In the 1980s, the development of geothermal business discharge characterized by Presidential Decree (PD) No. 22 of 1981 replaced the PD No. 16 of 1974. According to the provisions of PD. no. 22/1981, Pertamina was appointed to conduct the survey and exploitation of geothermal exploration in Indonesia. On that basis, since 1982, activities in Lahendong were continued by Pertamina to conduct a survey of geology, geochemistry, and geophysics.
In 1982
Pertamina also signed a working contract with a geothermal company, Unocal Geothermal of Indonesia (UGI), for geothermal wells in G. Salak, West Java, and started to produce 12 years later.
Meanwhile, in February 1983
Five years after the first Kamojang mono block was inaugurated, Kamojang Geothermal power plant was started for commercial use with a capacity of 30 MWe, which is then followed by unit 2 and 3 ( 2X 55 MWe) in 1988 and unit 4 5 years later. Scientific exploration on the Flores Island was intensified in the 1980’s and concentrated effort was directed towards Ulumbu, a geothermal area in Manggarai. Much of the scientific work was conducted by Vulcanological Survey of Indonesia (VSI) Bandung, a Governemnt of Indonesia institution, in collaboration with PLN, JICA (Japan International cooperation Agency) and NZ Government.
In 1985
Pertamina performed geology and geophysic survey to discover Wayang Windu geothermal field and it was then followed by shallow drilling at the site.
In 1989
A decision was made to asses the technical and economical feasibility of setting up a smal scale (3 MWe) geothermal plant.
 Years of 1990’s
In 1991
The Government replaced PD No. 22/1981 to PD No. 45/1991. In PD No. 45/1991 Pertamina get flexibility, along with the contractor, to conduct exploration and exploitation of geothermal. Pertamina was also given more freedom to sell steam or electricity to PLN or to any legal entity licensee to electricity. In addition, in 1991, PD No. 49/1991 also issued to replace PD No. 23/1981 which regulates the geothermal business tax from 46% to 34%. The aim is to stimulate increased use of geothermal energy.
In 1993
Under bilateral technical cooperation PLN and NZ Goverment carried out drilling activities in Ulumbu geothermal field, whilst production drilling activity commencd in 1994. By 1995, plans were in place for geoscientific studies of seven locations where a mini geothermal plant development was possible.
In 1994
Working contracts were signed between Pertamina’s geothermal and four private companies, such Wayang Windu, West Java (P.T. Mandala Nusantara), Karaha, West Java (P.T. Karaha Bodas), Dieng, Central Java (P.T. Himpurna California Energy), and Patuha, West Java (PT Patuha Power Limited). At the same time, 1994, Gunung Salak (unit-1 and –2/55 MWe each) and Darajat (unit-1/20 MWe) started to produce the electricity commercially.
Henceforth, in 1995
Pertamina and PLN signed a contract (JOC/joint operation contract & ESC/electricity sale contract) for the exploitation and utilization of geothermal in the area of Batukahu, Bali. At the same time Pertamina issued a MOU to PT PLN to build geothermal power plants (1×20 MWe) in Lahendong, North Sulawesi and monoblock (2 MWe) in Sibayak, North Sumatra, which was started to generate elctricity6 and 2 years later, respectively. Sibayak was investigated by Pertamina between 1989-1999 using various geoscientific methods and drilled 10 holes during 1991-1997 and then a 2 MWe monoblock was built to generate geothermal energy. Pertamina committed to develop new power generation using the steam resources from the other wells.
In 1997
Gunung Salak unit 3 (55 MWe) and 4 (65 MWe) geothermal power plant was inaugurated commercially. Meanwhile, Dieng unit-1 power plant was certified for commercial operation a year later, in July 1998 after 17 years since its first monoblock was inaugurated.
Comprehensive surveys were conducted in Ulubelu Lampung in 1990, and three years later (1993) three exploration holes had been drilled by Pertamina, while power plant construction was started 14 years later.
