[en] Highlights: • Methanol steam reformer system is modeled. • Power is produced for portable power generation applications. • Detailed parametric studies are performed. - Abstract: A methanol reformer system to produce power using a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) for portable power generation applications is modeled. A detailed parametric study using computer simulations is conducted to estimate effects of the steam-to-carbon ratio (SC), the reformer temperature, the current density of the fuel cell, the fuel cell temperature, the cathode stoichiometric ratio, the hydrogen utilization, and the rate of power production on the reformate gas composition, fuel cell performance, input fuel flow rate, and the heat duties of the system components. We specifically examined the effects of the reformate gas composition at various fuel cell temperatures on the performance of HT-PEMFC. The results confirm that the CO molar ratio in the reformate gas increases with a low SC ratio and high reformer temperature. However, the effect of CO molar ratio on the fuel cell performance decreases at elevated fuel cell temperatures. The fuel cell voltage decreases ∼78% with the variation of the current density from 0.1 A/cm"2 to 1 A/cm"2 for 160 °C fuel cell temperature and 0.9% CO molar ratio in the reformate gas while it is ∼61% for 180 °C fuel cell temperature. In addition, at elevated fuel cell temperatures from 160 °C to 180 °C, the input fuel flow rate to produce a given power generation from the system decreases, while enough heat is still available in the system to provide the heat requirement of different system components

[en] Highlights: ► Thermoeconomic optimization formulations of three new trigeneration systems using organic Rankine cycle. ► Thermoeconomic modeling is based on specific exergy costing. ► The optimization based on Powell’s method. - Abstract: This part I of the study presents the thermoeconomic optimization formulations of three new trigeneration systems using organic Rankine cycle (ORC): SOFC-trigeneration, biomass-trigeneration, and solar-trigeneration systems. A thermoeconomic modeling is employed using the specific exergy costing (SPECO) method while the optimization performed using the Powell’s method to minimize the product cost of trigeneration (combined, cooling, heating, and power). The results help in understanding how to apply the thermoeconomic modeling and thermoeconomic optimization to a trigeneration system

[en] Highlights: ► Three new trigeneration systems (SOFC-trigeneration, biomass-trigeneration, and solar-trigeneration systems) are thermodynamically examined and assessed. ► The overall exergy efficiency for the SOFC-trigeneration system becomes the highest. ► The maximum costs per exergy unit for the SOFC-trigeneration system is approximately 38 $/GJ. ► The solar-trigeneration system offers the best thermoeconomic performance. - Abstract: In this part II of the study, three new trigeneration systems are examined. These systems are SOFC-trigeneration, biomass-trigeneration, and solar-trigeneration systems. This study reveals that the maximum trigeneration-exergy efficiencies are about 38% for the SOFC-trigeneration system, 28% for the biomass-trigeneration system and 18% for the solar-trigeneration system. Moreover, the maximum cost per exergy unit for the SOFC-trigeneration system is approximately 38 $/GJ, for the biomass-trigeneration system is 26 $/GJ, and for the solar-trigeneration system is 24 $/GJ. This study reveals that the solar-trigeneration system offers the best thermoeconomic performance among the three systems. This is because the solar-trigeneration system has the lowest cost per exergy unit. Furthermore, the solar-trigeneration system has zero CO₂ emissions and it is based on a free renewable energy source

[en] A new conceptual integrated two-stage biomass gasifier and solid oxide fuel cell (SOFC) system is proposed and a multi-physics model for predicting the performance of this system is developed. A method coupling the modeling equations of a quasi 2-D model for SOFC, a 1-D model for pyrolysis reactor, and 0-D model for the remaining components is applied. Several parametric studies are conducted using the model developed. With the main objective of operating this system being maximizing the net power output, the results for the parametric studies conducted show that the number of SOFC stacks, the mass ratio of air to steam entering the gasifier, and the temperature of the pre-heated air entering the gasifier should be taken as high as possible; whereas the moisture ratio of the wet biomass should be minimized; and there is an optimum point for the rotational speed of the pyrolysis reactor. For the considered input data and the range of parameters studied, the maximum net power output of the system is found to be 93 kW. At this condition, the useful heat output, the electrical efficiency of the system, and the fuel utilization efficiency are calculated as 71 kW, 25%, and 44%, respectively. -- Highlights: ► A new integrated two-stage biomass gasifier and SOFC system is proposed. ► A multi-physics model for predicting the performance of this system is developed. ► For the given data, the maximum net power output that can be achieved is 93 kW. ► At this condition, electrical efficiency of the integrated system is found as 25%.

