Exergoeconomic Comparison Research Articles

Exergoeconomic comparison of a novel to a conventional small-scale power-to-ammonia cycle

Ammonia is a promising carbon-free energy vector with potential applications for low carbon energy storage, transportation, power production, and fertilizer use. Small-scale renewable Power-to-Ammonia (P2A) is particularly suited for remote, agricultural areas. Employing real cost data, this work presents an exergoeconomic comparison of a novel to a conventional prototype containerized P2A system. The novel system is designed for low investment cost and is going to be tested in late 2023. Both systems have an installed 18 kWel electrolyzer capacity, yielding 1.5 kg/h of ammonia. However, the novel system has 90 000 € lower purchased equipment costs of 400 000 € and 1 800 € lower operating and maintenance costs of 20 000 €/y. The exergoeconomic analysis rightly identifies the key component in the novel design, the recycle valve, as the highest operation cost driver. However, the investment cost advantage of the valve compared to a recycle compressor in the conventional layout results in a slightly lower Levelised Cost Of Ammonia (LCOA) of 161 €/kg for the novel compared to 173 €/kg of the conventional cycle, making the novel layout overall cost superior. These values are well above values reported in literature of below 1 €/kg. However, the data presented in this work refer to a research prototype application, whose costs are strongly affected by the high engineering cost and the low number of operating hours. A mass produced prototype with a higher utilization will have much lower costs.

Exergoeconomic study of reheat combined cycle configurations using steam and ammonia-water mixture for bottoming cycle parameters

The use of combined cycle power plants though had led the pathway to maximize the fuel en-ergy utilization but the part-load operation of these plants is of concern. In this work, an exer-goeconomic comparison of 11 different reheat combined cycle arrangements hasbeen carried out under their part-load operations for varying bottoming cycle parametersnamely steam-bleedfraction, deaerator pressure,separator temperature, absorber pressure, and condenser pressure.The results depict that the absorber has the highest exergy destruction with second law efficiency of 23.55% at thepart load of 25% for the combined cycle power plant having high pressure drum with steam as working fluid and low pressure drum with ammonia-wa-ter as working fluid. The comparison also shows the highest cost of electricity production as 0.1243USD/kWh for the combined cycle power plant having ammonia-water as working fluid in bottoming cycle and operating at part load of 25%. While the minimum price of electricity produced is 0.05USD/kWh at 25% part load for CCPP having double pressure HRVG’s at condenser pressure of 0.09 bar.

Exergo-economic comparison of waste heat recovery cycles for a cement industry case study

This work evaluates the performance regarding exergo-economic and emissions requirements of Waste Heat Recovery configurations (Organic Rankine cycle, Trilateral flash cycle, and Kalina cycle) under different operating conditions and working fluids. It was found that the best economic performance is presented by the Organic Rankine cycle that operates with Cyclo-Pentane and has two intermediate heat exchangers since it pushes the expansion temperature up while allowing a higher heat input to the cycle. As a result, it delivers 6.2 MW with a net present value, the net present value of 0.74 million dollars, saving up to 11480 tonnes of carbon dioxide per year. This performance far exceeds that obtained in the previous work, around 50% higher net-work with 80% higher net present value, and constitutes the best alternative in terms of performance to recover waste heat from the source evaluated. Regarding the Trilateral flash cycle, it can be stated that the net work and the exergetic performance are independent of the working fluid as long as there is not a very large volume change in the expander. The Kalina cycle presents slight exergy destruction, but the power delivered does not compensate for the high total capital cost due to the high pressures that must be handled, 55–120 bar, compared to the Organic Rankine cycle, 4–40 bar. An approach was made to more realistic cases where the methodology used facilitates selecting the best alternative when there is a budget restriction using the total capital cost and net work alternatively like a fixed requirement and net present value as the primary decision criterion.

