•A novel transcritical CO2 ejector based combined cooling and power system is introduced.•A thermoeconomical model is developed to evaluate the enhanced proposed system.•A multi-objective ...optimization is carried out to find the optimum operating condition.•Unlike old proposed systems, the net power output of this system is positive.
To reduce the fossil fuels consumption and their environmental impact, improve the waste heat efficiency, an enhanced transcritical CO2 ejector based combined cooling and power system is proposed using recovered waste heat. This system can employ in vehicles and make them run more environmentally friendly. The new proposed system includes a power generation part and a transcritical ejector based refrigeration system. A thermodynamical model is developed to evaluate the enhanced proposed system. A comprehensive parametric investigation and thermoeconomic analysis are presented to study the effects of key parameters on the thermoeconomic performance of the system. The results show that back pressure of ejector (gas cooler pressure) plays the main role to improve the system performance. A 10 bar increase in ejector back-pressure of ejector leads to an increase of 16.4% in energy efficiency while the exergy efficiency decreases of 9.2%. From exergy analysis, it is found that the biggest irreversibility in the system belongs to the internal heat exchanger used between pump and turbine outflows. For the cooling capacity of 10 kW, a multi-objective optimization is carried out and the optimal values of energy and exergy efficiencies obtained from the Pareto frontier results are 27.42% and 24.21%, respectively, while it leads to the net power output of 7.55 kW. In this case, the net present value and the simple payback period of the proposed system are equal to 0.3419 M$ and about 4 years and 6 months, respectively.
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•A new scheme of ORC integrated with solar pond and LNG cold energy is introduced.•The feasibility of the proposed system is evaluated from thermodynamic view point.•Overall system including is ...analyzed transiently for Urmia city, Iran.•Zeotropic mixture are used as working fluid in ORC to improve system performance.•The effect of design parameters on the overall system performance is investigated.
Thermodynamic feasibility evaluation is investigated for a salinity gradient solar pond-based power generation system. A dual-pressure evaporation organic Rankine cycle using the zeotropic mixture as working fluid is employed for power generation. To increase power generation, liquefied natural gas cold energy is used as a heat sink. Furthermore, to reach reliable results, transient analysis is conducted on the overall system. Also, the solar pond walls shading effect as well as heat losses that could not be ignored (i.e., evaporation heat loss from pond surface) is considered in the simulation. The results show that for a system located in Urmia, Iran, the annual average solar pond energy efficiency for the first year is obtained 20%. Different zeotropic mixtures are examined to achieve the optimal thermal performance of the system. It is concluded that the system using R245ca/R236ea with a mass fraction of 0.6/0.4 has the optimal thermal performance among selected zeotropic mixtures. In this case, the values of the system generated power and exergy destruction are obtained 95.67 MJ year−1 m−2 and 133.7 MJ year−1 m−2, respectively, with an energy efficiency of 3.28%.
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In this work, a novel integrated biomass based multigeneration energy system is presented and investigated for power, cooling and hydrogen production. The proposed system consists of a combination of ...biomass integrated gasifier-gas turbine cycle, a Rankine cycle, a cascade organic Rankine cycle, an absorption refrigeration system and a PEM to produce hydrogen. This system uses cold energy of LNG as a thermal sink. Comprehensive thermodynamic and economic analyses as well as an optimization are performed. The effects of operating parameters on thermodynamic performance and total cost rate are investigated for overall system and subsystems. The results show that the fuel mass flow rate is the dominant factor affecting the variation of energy efficiency and total cost rate. An increase in fuel mass flow rate from 4 kg s−1 to 10 kg s−1 leads to a decrease of 8.5% and an increase of 122.8% overall energy efficiency and total cost rate, respectively. Also, the largest increase in exergy efficiency occurs when gas turbine inlet temperature increases. The results of optimization showed that the highest net power output, mass flow rate of natural gas delivered to city and the flue gas temperature discharged to the environment are obtained for the exergy efficiency optimal design.
•A novel multigeneration system is investigated and optimized thermodynamically and economically.•This system is proposed for power, cooling and hydrogen production.•Proposed system uses LNG cold energy thermal sink that can generate power after vaporization.•The effects of operating parameters on energy and exergy efficiencies and total cost rate are investigated.•An optimization is applied based on the energy, exergy and economic viewpoints.
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•Four combined ORC geothermal power plant and LNG cold energy are investigated.•Energy, exergy and economic analyses are applied to the system.•The effects of operating parameters on ...energy and exergy efficiencies as well as total cost rate are investigated.•An optimization is applied based on the best performance and the minimum product unit cost.
