Organic Flash Research Articles

Analysis of the performance enhancement of dual-pressure organic flash cycle using a split-flow evaporator and an ejector driven by low-grade energy

To reduce the irreversibility of the throttling in a dual-pressure organic flash cycle (DOFC), this study presents a modified DOFC integrating a split-flow evaporator and an ejector (EE-DOFC). In the EE-DOFC, the flow from the preheater flows into the split-flow tank (ST) and then is split into two parts. One part enters the split-flow evaporator. The other part enters the ejector and entrains the high-pressure (HP) turbine exhaust vapor. The effects of the evaporation pressure, ejector entrainment ratio, and HP turbine outlet pressure on the EE-DOFC performance are studied. The performances of the DOFC, and EE-DOFC are compared under the maximum net power output conditions. The results reveal that after the split-flow evaporator and ejector are integrated, the irreversibility of the pump and mixer decreases and the exergy losses of the ejector and heat exchanger of the EE-DOFC become lower than those of the throttling valves and heat exchanger of the DOFC. The exergy loss of the discharged water is lower in the EE-DOFC than in the DOFC. The net power output and the corresponding levelized cost of electricity (LCOE) of the EE-DOFC are higher by 10.72 % and lower by 10.92 %, respectively, compared with those of the DOFC.

Techno-economic and advanced exergy analysis and machine-learning-based multi-objective optimization of the combined supercritical CO2 and organic flash cycles

In the past few years, attention has been directed towards the advancement of renewable-driven supercritical CO2 recompression Brayton (SCRB) cycles. This highlights the impacts of sustainable and efficient power production towards transition in the electricity sector. The combination of the SCRB cycle with the organic flash cycle (OFC) is comprehensively investigated from thermodynamic, techno-economic, environmental, and advanced exergy perspectives. Conventional thermodynamic analysis alone cannot provide information on the cause of irreversibilities, the interconnections between components, and the possibility of enhancing their performance; therefore, advanced exergy analysis is implemented. Furthermore, an examination has been conducted into the effects of different decision parameters on the exergoenvironmental indicators. Multi-objective optimization based on machine learning is performed on the SCRB/OFC plant to maximize exergy efficiency, net present value, and net power output. Results from advanced exergy analysis revealed that the reactor has the worst performance, with just 2.8 % of its total exergy destruction being avoidable. Furthermore, it is feasible to decrease its total exergy destruction rate by 21.6 % through enhancements in the performances of other components. Under the optimized conditions, exergy efficiency, net present value, and net power output are found to be 70.8 %, 1347.1 M$, and 306.4 MW, respectively, representing a 21.1 %, 68.9 %, and 21.1 % enhancement compared with the base conditions, respectively.

Thermodynamic analysis and optimization of the TI-PTES based on ORC/OFC with zeotropic mixture working fluids

Thermal Integrated Pumped Thermal Energy Storage (TI-PTES) is a promising technology for large-scale energy storage attributed to the advantages of geographical independence, high efficiency, low cost, and easy coupling with other systems. Little research has been dedicated to TI-PTES based on the organic flash cycle (OFC). This study established thermodynamic analysis of the TI-PTES based on the organic Rankine cycle (ORC) and OFC. The effects of system configurations and key parameters are explored. A multi-objective optimization is introduced to optimize the ORC-TI-PTES, and the P2P efficiency of 57.18 %, exergy efficiency of 37.47 %, and ESD of 4.4 kWh/m3 are achieved. The potential application of zeotropic mixture working fluids in the OFC-TI-PTES is investigated. The DOFC-TI-PTES with [R365mfc(60 wt%) + R1234ze(Z)] shows the best performance among the four OFC configurations. The achieved P2P efficiency and exergy efficiency are 46.66 % and 29.18 %, lower than the ORC-TI-PTES. However, the DOFC-TI-PTES provides an ESD of 11.487 kWh/m3, which is significantly higher than that of the ORC-TI-PTES. ORC-TI-PTES is suitable for energy storage applications that prioritize high thermal and exergy efficiencies, whereas OFC-TI-PTES is suitable for scenarios requiring high ESD.

