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The purpose of this paper is to optimize the performance of direct methanol fuel cells for portable applications by combining a non‐linear, fully coupled circuit model and a stochastic optimization procedure.

A novel non‐linear equivalent circuit that accounts for electrochemical reactions and charge generation inside catalyst layers, electronic and protonic conduction, methanol crossover through the membrane, mass transport of reactants inside diffusion layers is presented. The discharge dynamic of the fuel cell, depending on the initial methanol concentration and on the load profile, is modelled by using the mass conservation equation. The equivalent circuit is interfaced to a stochastic optimization procedure in order to maximize the battery duration while minimizing fuel crossover.

In the proposed circuit scheme, unlike semi‐empirical models, lumped circuit parameters are derived directly from mass transport and electric equations in order to fully describe the dynamic performance of the fuel cell. Physical and geometrical parameters are optimized in order to improve the system runtime. It is shown that a combined use of fuel cells and lithium batteries can improve the runtime of portable electronic devices compared to traditional supply systems based on lithium batteries only.

The one‐dimensional model of the micro fuel cell does not take into account possible transverse mass and electric charge flows in the fuel cell layers; most of the geometric and physics model parameters cannot be estimated from direct in situ or ex situ measurements.

Direct methanol fuel cells are nowadays a promising technology for replacing or complementing lithium batteries due to their high energy density. Most limiting features of direct methanol fuel cells are the fuel crossover and its slow oxidation kinetics. By using the proposed approach, fuel cell parameters can be optimized in order to enhance the discharge runtime and to reduce the methanol crossover.

The equivalent circuit model with optimized lumped non‐linear parameters can be used when designing power management units for portable electronic devices.

The purpose of this paper is to simulate micro direct methanol fuel cells (DMFCs) for portable electronic devices by means of a non‐linear equivalent circuit based on a fully coupled, dynamic, electrochemical model.

The equivalent circuit accounts for electrochemical reactions and electric current generation inside the catalyst layers, electronic and protonic conduction, fuel crossover across the membrane, mass transport of reactants inside the diffusion layers. The V‐I characteristic of the device is obtained by combining mass transport and electric equations. The transient dynamics is accounted for by an equivalent capacitance, while the slow dynamics by the mass conservation equation. The equivalent circuit is embedded in the Matlab/Simulink^® dynamic model of a hybrid system, consisting of a micro fuel cell and a Li‐ion rechargeable battery.

An original equivalent circuit of a passive DMFC suitable for static and dynamic simulations under variable loading conditions is proposed and validated.

The one‐dimensional model of the micro cell does not take into account transverse mass transfer and current density variations in the cell layers, which can be due to non‐homogeneous materials or to the complex dynamics of the convective mass flow in the reservoir and in the room air.

The equivalent circuit can be used for simulating the dynamic performance in realistic operating conditions when the fuel cell is used to supply the electronic equipment through a power management unit.

The DMFC is described from an electrical point of view as a controlled non‐linear generator; such equivalent representation is particularly suited for designing power management units for electronic portable devices.

The purpose of this paper is to simulate passive proton exchange membrane fuel cells (PEMFCs) for portable electronic devices by means of a non‐linear lumped circuit based on electrical, mass transfer and electro‐kinetic equations.

Electrical, mass transfer and electro‐kinetic equations are combined in order to derive a non‐linear lumped circuit. The dynamic circuit model is tested in realistic operating conditions.

An original equivalent circuit model for simulating the transient behavior of passive PEMFCs is proposed. The PEMFC is represented as a non‐linear equivalent circuit with controlled lumped parameters depending on pressure, temperature, hydration, and system capacity.

Lumped parameters are synthesized assuming a one‐dimensional fuel cell model since layer thicknesses are much smaller than other dimensions. Heat generation and transfer are not modeled even though lumped parameters depend on temperature.

The proposed circuit model can be implemented directly in circuit simulators for designing power management units needed to interface small‐passive PEMFCs and portable electronics such as PDAs, laptops, or mobile phones.

The fuel cell is represented as a non‐linear controlled generator whose parameters are derived directly from multiphysics equations rather than empirical relationships. The dynamic behaviour of PEMFCs can be simulated on completely different times scales, i.e. during transients or during the discharge phase.

The paper seeks to do the following. To provide an expression of the electromagnetic power flow that is alternative to the Poynting's theorem expression, overcomes its postulate feature, and is particularly suitable for electric circuit elements.

The paper proceeds from fundamental electromagnetic laws and, independently of Poynting's formulation, follows an approach that generalize established double formulations of the electrostatic and magnetostatic energies.

The paper proposes a compact and straightforward expression of the electromagnetic power flow based on the fundamental electromagnetic field sources, i.e. charge and current densities.

The achieved expression confirms Poynting's expression in the case of electric elements, overcoming its arbitrariness, generalizes previous partial results by other authors, deduced via the Poynting's power balance.

Is promising in the computation of power flow electromagnetic devices connected in electrical circuits, i.e. for coupled problems where the analysis of electromagnetic system interfaced to electric circuits is required. Due to its simple structure and straightforward deduction it has educational value to demonstrate the expressions of the electric power in circuit elements.

The purpose of this paper is to show the main features of the redox flow battery technology, present the current state-of-the-art of both industrial and research systems and to highlight the main research challenges.

The study is based on an extensive survey of recent literature as well as on the authors' own experience in the modelling of RFB systems.

RFBs present unique features which make them suitable for distributed storage and thus particularly interesting in the context of smart grids. Current research aims at resolving some outstanding issues which still limit the widespread use of RFBs.

A more widespread use of energy storage technologies, and RFBs in particular, will allow a much higher penetration of renewable energy sources.

The paper presents one of the few comprehensive studies on RFBs including both technological and modelling aspects.

In the last few years, environmental issues have become a matter of survival. In this sense, e-waste management is among the major problems since it may be a way of mitigating mineral depletion. In this context, the literature lacks e-waste supply chain studies that systematically map supply chain challenges and risks concerning material recovery.

Given this context, the authors' paper conducted a systematic literature review (SLR) to build a framework to identify the constructs of e-waste supply chain risk management.

The paper revealed the theoretical relationship between important variables to achieve e-waste supply chain risk management via a circular economy (CE) framework. These variables include reverse logistics (RL), closed-loop supply chains (CLSC), supply chain risk management, supply chain resilience and smart cities.

The literature contributions of this paper are as follows: (1) a complete list of the risks of the e-waste supply chains, (2) the techniques being used to identify, assess and mitigate e-waste supply chain risks and (3) the constructs that form the theoretical framework of e-waste supply chain risk management. In addition, the authors' results address important literature gaps identified by researchers and serve as a guide to implementation.