Single-flash Geothermal Power Plant Research Articles

Thermal modeling and simulation of a single-flash geothermal power plant involving non-condensable gas: a case study of Kamojang geothermal field in Garut, West Java, Indonesia

The presence of non-condensable gases (NCGs) in a geothermal fluid disrupts the vacuum process in the condenser, reducing turbine efficiency and decreasing the total power output of the geothermal power plant (GPP). Therefore, to optimize the thermodynamic efficiency of a GPP, NCGs should be removed using a gas removal system. Since there is a substantial lack of design and simulation software for a GPP including NCG removal alternatives, in this study, we aimed to model and develop a software-based interface to simulate mass and energy balance involving an NCG fraction in a single-flash GPP as well as examine the thermodynamic performance of the gas removal system, which is the most important step in the planning and designing phase of a GPP. This software was validated using outputs of Kamojang GPP Units 2, 3, and 4 located at Kamojang geothermal field, Garut, West Java, Indonesia. Units 2 and 3 use two ejectors which are installed in series, and Unit 4 utilizes a hybrid system (HS) that is mostly a combination of vacuum pumps and a steam jet ejector (SJE). Our results showed that Kamojang GPP Units 2 and 3 generate 55.295 MW of power with an absolute error of 0.53%, whereas Unit 4 generates 60.218 MW of power with a 0.36% absolute error concerning the field data. These results correspond with the expected minimum error; therefore, our model’s parameters are considered valid and can be used for simulation. We found that using the simulation, the total steam saved by the HS at Kamojang GPP Units 2 and 3 was 534 kW. Furthermore, the net power production was reduced by 1.6% for the HS and 2.03% for the SJE with every 1% increase in the NCG fraction. The power requirement of the vacuum pumps remained less than the power generated by the motive steam which the ejector requires to dispose of the same amount of NCG, indicating that Kamojang GPP Units 2 and 3 will be more efficient if an HS is used.

Exergy analyses and optimization of a single flash geothermal power plant combined with a trans-critical CO2 cycle using genetic algorithm and Nelder–Mead simplex method

Compared with conventional fossil fuel sources, geothermal energy has several advantages. The produced geothermal energy is safe for the environment and suitable for meeting heating power needs. Because the hot water used in the geothermal process can be recycled and used to generate more steam, this energy is sustainable. Furthermore, the climate change does not affect geothermal power installations. This study suggests a combined power generation cycle replicating using the EES software that combines a single flash cycle with a trans-critical carbon dioxide cycle. The findings demonstrate that, in comparison to the BASIC single flash cycle, the design characteristics of the proposed system are greatly improved. The proposed strategy is then improved using the Nelder–Mead simplex method and Genetic Algorithm. The target parameter is exergy efficiency, and the three assumed variable parameters are separator pressure, steam turbine outlet pressure, and carbon dioxide turbine inlet pressure. The system’s exergy efficiency was 32.46% in the default operating mode, rising to 39.21% with the Genetic Algorithm and 36.16% with the Nelder–Mead simplex method. In the final step, the exergy destruction of different system components is calculated and analyzed.Graphical

Thermal process simulation and multi-variable study/optimization of a novel geothermal-driven multi-generation process using bi-evaporator with zeotropic mixture

Bi-evaporator technology is a robust tool, operating in two levels of coolant production for normal cooling and freezing purposes. The current study is motivated to assess the feasibility of integrating a bi-evaporator technology and a single-flash geothermal power plant. The main novelty of this paper is to design a novel combined cooling and power (CCP) production cycle relying on an organic Rankin cycle and a modified bi-evaporator refrigeration cycle. In addition, the use of a zeotropic mixture (Pentane/Isobutane) fed to the CCP is another difference between the current research and the available literature review. In addition to the power and cooling, the entire system is boosted by the use of a multi-generation process, producing heating via a heating production unit and hydrogen (H2) via a low-temperature electrolyzer. The proposed system was analyzed from the energy, exergy, specific exergy costing, and net present value points of view. Therefore, a coherent single- and dual-sensitivity study is done, and the variability of the main performance metrics is viewed against the decision parameters. In addition, owing to the incompatible trend of the newly devised plant's chief performance metrics, an advanced triple-objective optimization through a NSGA-II method is regraded from the standpoints of thermodynamics and economics. The objective functions include the coefficient of performance, exergy efficiency, and sum unit cost of products, and the optimum solution reveals their values of 33.56%, 63.2%, and 6.0 $/GJ, respectively.