Performance Analysis and Optimization of Supercritical CO2 Recompression Brayton Cycle Coupled With Organic Flash Cycle With a Two-Phase Expander

Abstract In this work, a combined supercritical CO2 recompression Brayton cycle (SCRBC)/organic flash cycle with a two-phase expander (OFCT) system is proposed to improve the thermal efficiency of the SCRBC, which utilizes a two-phase expander to replace the high-pressure throttling valve of a basic organic flash cycle (OFC). In addition, the OFCT is coupled at the waste heat end of the SCRBC as the bottom cycle for the use of waste heat at low temperatures. A comprehensive comparison is carried out for different organic working fluids, including the R123, R245fa, R142B, R236ea, and R600, regarding the thermal performance, environmental effect, and safety levels. Furthermore, influences of various factors on the thermal performance of the combined SCRBC/OFCT cycle are also examined, including the top cycle pressure ratio, top cycle turbine inlet temperature, mass flowrate ratio, evaporation temperature, and the condenser's pinch point temperature difference. A multi-objective optimization approach is employed on the combined SCRBC/OFCT system, which considers both the thermal efficiency and the specific investment cost as the objective function, and the optimization procedure is implemented through the nondominated sorting genetic algorithm II (NSGA-II) algorithm. The Pareto solution set and the compromise solution are finally obtained. The results indicate that the optimized combined SCRBC/OFCT system can improve the thermal efficiency by 11.75% and 9.70% when compared with the SCRBC and SCRBC/OFC, respectively.

Study of two thermally integrated pumped thermal electricity storage systems using distinct working fluid groups: Performance comparison

As a competitive new energy storage technology, the thermally integrated pumped thermal electricity storage (TI-PTES) system has received much attention. In this work, two TI-PTES systems are constructed: the RHP-BORC system, which consists of a heat pump cycle (HP) with a regenerator and a basic organic Rankine cycle (BORC), and the RHP-EOFC system, which consists of a HP with a regenerator and an organic flash cycle with ejectors. Meanwhile, R1233zd(E) and Cis-butene are selected to form R1233zd(E)/R1233zd(E) (denoting the working fluid used in the charge and discharge cycles, respectively), R1233zd(E)/Cis-butene, Cis-butene/Cis-butene, and Cis-butene/R1233zd(E) groups. Thermodynamic and economic analyses as well as multi-objective optimization are performed for both systems. The results indicate that for the two systems with different working fluid groups, different parameters have distinct effects on the system performance, and the thermodynamic and economic performance of the RHP-BORC system is better than those of the RHP-EOFC system. For the RHP-BORC system, with the variations of thermal storage temperature, evaporation temperature of heat pump and pinch point temperature difference, the values of different performance metrics of the system with different working fluid groups are close respectively, such as power-to-power efficiency, energy storage density and annual emission reduction. For the RHP-EOFC system under different parameter conditions, when the system uses R1233zd(E)/Cis-butene and Cis-butene/Cis-butene, the performance is better. From the results of the multi-objective optimization, the optimal working fluid group of the RHP-BORC and RHP-EOFC systems are Cis-butene/Cis-butene and R1233zd(E)/Cis-butene, and the values of the power-to-power efficiency and the levelized cost of storage under the optimal solution conditions are 75.76 %, 0.234 $·kWh−1, and 84.31 %, 0.227 $·kWh−1, respectively. The results of the exergy destruction analysis under the optimal solution conditions show that the largest exergy destruction in the RHP-BORC and RHP-EOFC systems are in the condenser (480 kW) and compressor (1275 kW) of the HP cycle. This work expands the configuration of the TI-PTES system, showing promising development prospects. It also provides theoretical support for the further advancement of the TI-PTES system and offers valuable guidance for the design of such systems.

