Exergy Cost Research Articles

Techno-economic analysis and dynamic performance evaluation of an integrated green concept based on concentrating solar power and a transportable heat pipe-cooled nuclear reactor

The nuclear-solar hybrid system (NSHS) is regarded as a promising solution to meet the growing energy requirements of remote areas. Currently, design schemes and parametric analyses for small-scale application scenarios are still limited. This study has proposed an innovative transportable micro heat-pipe cooled nuclear reactor (HPR) coupled with a concentrating solar power (CSP) system to achieve flexible load regulation. First, a dynamic simulation model for the NSHS is established in the Simulink platform, considering turbomachine off-design characteristics and the power-load matching dispatch principle. Then, techno-economic analyses are carried out to explore the exergy and capital cost flow processes. The results reveal that the NSHS shows clear seasonal features with the highest load cover rate of 98.31 % in summer and the lowest of 73.82 % in winter. The total exergy effectiveness of the NSHS is 29.4 %, with an average electricity cover ratio of 88.67 % and a solar energy penetration ratio of 13.32 %. The calculated LCOE is 80.84 $/MWh, and the payback period is 3.62 years. The life cycle emission of the system is assessed as 10.23 g CO2 eq./kWh. Compared with the solar standalone system, the hybrid system with higher efficiency faces challenges in high-temperature resistance and thermal insulation.

4E analysis of a solar, wind and waste heat-driven CCHP system: A case study for a cruise ship

One of the most advanced technologies for meeting all cooling, heating, and electrical demands is Combined Cooling Heating and Power (CCHP) systems. This paper proposes using PV panels, wind turbines, and CCHP system based on an Organic Rankine Cycle integrated absorption chiller, for a cruise ship MS Birka Stockholm. A part of the electricity demand is provided by three wind turbines and PV panels, and another part is generated by the CCHP system. The proposed CCHP system works by recovering heat by three main engines in summer and mid-season and four main engines in winter. It’s important to mention that in actual condition the ship is working with eight engines. Decreasing the number of engines and using renewable energies could be a very alluring issue in the transportation systems. Energy, Exergy, Exergoeconomic, and exergoenvironmental (4E) analysis is done for the system and also components with the highest exergy destruction and cost rate and environmental effects are recognized. 4E analysis could give the researchers opportunity to compare their proposed systems results, that is never done in this field. Mentioned analysis are divided into three parts, including winter, mid-season and summer. For the summer, energy and exergy efficiencies are 65% and 40.13%, respectively. The coefficient of performance (COP) is also calculated 0.706. For mid-season, thermal efficiency is calculated 97.4% and exergy efficiency is calculated 24.31%. Therefore, for winter thermal efficiency is calculated 98% and exergy efficiency is calculated 9.3%. The cost associated with total exergy destruction is 1,193,099 €/year, and the total investment cost of the system is 179,592 €/year. The total environmental impacts associated with the exergy destruction and the total value of the component-related environmental impact of the system (Ẏ) were calculated as 2,479,713 mpts/year and 864,627mpts/year, respectively.

Experimental study and process evaluation of coproduction graphene, acetylene and hydrogen from methane pyrolysis by thermal plasma

This paper developed a process for the coproduction of graphene, acetylene and hydrogen from methane pyrolysis by thermal plasma. Bench-scale tests under three specific energy input (SEI) were carried out to investigate the morphology of carbon nanomaterials and the product selectivity. The process was evaluated by exergy and exergoeconomic analyses. Results indicated that a higher SEI improved the selectivity of graphene nanoflakes (GNFs) and reduced their defects. The product selectivity of GNFs played a critical role in the decrease of total fuel exergy per unit of GNFs as the SEI increased. The plasma reactor exhibited the highest exergy loss ratio in the entire process due to heat dissipation. The quenching device exhibited the second-highest exergy loss ratio in the process, stemming from irreversible entropy increase causing exergy loss. Improving the design of the plasma reactor to enhance thermal efficiency and implementing a feasible waste heat recovery system were identified as effective strategies to enhance exergy efficiency. Excluding consideration of co-products, GNFs with high SEI had the lowest cost of 199.41 CNY/kg, when co-products were considered, the lowest cost decreases by 30%, and the low SEI had the lowest GNFs cost at 140.71 CNY/kg. This indicated that there was enough investment potential to tailor the properties of GNFs produced by such processes for application scenarios. The unit exergy cost of GNFs decreased from 0.89 CNY/MJ to 0.80 CNY/MJ as the SEI of the plasma reactor increased. Subsequently, it rose to 1.16 CNY/MJ. Prioritizing the increase in investment costs for the plasma reactor to reduce exergy loss costs should be considered first, and optimizing the waste heat recovery process was also a key direction to minimize exergy loss costs.