Mataloko geothermal fields have been surveyed comprehensively using int egrated geoscientific study by VSI (Indonesia), NEDO an d Geological Survey of Japan (GSI-Japan) in 1997-2002 and followed by 4 drilledwells. The resource potential was estimated as 63 MWe.
The severe economic crisis that started in late 1997 has adversely affected the power sector demand and growth in the country. This had resulted in signifant delays to several geothermal projects in the advanced exploration and development stages, (i.e. 9 conventionally power IPP and 7 geothermal project).
Up to the year of 2000, or 3 years after the crisis (1997) no significant development in geothermal activities for new geothermal fields, except the existing geothermal plants was in creasing their electricity capacity.
Years of 2000’s
After struggling with the 1997 monetary crisiss that hit Indonesia, Pertamina acquired the
privilege to increase the capacity of Kamojang geothermal field from 140 to 200 MWe. During 1989-2002, Pertamina drilled 13 wells to secure a total steam potential of about 74 MWe at the wellheads. And then, after a 2 year costruction period the Kamojang Unit-4 commenced commercial operation in August 2008. At present, Kamojang delivers a total of 200 MWe of electricity.
After financial crisis in 1997, the first unit (110 MWe) at Wayang Windu was completed in 1999, and has been producing at full capacity since 2000, and then 9 years later on 2nd March 2009, Wayang Windu Unit-2 was offically opened with the generation capacity for single turbine of 117 MWe. So, Wayang Windu is now delivering a total of 227 MWe of electricity to PLN.
Planning is now to expand Wayang Windu further through an addition of a third unit with generation capacity of 127 MWe, that should be online by mid-2014.
In Lahendong, the 20 MWe PLTP unit-1 began its commercial operation in 2001, after an extended contruction period following the Asian financial crisis in 1997. The development of Lahendong PLTP unit-2 (20 MWe) began in 2004 and started its comercial operation in 2007. For Lahendong unit-3 (20 MWe), test operation has been carrid out in 2009, and then, 2 years later Lahendong unit-4 began its commercial operation in 2011. That means, up to know Lahendong PLTP is now delivering a total of 82.5 MWe of electricity to PLN.
Six years later after Darajat Unit-1 (55 MWe) started commercial operation in 1994, the Darajat PLTP Unit-2 was officially open in 2000, with generation capacity of 94 MWe, and then 7 years later in August 2007 Derajat Unit-3 (122 MWe) began its commercial operation. Currently Darajat is now delivering a total of 271 MWe of electricity.
In 2002
Gunung Salak unit 5 and 6 began its commercial operation, in which each unit can supply geothermal energy of 65 MWe.
In 2005
Unit 1-3 had been upgraded to 60 MWe each, that means the total capacity is 375 MWe.
Up to now Dieng PLTP has a capacity of 1x 60 MWe, and currently activities are being conducted to fulfill the target through capability upgrade and development of Dieng Unit 2 and 3 project with the capacity of 60 MWe each.
Currently there is no increasing electrical capacity at Sibayak geothermal power plant, and at present its still deliver of 12 MWe electricity.
Mataloko PLTP is a Government of Indonesia pilot project for small scale geothermal power plant in eastern Indonesia , and in 2011 Mataloko delivered a 1.8 MWe of electricity.
Intensive exploration and drilling activities in Ulubelu geothermal field was started in 2007, and up to 2009, 8 wells have been drilled to generrate 2X 55 MWe electric capacity. And then, in 2012, Ulubelu unit 1 and 2 started to operate commercially to deliver 110 MWe of electricity to PLN.
Trial exploration of the electricity that utilize the geothermal resources in Ulumbu began with drilling the first well in 2003. Drilling resumed later in 2006 for the second and the third wells. Testing of the power supply from Ulumbu geothermal Pawer plant (PLTP) officialy operated in the beginning of November 2011 for 100kW electricity from the total capacity of 2 x 2.5 MWe to 4 villages. Late November 2 x 2.5 MWe was distributed to the city of Ruteng, and in 2012 the elctricity went to neighboring districtsand then starting in 2013 across the mainland Flores.

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