Thermodynamic, economic, and environmental analyses and multi-objective optimization of an organic flash regenerative cycle with an ejector for geothermal heat utilization

Based on the existing organic flash regenerative cycle (OFRC), this paper presents a novel OFRC system incorporating an ejector (E-OFRC). The ejector replaces the high-pressure throttle valve for initial flash evaporation and utilizes a low-pressure throttle valve for the second flash evaporation of saturated liquid separated from the first flash. The gaseous working fluid from the second flash is employed as the ejecting fluid. The E-OFRC system employs an ejector to mitigate irreversible losses associated with high-pressure throttle and to drive gaseous working fluids from secondary flash to circulate to enhance overall system performance. Thermodynamic, economic, and environmental models are established, and the impacts of flash pressure (P4), endothermic pressure (P3), and geothermal water temperature (THS,in) on system performance are analyzed and compared with those of the OFRC system. Multi-objective optimization using the Dragonfly algorithm is conducted, while the TOPSIS method is utilized to determine optimal operating parameters for the E-OFRC system. The findings indicate that, in comparison to the OFRC system, the thermal efficiency of the E-OFRC system is only lower under P3, while its thermodynamic, economic, and environmental performance is enhanced under other considered conditions. This underscores the advantages of the E-OFRC system. The optimal operating parameters for the E-OFRC system are THS,in = 423.53 K, P3 = 1.89 MPa, P4 = 0.96 MPa; yielding a net output power of 84.75 kW, a specific investment cost of 2833.54$/kW, and an annual CO2 equivalent emission reduction of 0.807 × 106kg − providing valuable technical support for engineering applications.

Thermal integration process for waste heat recovery of SOFC to produce cooling/H2/power/freshwater; cost/thermal/environmental optimization scenarios

High-temperature fuel cells (HT-FCs) indeed hold significant promise for enhancing energy systems' efficiency and environmental sustainability. Consequently, there is growing interest in exploring and developing innovative strategies to optimize the integration of heat recovery processes with HT-FC technology. The current research presents an innovative and environmentally friendly poly-generation unit that integrates advanced subprocesses to generate essential products. These final products include electricity, refrigeration, pure water, and hydrogen. This study signifies a significant step towards sustainable and efficient energy production while meeting diverse needs for different utilities. The design unit incorporates a novel modified dual ejector-based organic flash cycle, reverse osmosis water purification, and a water electrolyzer for hydrogen extraction, all integrated with a high-temperature solid oxide fuel cell. Energy, exergy, economic, and environmental (4E) analysis is conducted to thoroughly evaluate the proposed plan. Furthermore, a comprehensive parametric analysis and sensitivity study are performed to pinpoint the key design parameters of the poly-generation unit. To attain the optimal operational status of the poly-generation unit, a three-objective NSGA-II optimization technique is employed to fine-tune the system's performance within the exergy-cost-environmental framework. This approach aims to strike a balance between maximizing efficiency, minimizing costs, and reducing environmental impact for sustainable operations. In addition, a net present value analysis spanning a 20-year timeframe was conducted to assess the profitability of the devised unit. Based on the findings, it is evident that the sensitivity index of the fuel cell operating temperature carries substantial importance, registering a notable value of 0.60. Additionally, the optimization outcomes reveal the system's enhanced performance metrics: an exergetic efficiency of 41.11 %, a unit cost of 58.96 $/GJ, and a carbon dioxide emission reduction rate of 418 kg/MWh. Also, the unit's payback period is shortened from 11.33 years to 8.817 years. Moreover, it improved the unit's sustainability index and net present value, raising them from 1.544 to 4.98 M$ to 1.66 and 7.38 M$.

Techno-economic comparison of organic fluid between single- and dual-flash for geothermal power generation enhancement

The geothermal energy has become a research focus due to its unique advantages as the renewable energy source. Organic Rankine cycle (ORC) is one of the important technologies for geothermal power generation, but ORC has a large irreversible loss and a low overall efficiency. The organic Rankine single-stage flash cycle (ORSFC) and organic Rankine dual-stage flash cycle (ORDFC) are proposed in this paper, and the corresponding mathematical models are established. The influence of operating parameters on techno-economic performance of three power generation systems is studied. Additionally, the comparison of the techno-economic performance of three power generation systems is conducted. The results show that the lower condensation temperature and pinch point temperature difference of heat exchangers improve the power generation performance. The evaporation temperature and flash temperature can be regarded as equivalent temperatures. Compared with the ORC system, the average increase in net output power of ORSFC and ORDFC systems is 22.87 % and 31.71 %, respectively, while the economic performance decreased by 0.98 % and 6.48 %, respectively. Therefore, it is recommended to use ORSFC as the incomplete evaporation power generation system. The R245fa is the optimal choice for ORC system, while the R601 and R601a are more suitable for ORSFC and ORDFC systems.