Exergoeconomic evaluation and optimization of a solar-powered polygeneration system producing freshwater, electricity, hydrogen, and cooling

This study presents a comprehensive exergoeconomic assessment and optimization of a pioneering solar-powered polygeneration system designed for simultaneous production of electricity, cooling, freshwater, and hydrogen, aiming to fill the gap in knowledge about such a polygeneration system. The study employs an advanced methodology to evaluate future improvement methods, considering the system's performance and economic viability. The Specific Exergy Costing (SPECO) method is used for exergoeconomic analysis, and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is preferred to reveal Multiple Criteria Decision Analysis (MCDA) for optimization.As an important conclusion, it is recognized that system modifications should reduce the financing cost while simultaneously increasing the system's lifespan and annual operational time. The most expensive components of the system are the PTC, ORC, and electrolyzer, which are responsible for 51%, 23%, and 18% of the total cost of energy destruction, respectively. Thus, purchase price reduction and improvement in the efficiencies of these units are crucial. Also, considering the exergoeconomic factor (fc) values calculated for the system components, it is necessary to increase the efficiency of the compressor and electrolyzer, which have fc values of 37.37% and 32.1%, respectively, even if it results in higher capital expenditures. Additionally, it should be preferred to reduce the capital costs of the other system components, which have higher fc values in the range of 46.68% and 52.47%, without reducing their efficiencies significantly.

Thermoeconomic analysis and environmental impact assessment of the Akkuyu nuclear power plant

Within the scope of this study, a thermoeconomic analysis was carried out for Akkuyu Nuclear Power Plant (ANPP), the first nuclear power plant of Türkiye. As a result of the analysis, it is aimed to reduce the cost of energy production and prevent thermal pollution at the same time by converting the heat discharged into the environment into useful heat due to the working principle of NPP. Thermodynamic analysis was performed in the Engineering Equation Solver (EES) program using equipment values equivalent to ANPP. Cost analysis was performed using the specific exergy costing (SPECO) method, which is based on the second law of thermodynamics and is the most widely used cost analysis method. The study concludes that the energy efficiency is 35%, while the economic analysis shows that the best case has an exergy efficiency of 68% with a payback period of 7–8 years, and an electricity cost of $0.0196 per kWh. It is possible to use the heat discharged from the plant indirectly in district heating (heating, hot water needs of the lodgings, guesthouses in the facility), greenhouse heating, agricultural drying and heating, considering the geographical conditions and livelihood of the region. Thus, 68% of the waste heat was utilized, the unit cost of the energy produced was reduced and at the same time thermal pollution was reduced at the same rate. The results of the study can contribute to the efforts preventing energy waste, thermal environmental pollution, and reducing greenhouse gas emissions. Additionally, it could aid in the development of more energy-efficient and environmentally friendly power generation systems, including pioneering nuclear power plants in developing countries.

