A review of the curious case of heat transport in polymer electrolyte fuel cells and the need for more characterisation

Abstract

As the polymer electrolyte membrane fuel cell matures performance keeps increasing -mainly in terms of conversion rate rather than efficiency. Increased conversion results in increased heat release. Fuel cell performance and degradation is a delicate balance of heat and work manipulated significantly by the transport and the state of water in the system. With high heat release rates and low thermal conductivities the maximum temperature can be up to 20 o C warmer than the coolant. While much work has been done in understanding the conductivity of fuel cell materials, even more is needed. Particular needs for continued research include: the thermal implications of material ageing, the nature and importance of the composite interface between the micro-porous layer and the porous transport layer, the impact of liquid water on thermal conductivity, a better understanding of phase change in electrodes and the heat capacities of fuel cell materials. Finally, the heat release in a fuel cell presents a significant opportunity to better understand the system and changes in the system. Fuel cell calorimetry has only begun to be used to explore heat and work in PEMFC and should be explored in greater detail.

Analysis of representative elementary volume and through-plane regional characteristics of carbon-fiber papers: diffusivity, permeability and electrical/thermal conductivity

“…This effect is especially critical for the TP electrical/thermal conductivity. Moreover, the impact of the surface region serves to explain some controversial behaviors, such as the counter-intuitive increase of the thermal conductivity of MPL-coated CFPs compared to CFP substrates alone [137][138][139]. This fact can be attributed to the interplay between compression and intrusion of the MPL (𝑘 eff mpl ~10 -1…”

The influence of graphitization on the thermal conductivity of catalyst layers and temperature gradients in proton exchange membrane fuel cells

“…Thus, knowing the temperature distribution in the PEMFC becomes even more important in the future. [20] The present work aims to shed light on the surprisingly large effect of graphitization on thermal conductivity, and bridges the two existing studies on thermal conductivities of catalyst layers, one using amorphous carbon [10] and the other graphitized carbon [12]. The measured thermal conductivities in the two studies differ by a factor of three.…”

“…The challenge of handling the considerable heat production in future PEMFCs with increased effectiveness has been discussed in a recent review by Burheim and Pharoah [20]. While maximizing the power output and electrical efficiency of the PEMFC the produced heat inevitably increases beyond what is common today.…”

“…Zhou et al (2018) recently coupled this thermal model with a two-phase flow model and analyzed the temperature distribution in a PEMFC with and without MPL [31]. Burheim and Pharoah (2017) pointed out the differences in modeled temperature distributions when taking all of the PEMFC layers into consideration [20]. They emphasize the future research needs on thermal gradients and heat aspects both experimentally and numerically.…”

The Role of Fluorinated Polymers in the Water Management of Proton Exchange Membrane Fuel Cells: A Review

“…Homogeneous heating inside the fuel cell is of great importance because it minimizes the risk of thermal stresses, which could reduce the durability of the components, and allows a better control on thermal profiles that determine the kinetics of reactions, species diffusivity, water evaporation, and electrical resistivity [70]. Similarly to what has been written for electrical conductivity, the addition of a weak thermally conductive polymer (k PTFE = 0.35 W m −1 K −1 [71]) should be detrimental to the performance of the carbon support of GDMs; however, other factors, such as clamping pressure, compressive cycles, operating temperature, MPL presence, and inlet gases' relative humidity must be also considered when designing a cell stack [72][73][74][75].…”