An Open-Cathode Fuel Cell for Atmospheric Flight

Abstract

We detail the relationships between operating environment and performance of a thin and lightweight open-cathode fuel cell based on flexible circuits that may be advantageous for unmanned air vehicle (UAV) propulsion. The open-cathode fuel cell performance is studied in a broad range of realistic atmospheric flight conditions by mounting it in a wind tunnel within an environmental chamber. The relationships between the operating environment and performance are quantitated in terms of polarization behavior and the underlying loss mechanisms are discussed qualitatively in the context of electrochemical impedance spectroscopy (EIS), DC resistance and infrared temperature measurements. The wind tunnel experiments demonstrate that open cathode operation is possible over wide ranges of ambient temperature (5–55°C), relative humidity (22–90% RH), air speed (0–15.4 m s−1) and altitude (240–3240 m). Forced airflow is shown to improve mass transport, waste heat rejection, and water management, broadening the effective operating envelope of this open-cathode fuel cell over others that rely on free convection. Sacrificing air preconditioning renders open-cathode fuel cell performance sensitive to the conditions of the surrounding environment. The lightweight open-cathode fuel cell in this study has high specific power, exceeding 1.3 kW/kgcell in favorable ambient conditions of 5°C, 50% RH at sea level.

Analysis of application status and development prospect of environmental chambers: A review

“…When studying the performance of batteries, especially automotive batteries, small environmental chambers are often used to simulate extreme environments. [108][109][110][111][112][113] The cooling performance, thermal insulation performance and startup performance in extreme environments are important indexes that could affect the safety and durability of batteries. Therefore, the application of environmental chamber to study the battery performance not only ensures the safety but also improves the utilization efficiency of resources.…”

Effect of the corrugated bipolar plate design on the self‐humidification of a high power density PEMFC stack for UAVs

“…Unmanned aerial vehicles (UAVs) represent a unique market niche for polymer electrolyte membrane fuel cell (PEMFCs) that benefit from both a low market penetration barrier and a high profit margin. In this application, PEMFCs can assure a stealthier flight than heat engines, as well as longer and faster flights (or a heavier payload) than any electrochemical battery [1][2][3][4][5][6][7][8]. However, in order F I G U R E 1 Open-cathode PEMFC system for use in UAVs.…”

“…The unnumbered arrows show the direction of air flow to achieve a superior performance (such as system-level specific energy 500-800 Wh kg −1 for the operating time of 4 h, vide infra), peripheral systems (such as humidifiers and heaters used in automotive PEMFCs) must be avoided. For this reason, PEMFC systems with a dead-end (occasionally purged to remove water and crossover N 2 ) [9] anode and an open cathode are commonly used in UAV applications [4,5,[10][11][12][13][14][15][16][17]]. An exemplary scheme of such system is shown in Figure 1, wherein dry H 2 is supplied from a high-pressure tank (1) through pressure reducer (2), pressure sensor (3), and fast electromagnetic valve (4) into the anodic compartment (5) of the stack.…”

“…The main routes of water production and removal (1)(2)(3)(4) and of across-the-membrane movement (I-III) in a single PEMFC cell cient for thin membranes, this mechanism cannot assure the required membrane hydration at high current densities, since the rate of the back diffusion of liquid water is independent of the operating current density [24][25][26]. In addition to the water concentration gradient normal to the membrane, one also needs to consider nonuniformity of the water distribution in the membrane and GDL planes [27].…”

Influence of Cathode Gas Diffusion Media Porosity on Open-Cathode Fuel Cells

“…However, operation in this planar configuration without a BOP renders the open-cathode fuel cells sensitive to the environmental conditions in which they are operated and susceptible to issues related to cell dehydration; this is the result of insufficient waste heat rejection at higher current densities or higher cell temperatures. 1,2 Previous studies on open-cathode fuel cells have found that they are sensitive to ambient temperature and ambient relative humidity, and that one of the greatest challenges associated with open-cathode fuel cell operation is improving thermal management to reduce cell temperatures and prevent excessive water evaporation and membrane and catalyst layer ionomer dehydration, [1][2][3][4][5][6][7][8][9] which will reduce the relatively high ohmic resistances.…”