Exergy and exergoeconomic comparison between multiple novel combined systems based on proton exchange membrane fuel cells integrated with organic Rankine cycles, and hydrogen boil-off gas subsystem

A comparative study is applied to evaluate four combined power producing systems based on low-temperature and high-temperature proton exchange membrane fuel cells (LT-PEMFC and HT-PEMFC) with equal power generation of 1056 kW. Single-stage organic Rankine cycle (SORC) and cascade two-stage ORC (CTORC) are employed to recover the waste heat from the fuel cells as well as exploiting the hydrogen boil-off gas for generating excess power, and feeding to the fuel cells. The performance of the proposed systems is compared to energy, exergy, and exergoeconomic viewpoints. Also, a parametric analysis is carried out to assess the effects on the thermodynamic and economic performance of the investigated systems by considering main parameters such as current density, fuel cell operating pressure and temperature, turbine inlet pressure, and expander lead. The results obtained from the parametric analysis reveal that with increasing the fuel cell operating temperature the overall exergy efficiencies for the proposed combined systems based on LT-PEMFC and HT-PEMFC decreases and increases, respectively. Also, the net output power and the total product unit cost of the considered systems are optimized at a specific value of BOG expander inlet pressure. The results indicate that albeit the highest values of energy and exergy efficiencies among the considered systems (61.42% and 63.20%) are related to LT-PEMFC/CTORC but the lowest total product unit cost of 33.75 $/GJ is related to HT-PEMFC/SORC.

Exergoeconomic Analysis for Optimized Combined Wet and Dry Cooling BinaryPower Plant at Olkaria I, Kenya

This study investigated a complete exergoeconomic comparison of wet and dry-cooled binary power plants. Simple organic Rankine cycles (ORC) for Olkaria geothermal field in Kenya using eight isobutane types of working fluids were proposed for analysis by the thermo-economic concept and sustainability index (SI). Network generated per heat transfer surface area was the optimized objective function, f(obj). Variable metric optimization method implemented in Engineers Equation Solver (EES) was applied to optimize plants for average fuel cost for geothermal fluid at 1.3 $/GJ. The exergoeconomic of the cooling tower contributed mainly to the investment cost of a water-cooled plant. Network of 1,628 kWe to 2,594 kWe was generated in wet cooled unit with SI of 1.654 to 2.701 for f(obj) of 1.5 to 1.8. For air-cooled plant, SI ranges were from 1.286 to 1.612 for the network from 1,446 kWe to 2,469 kWe with utilization efficiency of 34.77% to 59.37% and f(obj) values of 0.56 to 0.89. The cost of products range was from 18.3 $/GJ to 20.76 $/GJ for wet system and from 20.87 $/GJ to 23.4 $/GJ for dry-cooling. Selection of the suitable power plant based on exergoeconomic would be air-cooled systems with lower plant's cost rates of between 76.92 $/hr and 135.8 $/hr. The heat capacities are 20,806-20,610 kW for isobutene, 24,153-23,928 kW for isobutane, 13,727-13,595 kW for cis-2-butene and, 16,772-16,611 kW for n-butane for ambient temperatures between 0°C and 40°C. Application of air-cooled units would be advisable where water is scarce and in colder regions. Thermo-economic concept concludes that complete exergoeconomic of power plants presents a better investment decision by variable metric optimization method.

An Advanced Exergoeconomic Comparison of CO2-Based Transcritical Refrigeration Cycles

CO2-based transcritical refrigeration cycles are currently gaining significant research attention, as they offer a viable solution to the use of natural refrigerants (e.g., CO2). However, there are almost no papers that offer an exergoeconomic comparison between the different configurations of these types of systems. Accordingly, the present work deals with a comparative exergoeconomic analysis of four different CO2-based transcritical refrigeration cycles. In addition, the work is complemented by an analysis of the CO2 abatement costs. The influences of the variation of the evaporating temperature, the gas cooler outlet temperature, and the pressure ratio on the exergy efficiency, product cost rate, exergy destruction cost rate, exergoeconomic factor, and CO2 penalty cost rate are compared in detail. The results show that the transcritical cycle with the ejector has the lowest exergetic product cost and a low environmental impact.