Optimization of a Single Flash Geothermal Power Plant Powered by a Trans-Critical Carbon Dioxide Cycle Using Genetic Algorithm and Nelder-Mead Simplex Method

The usage of renewable energies, including geothermal energy, is expanding rapidly worldwide. The low efficiency of geothermal cycles has consistently highlighted the importance of recovering heat loss for these cycles. This paper proposes a combined power generation cycle (single flash geothermal cycle with trans-critical CO2 cycle) and simulates in the EES (Engineering Equation Solver) software. The results show that the design parameters of the proposed system are significantly improved compared to the BASIC single flash cycle. Then, the proposed approach is optimized using the genetic algorithm and the Nelder-Mead Simplex method. Separator pressure, steam turbine output pressure, and CO2 turbine inlet pressure are three assumed variable parameters, and exergy efficiency is the target parameter. In the default operating mode, the system exergy efficiency was 32%, increasing to 39% using the genetic algorithm and 37% using the Nelder-Mead method.

Thermodynamic investigation of a single flash geothermal power plant powered by carbon dioxide transcritical recovery cycle

The use of new energy sources, such as geothermal energy, is rapidly expanding worldwide, and it is a viable alternative to fossil fuels. This paper proposes a geothermal power generation system (combined single flash geothermal cycle with transcritical carbon dioxide recovery cycle). To improve system performance, a recuperator is used to recover some of the heat loss. The proposed system simulation is performed in EES software and then validated by previous research. The proposed system is analyzed from the perspective of energy and exergy. The effects of the proposed system separator pressure, carbon dioxide turbine inlet pressure and carbon dioxide condenser outlet temperature on energy efficiency, exergy efficiency and system net power output have been investigated. Findings show that the proposed system in recovery mode has a net power output of 401.40 kW, energy efficiency of 53.6 percent, and exergy efficiency of 46.32 percent, which are significantly higher than the basic mode’s values of 149.9 kW, 2.39 percent, and 12.12 percent, respectively.

Thermodynamic Investigation of a Single Flash Geothermal Power Plant Powered by Carbon Dioxide Transcritical Recovery Cycle

Thermodynamic Investigation of a Single Flash Geothermal Power Plant Powered by Carbon Dioxide Transcritical Recovery Cycle

Economic Feasibility of Green Hydrogen Production by Water Electrolysis Using Wind and Geothermal Energy Resources in Asal-Ghoubbet Rift (Republic of Djibouti): A Comparative Evaluation

The Republic of Djibouti has untapped potential in terms of renewable energy resources, such as geothermal, wind, and solar energy. This study examines the economic feasibility of green hydrogen production by water electrolysis using wind and geothermal energy resources in the Asal–Ghoubbet Rift (AG Rift), Republic of Djibouti. It is the first study in Africa that compares the cost per kg of green hydrogen produced by wind and geothermal energy from a single site. The unit cost of electricity produced by the wind turbine (0.042 $/kWh) is more competitive than that of a dry steam geothermal plant (0.086 $/kWh). The cost of producing hydrogen with a suitable electrolyzer powered by wind energy ranges from $0.672/kg H2 to $1.063/kg H2, while that produced by the high-temperature electrolyzer (HTE) powered by geothermal energy ranges from $3.31/kg H2 to $4.78/kg H2. Thus, the AG Rift area can produce electricity and green hydrogen at low-cost using wind energy compared to geothermal energy. The amount of carbon dioxide (CO2) emissions reduced by using a “Yinhe GX113-2.5MW” wind turbine and a single flash geothermal power plant instead of fuel-oil generators is 2061.6 tons CO2/MW/year and 2184.8 tons CO2/MW/year, respectively.