Thermo-economic analysis is applied to four combined liquefied natural gas (LNG) cold energy and (1) simple, (2) with internal heat exchanger, (3) regenerative and (4) dual-fluid ORCs. These power plants use geothermal fluid energy as low-grade heat source and cold energy of LNG as thermal sink. Also, after vaporization in the organic fluid condenser, natural gas expands in a turbine to generate power. The effects of operating parameters on energy and exergy efficiencies as well as total annual cost rate are studied for the proposed systems. The operating parameters considered include inlet pressure of the organic fluid and natural gas turbines, condensing temperature of organic fluid, minimum temperature difference in evaporator, inlet temperature and mass flow rate of geothermal fluid. Moreover, optimal values of operating parameters of the system are evaluated to maximize the energy and exergy efficiencies and minimize the total product unit cost. The results show that the highest energy and exergy efficiencies are obtained for regenerative system and for the system with internal heat exchanger, respectively, while the simple system has the lowest total product cost. Furthermore, the maximum net power output is obtained using dual-fluid system at the same operating condition. Also, the higher and lower total cost rate in optimum performance condition belong to dual-fluid and regenerative systems, respectively.
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•A double effect absorption heat transformer is introduced into the CO2 capture unit.•Innovatively apply transcritical CO2 power generation system to CO2 capture unit.•Low grade temperature steam is ...upgraded by DAHT to match solvent regeneration.•A portion of required electrical energy for CCU is compensated by CO2 power generation.•Energy, exergy and economic evaluations of the proposed system are presented.
This paper deals with a double effect heat transformer-aided carbon dioxide capture unit with transcritical carbon dioxide power generation for a coal-fired steam power plant. In the proposed system a double absorption heat transformer is used to upgrade low energy level steam into high-level and drive carbon dioxide capture unit. Also, a transcritical carbon dioxide power generation that is utilized captured carbon dioxide to generate power and compensate a portion of the required electrical energy of the carbon dioxide capture unit. This system avoids extracting high-grade temperature steam extracted from high-pressure stage of steam turbine and hence overall thermal efficiency of power plant increases compared to the reference systems. Comprehensive thermodynamic and economic evaluations are conducted to reveal the feasibility of the presented system. The results show that the evaporator temperature has the highest effect on net power output. An increase of 10 K in the evaporator temperature from 80 °C to 90 °C, leads to a reduction of 4.9% in generated power. However, a 50% increase in carbon dioxide capture rate from 40% to 90%, leads to a rise of 23.4% in the exergy destruction rate. Moreover, the payback period is approximately 4 years and 6 months.
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•A novel integrated power plant is investigated and optimized thermoeconomically.•This system consists of a gasifier, solid oxide fuel cell, gas turbine and Rankine cycles.•The effects of operating ...parameters on system performance and product cost are investigated.•A multi-objective optimization is applied based on the thermoeconomic viewpoint.
In this work, a novel combined biomass based power generation system is proposed and investigated. The proposed integrated system consists of a combination of biomass gasifier, solid oxide fuel cell, gas turbine cycle and a Rankine cycle. Three different biomasses are selected: Pine Saw Dust, Municipal Solid Waste and Fowl Manure. A comprehensive thermoeconomic analysis as well as a multi-objective optimization is carried out. The effects of most important operating parameters on thermodynamic performance, unit production cost and total cost rate are investigated for the overall system and components. The operating parameters considered include biomass mass flow rate, compression ratio of air compressor, current density of solid oxide fuel cell and exit temperature of solid oxide fuel cell. The results show that the fuel mass flow rate and current density are the dominant factors affecting the variation of energy and exergy efficiencies as well as unit production cost. Moreover, the best thermodynamic and economic performances are corresponded to the Pine Saw Dust fueled system. Nevertheless, the best environmental performance is related to the Fowl Manure fueled system mainly due to the lowest content of CO2 in flue gas leaving the system to the atmosphere.
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•A novel solar-biogas based multigeneration system is introduced.•The proposed system produces power, heat, methanol and hydrogen simultaneously.•This system is analyzed thermodynamically and ...exergoenvironmentally.•It is found that reformer temperature has the greatest effect on the system performance.
