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Geothermal energy is one of the strategies employed by the Indonesian government to meet rising electricity demand. Developing geothermal energy is often characterized by uncertainties and requires sequential decision-making which is divided into four development phases: 1) identification, 2) exploration, 3) exploitation, and 4) engineering, procurement, construction, and commissioning (EPPC) before it can be commercialized. Traditional valuation techniques often produce a negative net present value (NPV), suggesting decision to reject the project's investment plan. This paper investigates the economic viability of a geothermal power generation project using both NPV and real options analysis (ROA). Costs and uncertainties associated with the various development phases as well as the investment structure of geothermal projects are studied. We develop a framework for assessing the impact of four uncertainties using a binomial lattice: capacity factor, electricity price, make-up well-drilling costs, and operation and maintenance (O&M) costs. Secondary data from an Indonesian context geothermal power plant was used. Positive option values were found for the lattice approach compared to negative values found for the common NPV calculation. The result of this study showed the successful outcome of the exploration stage is very critical to determining the continuation of the project. The framework supports decision-makers in evaluating the impact of geothermal power generation projects in the face of uncertainty by providing a rigorous analysis. The movement of the underlying asset's value in the whole project's lifetime will assist the management in deciding on whether to exit or continue.

Using hybrid renewable energy systems is a smart choice for reducing the carbon emitted by power plants. It also helps climate change mitigation and global warming, leading to universal health for humans and the environment. The efficiency of these systems depends on choosing the right combination of renewable sources, their sizes, and proper scheduling of the generating units. This paper suggests an optimisation method for sizing a geothermal/PV/wind/diesel system, both in off-grid and grid-connected configurations. In the grid-connected mode, the possibility of selling surplus energy generated by renewable resources to the network is considered. Investigations reveal that without accurate control of geothermal reservoirs, they may become depleted. In this study, a strategy is suggested for unit commitment; moreover, the harmony search algorithm is used to find the optimal size of the hybrid system in both configurations. The effectiveness of the proposed approach is represented by simulating an HRES for Ferdows/Iran.

Today, due to the challenges of fossil fuels and environmental crises, the use of geothermal energy as a renewable energy source can be useful. Since the two wells used for Sabalan geothermal power plant have different thermodynamic, in the present article, a new combined layout based on two flash cycles is proposed and investigated. In the introduced energy cycle, the transcritical Rankin and Kalina cycles are also used as downstream cycles to generate more power. In addition, heat exchangers are used to transfer heat to the liquefied natural gas (LNG) cycle to prevent energy and exergy losses in the downstream cycles. Relying on the proposed layout can prevent heat loss of downstream cycle's condensers. LNG cycle, in addition to generating more power by using heat losses, can supply natural gas to the system and suburban villages. It was determined that the proposed energy cycle is able to produce a net power of ~27.8 MW with a thermal efficiency of ~26%. In addition, the total exergy destruction and exergy efficiency of the cycle are 29.9 MW and 52.6%, respectively. The proposed energy cycle is evaluated from the energy and exergy points of view. In addition, a parametric evaluation is presented to assess the effect of various factors on the performance of the proposed energy cycle. Moreover, the net power and performance of the energy cycle have been optimized subject to various input variables using a genetic algorithm. [ABSTRACT FROM AUTHOR]

Using hybrid renewable energy systems is a smart choice for reducing the carbon emitted by power plants. It also helps climate change mitigation and global warming, leading to universal health for humans and the environment. The efficiency of these systems depends on choosing the right combination of renewable sources, their sizes, and proper scheduling of the generating units. This paper suggests an optimisation method for sizing a geothermal/PV/wind/diesel system, both in off-grid and grid-connected configurations. In the grid-connected mode, the possibility of selling surplus energy generated by renewable resources to the network is considered. Investigations reveal that without accurate control of geothermal reservoirs, they may become depleted. In this study, a strategy is suggested for unit commitment; moreover, the harmony search algorithm is used to find the optimal size of the hybrid system in both configurations. The effectiveness of the proposed approach is represented by simulating an HRES for Ferdows/Iran. [ABSTRACT FROM AUTHOR]