Exergoeconomic analysis and optimization of wind power hybrid energy storage system

The hybrid energy storage system of wind power involves the deep coupling of heterogeneous energy such as electricity and heat. Exergy as a dual physical quantity that takes into account both 'quantity' and 'quality, plays an important guiding role in the unification of heterogeneous energy. In this paper, the operation characteristics of the system are related to the energy quality, and the operation strategy of the wind power hybrid energy storage system is proposed based on the exergoeconomics. First, the mathematical model of wind power hybrid energy storage system is established based on exergoeconomics. Then, wind power experiments of three forms of thermal-electric hybrid energy storage are carried out, and RSM is used to analyze the power quality and exergoeconomic characteristics of the system, and the optimal working conditions of the experiment are obtained. Finally, an optimization strategy is proposed by combining experiment and simulation. The system efficiency, unit exergy cost and current harmonic distortion rate are multi-objective optimization functions. The three algorithms evaluate the optimal solution based on standard deviation. The results show that the exergoeconomics can effectively judge the production-storage-use characteristics of the new system of ' wind power + energy storage'. The thermal-electric hybrid energy storage system can absorb the internal exergy loss of the battery, increase the exergy efficiency by 10%, reduce the unit exergy cost by 0.03 yuan/KJ, and reduce the current harmonic distortion rate by 8%. It provides guidance for improving the power quality of wind power system, improving the exergy efficiency of thermal-electric hybrid energy storage wind power system and reducing the unit cost.

Thermodynamic analysis of a multiple energy production system based on geothermal energy for commissioning in Canada and optimization by response surface method (RSM)

The thermodynamic analysis of a geothermal-based integrated energy system to produce liquid hydrogen, cooling, hot water, and power was presented in this study. The investigated system consists geothermal subsystems, a modified organic Rankine cycle (ORC), a PEM electrolyzer, and a liquid hydrogen storage source. Different organic fluids including refrigerants R113, R123, and R134a were investigated to increase the system performance. Analysis of organic fluids showed that the best organic fluid is R123 because it helps to increase the performance of the system. The authors employed the Design-Expert software and RSM for optimum results purposes, and the objective functions were chosen to be exergy efficiency (EE) and cost rate (CR). Following introduction of design variables, the mass flow rate of input to the evaporator, the temperature of input to heat recovery vapor generator, turbine efficiency, turbine input temperature, evaporator pinch point temperature, and pump efficiency, their impact on the system's performance were investigated. The optimal values for EE and CR were ultimately found to be 43.91 % and 45.12 $/h, respectively. Also, in this research, seven regions within Canada were investigated for the launch of the proposed system. The studied cities were Victoria, Vancouver, Regina, St. John's, Dawson Creek, Whitehorse, and Port Alberni. Finally, Regina was chosen because of the system's superior performance in electricity production at a reasonable cost in that area. The environmental results showed that the presented energy system in Regina city could help to expand 5 ha of green space by producing electricity at the rate of 4993.03 MWh in one year. The findings indicated that implementing the suggested system in Regina would help prevent 1018.6 tons of CO2/MWh from being emitted into the environment yearly, only by chipping in 24445.9 $/ton of CO2 per year.

Exergy, exergoeconomic, and exergoenvironmental analyses of novel solar- and biomass-driven trigeneration system integrated with organic Rankine cycle

This study proposes a combined cooling, heating, and power (CCHP) system driven by biomass and solar energy integrated with an organic Rankine cycle (ORC). Its exergy, exergoeconomic, and exergoenvironmental performances are investigated. First, the thermodynamic parameters of each material and energy flow for the proposed CCHP system are simulated using Aspen Plus. Second, the exergy and exergoeconomic performances of the system are investigated, and an exergoenvironmental analysis of the system is performed. The results show that the unit exergy costs (UEC) of domestic hot water, electricity generated by an internal combustion engine (ICE) and the ORC, and chilled/heated water under summer/winter conditions are 2.742/2.742, 6.713/6.629, 12.930/12.930, and 27.100/12.530 MW/MW, respectively, with corresponding unit exergoeconomic costs (UEEC) of 41.11/41.11, 124.40/139.20, 181.80/181.80, and 507.10/302.60 USD/MWh, respectively. Meanwhile, the corresponding environmental impact rates per exergy unit are 0.616/0.616, 2.988/3.023, 0.030/0.030, and 6.567/3.072 mPts/MJ, respectively. The results highlight the urgency to prioritize improvements to the solar collector performance to reduce the UEC of electricity generated by the ORC. The absorption chiller/heater, heat exchanger, and ICE exhibit significant potential for enhancing their exergoeconomic performance. Additionally, the gasifier, ICE, and ORC can be optimized to mitigate their environmental impact with relatively minimal exertion.

