Results 1 - 10 of 29
Results 1 - 10 of 29. Search took: 0.017 seconds
|Sort by: date | relevance|
[en] Highlights: • Exergoeconomic analyses is done on an integrated cryogenic air separation unit. • Liquefied natural gas cold energy is used in the process. • The main multi stream heat exchanger is the worst device based on the results. - Abstract: Exergoeconomic and sensitivity analyses are performed on the integrated cryogenic air separation unit, oxy-combustion Carbon dioxide power cycle and liquefied natural gas regasification process. Exergy destruction, exergy efficiency, cost rate of exergy destruction, cost rate of capital investment and operating and maintenance, exergoeconomic factor and relative cost difference have been calculated for the major components of the process. The exergy efficiency of the process is around 67.1% and after mixers, tees, tank and expansion valves the multi-stream heat exchanger H-3 have the best exergy efficiency among all process components. Total exergy destruction rate of the process is 1.93 × 10"7 kW. Results of exergoeconomic analysis demonstrates that maximum exergy destruction and capital investment operating and maintenance cost rate are related to the multi-stream heat exchanger H-1 and pump P-1 with the values of 335,144 ($/h) and 12,838 ($/h), respectively. In the sensitivity analysis section the effects of the varying economic parameters, such as interest rate and plant life time are investigated on the trend of the capital investment operating and maintenance cost rate of the major components of the process and in another cases the effect of the gas turbine isentropic efficiency on the exergy and exergoeconomic parameters are studied.
[en] Highlights: • An irreversible solar-driven heat engine is optimized. • Developed multi objective evolutionary approaches is used. • Power output, ecological function and thermal efficiency are optimized. - Abstract: The present paper illustrates a new thermo-economic performance analysis of an irreversible solar-driven heat engine. Moreover, aforementioned irreversible solar-driven heat engine is optimized by employing thermo-economic functions. With the help of the first and second laws of thermodynamics, an equivalent system is initially specified. To assess this goal, three objective functions that the normalized objective function associated to the power output (F_P) and Normalized ecological function (F_E) and thermal efficiency (η_t_h) are involved in optimization process simultaneously. Three objective functions are maximized at the same time. A multi objective evolutionary approaches (MOEAs) on the basis of NSGA-II method is employed in this work
[en] Highlights: • A small scale transcritical Carbon dioxide cycle is investigated. • Exergy analysis of a transcritical CO_2 power cycle driven by geothermal energy with liquefied natural gas as its heat sink. • Multi-objective optimization approach is carried out for performance optimization. • Three decision-making methods are employed to select final answers. - Abstract: The main objective of this research is to study a transcritical CO_2 cycle via geothermal resources to produce electrical energy. Heat sink of this cycle is Liquefied natural gas (LNG) to drop back pressure of the CO_2 turbine greatly. It is presumed that the system works under steady state situations to establish the mathematical model of the transcritical CO_2 geothermal power generation system. To evaluate the impacts of different main thermodynamic parameters in the performance of the system a parametric investigation is employed. Furthermore, to determine an optimum system performance from an economical and thermodynamic point of view, a multi-objective optimization jointed to NSGA-II algorithm is employed. To calculate the final solution three decision makers comprising TOPSIS, LINAMP and FUZZY were use. Moreover, sensitivity analysis and error examination were performed on the solutions gained from the decision makers. In conclusion, outputs achieved from this investigation were compared to the other related studies and this comparison reveals that the solutions gained in this study are satisfactory compared to the previous works.
[en] Highlights: • Solar Kalina cycle is modeled and examined throughout the year. • Exergy analysis shows the main sources of destruction and exergy efficiency. • Economic analysis calculates the levelized cost of electricity and payback time. - Abstract: Recently, with decreasing oil resources and environmental issues associated to use of fossil fuels, solar thermal power plants have attracted much attention among researches mainly due to zero emission and huge fuel savings they bring about. In this study, a small scale parabolic Trough collector and a thermal storage tank along with an auxiliary heater are coupled to a Kalina cycle to study the performance of the system throughout the year, both thermodynamically and economically. To examine the effect of solar collectors in the system, the model is compared to a fuel driven Kalina cycle. Results show that in 5 months of the year, the solar fraction is more than 50%. The exergy analysis reveals that the main source of destructions are solar collectors (more than 50% of total) and vapor generator. The solar collectors and vapor generator have an improvement potential of 69% and 65%, respectively. The Kalina cycle is responsible for a minor portion of total exergy destruction, thus more investment should be put on solar collectors. Economic analysis shows that, under design conditions, solar Kalina cycle has a levelized cost of electricity of 0.4274 $/kW h which is higher compared to that of fuel driven cycle with 0.3113 $/kW h. On the other hand, the solar system has a yearly fuel saving of almost 40,000 kg/year (natural gas) which is half of fuel driven cycle and can save more than 100 tons of carbon dioxide. Also, solar fraction and daily mean sun to electricity exergy efficiency of 67.71% and 5.24% are obtained, respectively, for July. Also, the thermal storage tank has a vital role on maintaining the stable working condition of Kalina cycle. To find the effect of key parameters on the performance and economic of solar system, a parametric study has been done. The results show that ammonia mass fraction variation has the most effect on exergy efficiency, solar fraction and levelized cost of electricity. This paper provides the reader to examine the performance of a small scale solar plant from exergetic view point and to estimate the overall costs associated to the system.
