A single-phase, non-isothermal model for PEM fuel cells

Effect of GDL permeability on water and thermal management in PEMFCs—I. Isotropic and anisotropic permeability

A comprehensive single-phase non-isothermal MEA model, which accounts for all applicable heat sources, viz., entropic and irreversible heating associated with electrochemical reactions, protonic and electronic ohmic heating, phase change, and heat release/absorption due to sorption/desorption of water in electrolyte is presented. Starting from a general energy transport equation, layer-specific thermal transport equations are derived. The model expands upon the isothermal model by Secanell et al. [1] and accounts for multi-step reaction kinetics for the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) [2]. The model accounts for water management in two phases, viz., vapour and sorbed phase, and accounts for thermal effects on water transport such as temperature driven vapour diffusion, and thermal osmosis. The model is integrated into openFCST, a finite element based, open-source, fuel cell simulation framework, which is available for download online at http://www.openfcst.mece.ualberta.ca/.The non-isothermal model is used to estimate the maximum temperature inside the membrane electrode assembly under different operating conditions such as hot and dry, and cold and wet. At low humidity conditions, the mathematical model predicts a significant performance drop in the cell due to drying out of ionomer. The cathode catalyst layer is found to be the hottest, with temperatures rising by more than 10ºC at high current densities (Figure 1). A detailed breakdown of various heat sources inside the cell at different current densities is also provided (Figure 2). It is observed that heat of sorption, which has generally been ignored in previous non-isothermal models, is more significant than protonic ohmic heating at medium current densities, and causes a shift in temperature distribution in the in-plane direction. At high current densities, heat of sorption accounts for roughly 15% of the overall heat generated in the cell, and it is concluded that this term cannot be ignored.There is ambiguity in the literature regarding reversible heat distribution between the half-cell reactions of the ORR and HOR [3]. Based on the data by Ramousse et al. [3], the HOR should be exothermic. This is contrary to the general practice of assuming the HOR to be athermic. Using the non-isothermal model with an exothermic HOR, it is shown that the assumption causes a cell performance drop and the maximum temperature of the cell to shift from the cathode catalyst layer (CCL) to anode catalyst layer (ACL).Thermal management strongly affects water transport in the cell. Therefore, the thermal transport equation is solved with a detailed water management model including thermal-osmosis. The non-isothermal model predicts higher sorbed water movement from the ACL to CCL due to drying out of ionomer in the CCL when compared to an isothermal model (Figure 3). The contribution of thermal osmosis to sorbed water flux is as much as 15% as shown in Figure 3.The thermal conductivity of microporous layer is found to significantly influence the cell performance predictions. If reduced considerably, the model predicts self-heating of the MEA and a complete dryout of the cell (Figure 4).In summary, a detailed single-phase non-isothermal MEA model is developed. The non-isothermal fuel cell model governing equations include a thermal transport equation, a sorbed water transport equation, the mass and charge transport of all species, and multi-step kinetics for HOR and ORR electrochemical reactions. Using the model, the importance of several critical physical phenomena is analyzed.

Three dimensional (3D) integration offers numerous electrical advantages like shorter interconnection distances between different dies in the stack, reduced signal delay, reduced interconnect power and design flexibilities. The main enabler of 3D integration is through-silicon-vias (TSVs) and stacking of multiple dies. Irrespective of these advantages, thermal management in 3D stacks poses significant challenges for the implementation of 3D integrated circuits. Even though extensive research work has been done in understanding the thermal management in two dimensional (2D) planar circuits for the past several decades, 3D integration offers a new set of challenges in terms of thermal management, which makes it difficult to readily apply the thermal management strategies available for 2D planar circuits. Over the past decade, some work has been done in thermal analysis and management of 3D stacks but still, knowledge is scattered and a comprehensive understanding is lacking. This research work focuses on bringing together the limited work on thermal analysis and thermal management in 3D vertically integrated circuits available in the literature. A compilation and analysis of the results from investigations on thermal management in 3D stacks is presented in this review with special emphasis on experimental studies conducted on different thermal management strategies. Furthermore, 3D integration technologies, thermal management challenges, and advanced 2D thermal management solutions are discussed.

Water and thermal management in PEM fuel cells using feasible humidity plots and model predictive controllers

Challenges and opportunities in modelling of proton exchange membrane fuel cells (PEMFC)

High current density (HCD) operation in proton exchange membrane fuel cells (PEMFCs) presents significant water and thermal management challenges, mainly due to excessive production and uneven distribution of water and heat. Constructing an in-plane temperature difference (TD) in the cathode to match the water–gas state variations is a promising approach. This study innovatively reconstructs the cathode liquid cooling channels of a hydrogen-air PEMFC to create an in-plane TD, experimentally investigating various designs across different inlet relative humidities (RH), with deeper mechanism analysis, including electrochemical impedance spectroscopy (EIS) and local current density distribution. Results show that a positive temperature difference (PTD) enhances HCD performance, improving voltage and current uniformity by 10% and 2% at 2100 mA/cm2, while the enhancement weakens with increasing inlet humidity. Reverse temperature differences (RTDs) persistently have an adverse effect, which worsens with higher difference amplitude and RH. Mechanism exploration for TDs reveals that PTD improves membrane hydration upstream and reduces flooding downstream under low humidity conditions while tending to cause flooding upstream under high humidity conditions. RTD causes drying upstream and exacerbates downstream flooding, which is more pronounced at higher humidity. This research provides novel insights into optimizing thermal management at HCDs in low-humidity environments like automotive applications and high-humidity environments.