Energy, exergy, and exergoeconomic cost optimization of wind-biomass multi-energy systems integrated for hydrogen production

Energy, exergy, and exergoeconomic cost optimization of wind-biomass multi-energy systems integrated for hydrogen production

Thermodynamic, environmental, and exergoeconomic analysis of multi-ejector expansion transcritical CO2 supermarket refrigeration cycles in different climate regions of Türkiye

Restrictions on high-GWP refrigerants have made the use of transcritical CO2 refrigeration systems widespread. Using transcritical booster refrigeration cycle in warm climates is unsatisfactory due to its high energy consumption. This paper presents theoretical analysis and performance comparison of three different transcritical CO2 supermarket refrigeration cycle configurations with ejector expansion in Türkiye, which has different climatic regions. Bin-hour data were derived using hourly dry-bulb temperature values for provinces from 7 different regions in Türkiye. The applicability of multi-ejectors to each modeled cycle was also investigated. Annual energy consumption and environmental impact reductions of up to 17% were obtained using ejector expansion cycle compared to booster cycle. Ejector expansion cycles achieved higher performance than booster cycle up to 46% in terms of exergy efficiency at investigated ambient temperatures. Unit product exergy costs of the ejector cycles were found up to 28% lower than booster cycle.

Comprehensive analysis and optimization for a novel combined heating and power system based on self-condensing transcritical CO2 Rankine cycle driven by geothermal energy from thermodynamic, exergoeconomic and exergoenvironmental aspects

In this paper, a novel combined heating and power (CHP) system is proposed to realize full-scale utilization of geothermal energy and efficient multi-generation, which not only performs preferable overall performance than previous homogeneous system, but also offers an effective energy cascade utilization approach for self-condensing transcritical CO2 (TCO2) Rankine cycle. Based on the established mathematical models, the performance comparison is conducted for proving the superiority of the novel CHP system. Then, an overall performance analysis is implemented to reveal the combined effects for six key parameters on system thermodynamic, exergoeconomic and exergoenvironmental performances. Furthermore, multi-objective optimization considering system overall performance is conducted. The results show that for the novel CHP system, the largest relative improvement rate of system exergy efficiency (ηexg) and declining rate of total unit product exergy cost (cP,total) versus the previous CHP system are 15.03 % and 18.89 %, respectively. The final optimization results of ηexg, cP,total and total unit product exergy environmental impact (bP,total) are determined as 51.10 %, 14.12 $/GJ and 9.00 mPts/GJ, respectively. This paper fulfills an elaborate performance analysis and optimization for the novel CHP system, which fills the research gap of efficient and promising CHP system based on self-condensing TCO2 Rankine cycle.

Energy, Exergy, Exergoeconomic, and Environmental (4E) Analysis of the Existing Gas Turbine Power Plants in BOB - PT. Bumi Siak Pusako Pertamina

The power plants in Indonesia are mostly used to supply energy for the industrial sector, including the upstream oil and gas as well as mining companies. Several companies operating in Riau contribute to the status of the region as the largest oil producer in Indonesia. These companies rely on self-generated electricity for their operations with subsequent impact on the environment. Therefore, this research was conducted to analyze the flow of energy, exergy, exergoeconomic, and environment at the 6 MW power plant operated by BOB - PT Bumi Siak Pusako - Pertamina Hulu. The second law of thermodynamics was used to evaluate energy efficiency as the maximum achievable effort. This was further integrated with economic principles to appraise the useful and wasted costs associated with thermodynamic systems through the concept of exergoeconomics. The results showed that the thermal efficiency of the gas turbine power plant was 42.85% and the exergy efficiency was 33.22% with the largest loss recorded in the combustion chamber to be 3.091 MW in the form of vibration, friction, or expansion of the components. It was also discovered that the exergy efficiency of each component was above 75%, thereby indicating the components of the gas turbine power plant components were in good condition. Moreover, the largest exergy destruction cost was 2349.16 USD/h and the exergy cost was 3,778.05 USD/kWh. The exhaust emission generated by the gas turbine power plant was 0.21 kg/s or equivalent to 0.1425 kg/kWh requiring a forest area of 11.63 ha. The results showed that the analytical method used could be comprehensively developed and applied to other power plants in Indonesia. It could also be used to understand system performance, identify energy losses, optimize energy efficiency, and link economic aspects with energy use.

