TECHNICAL FEASIBILITY OF UTILIZATION OF CARBON DIOXIDE AS A HEAT TRANSFER MEDIUM FOR GEOTHERMAL ENERGY EXTRACTION IN INDONESIA BASED ON SIMULATION STUDIES
Open Access
- Author:
- Pardede, Fabiola Marella
- Graduate Program:
- Energy and Mineral Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 24, 2017
- Committee Members:
- Sarma Pisupati, Thesis Advisor/Co-Advisor
- Keywords:
- geothermal
carbon dioxide
supercritical
Indonesia
IGCC
utilization
sequestration
simulation - Abstract:
- There is a need to generate clean, sustainable power to meet the current demand in Indonesia. The current capacity only meets 86.4% of population demand even though Indonesia is ranked 10th in global coal reserves and 4th in geothermal potential. According to Indonesia’s 35,000 MW power plan, the government is making an effort to increase energy consumption from coal and renewable energy by 2025. Coal and biomass power plants play an important role in the generation of electricity in Indonesia. Approximately 25% of Indonesia’s energy consumption is from coal, and power generation is continually moving towards cleaner methods, such as gasification and utilization of renewable energy. Due to high volcanic and tectonic activities, it is predicted that more than 27,000 MW of potential untapped geothermal energy is available in Indonesia. Combining several of the most advanced clean technologies could change the foreseeable focus of power generation methods. Coal-based, gasification combined cycle power plants integrated with supercritical carbon dioxide (CO2)-based geothermal systems could potentially generate electricity with high efficiency and low carbon emissions, without the intermittency associated with solar and wind power. There is an increased need for carbon dioxide sequestration from fossil fuel plants, due to rapid increase in atmospheric CO2 levels. Ready-to-sequester carbon dioxide is available from a coal based, Integrated Gasification Combined Cycle (IGCC) power plant with high efficiency. This CO2, while being sequestered, can also be used as a heat transfer medium in a geothermal power generation system in Indonesia. This thesis examines the novel concept of utilizing CO2 from a coal-based IGCC power plant as a heat transfer medium to extract renewable geothermal energy in order to offset the energy required for compression in the CO2 sequestration process. The Darajat geothermal field in Indonesia has a high reservoir temperature that is available at relatively shallow depths. Based on earlier work, it is assumed that 10% of the carbon dioxide is sequestered within the reservoir while drawing thermal energy from a 2.6 km depth, to generate power using a direct CO2 turbine and a binary power plant. All 680 kg/s of supercritical CO2 are distributed evenly among 10 injection wells in the reservoir to be used as a heat transfer medium, and for partial sequestration. The carbon dioxide stream from the 10 production wells and the compressed supercritical CO2 from the IGCC plant are recirculated back to the injection wells. Heat rejection from the CO2 produced is accepted by the Organic Rankine Cycle to generate power. The IGCC plant CO2 output from the pre-combustion and post-combustion processes is matched with the amount of CO2 sequestered to maintain constant circulation for the geothermal plant. ASPEN Plus® software was used to simulate the geothermal power plant, circulation system, carbon dioxide heat extraction from the reservoir, and each fluid necessary to drive a closed loop Organic Rankine Cycle. Among the working fluids examined, isobutane, n-butane, R134a, and R245fa, the most suitable for the Darajat system, which has a 200°C reservoir temperature, was isobutane. This study also discusses the energy generated from a carbon dioxide turbine and a recuperated Organic Rankine Cycle by varying the temperatures and pressures of carbon dioxide injection based on an existing Darajat geothermal reservoir located in Indonesia. Power generated by a direct CO2 turbine and a binary power plant is compared with the 17.4 MW of power required to compress the CO2 for sequestration. CO2 utilization in the supercritical phase is found to be more advantageous than subcritical CO2 for power generation when using a direct CO2 turbine. A deeper, 3.6 km injection point for the Darajat-Enhanced Geothermal System yields 18.3 MW with approximately 15 years of lifetime, while a natural Darajat geothermal system with the existing wells can potentially improve the technical feasibility with a larger CO2 flow rate for additional power generation.