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Calculation of gross electrical power from the production wells in Lahendong geothermal field in North Sulawesi, Indonesia

Maluegha, Benny Lokombanua (2010) Calculation of gross electrical power from the production wells in Lahendong geothermal field in North Sulawesi, Indonesia. Masters by Coursework thesis, Murdoch University.

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Geothermal energy in the Province of North Sulawesi in Indonesia has potential to produce 865 MW of electricity. One of the geothermal prospects in North Sulawesi that has been developed to generate electricity is Lahendong geothermal field. Nine production wells have been drilled and produce two phase fluid (mixture between vapour and liquid) with temperature ranges from 250oC to 350oC. Currently, three 20 MW geothermal power plants have been constructed (Unit 1, Unit 2, and Unit 3) in the field. Power plant Unit 1 and Unit 2 have been operated to supply electricity, while Unit 3 is still undergoing operational tests since April 2009.

The main objective of this dissertation is to calculate the gross electrical power of production wells in Lahendong geothermal field by using thermodynamic analysis for a single-flash steam plant. Unfortunately, only data of seven production wells (LHD-8, LHD-10, LHD-11, LHD-12, LHD-15, LHD-17, and LHD-18) in June 2008 are available. The data consist of daily average of wellhead pressure of each production well and daily average of combined flow rates of the steam from the seven production wells that is used to drive the turbines in power plant Unit 1 and Unit 2 during June 2008. Therefore, the calculation is conducted based on the available data.

Two kinds of calculations are conducted in this dissertation. First, the calculation of gross electrical power of each production well; and second, the calculation of gross electrical power that can be generated by the combined flow rates of the steam from the production wells. All calculations are performed for a range of separator temperatures and sink temperatures, using multiplies of 5oC.

Mass flow rate of the geothermal fluid of each production well is not provided; accordingly, only the specific gross electrical power (kW/(kg/s)) of each well can be calculated. From the calculation, it is found that the steam produced by LHD-18 has the lowest specific gross electrical power i.e. 26.12 kW/(kg/s), which is produced at reservoir temperature of 171.4oC and sink temperature of 60oC. The highest specific gross electrical power, 128.56 kW/(kg/s), is produced by LHD-17 at reservoir temperature of 286.5oC and sink temperature of 45oC. The specific gross electrical power depends on the reservoir temperature (wellhead temperature), separator temperature, and sink temperature.

Based on the data of daily average of total mass flow rate in June 2008, in normal condition, the steam supplied to power plant Unit 1 is almost equal to Unit 2 that is around 143 to 146 tonnes/hour. This flow rate enables each power plant to generate electricity from 14.13 MW to 21.33 MW. Equipment failures will significantly reduce electricity production.

Item Type: Thesis (Masters by Coursework)
Murdoch Affiliation(s): School of Engineering and Energy
Supervisor(s): Pryor, Trevor
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