[en] In this study, greenhouse gas emission and exergy assessments of an integrated organic Rankine cycle (ORC) with a biomass combustor for combined cooling, heating, and power production as a trigeneration system are conducted. This trigeneration system consists of a biomass combustor, an ORC, a single-effect absorption chiller, and a heat exchanger. Four special cases are considered in this comprehensive study, namely, electrical power, cooling-cogeneration, heating-cogeneration, and trigeneration cases. Various exergetic and environmental output performance parameters, namely, exergy efficiency, exergy destruction rate, and greenhouse gas emissions, are examined under varying ORC evaporator pinch point temperature, pump inlet temperature, and turbine inlet pressure. This study shows that using trigeneration considerably increases both energy and exergy efficiencies and decreases the greenhouse gas emissions as compared to the electrical power case. This study reveals that the heating-cogeneration and trigeneration cases are less sensitive to the considered temperature and pressure variations as compared with the electrical power and cooling-cogeneration cases. In addition, the results show that when the trigeneration case is used, the exergy efficiency increases significantly to 27% as compared with the exergy efficiency of the electrical power case, which is around 11%. It is also found that the main two sources of exergy destruction are the biomass combustor and ORC evaporator. Moreover, this study shows that the emissions of CO₂ in kg/MWh are significantly high for the electrical power case while for the trigeneration case, the emissions per MWh of trigeneration drop significantly to relatively low level. Specifically, the emissions drop to around one seventh per MWh produced when trigeneration is used as compared with only electrical power production case.

[en] Highlights: • Segmented coating design in a microchannel methanol reformer is investigated. • Performance of the segmented coating is compared with conventional coating. • Convergence issues in numerical solver are resolved by stepwise solution schema. • Segmented coating can increase the methanol conversion by ∼25% with less catalyst. -- Abstract: A numerical model is developed to predict the performance of a microchannel methanol steam reformer with different catalyst layer configurations to produce hydrogen-rich syngas for a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). A solution schema is developed to compare continuous catalyst layer configurations and various segmented catalyst layer configurations without any convergence issue in numerical analysis. In this work, heat is provided to the endothermic reforming-side via methanol combustion. The results show that higher heat transfer rates can be provided by applying segmented catalyst layer configurations thus, resulting in significant performance improvement of the microchannel methanol steam reformer. The results reveal that methanol conversion can be increased by ∼25% by using segmented catalyst layer configurations with less catalyst in the reforming and combustion sides. The results also indicate that even though there is no significant improvement in methanol conversion with increasing catalyst layer thickness, the greater catalyst layer thickness provides the advantage of reduced high temperature elevations across the reformer length. Overall, the segmented catalyst layer configurations can play an important role in designing a next generation of microchannel reformers for fuel cell power generation systems to maximize power, minimize reformer size, and decrease the required quantity of the catalyst.

[en] In this study, energy and exergy analyses of a biomass trigeneration system using an organic Rankine cycle (ORC) are presented. Four cases are considered for analysis: electrical-power, cooling-cogeneration, heating-cogeneration and trigeneration cases. The results obtained reveal that the best performance of the trigeneration system considered can be obtained with the lowest ORC evaporator pinch temperature considered, T_pp = 20 K, and the lowest ORC minimum temperature, T₉ = 345 K. In addition, this study reveals that there is a significant improvement when trigeneration is used as compared to only electrical power production. This study demonstrates that the fuel utilization efficiency increases, in average, from 12% for electrical power to 88% for trigeneration. Moreover, the maximum exergy efficiency of the ORC is 13% and, when trigeneration is used, it increases to 28%. Furthermore, this study reveals that the electrical to cooling ratio can be controlled through changing the ORC evaporator pinch point temperature and/or the pump inlet temperature. In addition, the study reveals that the biomass burner and the ORC evaporator are the main two sources of exergy destruction. The biomass burner contributes to 55% of the total destructed exergy whereas the ORC evaporator contributes to 38% of the total destructed exergy. -- Highlights: ► The best performance can be obtained with the lowest ORC evaporator pinch temperature and the lowest ORC minimum temperature. ► There is, on average, 75 % gain in energy efficiency for trigeneration compared to electrical system. ► There is, on average, 17% gain in exergy efficiency when trigeneration is used as compared to electrical system. ► The electrical to cooling ratio is sensitive to the variation of the pinch point temperature and pump inlet temperature. ► The two main sources of the exergy destruction are the biomass burner with 55% and the ORC evaporator with 38%.

