. Distribution is shown in Fig. 22. To evaluate the impor-tance of reservoir temperature, all geothermal fields consid-ered were assigned to one of two temperature categories: “Hotter” (temperature equal or higher than 250°C) or “Cooler” (temperatures lower than 250°C). The mean and standard deviation for the correspond-ing production indices, well density, and well productivity are given in Table 18. The data seem to indicate that reservoir temperatures do not affect well density, but this should be considered only as a statistical value of average well spacing. On the other hand, resource temperature has a slight influ-ence on well productivity, and as a consequence, on power density. This variation is not statistically significant, how-ever, because of relatively high standard deviations.

Acknowledgments The author would like to express his gratitude to the International Geothermal Association (IGA) Board of Directors and to IGA-af-filiated organizations for their contribution of data for this paper. Sincere thanks are also due to Iris Perticone for her help in collating geothermal field data. Authors of Country

Update reports presented at WGC2005 are also warmly acknowledged for their help in clarifying many points. Last but not least, Marnell Dickson, Roland Horne, Gerry Huttrer, Marcelo Lippmann, John Lund, Valgardur Stefansson, Jim Combs, Ted Clutter, and Kelley Versteegh are thanked most warmly for their contribution to im-proving the final manuscript.



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