Energy, exergy, economic and exergoenvironmental analyses of transcritical CO2 cycle powered by single flash geothermal power plant

Abstract The need for energy is increasing worldwide as the population has a continuous trend of increase. The restrictions on energy sources are becoming tougher as the authorities set these developed and developing countries. This leads to looking for other alternative energy sources to replace the conventional energy sources, leading to greenhouse emissions. Environmentally friendly energy sources (renewable energies), for example, geothermal, solar and wind, are viewed as clean and sustainable energy sources. Among these kinds of energy sources, geothermal energy is one of the best options because, like solar and wind energy sources, it does not depend on weather conditions. In this work, a single flash geothermal power plant is used to power a transcritical CO2 power plant is proposed. The energy and exergy analysis of the proposed combined power plant has been performed and the best possible operating mode of the power plant has been discussed. The effects of parameters such as separator pressure, CO2 condenser temperature and CO2 turbine inlet pressure and the pinch point on the energy efficiency, exergy efficiency and output power are determined and discussed. Our results indicate that the highest exergy destruction is in the CO2 vapor generator of 182.4 kW followed by the CO2 turbine of 106 kW, then the CO2 condenser of 82.81 kW and then the CO2 pump 58.76 kW. The lowest exergy destruction rates occur in the single flash geothermal power plant components where the separator has exactly zero exergy destruction rate. The results also show that the combined power plant produces more power and has better efficiencies (first law and second law) than the stand-alone geothermal power plant. Finally, Nelder–Mead simplex method is applied to determine the optimal parameters such as separator pressure, power output and pumps input power and second law efficiency. The results show that the power plant should be operated at a lower pinch temperature to reduce damage to the environment. As the condenser pressure increases, the environmental damage effectiveness coefficient decreases sharply until it reaches the minimum value of 1.2 to 1.7 MPa and then starts to increase. The trend of the impact of sports on environmental improvement is exactly the opposite of the trend of the effectiveness of environmental damage. Therefore, from an environmental point of view, it is recommended to operate the gas turbine at a high inlet pressure.

Energy and exergy and economic (3E) analysis of a two-stage organic Rankine cycle for single flash geothermal power plant exhaust exergy recovery

A two-stage ORC (Organic Rankine Cycle) is being proposed for the recovery and utilization of low-grade heat from single flash geothermal power plant exhaust flue fluids. The working fluids for two-stage the recovery system are R227ea and R116. The impact of essential design parameters such as inlet temperature of the cycle, ambient temperature, geothermal turbine inlet pressure, geothermal condensation temperature on system performance are investigated using thermodynamic mathematical models regarding energy and exergy efficiencies as the objective function. The addition of the recovery section to the base cycle improves the thermal efficiency from 0.2023 to 0.2178, a 7.66% improvement in this critical metric. Furthermore, the exergy efficiency rises from 0.55044 to 0.5803, representing a 15.04% boost in exergy efficiency. Furthermore, the system's overall output rises from 7690 kW to 9898 kW, representing a substantial gain of 28.71%. The suggested recovery system's cycle has a lower LEC than a single flash geothermal cycle from an economic standpoint. LEC Reduced from $ 0.125 per kilowatt to $ 0.108 per kw, a cost savings. As a result, including a recovery section in the basic single flash geothermal cycle will significantly improve system performance.

An update of second law analysis and optimization of a single-flash geothermal power plant in Dieng, Indonesia

Dieng geothermal power plant is one of the Geothermal plants located in Indonesia with a total estimated potential of 400 MWe. The reservoir is characterized by water-dominated with 240 to 333°C temperature. Recently, the company operated one unit of single-flash system with a capacity of 60 MW. To improve its capacity, unit expansion of unit 2 and 3 are designed with each capacity of 60 MW. Apart from this expansion, another effort is optimizing the existing plant. It can be conducted with a thermodynamic approach using energy and exergy analysis. Therefore, this study aims to evaluate and optimize the existing geothermal power plant using energy and exergy analysis. With the latest data obtained, the results show that the exergy value of production wells is around 106,515 kW. The electricity production with the system is around 40,680 kW, resulting in an exergy efficiency of about 38.19%. Furthermore, the optimization is carried out on the turbine because it shows the greatest irreversibility of 11,217 kW. Optimization is done by varying the incoming turbine pressure. These results indicate that higher inlet pressure increases irreversibility and lowers energy efficiency. Furthermore, the optimum inlet turbine pressure is achieved at 5.5 bar with the maximum change depending on the ambient temperature.