Solar energy harvesting potential of a photovoltaic-thermoelectric cooling and power generation system: Bidirectional modeling and performance optimization

In the present work, a comprehensive thermodynamic and exergoeconomic comparison between concentrated photovoltaic-thermoelectric cooling (CPV-TEC) and concentrated photovoltaic-thermoelectric generation (CPV-TEG) systems was introduced and explored, aiming to actively investigate the energy harvesting potential of the photoelectric-thermoelectric cooling and power generation processes. Transitional characteristics of thermoelectric conversion in concentrated photovoltaic-thermoelectric hybrid (CPV-TEH) system have been outlined through multiple evaluation indicators, including output electricity, cell temperature, thermodynamic efficiency, exergy destruction and unit exergy cost under various decision parameters. Furthermore, operating mode and conversion conditions of thermoelectric device in CPV-TEH system have been sensitively identified to obtain the dual action mechanism of cooling and power generation sequentially. Theoretical models have been compared and validated well with former published results. Results indicate that the operating mode of thermoelectric device could be fully converted from TEG to TEC when the operating current is around 0.27 A; the minimum unit exergy costs are respectively found to be 0.263 $/kwh, 0.148 $/kwh and 0.113 $/kwh for CPV-TEG system and 0.266 $/kwh, 0.152 $/kwh and 0.118 $/kwh for CPV-TEC system at CG = 1, 2, and 3 kW/m2. Present research may be helpful for the design and optimization of the CPV-TEH system to harvest the thermal and electric energy from the sunlight, thus enhancing its energy conversion efficiency.

Exergoeconomic comparison of syngas production from biomass, coal, and natural gas for dimethyl ether synthesis in single-step and two-step processes

Abstract Dimethyl ether (DME) as a promising alternative fuel can be produced through two-step and single-step processes with differently suitable H2/CO ratio in syngas. Natural gas, coal, and biomass are potential energy sources for syngas production to synthesize the DME. In order to analyze the proper process of syngas production for the DME synthesis, this work aims to compare the syngas production processes from biomass gasification, coal gasification, and methane tri-reforming for the sinle-step and two-step processes through the exergoeconomic analysis. The results showed that from the coal gasification achieves the highest energetic efficiencies of the syngas production for both single-step and two-step processes while the methane tri-reforming shows the highest exergetic efficiencies at H2/CO of 2. In the exergoeconomic analysis, the air-steam coal gasification showed the lowest syngas unit cost of 0.65 $/kg for the two-step process, while biomass gasification with air-steam agent presents the lowest unit cost of syngas of 0.54 $/kg for the single-step process. When considering the environmental point of view, the intensity of CO2 emission of biomass gasification with oxygen-steam agent for the single-step process of DME synthesis is the lowest about 2.83 tonne CO2/tonne syngas.

Exergoeconomic comparison and optimization of organic Rankine cycle, trilateral Rankine cycle and transcritical carbon dioxide cycle for heat recovery of low-temperature geothermal water

Depleting fossil fuel resources and the horrible environmental impacts due to burning fossil fuels emphasize the importance of using renewable energy resources such as geothermal and solar energies. This paper compares performance of CO2 transcritical cycle, organic Rankine cycle, and trilateral Rankine cycle using a low-temperature geothermal heat source. Thermodynamic analysis, exergetic analysis, economic analysis, and exergoeconomic analysis are applied for each of the aforementioned cycles. In addition, a sensitivity analysis is performed on the system, and the effects of geothermal heat source temperature, evaporator pinch point temperature, and turbine inlet pressure on the cycle's performance are evaluated. Finally, the systems are optimized in order to minimize product cost ratio and maximize exergetic efficiency by using the genetic algorithm. Results indicate that the maximum thermal efficiency is approximately 13.03% which belongs to organic Rankine cycle with R123 as working fluid. CO2 cycle has the maximum exergetic efficiency, equals to 46.13%. The minimum product cost ratio refers to the organic Rankine cycle with R245fa as working fluid. Moreover, sensitivity analysis shows that increasing geothermal heat source temperature results in higher output power, product cost ratio, and exergy destruction ratio in all cycles.

