The Ulubelu II geothermal power plant, comprising two units of 55MW each, was developed adjacent to the 110MW Ulubelu I geothermal facility in the Ulubelu district of Lampung Province, located in the southern region of Sumatra Island, Indonesia. Pertamina Geothermal Energy (PGE) is developing the project to incorporate the substantial geothermal resources of the surrounding mountainous areas.

With a gross power output of 116MW, the project is expected to generate 867GWh a year with a load factor of 90%.

The Indonesian Ministry of Mining and Energy awarded the Ulubelu geothermal field concession area to PGE’s parent company Pertamina in October 1990. Construction of the first unit (unit 3) was completed in July 2016, while the second unit (unit 4) was completed in March 2017.

The Ulubelu I geothermal power plant is owned by state-owned Perusahaan Listrik Negara (PLN) and is not related to the Ulubelu II plant, except for sharing the name and geographical location.

Ulubelu II geothermal power plant location and make-up

The Indonesian geothermal power plant falls under the Ulubelu geothermal field, which consists of two main areas. The first area consists of more than 20 active geothermal wells and supplies steam to the Ulubelu I power plant. The second area, which supplies steam to the Ulubelu II power plant, consists of an additional 16 production wells and five injection wells.

Ulubelu II comprises a steam turbine generator, gas extraction system, switchyard and utility system. It includes the development of a steam field consisting of six well clusters, with four (B, E, G and H) used for steam production, while the other two are used for condensate and brine reinjection.

The above-ground steam field system comprises a separator station specifically for clusters B and G, with two other separators located on clusters E and H. Steam pipelines run from the separators to the power plant whereas brine pipelines run from the separators to the reinjection clusters A and F.

Two-phase pipelines were installed to connect the clusters (without separators) to the separator station. The reinjection clusters A and F are connected to the power plant by condensate pipelines.

The steam collected at Ulubelu II is separated from condensate and fed into steam turbine generator systems (direct steam expansion). Condensate returning from the turbine and the steam separator is re-injected into the geothermal field.

Power transmission and off-take from Ulubelu II

The power generated by Ulubelu II is transmitted to the interconnection point of the Ulubelu I geothermal power plant, and then onto the Sumatra interconnected grid system.

PLN purchases the entire power output under a power purchase agreement signed in March 2011.

Ulubelu II geothermal power plant financing

PGE received a $300m loan from the World Bank for developing the 110MW Ulubelu II geothermal energy facility and the 40MW Lehendong geothermal plants in Indonesia.

The financing package comprises a $175m loan from the International Bank for Reconstruction and Development and a $125m concessional loan from the Clean Technology Fund.

Contractors involved with the Ulubelu II power plant development

PGE awarded the engineering, construction and procurement (EPC) contract for the Ulubelu II geothermal power plant to the consortium of Sumitomo and Rekayasa in August 2014.

Rekayasa was contracted with the construction and installation of the two units and the above-ground steam field system.

Fuji Electric is the manufacturer of geothermal steam turbines and power generators to be installed at the geothermal plant.

Pertamina Geothermal Energy engaged Mott MacDonald for preparing the environmental and social impact assessment (ESIA) report for the project.

Geothermal market in Indonesia

Indonesia hosts the world’s biggest resources of geothermal energy and is estimated to have a geothermal capacity of approximately 29,000MW. Despite abundant geothermal resources, the nation is only able to generate about 1,340MW power from geothermal source, which is equivalent to 5% of its entire power production.

The Indonesian Government plans to develop new projects to achieve geothermal power generation of 9,500MW by 2025 in order to exploit the available resources.