Development and Analysis of the Novel Hybridization of a Single-Flash Geothermal Power Plant with Biomass Driven sCO2-Steam Rankine Combined Cycle.

This study investigates the hybridization scenario of a single-flash geothermal power plant with a biomass-driven sCO2-steam Rankine combined cycle, where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EBSILON®Professional. A topping sCO2 cycle is chosen due to its potential for flexible electricity generation. A synergy between the topping sCO2 and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger, where the waste heat from the topping cycle is utilized in the bottoming cycle. The high-temperature heat addition problem, common in sCO2 cycles, is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and a biomass-to-electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found to be 2.2 kg/s.

Energy and exergy analyses of single flash geothermal power plant at optimum separator temperature

Abstract In this work, a thermodynamic analysis consisting of energy and exergy analyses is carried out to determine the performance of a single flash geothermal power plant. A new derivation for determination of the optimum separator temperature, which results in maximum turbine power output, is achieved. The energy and exergy analyses are carried out at that optimum separator temperature. The thermodynamic derivation showed that the separator would result in maximum performance of the power plant when it operates at the average value of the production well and condenser temperatures. Moreover, the derivation was numerically validated by calculating three different values for the geothermal well temperatures. The results show that the highest exergy destruction rate is in the expansion valve followed by the steam turbine, the mixing process and the pump. The separator has exactly zero exergy destruction rate while the condenser has almost zero exergy destruction rate. The results also show that the exergy destruction rate for all components of the power plant decreases with reduction in the geofluid temperature of the production well except for the condenser. The maximum energy efficiency of the power plant is about 12.5, 11 and 9.5% when the geofluid of the geothermal well temperature is 300, 275 and 250°C, respectively.

Comparative technical and economic study of Hybrid Solar-Geothermal Power Plant in Ethiopia

This paper presents a techno-economic assessment of a hybrid solar-geothermal power plant that is modelled taking into account the available geothermal and solar energy resources at the Tendaho-1 (Dubti) geothermal field in Ethiopia. The hybrid power plant combines a single-flash geothermal power plant with a parabolic trough solar thermal plant to increase the energy level of geothermal steam. The geothermal fluid from one of the production wells at the geothermal site and the direct normal solar irradiance prevailing in the area offer the primary sources of energy used in the modelling. A thermodynamic analysis based on the principles of mass and energy conservation and a figure of merit analysis that allows evaluating the energy and economic performance of the hybrid power plant were performed. The technical and economic efficiency assessment was performed by comparing the performances of the hybrid power plant with a power system consisting of stand-alone geothermal and solar power plants. Results of the techno-economic assessment showed that for the same amount of energy inputs, depending on the available thermal energy storage capacity, a hybrid power plant generates up to 10.4% more electricity than a power system of two stand-alone power plants while generating a higher net present value at a lower cost of generation. In addition, the hybrid power plants with and without thermal storage system exhibit an economic figure of merit values of 2.62 and 3.42, i.e. the cost of solar resource per kWh of electricity in the hybrid energy system is reduced by 70.5% and 61.5%, respectively.

Renewable hybrid energy systems using geothermal energy: hybrid solar thermal–geothermal power plant

Abstract New and innovative solutions are being developed to overcome the challenges of detrimental effects that the traditional energy systems cause. This means that sustainable methods are implemented to do so, noting that when such developments are taken into consideration and are studied, this leads to a significant drop in the cost of renewable energy systems. In this work, a hybrid system consisting of a single flash steam geothermal power plant and a solar thermal system using a parabolic trough collector (PTC) is studied. Based on the available works in literature, the required design materials and modeling equations are chosen and discussed. The heat transfer fluid (HTF) as water is chosen as the working fluid for the PTC due to its low cost and high specific heat capacity. The calculations are carried out for the PTC on a specific day, time and location, and the simulations for the geothermal power plant (GPP) are carried out using System Advisor Model (SAM) software, assuming a specific increase in the temperature of the geofluid due to the additional heat transfer from the HTF of the PTC. The power plant output is 20 MW powered by four production wells. The results show that the energy production is ~15 GWh in January, which is the highest during the year due to the required energy demand for electricity consumption and district heating. Moreover, a mini review of the mathematical modeling of PTC and single flash geothermal power plant is presented.