Triple-objective optimization using ANN+NSGA-II for an innovative biomass gasification-heat recovery process, producing electricity, coolant, and liquefied hydrogen

A novel thermal integration approach is introduced for a biomass-driven gas turbine power plant that generates electricity, coolant, and liquefied hydrogen. The designed scheme encompassed an organic flash cycle, a bi-evaporator ejector refrigeration unit, a high-temperature water electrolyzer for hydrogen production, a multi-effect desalination cycle for supplying water for electrolysis process, and a Claude cycle for hydrogen gas liquefaction. The designed system's importance comes back to using biomass feedstock as the input fuel and utilizing the hydrogen liquefaction method. In addition to the possibility of deploying the system in remote areas, it provides the opportunity for hydrogen storage in a smaller volume for more accessible storage and transportation. On the other hand, using a comparative method for selecting an environmentally friendly fluid for the heat recovery subsystem is another crucial aspect of the present study from the environmental aspect. It is found that R161 is the appropriate choice among the seven studied working fluids. Subsequently, a comprehensive evaluation of the entire system's thermodynamic and environmental aspects is performed using an intelligent process. By considering energy and exergy efficiencies along with CO2 emissions as the objective functions, a thorough sensitivity analysis and a triple-objective optimization are carried out. Hence, artificial neural networks for the objectives are developed and integrated into the NSGA-II optimization method. Employing LINMAP decision-making, the values of objective are attained, exhibiting 39.6 % for energy efficiency, 36.1 % for exergy efficiency, and 631.7 kg/MWh for CO2 emissions. Considering the optimum solution, the proposed system is capable of producing electricity, cooling, and liquefied hydrogen with capacities of 4526 kW, 1875 kW, and 21.22 m3/day, respectively. Additionally, the scenario yields an exergoenvironmental index of 0.579 and an exergetic stability index of 0.61. and a liquefied hydrogen generation rate of 21.22 m3/day.

Proposal of a geothermal-driven multigeneration system for power, cooling, and fresh water: Thermoeconomic assessment and optimization

The depletion of fossil fuel reserves and environmental challenges have prompted the exploration of alternative energy sources. Geothermal energy, extractable from within the Earth's crust, emerges as a reliable renewable option throughout the mentioned shift. In this regard, the presented study introduces a geothermal-powered multigeneration system designed to generate power, manage cooling loads, and produce fresh water. This comprehensive system incorporates an organic flash cycle, a half-effect absorption refrigeration unit, a Kalina cycle, and a humidification-dehumidification desalination unit. Evaluating the system's thermoeconomic performance involves considering input parameters and simplifying assumptions to determine the performance profitability of the presented system. Furthermore, a parametric examination is conducted which is followed by the employment of an optimization analysis across three diverse scenarios to identify the most favorable operating conditions. The results of the presented research reveal that the suggested system can deliver power, cooling capacity, and freshwater production at rates of 342.3 kW, 301.7 kW, and 0.233 kg/s, respectively. Additionally, the system demonstrates an exergy efficiency of 31.52 % and achieves a payback period of 5.85 years.

4E optimization comparison of different bottoming systems for waste heat recovery of gas turbine cycles, internal combustion engines, and solid oxide fuel cells in power-hydrogen production systems

Gas turbine cycles (GTC), internal combustion engines (ICE), and solid oxide fuel cells (SOFC) are three important sources of waste energy, and although some studies have been done about their waste heat recovery (WHR) systems individually, there is a lack of a study comparing them to select the best solution. In the present research, the steam Rankine cycle, CO2 supercritical Brayton cycle (SBC), inverse Brayton cycle (IBC), and air bottoming cycle are used for WHR of high-temperature exhausted gas of 500 kW natural gas-fueled GTC and ICE. Furthermore, the organic Rankine cycle (ORC), trilateral cycle, organic flash cycle, Kalina cycle, and CO2 SBC are utilized for the WHR of the SOFC-gas turbine (GT). The performance of 13 proposed configurations is compared through 4E (energy, exergy, exergy-economic, and environmental) three-objective optimizations. Considering exergy efficiency, total cost rate, and unit cost of products as target functions, the SOFC-GT-ORC system has the best performance with exergy efficiency, total cost rate, and unit cost of 64.74%, 92.51 $/h, and 19.03 $/GJ. Furthermore, GTC-IBC and ICE-IBC have the best performance in their respective categories.