The limited fossil resources spent on thermal and nuclear power plants are alarming. In addition, their use significantly worsens the environmental situation. The use of renewable energy sources as a primary fuel is a very promising area in the production of electricity and heat. In recent years, much attention has been paid to geothermal energy, i.e. thermal processes occurring in the bowels of the Earth, to produce not only heat but also electricity. A curious engineer and talented scientist Oleksandr Kalina made a significant contribution to the creation of efficient geothermal plants of this type. He created a cycle named after him, in which an ammonia- water solution is used as a working fluid. The peculiarity of the installation that implements the Kalina cycle is that its main elements provide for such changes in solution concentrations, which cause a significant increase in thermal efficiency. Cycles and schemes of installations using ammonia-water solution are considered. Their high efficiency is confirmed. It is shown that during the transition from water to water-ammonia solution, a marked increase in specific work can be observed. It is noted that at the initial stage geothermal stations were built in areas of high volcanic activity, hot springs and geysers. It is reported that the construction of stations with the Kalina cycle can focus on the technology of "Hot Dry Rock", which allows you to place them almost anywhere on our planet. It is noted that the mitigation of the requirements for the temperature of the upper heat source in the Kalina cycle allows the development of underground layers, which were previously considered unpromising. The possibilities of more efficient electricity generation using the Kalina cycle, which uses the natural temperature difference between the heated surface of the ocean and its cold depths, are analyzed. It is noted that alternative energy, based on geothermal energy, the Kalina cycle and HDR technology, has a successful future. [ABSTRACT FROM AUTHOR]

Abstract Geothermal energy is the energy that is stored inside the earth and which may be used by man either directly (with no transformation) or to generate electricity by means of a geothermal power plant. This article estimates the participation of geothermal energy in Colombia’s electricity market by the year 2025, based on a review of current installed capacity in the country; potential sources of geothermal energy for electric power generation; the existing regulatory framework for projects involving renewable sources, and the geothermal projects currently under development in the national territory. Demand for electricity in Colombia will continue to increase, which implies that new electric power generation projects must be undertaken in order to meet the country’s demand. The conclusion is that geothermal energy is a good alternative to help achieve this objective. By 2025, geothermal sources are expected to generate at least 1400 GWh of electric power per year, equivalent to 1.65% of total electricity estimate demand in Colombia. If the full potential that has been assessed were exploited, generation capacity could reach up to 17,400 GWh/year (equivalent to close to 20% of the country’s demand) by 2025.

Finding an appropriate solution to find stable and continuous green energy is one of the significant problems of scientists in the field of renewable energy. In this study, a mixed type of system implementing two geothermal gas turbine energy combined using an innovative method, the suggested system continuously merits productivity of different production. Also, it implements renewable energies to provide the required power to generate conducts which is considered important in the green transient of governments. In addition, thermodynamic rules were used to analyze the suggested system. The results obtained from analysis and equations in the EES software show that power production and thermal load and cooling equal 1432.3kw, 937.9kw and 128.8kw, respectively. the total energy and exergy efficiency is calculated at 58.31 % and 42.17 %. The system's return on investment is calculated in twenty years, with the electricity price of 0.15$/GJ, 6.02 years and with the fuel price of C fuel = 21$/GJ, 7.15 years, and the system reaches profitability. to improve system function, the multiple optimized genetic algorithm is used. The objective function in optimizing the system is exergy efficiency and total cost, which is considered optimization MATLAB software, which means a decrease of total cost and an increase of exergy efficiency. [ABSTRACT FROM AUTHOR]

The exergy analysis method constitutes an alternative but very important technique for the evaluation of the utilization level of thermal plants as well for the comparison of different conversion processes. The loss of exergy provides a figure of merit for the inefficiencies of a process and a measure of the quality of the different forms of energy in relation to given environmental conditions. In this paper, data from an experimental geothermal drill in the Greek Island of Nisyros, located in the south of the Aegean Sea, have been used in order to estimate the maximum available work and the efficiency of a potential power plant. Different methods for estimating the exergy term are used and several types of conversion efficiencies have been calculated in order to obtain a more complemented view of the analysis. Overall, a system exergetic efficiency of 41% and a thermal one of 12.8% have been resulted supporting technical feasibility of the proposed geothermal plant. [ABSTRACT FROM AUTHOR]

Geothermal energy is a renewable form of energy, however due to misuse, processing and management issues, it is necessary to use the resource more efficiently. To increase energy efficiency, energy systems engineers carry out careful energy control studies and offer alternative solutions. With this aim, this study was conducted to improve the performance of a real operating air-cooled organic Rankine cycle binary geothermal power plant (GPP) and its components in the aspects of thermodynamic modeling, exergy analysis and optimization processes. In-depth information is obtained about the exergy (maximum work a system can make), exergy losses and destruction at the power plant and its components. Thus the performance of the power plant may be predicted with reasonable accuracy and better understanding is gained for the physical process to be used in improving the performance of the power plant. The results of the exergy analysis show that total exergy production rate and exergy efficiency of the GPP are 21MWand 14.52%, respectively, after removing parasitic loads. The highest amount of exergy destruction occurs, respectively, in condenser 2, vaporizer HH2, condenser 1, pumps 1 and 2 as components requiring priority performance improvement. To maximize the system exergy efficiency, the artificial bee colony (ABC) is applied to the model that simulates the actual GPP. Under all the optimization conditions, the maximum exergy efficiency for the GPP and its components is obtained. Two of these conditions such as Case 4 related to the turbine and Case 12 related to the condenser have the best performance. As a result, the ABC optimization method provides better quality information than exergy analysis. Based on the guidance of this study, the performance of power plants based on geothermal energy and other energy resources may be improved. [ABSTRACT FROM AUTHOR]

