Investigation of Energy and Exergy of Geothermal Organic Rankine Cycle (original) (raw)
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The present study considers a thermodynamic analysis and performance optimization of small binary-cycle geothermal power plants operating with moderately low-temperature and liquid-dominated geothermal resources in the range of 110 o C to 160 o C. The paper consists of an analytical and numerical thermodynamic optimization of selected Organic Rankine Cycles (ORC) to maximize the cycle power output. The optimization process and Entropy Generation Minimization (EGM) analysis were performed to minimize the exergy loss of the power plant. Optimal operating conditions were determined for maximum cycle power output per unit mass flow rate of the geothermal fluid. The maximum cycle power output was observed to increase exponentially with the geothermal resource temperature, whereas the optimal turbine inlet temperature increased almost linearly with the increase in the geothermal heat source. In addition, a performance analysis of selected organic working fluids, namely refrigerants R123, R152a, isobutane and n-pentane, was conducted under saturation temperature and subcritical pressure operating conditions of the turbine. Organic fluids with higher boiling point temperature, such as n-pentane, were recommended for the basic type of ORCs, whereas those with lower vapour specific heat capacity, such as butane, were more suitable for the regenerative ORCs.
Applications of Geothermal Organic Rankine Cycle for Electricity Production
Journal of Cleaner Production, 2020
This review deals with organic Rankine cycle powered by geothermal resource which is one favorable substitute for conventional fossil energy. Organic Rankine cycle power plants are suitable for utilization of low-temperature energy sources (low grade energy) such as geothermal resource having low temperature (below 150 ᵒC). The applications of organic Rankine cycle for electricity production from geothermal energy resource was reviewed first, where the choice of geothermal energy resources and organic fluids was discussed for different ORC configurations and operating conditions. Hybrid optimization approaches for the purpose of maintaining long term performance of enhanced geothermal system reservoirs were also summarized. Furthermore, an in-depth review of energy and exergy efficiencies of ORCs was conducted. Key factors that influence the energy and energy efficiencies of organic Rankine cycle were discussed in detail. Then, the economic indexes such as electricity production cost and levelized cost of electricity for different organic Rankine cycle configurations were compared with other conventional power generation systems to examine the commercialization of the Organic Rankine cycle. Finally, life cycle assessment that evaluates the whole life performance of geothermal organic Rankine cycle energy systems was reviewed. The Environmental impacts of geothermal ORC were also considered. Compared with other review papers on geothermal organic Rankine cycle s, the present review provides the latest materials for more systematically surveying the geothermal organic Rankine cycle, which will be a valuable source of guidance and directions for engineers and researchers in this field.
Comparison of Enhanced Organic Rankine Cycles for Geothermal Power Units
2014
Binary cycles have drawn the attention as a technical solution for the geothermal power production. This attention is mainly due to the huge potential of medium-low temperature geothermal sources, typically exploited by means of a binary cycle, and the relevance of the environmental concern, which can be conveniently dealt with by means of a closed cycle. The binary cycle has been therefore the object of an extended research activity, in order to attain higher plant performance. A crucial matter is the improvement of the heat introduction process. For a given geothermal fluid in liquid state, i.e. for a variable temperature heat source, in a conventional ORC the working fluid evaporation process is responsible for an important second law loss: removal of this loss allows greater power and possibly higher cycle efficiency to be attained. Aim of the present paper is to investigate and compare recently proposed technical solutions based on the current technology, which do not entail co...
SUMMARY The present study considers a thermodynamic analysis and performance optimization of geothermal power cycles. The proposed binary-cycles operate with moderately low temperature and liquid-dominated geothermal resources in the range of 110°C to 160°C, and cooling air at ambient conditions of 25°C and 101.3 kPa reference temperature and atmospheric pressure , respectively. A thermodynamic optimization process and an irreversibility analysis were performed to maximize the power output while minimizing the overall exergy destruction and improving the First-law and Second-law efficiencies of the cycle. Maximum net power output was observed to increase exponentially with the geothermal resource temperature to yield 16–49 kW per unit mass flow rate of the geothermal fluid for the non-regenerative organic Rankine cycles (ORCs), as compared with 8–34 kW for the regenerative cycles. The cycle First-law efficiency was determined in the range of 8–15% for the investigated geothermal binary power cycles. Maximum Second-law efficiency of approximately 56% was achieved by the ORC with an internal heat exchanger. In addition, a performance analysis of selected pure organic fluids such as R123, R152a, isobutane and n-pentane, with boiling points in the range of À24°C to 36°C, was conducted under saturation temperature and subcritical pressure operating conditions of the turbine. Organic fluids with higher boiling point temperature , such as n-pentane, were recommended for non-regenerative cycles. The regenerative ORCs, however, require organic fluids with lower vapour specific heat capacity (i.e. isobutane) for an optimal operation of the binary-cycle.
Organic Rankine Cycle (ORC) in geothermal power plants
Journal of Physics: Conference Series, 2019
Organic Rankine Cycle is a technology that convert low-temperature heat sources into a mechanical energy, and it can be used to produce electrical energy in a closed system. The heat sources can be received from renewable energy such as geothermal, solar, and biomass. Furthermore, the ORC system can also be used to increase energy efficiency in the industry by utilizing the waste heat produced. Therefore, there are two classification of the ORC system, namely a heat recovery system and binary power plant. Recently, the ORC system has made a thrive in the geothermal power plant. The ORC system can be applied to resources with low to medium temperature characteristics (<90°C - 150°C). This paper will present an overview of the implementation, model, and innovation of ORC system technology in geothermal resources.
Analysis of organic Rankine cycle based on thermal and exergy efficiency
Journal of Physics: Conference Series, 2020
The binary power plant is a geothermal power generation system used at low to medium temperature levels and used indirect system. In this system, the heat generated from the reservoir is channelled to the secondary working fluid which has a lower boiling point than water using a heat exchanger. In this case, the Organic Rankine Cycle (ORC) is a suitable system for use. This improves the performance and efficiency of the plants. However, in this system, the installation configuration of the ORC model is an important factor that can affect its performance. The selection of an improper ORC design reduces the thermal efficiency of the system. Therefore, it cannot utilize heat optimally. In this study, Engineering Equation Solution (EES) simulation program is used to run the system as in operation conditions. A comparative analysis is conducted using ORC, Regenerative ORC (RORC), and RORC with Internal Heat Exchanger (IHE). The results indicate that RORC with IHE has the greatest value f...