[en] Highlights: • A combined solar thermophotovoltaic power generation system is proposed. • High-temperature solid oxide electrolyzer is used for hydrogen production. • Solar to electrical efficiency of the scaled-up STPV device is 17%. • Total efficiency of the integrated system is 34%. - Abstract: This study proposes a novel integrated solar-TPV device with a solid oxide electrolyzer cell to utilize the solar energy for hydrogen production. It explores the possibility of employing a high temperature solar-thermal-photovoltaic power generation technology as a power source for a steam electrolyzer as a high-efficiency and applicable hydrogen production method. Mathematical and electrochemical modeling of the subsystems is conducted and performance of the system in different operating conditions such as current density, temperature, and steam mole fraction of SOEC is analyzed. An STPV device of multiwalled carbon nanotube (MW-CNT) absorber and 1D Si/SiO2 PhC emitter and InGaAsSb PV cell is employed to maximize the solar energy utilization. A detailed system level model in this part is conducted and the solar to electrical efficiency of the scaled-up STPV device reached to 17%. The results show that this STPV device can provide the power demand in SOEC system. A planar cathode-supported high-temperature electrolyzer cell was designed to perform in an exothermic mode and the result was validated by the experimental data precisely. The sensitivity analysis showed that 7458 kg/h hydrogen can be produced in the proposed system with 54% electrical for SOEC efficiency. The major implementation challenges are presented to provide a comprehensive insight into performance, potential development, limitations and challenges of the integrated system. The proposed combined system shows the overall efficiency can reach to 34%. This high efficiency makes this novel hybrid system a competitive option in solar-based hydrogen production technologies.
[en] Highlights: • Techno-economic analysis is performed on a solid oxide electrolyzer cell. • Electrical and thermal energy of the electrolyzer is provided by dish collectors. • ORC system is used to recover energy from electrolyzer outlet streams. • Aperture diameter of dish collectors considerably affect the system performance. • Higher temperature of the cell benefits the system thermo-economically. - Abstract: Hydrogen is considered as one of the best alternatives for fossil fuels, especially when it is produced using renewable energy resources. In this paper, dish collector is used to provide the required energy of a solid oxide electrolyzer cell (SOEC) to produce hydrogen. Since dish collectors operate at high temperature, they would be an ideal match for high temperature electrolyzers. These electrolyzer cells need both thermal and electrical energy to produce hydrogen. A compressed air energy storage (CAES) system is used to produce electricity. To reduce its fuel consumption, it is combined with a dish collector. Another dish collector is also used to produce thermal energy. To analyze the system, both thermodynamic and economic analyses are conducted. The results showed that the system could produce 41.48 kg/day hydrogen. It is shown that efficiency of the power cycle and the electrolyzer cell is equal to 72.69% and 61.70%, respectively and levelized cost of hydrogen is 9.1203 . To study the effect of key parameters on the system performance, sensitivity analysis is performed. It was concluded that maximum and minimum pressure of air cavern in the CAES system have the highest effect on the levelized cost of hydrogen. Also higher operating temperature of the electrolyzer cell benefits the system both thermodynamically and economically.