Pakistan is among the naturally gifted countries that are rich in conventional and renewable energy resources. Despite the massive potential of energy resources, Pakistan is still an energy deficient country and have to import petroleum products to barely accomplish its energy demand. Geothermal energy is still one of the unexplored energy resources for electric power generation in Pakistan. Pakistan can overcome the energy shortage to a significant level by harnessing renewable energy resources, such as, geothermal energy. Majority of the geothermal hot springs and mud volcanoes exists within the seismic belt of Pakistan. Therefore, the country has viable geothermal energy manifestations. Several hot springs in Gilgit and Hunza region are originated due to the collision of Indian Plate with Eurasian Plate. Similarly, various geothermal reservoirs exist in Northeast to Southeast narrow belt along Indus basin margin. The survey discusses the current energy crisis in Pakistan and addresses the role of geothermal energy for the economic development of Pakistan. We served the manifestation and geographies of geologically active zones of Pakistan, like fault lines, plate tectonics, belt, and tectonic thrust, cleanest, base load, reliable, renewable, and sustainable geothermal energy resources. In our work, the hot springs and mud volcanoes of geologically active areas in maps are enlisted in Tables with potential features. The schemes used for extraction of geothermal energy for electric power generation are also investigated. The global electric power production from geothermal energy is visualized and discussed. Moreover, the suitable moderate temperature Binary Cycle Geothermal Power Plant for electric power generation in Pakistan is also described in detail. Furthermore, geothermal plants are experimentally summarized in different case studies. Finally the performance of geothermal and conventional thermal plants is critically analysed. [ABSTRACT FROM AUTHOR]

SUMMARY Higher demand for energy consumption and importance of environmental issues has encouraged researchers and policy makers to consider renewable energies more seriously. Geothermal resources are a green energy source that can make a considerable contribution in some countries. Japan has the third ranking geothermal energy potential, and its geothermal electricity production is currently eighth in the world. Since the nature of geothermal resources dictates its method of utilization, it is important to categorize available resources. There is no consensus on classification of geothermal resources. Most scientists, from geologist to engineers, agree on the term temperature. However, temperature or enthalpy alone cannot describe the nature of fluids; they can have same temperature with different phases, such as saturated water or saturated steam. Using exergy for resource classification benefits their comparison, according to their ability to do work. In this paper, exergetic classification of geothermal resources was applied to 18 under-operating geothermal power plants in Japan. Six geothermal fields have high exergy resources according to their SExI values in excess of 0.5. The remaining geothermal fields in Japan are classified in the medium resources zone. Classification results can be used by decision makers as a reference for future geothermal development. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Based on available surveys, it has been shown that Iran has substantial geothermal potential in the north and north-western provinces, where in some places the temperature reaches 240°C. In order to better exploit these renewable resources, it is necessary to study this area. Thus, the aim of this paper is a comparative study of the different geothermal power plant concepts, based on the exergy analysis for high-temperature geothermal resources. The considered cycles for this study are a binary geothermal power plant using a simple organic Rankine cycle (ORC), a binary geothermal power plant using an ORC with an internal heat exchanger (IHE), a binary cycle with a regenerative ORC, a binary cycle with a regenerative ORC with an IHE, a single-flash geothermal power plant, a double-flash geothermal power plant and a combined flash-binary power plant. With respect to each cycle, a thermodynamic model had to be developed. Model validation was undertaken using available data from the literature. Based on the exergy analysis, a comparative study was done to clarify the best cycle configuration. The performance of each cycle has been discussed in terms of the second-law efficiency, exergy destruction rate, and first-law efficiency. Comparisons between the different geothermal power plant concepts as well as many approaches to define efficiencies have been presented. The maximum first-law efficiency was found to be related to the ORC with an IHE with R123 as the working fluid and was calculated to be 7.65%. In contrast, the first-law efficiency based on the energy input into the ORC revealed that the binary cycle with the regenerative ORC with an IHE and R123 as the working fluid has the highest efficiency (15.35%). Also, the maximum first-law efficiency was shown to be given by the flash-binary with R123 as the working fluid and was calculated to be 11.81%. [Copyright &y& Elsevier]