Design and multi-criteria optimization and financial assessment of an innovative combined power plant and desalination process

Geothermal power generation programs are crucial due to their long-term sustainability and environmentally friendly characteristics, particularly for potential energy-based applications in the future. Innovative designs can yield improve efficien by mitigating irreversibility, resulting in enhanced power production. Hence, this study investigates an innovative cascade thermal design model that employs geothermal resources to enhance the efficiency and output of low-temperature power generation systems, specifically through the integration of organic flash and organic Rankine cycles. Additionally, this model introduces a novel cogeneration approach by incorporating a desalination unit based on humidification-dehumidification processes, aiming to concurrently produce electricity and fresh water. Employing a combination of thermodynamic analysis and financial assessment, the system's performance was simulated and optimized in MATLAB, using the Multi-Objective Particle Swarm Optimization (MOPSO) method. A sensitivity analysis preceded the optimization, leading to the development of three distinct optimization scenarios focused on balancing power and freshwater production, maximizing exergetic efficiency and net present value, and optimizing fixed capital investment for maximum financial viability. The results highlight the second scenario as particularly effective, achieving a power generation of 254.3 kW, an exergetic efficiency of 44.84 %, and a net present value of $405,099. Conversely, the third scenario offers the best balance between freshwater production capacity (0.504 kg/s), fixed capital investment ($820,822), and a payback period of 7.12 years. This research demonstrates the potential of integrating advanced thermal models with geothermal resources for sustainable and efficient energy and freshwater production, marking a significant step forward in the development of eco-friendly cogeneration systems.

Exergy-economic performance comparison of three organic flash cycles integrated with an LNG subsystem to produce electricity and sub-zero cooling

The performances of three organic cycles based on the flash process combined with a liquefied natural gas (LNG) subsystem are assessed and compared from thermodynamic and economic standpoints. The thermodynamic analysis of the systems comprises energy and exergy analyses, and the specific exergy costing technique was employed to conduct the economic analysis of the systems. The topping cycle is an organic flash cycle (OFC), an organic flash regenerative cycle (OFRC), or a double-expansion organic flash cycle (DEOFC). Enjoying three advantages, the LNG subsystem is utilized in the configurations. First, it improves the topping cycle performance by reducing the condensation temperature and pressure. Second, the cryogenic exergy of the natural gas in the bottoming system is utilized in two stages to produce sub-zero cooling. Third, a high amount of the LNG exergy can be converted into power through a turbine. The optimized performance of the three configurations revealed the superiority of the DEOFC-based system over the two other systems with an exergy efficiency of 43.4%, a total cost rate of 223.7 $h-1, and a specific cost of cogeneration of 29.69 $GJ-1. Moreover, the net output power and the total cooling rate produced by the DEOFC-based system are higher than the other systems. A comparison between the performances of the topping cycles and those of a study in the literature indicates a significant improvement in the exergy efficiency and the specific work produced by the topping cycles due to the use of the LNG subsystem. The exergy efficiency of the OFC, OFRC, and DEOFC is improved by 26.4% points, 26.5% points, and 36.8% points, respectively. Moreover, the present setups outperform many previously-introduced configurations, as evidenced by comparing the performances of the three systems and those proposed in the literature.

Experimental study on dynamic power generation of three ORC-based cycle configurations under different heat source/sink conditions

Organic Rankine cycle (ORC) is used for geothermal power generation, and other two derived cycle configurations, parallel double-stage organic Rankine cycle (PDORC) and organic Rankine flash cycle (ORFC), have been proposed to improve the geothermal power generation performance. However, no experimental comparison have been done before. An experimental device that can switch between three cycles was designed and constructed to compare the power generation performance of three cycles. The operational performance of the three cycles at different heat source and heat sink temperatures are analyzed in this paper. The results show that under the heat source temperature of 90 °C and heat sink temperature of 15 °C, the output power of ORFC is 876.59 W, which is higher than that of the PDORC and ORFC. Moreover, the exergetic efficiency is greater than other two cycles due to the smallest irreversible loss of ORFC. The exergetic efficiencies of the ORC, PDORC and ORFC are 31.87 %, 31.32 % and 34.79 %, respectively. The increase of heat sink temperature is beneficial for the isentropic efficiency of the expander, but not conducive to power generation performance and energy utilization. PDORC and ORFC promote the effective utilization of heat source, outputting more power but with a lower efficiency.