Numerical and thermodynamic modeling for estimating production capacity of NW Sabalan geothermal field, Iran

In this paper, a new estimate of the power production capacity of the NW Sabalan reservoir is presented based on an evaluation of the recent field data. An improved three-dimensional numerical model (EOS1) was created utilizing the Tough2 simulator code. A rectangular prism with a length of 11.5 km and a width of 8 km (92.9 km) and a depth of 5.11 km is assumed for modeling. Also, 17 horizontal layers were considered for the model, with a layer thickness ranging from 100 to 1000 m, extending from the elevation of -1000 to 4110 masl. The model was validated using temperature and pressure profiles at ten deep exploration wells. The best-fit model of the natural state demonstrated the existence of an upflow of high-temperature fluid in the southern part of the area (with a recharge rate of 108 kg/s). For evaluating and predicting the power production, a thermodynamic model of the single-flash geothermal power plant was developed for the NW Sabalan field. The optimum separation pressure of approximately 5.1 bar was obtained, assuming the quality of the turbine outlet steam is equal to 0.86. At this pressure, the system yields about 31 MW of electricity as a best estimate. Then simulations of four scenarios of 25, 50, 100, and 150 MWe were carried out for 30 years using the TOUGH2 code. The results of the scenarios showed that the main factors controlling the production capacity in the NW Sabalan field are the expected pressure drop and the enthalpy of the produced fluid. This field cannot provide the required enthalpy of the produced fluid for more than 150 MWe. The field can provide enough high enthalpy fluid for a maximum capacity of 114 MWe for 70 years. For this capacity, a limit of 3.125 km2 was identified on the area of the main production zone.

Hybrid power system for effective utilization of natural energy resources

An evaluation on the technoeconomic assessment of a hybrid solar-geothermal power plant is performed taking into account the geothermal and solar energy resources available at Tendaho -1 (Dubti) geothermal site in Ethiopia. A hybrid power plant in which a single-flash geothermal power plant integrated with a parabolic trough concentrated solar power system is used as a base for the technoeconomic analysis. The technoeconomic performance of the hybrid system was compared with a power generation system composed of stand-alone solar and geothermal power plants. Results showed that the that by combining the solar and geothermal energies, in hybrid power system it is possible to generate 10.4% more electricity than it would be generated by two-stand-alone power plants. Moreover, the economic figure of merit values is found to be 3.42 and 2.62 for the hybrid power plant with and without TES respectively. This mean that the specific cost of utilizing the solar energy in the hybrid power system is lower by 70.5% and 61.5% than the specific cost of utilizing the solar energy in stand-alone solar power plant.

Wellhead Power Plants Improvement by Introduction of Double Flashing Cycle

Kenya Electricity Generating Company Ltd (KenGen) has harnessed geothermal energy for over thirty seven years at the Olkaria geothermal field. The total installed capacity of geothermal energy in Kenya currently stands at 703.5 MW generated mostly by single flash and binary geothermal power plants. In the 1990s KenGen considered the Wellheads concept in which modular containerized single flash power plants were to be designed, customized and built on a wellpad for optimized well potential; this approach has largely been successful currently having an installed capacity of 83.5 MW and accounting for 15.7% of KenGen's total geothermal installed capacity. This was done to address an inherent deficiency in the construction of conventional geothermal power plants which was identified as the long period taken to put up the power plants. The wells that have been drilled by KenGen and GDC, tested and shut in awaiting the installation of power plants are rated at about 600 MW. The Wellhead power plant cycle is a single flash geothermal power plant; this research intended to improve the current Wellheads power cycle by introducing a second low pressure separator to harness more energy from the wellheads, design a turbine to be driven by the low pressure steam and evaluate an economic justification for introducing the double flashing cycle. A case study was carried out at Wellhead 914 and Wellhead 915. Data collected indicated that the combined mass flow rate of brine from wells in the two wellpads was 240.4 tonne per hour. This brine was saturated at 13.5 bar-a and at a temperature of 193.40C as it exits the high pressure separator for disposal. The optimal pressure of the low pressure separation was designed at 2.5 bar-a, 127.40C and had an ability to generate 3871 kW of electric power. A turbine operating at a steam inlet pressure of 2.5 bar-a, a speed of 6804 rpm and having an exhaust pressure of 0.075 bar-a was designed. The designed turbine had 4 stages of both stationary and moving blades with a maximum rotor disc diameter of 0.62 meters and an output of 4195 kW. The simple payback period for this project was estimated to be 1.9 years with a rate of return on investment of 42.24%. This would also minimize energy wastage by improving efficiency and footprints on the environment arising from the Wellhead power plants.