[en] In this paper, energetic performance comparison of three trigeneration systems is presented. The systems considered are SOFC-trigeneration, biomass-trigeneration, and solar-trigeneration systems. 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 trigeneration. Different key output parameters are examined: energy efficiency, net electrical power, electrical to heating and cooling ratios, and (GHG) GHG (greenhouse gas) emissions. This study shows that the SOFC-trigeneration system has the highest electrical efficiency among the three systems. Alternatively, when trigeneration is used, the efficiencies of all three systems considered increase considerably. The maximum trigeneration efficiency of the SOFC-trigeneration system is around 76% while it is around 90% for the biomass-trigeneration system. On the other hand, the maximum trigeneration efficiencies of the solar-trigeneration system is around 90% for the solar mode, 45% for storage and storage mode, and 41% for the storage mode. In addition, this study shows that the emissions of CO₂ in kg per MWh of electrical power are high for the biomass-trigeneration and SOFC-trigeneration systems. However, by considering the emissions per MWh of trigeneration, their values drop to less than one fourth. -- Highlights: → We have compared the energetic performance of three potential trigeneration systems. → These systems are SOFC, biomass, and solar-trigeneration systems. → The SOFC-trigeneration system has the highest electrical efficiency. → The trigeneration efficiencies of the biomass-trigeneration system and solar mode of the solar-trigeneration system are the highest. → The CO₂ emissions per MWh of combined cooling, heating, and power production drop significantly when trigeneration is used.

[en] Highlights: • Compared the electrodes made of CCM and CCS methods. • Characterized electrode pore structure, and diffusion and permeation resistivity. • Observed significant performance drop for low-Pt-loading CCS electrodes. • Quantified the effect of the penetration of catalyst materials into GDL pores. • Measured larger surface area and transport resistivity for CCM electrodes. -- Abstract: Electrode structure determines the rate of transport and electrochemical reactions and is significantly affected by the catalyst deposition method. In this study, the effect of catalyst deposition is investigated on the pore structure, mass transport, and operating performance of the catalyzed electrodes prepared by the methods of catalyst coated on membrane (CCM) and catalyst coated on substrate (CCS). The result indicates that the CCS electrode is thinner, yielding larger porosity, smaller geometric pore surface area, smaller diffusion and permeation resistivity, and lower cell performance. The maximum power density of the CCS electrodes is only about 4% smaller than that of the CCM electrodes at high Pt loadings (0.4 mg·cm⁻²), while it is as much as 60% less than that of the CCM counterparts at low Pt loadings (0.1 mg·cm⁻²). The significant performance drop for the low-Pt-loading CCS electrodes is due to the relatively low surface area in the catalyst layers resulted from catalyst penetration into the pores of the gas diffusion layer, even though the mass transfer resistivity is smaller than their CCM counterparts. The CCS method is therefore unsuitable for low-Pt-loading electrodes (<0.1 mg·cm⁻²) unless the material penetration and the resulting performance deterioration can be inhibited.

[en] Graphical abstract: - Highlights: • The LIB model is simplified for a range of cell designs and operating conditions. • Ragone plots are employed to estimate the accuracy of the simplified model. • Diffusion contribution in ion transfer in electrolyte is less significant than the migration. • Diffusive ion transfer can be neglected in most LIB designs and operating conditions. • Salt concentration gradient can be neglected in some LIB designs and operating conditions. - Abstract: The simulation of lithium-ion batteries based on a fundamental multi-physicochemical model requires extensive computational resources and remains sluggish for real-time or battery pack analysis applications. In these applications, simplification of the model is required to reduce computational costs while maintaining the model accuracy in estimation of one or more performance parameters. In this study, the effects of neglecting the lithium-ion diffusive charge transfer and the salt concentration gradient in electrolyte on the model accuracy are investigated. The results indicate the feasibility of simplifying the model for a range of cell designs and discharge rates without sacrificing the preciseness of the cell energy and power density predictions