Sarulla Geothermal Powerplant: The largest single-contract geothermal powerplant
One only has to experience a power outage to be reminded of how much we take electricity for granted. Our lighting and cooling systems no longer operate. Computers, televisions, videos and other telecommunication system become unusable. Traffic control lights become useless; elevators no longer move people; and industries, schools, and commercial buildings become virtually inoperable.
We are clearly dependent on electricity for most of our every day activities. This dependence also demonstrates why electricity is regarded one of the most significant sociological inventions of the 20th Century. Although Java enjoy the full benefits of electricity, other islands simply does not. Supplying electricity to these areas under various economic, environmental, social, and political constraint is the major challenges in the 21st Century.
In Sumatra where power outage is a common occurrence, there is an urgency to develop new power plant to fulfill the needs especially around North Tapanuli, North Sumatra. Pertamina through Pertamina Geothermal Energy (PGE) has Joint Operation Contract (JOC) with Sarulla Operation Limited [Itochu-Kyushu-Ormat-Medco] to operate the largest single-contract geothermal power plant. The Construction of phase one already started in 2014 and the first phase started in 2017.
On March 2018 I actually went to Sarulla to help commission the newly installed steam turbine. The Powerplant is using geothermal combined-cycle units. What makes Sarulla Powerplant interesting is that they used what is called binary cycle + single flash system cycle which makes it truly novel, since the reservoirs are liquid dominated (around 70% liquid and 30% steam).
Hot brine is pumped from the reservoir through counter-flow heat exchanger. A working fluid such as pentane is vaporized in the heat exchangers. The vapor is piped to the turbine generator, expanded, condensed and returned to the heat exchanger. the brine itself then reinjected to the well. The binary pressure have significant impact and application for geopressure and hot dry rock reservoirs. This cycle needs a specialized equipments since the working fluid is not water.
On top of that the steam from reservoir is also use to generate power using single flash system which looks like this:
Combined, the two cycle and BOOM, you have combined cycle power plant. The technology itself is borrowed from US-Israel company Ormat Technology. Ormat’s technology allows practically 100% re-injection of the geothermal fluid back into the reservoir, maintaining the sustainability of the geothermal resource thus increasing power and mitigates the negative effect of gases, It also minimizes leaks of non-condensable gas. The selected configuration provides the lowest project risks related to brine chemistry and maximizes the life of the reservoir.
Here are the key findings for policy makers:
- When fully operational in 2018, Sarulla GPP will increase geothermal capacity by 20%, increase renewable capacity by 5% and meet 10% of the projected geothermal capacity additions in Indonesia between 2013 and 2020. The project is also estimated to save 1.3 mt of CO2 annually (SOL 2013), create thousands of additional jobs and may spur the local economy through the creation of new business, such as food, transportation and accommodation.
- Increasing geothermal capacity fivefold by 2025 to meet its 7.6 GW target, may require the government to take a larger role — especially in exploration. Many countries’ experience suggests the high risks associated with exploration remain a significant barrier to the scale up of geothermal. In fields where there is little interest in private exploration, government could play a larger role by either performing the exploration itself before tendering out proven concessions to the private sector or providing financial support to the private sector.
- Sarulla GPP delivers power at a comparable cost to other geothermal projects globally, but is still a more expensive source of baseload power in Indonesia than coal. CPI estimates that the project’s levelized cost of electricity (LCOE) amounts to USD 7.8–8.2 ¢/kWh and would increase by USD 1 ¢/kWh in the absence of public support. The cost, with or without public support, is broadly competitive with various benchmarks for geothermal projects in Indonesia and globally. However, even when public support is not taken into account, the cost of baseload power from Sarulla GPP is still 40–60% higher than coal in Indonesia if the cost of emission and health impacts are disregarded.
- Geothermal development worldwide is typically hampered by high costs, usually requiring at least 70% of expected capacity to be drilled before commercial financing is available. While the involvement of commercial lenders in Sarulla’s field development “may not always be replicable in other projects,” the project’s completion despite a complicated regulatory framework, concerns about electricity tariffs, and complex financing and bankability issues deserves recognition.
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