Cryogenic energy storage powered by geothermal energy

Geothermal energy is one of the promising alternatives of power generation suitable for energy storage applications for load shifting operations. Cryogenic energy storage (CES) is an attractive option for energy storage driven by geothermal power. In this study, thermodynamic assessment of a cryogenic energy storage unit integrated to a single-flash geothermal power plant is performed and the effect of geothermal source temperature on the system performance is investigated. Initially, a resource that can supply geothermal water at 180 °C at a rate of 100 kg/s is considered. Power generated from the geothermal plant during off-peak hours is used to produce and store liquefied air. This liquefied air is used to generate power during peak hours using the heat of geothermal water. Our analysis indicates that the liquefaction unit consumes 4304 kW power in order to liquefy air for a 6-h charging period. In the discharge mode, the CES unit can produce a net power output of 12,049 kW for a 1-h operation. The flashing pressure is optimized at 255 kPa for which the total power output is 16,100 kW. The round-trip efficiency of the CES unit is determined to be 46.7% while the overall efficiency of the integrated system is 24.4%.

Performance improvement of a single-flash geothermal power plant in Dieng, Indonesia, upon conversion to a double-flash system using thermodynamic analysis

We investigated proposed design of a double-flash system and compared it to the existing single-flash power plant in Dieng, Indonesia, which uses waste brine from a high pressure separator. The performance of the double-flash system was evaluated using the second law of thermodynamics, and this was based on energy and exergy analyses. The Engineering Equation Solver (EES) was used to solve the relevant mathematical equations.Our results indicate that the double-flash design is interesting for application in Dieng since the power output would increase by 19.97%. Moreover, the precipitation system to avoid silica deposition in the injection well does not have to change much. Therefore, the building costs associated with the new double-flash system would be minimal. The available exergy from the reservoir is 66,204 kW based on the enthalpy determined by TFT (Tracer Flow Test) measurements. The single-flash power plant has a net power output of 23,400 kW with a second law efficiency of 36.7%. In the double-flash design, components such as a LPS, a second purifier and an HPT would be added to the plant. Furthermore, our calculations indicate that the power plant's output and second law efficiency would increase to 29,155 kW and 44.04%, respectively. The waste brine disposed of using this precipitation system would decrease by 8.22% at 5443 kW.

Exergy analysis and optimization of Dieng single-flash geothermal power plant

Exergy analysis and optimization of a single-flash geothermal power plant are conducted by developing a mathematical model that is applied to the Dieng geothermal power plant in Indonesia. Calculations are conducted by using the Engineering Equation Solver (EES) code using methods based on the laws of thermodynamics. The exergy flow and efficiency are computed at several plant components, including the separator, turbine, condenser, and for the whole power plant.The exergy of the geothermal fluid that is discharged from the production wells is estimated to be 59.52MW. This amount of fluid produces 21.71MW of electricity from the power plant overall, with second law efficiency to be 36.48%. There is a considerable amount of waste brine, amounting to 17.98% (10.70MW) of the total available exergy, which is disposed of in the plant’s reservoir. The optimization of the plant is carried out by adjusting the separator pressure. The results show that a slight increase of 20kW in the output power can be attained by lowering the separator pressure to 9bar from 10bar. The Grassmann diagram shows the exergy losses at each component in the power plant. The turbine and separator losses are 7.51MW (12.62%) and 8.04MW (13.5%), respectively, while the cooling tower has an exergy loss of 2.62MW (4.40%). The total condenser loss is 5.8MW (9.75%).