Construction on the Sarulla geothermal power plant began in May 2014. Image courtesy of Toshiba Corporation.
The Sarulla geothermal plant is operated by Sarulla Operations Limited (SOL). Image courtesy of ITOCHU Corporation.
The first unit of the Sarulla geothermal plant came on line in March 2017. Image courtesy of INPEX CORPORATION.
The second unit of the Sarulla geothermal plant was commissioned in October 2017. Image courtesy of INPEX CORPORATION.

The 330MW Sarulla geothermal power plant, located in North Sumatra province of Indonesia, is one of the biggest geothermal power plants in the world.

Construction on the $1.7bn project began in May 2014 and the first and second generating units of the plant became operational in March 2017 and October 2017 respectively.

The project achieved full commercial operation following the completion of the third 110MW unit in May 2018.

The plant is owned and operated by Sarulla Operations (SOL), a consortium of five companies including Kyushu Electric Power (25%), Itochu (25%), PT Medco Power Indonesia (18.99%), INPEX (18.25%), and ORMAT International (12.75%).

It can generate sufficient electricity to power approximately 2.1 million Indonesian households and offset approximately 1.3 million tonnes (Mt) of carbon dioxide emissions a year.

Sarulla geothermal project history and development

During 1993 and 1998, Unocal North Sumatra Geothermal (UNSG), in a joint operation contract (JOC) with Indonesia’s national energy company PT Pertamina, drilled 13 deep exploration wells and discovered 330MW of geothermal resources at the Sarulla geothermal project site.

Indonesia’s national electricity utility PT Perusahaan Listrik Negara (PLN) acquired Unocal‘s interest in the project in February 2004 and retendered the project in December 2004.

A consortium formed by Medco Energi Internasional, Ormat Technologies, and Itochu won the tender to develop the power project in 2006. Kyushu Electric Power joined the consortium in 2007.

The joint operation and energy sales contracts for the project were finalised in April 2013 after a series of renegotiations.

Loan agreements worth $1.17bn were signed by SOL with Asian Development Bank (ADB), Japan Bank for International Cooperation (JBIC) and six other commercial banks in March 2014. The project achieved financial closure two months later, in May 2014.

The Government of Indonesia, through the Ministry of Finance, issued a 20-year business viability guarantee letter (BVGL) to provide guarantee for PLN’s financial obligation.

Sarulla geothermal power plant location and design details

The Sarulla geothermal power station is located in Pahae Jae and Pahae Julu sub-districts in North Tapanuli Regency, North Sumatra Province.

The project uses an integrated geothermal combined-cycle power plant (IGCC) concept developed by Ormat. It comprises three geothermal power generation units with a nameplate capacity of 110MW each. The first unit is located at Silangkitang (SIL) in Pahae Jae, while the other two are located at Namora-I-Langit (NIL) reservoir in Pahae Julu.

The power generating units of the plant are supplied with geothermal fluid from the steam production and injection facilities at Silangkitang and Namora-I-Langit reservoirs.

Each unit is installed with one geothermal combined-cycle unit (GCCU) and two back pressure steam turbines, and two bottoming Ormat Energy Converters (OECs) to produce power using low-pressure steam and the separated brine captured from the wells.

The gases and fluids generated during the power production are injected back into the ground using air-cooled condensers, in order to improve sustainability.

Power transmission from the Sarulla geothermal project

A 20km-long 150kV power transmission line was built from the Silangkitang and Namora-Langit fields to the PLN’s 150/275kV substation to transmit electricity from the Sarulla geothermal power plant to the national grid.

Key players involved

PT Pertamina Geothermal Energy (PGE) signed a Joint Operation Contract (JOC) with Sarulla Operations in April 2013 to develop and operate the geothermal field for 30 years.

PLN purchases the electricity generated at the plant, under a 30-year power purchase agreement signed with Sarulla Operations in the same month.

Hyundai Engineering and Construction was selected as the engineering, procurement and construction (EPC) contract for the plant.

Ormat supplied provided the GCCU conceptual design well as the energy converters for all the three units of the plant.

Toshiba was contracted in July 2014 to supply three 60MW geothermal steam turbines and generators (STGs) for the flash systems.

Halliburton undertook drilling of the steam production and injection facilities and provided integrated process management services, under a contract awarded by SOC.

Thermochem provided well testing services for the Sarulla geothermal power plant.