Exergoeconomic comparison of solar-assisted absorption heat pumps, solar heaters and gas boiler systems for district heating in Sarein Town, Iran

The feasibility of solar-assisted absorption heat pumps for space heating is assessed with exergoeconomics and compared with gas boilers and solar heating systems for the town of Sarein in Iran. In the study, single-effect LiBr/H2O and NH3/H2O absorption and absorption compression-assisted heat pumps are analyzed for heating loads of 50–2 MW. Using the geothermal hot springs located in Sarein as heat sources for refrigerant evaporation, the problem of freezing is prevented. In addition, a multi-objective optimization is performed to specify the optimal design points considering the temperatures of the evaporator and generator as decision parameters. Simulations show that the gas boiler and the solar heating system have the lowest and second lowest values of exergy efficiency, at about 45% and 35% lower than the exergy efficiency for NH3/H2O absorption systems. The maximum achievable exergy efficiency for the NH3/H2O and LiBr/H2O absorption systems are 0.23 and 0.25, respectively. But, the solar heating system has the highest product unit cost, mainly due to its high capital costs. The minimum obtainable product unit costs for the NH3/H2O and LiBr/H2O absorption systems occur in April, and are about 22 $/GJ and 55 $/GJ, respectively.

A comprehensive exergoeconomic analysis of absorption power and cooling cogeneration cycles based on Kalina, Part 2: Parametric study and optimization

A comprehensive exergoeconomic comparison of the absorption power and cooling cogeneration cycles based on Kalina is investigated in this study. After thermodynamic and exergoeconomic simulation of the double effect absorption refrigeration/Kalina as well as the first and second configurations of simple absorption refrigeration/Kalina cogeneration cycles, in this part, a widespread parametric study is done and the effects of the simultaneous variations of all studied cogeneration cycles operating parameters are examined on the thermodynamic and exergoeconomic performance of the cogeneration cycles. Also, for a better comparison of the considered cycles, the optimization is done and the considered cogeneration cycles are comprised regarding to five objective functions including the minimum unit cost of products, maximum energy and exergy efficiencies, minimum unit cost of produced exergy and minimum the sum of exergy destruction and capital investment cost rates. Finally, the payback period of the studied cogeneration cycles is calculated in all optimum states. The results show that the minimum unit cost of products for the first configuration of SAR/Kalina cycle is 16.46% and 9.27% less than the corresponding values for the DEAR/Kalina cycle and the second configuration of SAR/Kalina cycle, respectively. Also, the value of ĊD+Ż parameter for the first configuration of SAR/Kalina cogeneration cycle is 28.32% and 33.12% less than the corresponding values for the second configuration of SAR/Kalina cycle and DEAR/Kalina cycle, respectively. Also, in all optimum states except for the minimum unit cost of produced exergy, the first configuration of SAR/Kalina cycle has the lowest amount of payback period.

A comprehensive thermodynamic and exergoeconomic comparison between single- and two-stage thermoelectric cooler and heater

Energy, exergy and exergoeconomic analysis are carried out for single- and two-stage thermoelectric devices which can be used for either heating or cooling implementation. Coefficient of performance, exergetic efficiency and unit cost of heating/cooling power are investigated as the main target of energy, exergy and exergoeconomic analysis, respectively. A comprehensive comparison between single- and two-stage thermoelectric performances has outlined in different values of current and temperature difference between hot and cold sides. An effective range of current is defined for energy (COP>0.5×COPmax), exergy (ε>0.5×εmax) and exergoeconomic (cC/H<2×cC/H,min) analysis. Thermodynamic analysis results reveal that the maximized energy and exergy efficiency of two-stage thermoelectric is higher in comparison to the single-stage thermoelectric for both heating and cooling modes. Also, based on exergoeconomic results, minimum unit cost of single-stage thermoelectric product is less than that of two-stage thermoelectric for all temperature differences and effective range of current is more widespread for the case of single-stage thermoelectric. Obtained results reveal that the minimum unit cost of cooling power for single- and two-stage cooler is 3.967 and 16.22$/kWh, respectively, for temperature difference of 10K.