Definition of Exergetic Efficiency in the Main and Emerging Thermal Desalination Technologies: A Proposal

Increasing attention is being given to reduce the specific energy consumption in desalination processes, which translates into greater use of exergy analysis. An exergetic analysis provides relevant information related to the influence of the efficiency of a single component in the global plant performance and in the exergy cost of the product. Therefore, an exergy analysis identifies the main improvement potentials in a productive thermodynamic process. Related to desalination technologies, many previous papers deal with the calculation of the parameters involved in the exergy analysis, the exergetic efficiency of different processes, plants, and technologies among them. However, different approaches for formulating the exergetic efficiency have been suggested in the literature, often without sufficient understanding and consistency. In this work, these formulations, applied to the main desalination components and processes, are compared and critically reviewed. Two definitions of exergy efficiency are applied to the desalination components of the three main thermal desalination processes (multieffect distillation–thermal vapour compression, multistage flash distillation, and direct-contact membrane distillation). The results obtained for the exergy efficiency of the MED-TVC, MSF, and DCMD processes for the input–output approach are 21.35%, 17.08%, and 1.28%, respectively, compared to the consumed–produced approach that presented 3.1%, 1.58%, and 0.37%, respectively. The consumed–produced approach seems to better fit the thermodynamic behaviour of thermal desalination systems.

3E analyses and multi-objective optimization of a liquid nitrogen wash based cogeneration system for electrical power and LNG production

A liquid nitrogen wash based novel system is proposed for electricity generation and LNG production. This system utilizes cold energy of methane rectification for power generation, and realizes the LNG production through methane recovery from exhaust gas. Effects of operational parameters on net generation capacity (NEG) and energy efficiency are studied. Exergy destruction/efficiency and exergy cost are obtained. Advanced exergy/exergo-economic analyses are conducted to clarify the improvement potential and improvement strategy. Finally, the optimal solutions are obtained in multi-objective optimization. Results show that propane could be used as the organic working medium and the maximum NEG is 675.95 kW and the energy efficiency is 19.34 %. As 88.8 % of the system investment cost is for the equipment, reduction on exergy destruction cost of equipment should be considered. Advanced analysis indicates that 27.27 % of the exergy destruction, 30.02 % of the exergy cost and 7.20 % of the investment cost can be avoided. The thermodynamic optimization shows that the highest energy efficiency is 67.26 %, the highest exergy efficiency is 76.95 % and the lowest exergy cost per unit is 28.45 $/GJ. The economic optimization shows that exergy efficiency is improved by 2.83 % and NEG is improved by 47.95 % when increasing the investment cost for 6.13 %.

Modeling and exergy-economy analysis of residential building energy supply systems combining torrefied biomass gasification and solar energy

A novel hybrid energy system driven by torrefied biomass gasification and solar energy is proposed for the first time, and their complementarity to enhance the system’s energy efficiency is analyzed and shown. The system mainly combines biomass torrefaction, biomass gasification subsystem, solar heat collection and absorption refrigeration technology. The effects of different operating parameters on the gasification products were studied. The economic analysis is carried out based on the theory of exergy economy. The results show that torrefaction pretreatment of biomass can significantly improve its fuel quality and gasification performance. With the increase of torrefied temperature, the volume fraction of CO2 and H2 decreased while the volume fraction of CH4 and CO increased. The economic analysis shows that the expected annual income is $72,735, and the investment recovery period is 2.89 years. Through the calculation of the energy-saving and environmental benefits, it can be concluded that the hybrid energy system can save 1.05 × 106 MJ of heat per year. This equates to about 358.26 tons of standard coal or a CO2 emission reduction of 550.59 tons, the participation of solar energy is conducive to the system emission reduction. By tuning the parameter sensitivity, the influence of biomass price change on the unit exergy cost of system products was more obvious.