Investigation of a novel scheme utilizing solar and geothermal energies, generating power and ammonia: Exergoeconomic and exergoenvironmental analyses and cuckoo search optimization

The integration of solar and geothermal energy sources presents a promising avenue for enhancing the efficiency and output of energy systems. This research introduces a novel hybrid system combining solar and geothermal energy for the co-generation of power, cooling, and ammonia. The proposed system integrates several cycles and technologies, including an organic Rankine cycle, an ejector refrigeration cycle, an organic flash cycle, a proton exchange membrane electrolyzer, and an ammonia synthesis reactor. Through a comprehensive 4E (energy, exergy, economic, and environmental) analysis, utilizing thermodynamic, exergoeconomic, and exergoenvironmental methodologies, this study evaluates the system's performance. The findings reveal that solar collectors are the primary contributors to system irreversibility, accounting for 78 % of the total. Notably, an increase in the condenser outlet temperature significantly decreases the cooling load, whereas elevating the turbine 1 exit pressure enhances overall power production. At optimal operating conditions, the system generates a net power of 104 kW, provides 26.07 kW of cooling capacity, and produces 3.55 kg/h of ammonia. This performance translates into a product cost of 1.193 USD/h and an exergoenvironmental impact rate of 25.31 mPts/h, alongside achieving an exergy efficiency of 9.34 %. Financially, the system promises a payback period of 2.34 years and a net present value of 1.259 million USD, highlighting its economic viability and environmental benefits.

Performance improvement analysis of the regenerative dual-pressure organic flash cycle assisted by ejectors

We proposed a dual-ejector-based regenerative dual–pressure organic flash cycle (DEj–RDPOFC) with higher performance than the RDPOFC. The effects of high and low pressures and the entrainment ratio of the ejector on the DEj–RDPOFC performance were analyzed from the viewpoints of thermodynamics and thermoeconomics. An exergy-flow distribution diagram revealed why the DEj–RDPOFC outperformed the RDPOFC. Next, the performances of the DEj–RDPOFC and dual–pressure organic Rankine cycle (DORC) were compared under the same boundary conditions. Finally, the performance of the DEj–RDPOFC was optimized using the nondominated sorting genetic algorithm (NSGA-II). According to the results, the power output of the high-pressure (HP) turbine of the DEj–RDPOFC can be increased by replacing the HP throttling valve (TV) with an ejector (which increases the working fluid dryness of the HP vapor separator and the mass flow rate of the HP turbine) and the low-pressure (LP) TV with an ejector (which increases the HP turbine expansion ratio). The DEj–RDPOFC achieves a higher maximum net power output (Wnet) and a lower corresponding levelized cost of electricity (LCOE) than the DORC. Under the optimum condition, the Wnet and LCOE of the DEj–RDPOFC are 9.71 % higher and 6.59 % lower, respectively, than those of the RDPOFC.

A novel zero emission combined power and cooling system for concentrating solar power: Thermodynamic and economic assessments and optimization

This study aims to develop a zero-emission multi-generation system based on concentrated solar power to reduce solar thermal power cost and improve the efficiency of power generation. The multi-generation system mainly includes concentrated solar power system, supercritical carbon dioxide recompression Brayton cycle, organic flash cycle and absorption refrigeration cycle. A comprehensive energy, exergy, environment and economic analysis is carried out. Five key parameters are considered to assess the effect of decision parameters on system performance. An optimization method combining genetic algorithm and machine learning is used to accelerate the optimization process. Results display that compared with the stand-alone supercritical carbon dioxide recompression Brayton cycle, the energy utilization factor and exergy efficiency of the multi-generation system can improve 18.7 % and 6.4 %, respectively, and the decrement of levelized cost of electricity is reduced by 4 %. A higher turbine-Ⅰ inlet temperature can improve the exergy efficiency and reduce the levelized cost of electricity. Using the proposed optimization method, the long optimization time of complex multi-generation system is overcome. Comparing the exergy efficiency optimization case with the basic case and the cost optimization case, the exergy efficiency optimization case has the highest net power output and exergy efficiency. This work exhibits great potential in utilizing solar energy for power and cooling.