Exergoeconomic Analysis and Optimization of a Supercritical CO2 Cycle Coupled with a Kalina Cycle

AbstractA novel combined cycle system comprising of a supercritical CO2 (sCO2) cycle and a Kalina cycle is proposed in this paper. Exergoeconomic comparison between the combined sCO2/Kalina cycle a...

Exergoeconomic comparison of three novel trigeneration systems using SOFC, biomass and solar energies

In this paper, comparison of exergetic performance and exergoeconomic optimization of the three novel trigeneration systems are presented. The systems considered are integrated SOFC-trigeneration, integrated biomass-trigeneration, and integrated solar-trigeneration plants. This study compares the performance of the systems considered when there is only electrical power and the efficiency improvement of these systems when there is a trigeneration. This study shows that the integrated SOFC-trigeneration system has the highest electrical exergy efficiency among the three systems. Alternatively, when trigeneration is used, the efficiencies of all three systems considered increased considerably. The maximum trigeneration exergy efficiency of the SOFC-trigeneration system is 64.5% while it is around 60% and 56% for the integrated biomass-trigeneration system and integrated solar-trigeneration system. Also, the cost per exergy unit of the SOFC-trigeneration system is the highest while this cost is the lowest for the biomass-trigeneration system. In addition, this study shows that the CO2 emissions in kg per MWh and CO2 emissions cost in $/MWh of electrical power are high for the biomass-trigeneration systems. However, by considering the emissions per MWh of trigeneration, their values drop significantly.

Exergoeconomic comparison of TLC (trilateral Rankine cycle), ORC (organic Rankine cycle) and Kalina cycle using a low grade heat source

Recently, the TLC (trilateral power cycle) has attracted significant interest as it provides better matching between the temperature profiles in the evaporator compared to conventional power cycles. This article investigates the performance of this cycle and compares it with those for the ORC (organic Rankine cycle) and the Kalina cycle, from the viewpoints of thermodynamics and thermoeconomics. A low-grade heat source with a temperature of 120 °C is considered for all the three systems. Parametric studies are performed for the systems for several working fluids in the ORC and TLC. The systems are then optimized for either maximum net output power or minimum product cost, using the EES (engineering equation solver) software. The results for the TLC indicate that an increase in the expander inlet temperature leads to an increase in net output power and a decrease in product cost for this power plant, whereas this is not the case for the ORC system. It is found that, although the TLC can achieve a higher net output power compared with the ORC and Kalina (KCS11 (Kalina cycle system 11)) systems, its product cost is greatly affected by the expander isentropic efficiency. It is also revealed that using n-butane as the working fluid can result in the lowest product cost in the ORC and the TLC. In addition, it is observed that, for both the ORC and Kalina systems, the optimum operating condition for maximum net output power differs from that for minimum product cost.

Exergoeconomic comparison of double effect and combined ejector-double effect absorption refrigeration systems

At a particular temperature range, heat sources are not hot enough to drive lithium bromide double effect absorption refrigeration systems efficiently and are too hot to be used for the single effect systems because of the risk of crystallization. A combined ejector-double effect absorption cycle is a good choice to make effective use of heat sources at this temperature range for refrigeration purposes. In this study, detailed exergoeconomic analyses are performed for series flow double effect and combined ejector double effect systems in order to investigate and compare the influence of various operating parameters on investment costs of the overall systems and product cost flow rates. In addition, the proportion of component costs in the overall systems costs and exergoeconomic results are obtained. The results show that the combined cycle operates more economically compared to the double effect system.