Multi-criteria optimization of a combined power and freshwater system using modified NSGA-II and AHP-entropy-topsis

This paper proposed an innovative hybrid system to generate electricity and fresh water with higher energy efficiency. A subsystem is employed by integrating DCMD and heat pump to recover waste heat of PEMFC to produce fresh water. The thermodynamic and exergoeconomic models are established to evaluate the system comprehensive performance. Compared with the PEMFC alone, the results demonstrated that the proposed hybrid system achieves a 42.07 % increase in energy efficiency and provides 177.86 kg/h of fresh water. The components with high exergy destruction are PEMFC, Relief value, Inverter, Separator 2 and DCMD with the exergy destruction rate of PEMFC stack accounting for 54.55 %. The parametric analysis results indicate that the variation of the membrane filament number, feed and permeate flow rates all have evident impacts on the thermodynamic and economic performances of the hybrid system. The multi-objective optimization is conducted by adopting NSGA-II and three decision-making methods. The optimal solution obtained by AHP-entropy-TOPSIS approach for the net power out, exergy efficiency, WPC, and total exergy cost rate are 96059W, 0.5293, 0.2995 $/m3, and 14.27 $/h, respectively. In addition, the obtained results shown that the simulation times of NSGA-II are significantly reduced from 89.30 to 11.20 h by introducing BP-ANN to improve the simulation efficiency.

Optimal 4E evaluation of an innovative solar-wind cogeneration system for sustainable power and fresh water production based on integration of microbial desalination cell, humidification- dehumidification, and reverse osmosis desalination

Reliable freshwater production is vital for tackling two of the most critical challenges the world is facing today: climate change and sustainable development. Present work presents an innovative cogeneration system based on solar and wind energies for sustainable production of freshwater, power, and wastewater treatment. For freshwater production and wastewater treatment in this system, the integration of a microbial desalination cell with a humidification-dehumidification and reverse osmosis desalinations has been used. The mentioned systems provide their heat demand from solar energy, and when solar radiation is unable to provide this heat, a hydrogen internal combustion engine drive produces the required heat for the freshwater plant. Excess heat from the hydrogen internal combustion engine is fed into the organic Rankine cycle for more power generation in the whole system to reduce system waste heat and increase efficiency. PEM electrolyzer has been used to supply the hydrogen needed by the internal combustion engine, and this system uses wind turbines to supply the power demand. To evaluate the performance of the whole system, energy, exergy, exergeoeconomic, and exergoenvironmental (4E) analyses have been carried out. Finally, to improve the performance parameters of the system, multi-objective optimization using the Salp swarm algorithm has been used. Investigation of the results show that the proposed system can produce 720 kW of electricity and 5.36 m3/h of freshwater. The energy efficiency of the system is 22.09 %, and its overall cost rate and overall environmental impact rate are 540.33 $/hr and 17.37 Pt/h, respectively. Among the qualitative results obtained in this research, it is possible to mention the high exergy destruction, cost destruction, and environmental impact destruction of the internal combustion engine compared to other equipment used in the proposed system, and this point shows the need to improve this equipment, similar to previous researches. The five-objective optimization results of the proposed system showed that the performance parameters of the system, such as polygeneration energy efficiency, total cost rate, and total environmental impact rate, can be improved by 6.2 %, 1.44 %, and 0.52 %, respectively. The payback period of the proposed system in the optimal state is 6.95 years.