Thermal modeling and heat management of supercapacitor modules for vehicle applications

Recent progress in lithium-ion battery thermal management for a wide range of temperature and abuse conditions

Experimental study on the thermal management of an open-cathode air-cooled proton exchange membrane fuel cell stack with ultra-thin metal bipolar plates

Traditional macroscopic method is incapable of describing the heat generation and transfer mechanism in high-power electronic devices, when either characteristic dimensions become comparable or less than the mean free path of phonons,or characteristic timescale of devices equals to or smaller than the relaxation time of phonons. In order to reveal the heat generation and transfer mechanism in micro/nano-scale devices, a multiscale lattice Boltzmann modeling of field effect transistor (FET) with different conditions is proposed. In this model, a source term is introduced to describe the scattering of phonons and electrons. Under different working conditions and thermal managements (such as the location of hot spot, peak value of temperature, average temperature),the temperature distribution of a FET is investigated. By analyzing heat generation and transfer mechanism of FET in micro/nano-scale, it provides theoretical reference to engineers.

Thermal effect in CFRP machining: Temperature field characteristics, heat generation mechanism and thermal damage management

Dynamic variable coupling analysis is an important tool to properly design a control structure for complex multivariable and multi-physique systems, such as fuel cells. Fuel cell is an electrochemical energy conversion device which contains different inter-coupled dynamic phenomena in electrochemical, fluidic and thermal domains. Among those dynamic phenomena, the management of water and thermal dynamics play an important role to achieve the optimized fuel cell performance. In this paper, a control variable coupling analysis of fuel cell dynamic behaviors are presented and discussed based on a dynamic proton exchange membrane (PEM) fuel cell model, which considers in particular the transient behaviors of membrane water content and cell temperature. Through the analysis based on the relative gain array (RGA) method, the effects of nonlinear coupling among different fuel cell control variables are shown. The analysis results can be used to optimize the controller design for fuel cell system.

Power semiconductors and chips are essential in modern electronics, driving applications from personal devices and data centers to energy technologies, vehicles, and Internet infrastructure. However, efficient heat dissipation remains a critical challenge, directly affecting their performance, reliability, and lifespan. High-power electronics based on wide- and ultrawide-bandgap semiconductors can exhibit power densities exceeding 10 kW/cm2, hundreds of times higher than digital electronics, posing significant thermal management challenges. Addressing this issue requires advanced materials and interface engineering, alongside a comprehensive understanding of materials physics, chemistry, transport dynamics, and various electronic, thermal, and mechanical properties. Despite progress in thermal management solutions, the complex interplay of phonons, electrons, and their interactions with material lattices, defects, boundaries, and interfaces presents persistent challenges. This Account highlights key advancements in thermal management for power semiconductors and chips, with a focus on our group's recent contributions. Our approach addresses several critical issues: (1) developing materials with ultrahigh thermal conductivity for enhanced heat dissipation, (2) reducing thermal boundary resistance between power semiconductors and emerging 2D materials, (3) improving thermal and mechanical contacts between chips and heat sinks, (4) innovating dynamic thermal management solutions, and (5) exploring novel principles of thermal transport and design for future technologies. Our research philosophy integrates multiscale theoretical predictions with experimental validation to achieve a paradigm shift in thermal management. By leveraging first-principles calculations, the recent studies redefined traditional criteria for high-thermal-conductivity materials. Guided by these insights, we developed boron arsenide and boron phosphide, which exhibit record-high thermal conductivities of up to 1300 W/mK. Through phonon band structure engineering, we reduced TBR in GaN/BAs interfaces by over 8-fold compared to GaN/diamond interfaces. The combination of low TBR and high thermal conductivity significantly reduced hotspot temperatures, setting new benchmarks in thermal design for power electronics. We further explored the anisotropic TBR properties of two-dimensional materials and Moiré patterns in twisted graphene, expanding the thermal design landscape. To address challenges at device-heat sink interfaces, we developed self-assembled boron arsenide composites with a thermal conductivity of 21 W/mK and exceptional mechanical compliance (∼100 kPa). These composites provide promising solutions for thermal management in flexible electronics and soft robotics. In dynamic thermal management, we pioneered the concept of solid-state thermal transistors, enabling electrically controlled heat flow with unparalleled tunability, speed, reliability, and compatibility with integrated circuit fabrication. These innovations not only enhance thermal performance but also enable the exploration of novel transport physics, improving our fundamental understanding of thermal energy transport under extreme conditions. Looking forward, we reflect on remaining challenges and identify opportunities for further advancements. These include scaling up the production of high-performance materials, integrating thermal solutions with existing manufacturing processes, and uncovering new physics to inspire next-generation power electronics technologies. By addressing these challenges, we aim to inspire future codesign strategies that enable the development of more efficient, reliable, sustainable, and high-performance electronic systems.

Operation and durability of low temperature fuel cells

The bibliography provides information on semiconductor thermal characteristics, measurement techniques and results, management techniques, hardware applications, modeling and computational techniques, and other pertinent information. Areas covered include thermal and temperature measurements, thermal management, device and package performance, modeling, computations, and software techniques.