[en] Highlights: • Exergoeconomic analysis is performed for single mixed refrigerant process. • Cost of exergy destruction and exergoeconomic factor are calculated. • Sensitivity of exergoeconomic factor is investigated. - Abstract: Exergy and exergoeconomic analysis is performed for single mixed refrigerant Linde and Air Products and Chemicals Inc, processes, which are among the most important and popular natural gas liquefaction processes. Cost of exergy destruction, exergoeconomic factor, exergy destruction and exergy efficiency are calculated. Results of exergy analysis demonstrates that exergy efficiency of Linde process is around 40.2%, and its total exergy destruction rate is 93,229 kW. The exergy efficiency and exergy destruction rate for Air Products and Chemicals Inc, process are 45.0% and 72,245 kW respectively. Results of exergoeconomic analysis suggests that maximum exergy destruction cost for Linde process is related to E-2 heat exchanger which is 34,072 $/h and for Air Products and Chemicals Inc, process maximum exergy destruction cost is related to E-2 heat exchanger with the value of 4125 kW. Sensitivity of cost of exergy destruction and exergoeconomic factor to operating variables of the processes are studied and analyzed
[en] Highlights: • Advanced exergoeconomic analysis is performed for mixed refrigerant systems. • Cost of investment is divided into avoidable/unavoidable and endogenous/exogenous. • Results show that interactions between the components is not considerable. - Abstract: Advanced exergoeconomic analysis is applied on three multi stage mixed refrigerant liquefaction processes. They are propane precooled mixed refrigerant, dual mixed refrigerant and mixed fluid cascade. Cost of investment and exergy destruction for the components with high inefficiencies are divided into avoidable/unavoidable and endogenous/exogenous parts. According to the avoidable exergy destruction cost in propane precooled mixed refrigerant process, C-2 compressor with 455.5 ($/h), in dual mixed refrigerant process, C-1 compressor with 510.8 ($/h) and in mixed fluid cascade process, C-2/1 compressor with 338.8 ($/h) should be considered first. A comparison between the conventional and advanced exergoeconomic analysis is done by three important parameters: Exergy efficiency, exergoeconomic factor and total costs. Results show that interactions between the process components are not considerable because cost of investment and exergy destruction in most of them are endogenous. Exergy destruction cost of the compressors is avoidable while heat exchangers and air coolers destruction cost are unavoidable. Investment cost of heat exchangers and air coolers are avoidable while compressor’s are unavoidable
[en] Highlights: • Successful production of biodiesel using electrolysis method. • The modified zeolite/chitosan were used as a natural and cost-effective catalyst. • Waste cooking oil is potential feedstock for biodiesel. - Abstract: Used waste cooking oil (WCO) or frying oils are being considered as rich sources of economical feedstock for biodiesel production. To carry out the process of trans-esterification of WCO to methyl esters (biodiesel), zeolite/chitosan/KOH composite was used as solid heterogeneous catalysts. The composite was analyzed using Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope coupled with Energy Dispersive X-ray (SEM-EDX) analysis, and X-ray diffraction (XRD) analysis. It was found that the treatment of the natural zeolite (clinoptilolite zeolite) with KOH significantly decreased its silica content by desilication and increased its K+ content by formation of hydroxylpotaslite. Electrolysis method (EM) is used as an applicable technology for recovery of energy and resources during waste treatment. Theoretically, EM can convert any biodegradable waste into H2, O2, biofuels, as well as other by-products such as glycerol. However, the system efficacy can vary significantly under different circumstances. The conversion of biodiesel from WCO was obtained for 1 wt.% catalyst concentration and alcohol/oil ratio of 1:7 at 40 V in the presence of water as 2 wt.% of the whole solution in 3 h, produced 93% yield. The optimum conversion process was achieved as a result of using co-solvent as acetone. Fourier Transform Infrared (FT-IR) and Viscosity characterization were used the assessing techniques for detection of WCO and biodiesel.
[en] Highlights: • A solar-driven Kalina cycle is investigated by advanced exergoeconomic analysis. • The highest exergy efficiencies are related to the separator and turbine with the values. • Rotary machinery have more than 83% avoidable share of exergy destruction rate. - Abstract: A Kalina cycle driven by solar energy resource is evaluated by conventional exergy and exergoeconomic analysis methods. Because conventional exergy analyses isn’t able to give information about costs of the irreversibilities and investment, advanced exergy is investigated. Based on the conventional exergy analyses, the most exergy destruction occurs in a heater with a value of 94.44 kW. Also the highest exergy efficiencies are related to the separator and turbine with the values of 99.67% and 89.81%, respectively. Advanced exergy analyses demonstrates absorber (1.3 $/h) and one of the pumps (0.009 $/h) have the highest and lowest exergy destruction cost rate, respectively. Also the results show turbine (85.88%) and separator (1.105%) have the highest and lowest exergoeconomic factor, respectively. Finally, in order to determine optimum point of the inlet temperatures and pressure ratio of the pumps and turbine (rotary machines), a parametric study is applied at different stages.