Comparative study on the organic rankine cycle off-design performance under different zeotropic mixture flow boiling correlations

Zeotropic mixture utilization enhances the performance of the Organic Rankine cycle (ORC) significantly. For geothermal ORC power plants, the zeotropic mixture flow boiling correlation plays a vital role in both evaporator design and system performance evaluation. Based on the screened zeotropic mixture R1224yd(Z)/R1234ze(E) (0.452/0.548), a comparative analysis of 4 flow boiling correlations is performed to assess their impact on both evaporator design and system performance under off-design conditions. The results underscore a substantial impact of these correlations on determining the plate length, with the largest relative difference being 53.8%, consequently resulting in uncertainties of 31.7% and 23.4% for the evaporator exergy loss and cost, respectively. Under off-design working conditions, the relative difference in net power output varies from 16.43% to 7.67%. The exergy efficiency variation is up to 11.82% and the electricity production cost (EPC) uncertainty is up to 11.2% at the working condition with the maximum difference in net output work. This study provides valuable insights for selecting the appropriate zeotropic mixture flow boiling correlation in practical evaporator design and evaluating the off-design performance of ORC systems.

Design and optimization of a combined supercritical CO2 recompression Brayton/Kalina cycle by using solar energy and LNG cold energy

Solar energy and LNG cold energy have broad application scenarios as two renewable sources, but their complementary potential has not been fully explored. To fill this gap, this paper constructs a novel combined cycle that utilizes solar energy and recovers LNG cold energy to generate power. This combined cycle consists of a supercritical carbon dioxide recompression Brayton cycle, an ammonia-water mixture Kalina cycle, and an LNG cryogenic power system. A systematic evaluation was conducted on the thermodynamics and exergoeconomic of the model, and the simulation results under basic operating conditions show that the first law efficiency, second law efficiency, net power output and total unit cost reach 55.73 %, 47.72 %, 13.709 MW and 27.44 $·GJ−1 respectively. The genetic algorithm and elitist non-dominated sorting genetic algorithm are used to optimize the system performance. By using the parallel direct search method, the maximum first law efficiency, as well as second law efficiency and a minimum total unit cost of 59.45 %, 52.23 % and 24.81 $·GJ−1 are obtained respectively. The optimal first law efficiency, second law efficiency, and total unit cost of the system, which are 53.52 %, 50.33 % and 26.44 $·GJ−1 respectively, are searched simultaneously from the multi-objective optimization results by LINMAP decision-making method. Furthermore, this paper analyzes the exergy flow rate of the system and heat transfer processes of the heat exchangers under optimal operating condition. A total of 23,059.35 kW of LNG cold energy is fully utilized by the system in the LNG gasification process. The exergy loss ratio and cost ratio of each equipment analysis demonstrates that the heat exchangers (HX) have the largest percentage both exergy loss ratio and cost ratio, especially the HX4.

Tri-generation design and analysis of methanol-reforming high-temperature fuel cell based on double-effect absorption cooling power cycle

The methanol-reforming based high-temperature proton exchange membrane fuel cells is promising in both stationary and mobile applications, due to the trade-off between the efficiency and durability. However, challenges arise in the system integration due to the coupling of various-grade heat flows. Additionally, the exiting waste heat recovery systems face thermal-electric coupling issues, leading to limited flexibility in the energy supply. To this end, a thermally coupled tri-generation system based on methanol-reforming high-temperature proton exchange membrane fuel cell and double-effect absorption cooling power cycle is proposed. The cooling oil cycle absorbs heat from the fuel cell stack and burner, supplying heat for the preheaters, methanol reformer and double-effect absorption cooling power cycle. The cooling and power outputs of the double-effect absorption cooling power cycle are flexibly adjusted by varying the vapor split ratio. The mathematical models are developed and validated, based on which the exergy, exergoeconomic, economic and environmental performances are investigated. Under the design conditions, the tri-generation system yields net power, cooling, and hot water of 102.8 kW, 64.75 kW, and 43.83 kW, respectively, with exergy efficiency of 39.0% and unit exergoeconomic cost of product exergy of 65.09 $/GJ. The economic and environmental analyses indicate that, compared to the conventional system, a 54.2% reduction in carbon dioxide emissions is achieved, and the payback periods stand at 4.0, 5.6 and 9.0 years for the methanol prices of 0.40, 0.45 and 0.50 $/kg, respectively.