Scrutiny of a Bi-evaporator poly-generation system includes distilled water production unit: Comparative study and Bi-objective optimization

While geothermal energy is typically associated with beneficial environmental effects, it is crucial to acknowledge that it can lead to greenhouse gas emissions. Therefore, the implementation of geothermal systems should include an environmental assessment. This study presents and evaluates an innovative geothermal-powered bi-evaporator poly-generation system from seven perspectives: thermodynamic, extended-environmental, exergoenvironmental, exergoeconomic, net present value, and bi-objective optimization. The designed ploy-generation system comprises a desalination unit, a unit for extracting hydrogen, and a modified organic flash cycle, all integrated with a single geothermal flash cycle. These subsystems work in unison to create a comprehensive and integrated system for simultaneously generating purified water, green hydrogen, electricity, and meeting refrigeration load requirements. Regarding the findings at the base mode, the designed system is able to generate net power, refrigeration load, distilled water, and H2 production rates of 244.9 kW, 741.4 kW, 0.4443 kg/s, and 1.062 kg/h, respectively. By employing NSGA-II optimization, the values of commodities are substantially increased, which enhanced the poly-generation system product cost and energetic efficiency by 7.13 % and 30.48 %. Also, the net electricity selling price significantly affects NPV, so the payback period reduces to 8.56 years.

Process development and multi-criteria optimization of a biomass gasification unit combined with a novel CCHP model using helium gas turbine, kalina cycles, and dual-loop organic flash cycle

The non-renewable nature of conventional power plants and the challenges associated with fuel costs and environmental impact highlight the need for innovative solutions. This research proposes a biomass-based combined system designed to produce multiple products, including electric power, coolant, and heat, addressing the drawbacks associated with conventional power generation. The proposed system integrates a biomass gasification unit with a helium gas turbine and a Kalina power unit. Additionally, a domestic water heater is incorporated into the Kalina cycle for heat generation, and the heat loss from the helium gas turbine is utilized in a modified Kalina cycle with a refrigeration unit. To further enhance efficiency, a dual-loop organic flash cycle is employed to recycle waste heat from the modified Kalina cycle. The analysis of this framework encompasses technical aspects, including energy, exergy, and economic considerations. The system is optimized using the multiple-objective particle swarm optimization method. Two scenarios are explored based on the desired product capacities: heat-electric power and coolant-electric power. In the first scenario, the system demonstrates an optimal electric power generation capacity of 6239.56 kW, along with favorable exergetic and economic outcomes. The optimal exergetic efficiency, net present value, and payback period are determined as 35.57 %, 15.07 M$, and 3.97 years, respectively. This research presents a comprehensive approach to biomass-based power generation, considering both technical and economic aspects, and provides valuable insights for sustainable energy solutions.

Hybridized power-hydrogen generation using various configurations of Brayton-organic flash Rankine cycles fed by a sustainable fuel: Exergy and exergoeconomic analyses with ANN prediction

This paper investigates different configurations of organic Rankine flash cycles combined with a Brayton cycle by performing thermodynamic, exergy, and exergoeconomic analyses. The thermal energy of the cycle is produced through burning gaseous methane generated via gasification of biomass. A systematic analysis of these configurations is conducted to enhance the exergy efficiency of the cycles. Additionally, the reutilization of the thermal energy that would otherwise be wasted in the Brayton cycle contributes to a notable enhancement in the overall thermal efficiency of the combined cycle. A range of working fluids, namely m-Xylene, o-Xylene, p-Xylene, toluene, and ethylbenzene are analyzed for the organic Rankine cycle. Predictions using an artificial neural network (radial base function) are also carried out. The results indicate that the p-Xylene increases exergy efficiency more than other working fluids. Further, the improved organic Rankine cycle mitigates exergy destruction by 10 %. Although applying double flash evaporators improves the exergy efficiency by 3 %, it increases the unit cost of power generated by more than 10 %. The application of a data-driven model to predict various configurations of combined organic Rankin cycle with a Brayton cycle fed by biomass has rarely been investigated.