This paper deals with a novel solar-biogas fueled combined heat and power system with methanol and hydrogen production. The proposed energy system consists following subsystems: solar based biogas-steam reformer, gas turbine cycle, Rankine and organic Rankine cycles, pressure swing adsorption, carbon capture and sequestration and methanol synthesis unit. The selected solar system is molten salt tower-based concentrated solar thermal plant that provides required thermal energy for reforming process. The multigeneration system is comprehensive analyzed thermoeconomically and exergoenvironmentally. A parametric study is conducted to find the effects of key parameters on the system performance. The considered key parameters include steam to carbon ratio of reforming process, operating temperature and pressure of reformer. The results show that Tr is the most effective parameters for improving system performance. A 200 K increase in reforming temperature, from 923 K to 1123 K, leads to decreases of 15% and 10% in the energy and exergy efficiencies, respectively. The opposite trend is observed for net power output and mass flow rate of produced methanol when key parameters change. Nevertheless, mass flow rate of produced methanol plays most important role for evaluating energy and exergy efficiencies. Also, gas turbine cycle and reformer have highest exergy destruction rate of 140 MW and 134 MW, respectively when system operates in optimum condition. Moreover, best exergoenvironmental parameters are obtained at higher value of reforming temperature and lower values of reforming pressure and steam to carbon ratio of reforming process.
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•Two flash geothermal integrated with trans- and supercritical ORCs are introduced.•A thermoeconomical model is developed to evaluate the proposed systems.•The design parameters of the ORC evaporator ...are defined for various conditions.•A multi-objective optimization is presented to find the optimum operating condition.•The performance of the systems is compared from viewpoint of energy and economic.
In this research, the integration of an enhanced single flash geothermal cycle with a transcritical organic Rankine cycle (TORC) is proposed. To discover the feasibility and thermoeconomic improvement, the proposed system is investigated and compared thermoeconomically with a subcritical ORC integrated to single flash geothermal. Thermoeconomic evaluation is conducted with consideration Pseudo-critical point effect in supercritical condition as well as Bauman rule in geofluid turbine. The considered key parameters to conduct a parametric study are heat source temperature, separator pressure, and geofluid condenser pressure. To perform the thermoeconomic analysis, the heat transfer areas, as well as overall heat transfer coefficients of all heat exchangers, are calculated. Moreover, the total cost rate and levelized cost of energy for the considered systems are obtained. The results reveal that the heat source temperature plays an important role in the power production variation, while the separator and flash condenser pressures are kept constant. An increment of 20 °C in the heat source temperature leads to an increase of up to 22% in generated power for both considered systems. Also, based on the comparative study, a combination of the flash-transcritical ORC cycle has 7.2% higher power production compared to the combination of flash-subcritical one. A multi-objective optimization based on the genetic algorithm method is performed. The optimization results show that the energy and exergy efficiencies, exergy destruction rate, and total cost rate is well improved in single flash-TORC compared to the subcritical one.
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This work deals with a comparative study for different basic and enhanced integrated geothermal flash and Kalina cycles from the thermoeconomic point of view. The considered cycles include different ...combination of basic and modified Kalina cycles, basic geothermal single flash cycle, double flash cycle and its enhanced modes. The basic Kalina cycle is modified by employing a two-phase expander instead of the throttling valve. Also, in order to enhance geothermal flash cycle, the geofluid steam is heated by a part of the heat contained in the geofluid at the wellhead before entering the turbine. Moreover, the effects of different key parameters on the thermodynamic and economic performances are investigated and optimized using the genetic algorithm method. The results show that when enhanced double flash/modified Kalina cycle is used, generated power increases by 6% compare to the basic cycle under the optimum operating condition. In this case, the increment of unit production cost is ignorable compared to the basic cycle. The exergy destruction rate of each component is calculated under the optimum operating condition. For all considered cycles, the highest value of exergy destruction rate belongs to the evaporator.
•Enhanced geothermal flash cycle integrated with modified Kalina cycle is proposed.•Thermoeconomic performance of proposed cycle is compared with similar basic cycle.•Basic and enhanced proposed cycles are optimized using genetic algorithm.•An improvement of 6% is achieved in generated power by using enhanced cycles.•Enhancing the basic cycle leads to the ignorable increase in unit production cost.
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► Simplified analytical model for solidification of PCM in shell and tube finned storage. ► We formulate energy equation in the presence of a heat thermal fluid on the walls. ► We compare ...solidification time for PCM in cylindrical shell and rectangular storages. ► We investigate the effects of inlet air temperature on thermal storage performance. ► We investigate the effects of air flow rate on thermal storage performance.
Due to the advantages offered by latent heat thermal storages, phase change materials (PCM) are used in numerous applications including building air conditioning systems. In this study, the development is reported of an approximate analytical model for the solidification process in a shell and tube finned thermal storage. A comparative study is presented for solidification of the PCM in cylindrical shell and rectangular storages having the same volume and heat transfer surface area. The PCM solidification rate in the cylindrical shell storage is found to exceed that for the rectangular storage. The effects are investigated of heat thermal fluid (HTF) inlet temperature and flow rate on thermal storage performance.
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