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![12-Exchange current density per Pt area plotted as a function of temperature. The colour bar denotes the acid concentration in H 3 PO 4 mass fraction. Fit compared to data [104, 112-114].](profile/Jakob-Vang/publication/273770491/figure/fig20/AS:669399660896257@1536608724064/Exchange-current-density-per-Pt-area-plotted-as-a-function-of-temperature-The-colour.png)
12-Exchange current density per Pt area plotted as a function of temperature. The colour bar denotes the acid concentration in H 3 PO 4 mass fraction. Fit compared to data [104, 112-114].
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As part of the process to create a fossil free Denmark by 2050, there is a need for the development of new energy technologies with higher efficiencies than the current technologies. Fuel cells, that can generate electricity at higher efficiencies than conventional combustion engines, can potentially play an important role in the energy system of t...
Citations
... The parameter φ = 1.24-5.98 is not the same as the literature values for LT and HT-PEMFCs; however, it is of the same order of magnitude: 1.75 [46,47], 1.5 ([48] p. 122) [49][50][51], and 1.73 to 2.07 ( [52] p. 67). The parameter σ = 4.15-8.24 is not used in the state of the art. ...
In this work, three commercially available Membrane Electrode Assemblies (MEAs) from Advent Technology Inc. and Danish Power Systems, developed for a use in High Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC), were tested under various Operating Conditions (OCs): over-stoichiometry of hydrogen gas (1.05, 1.2, 1.35), over-stoichiometry of air gas (1.5, 2, 2.5), gas oxidant (O2 or air) and temperature (140 °C, 160 °C, 180 °C). For each set of operating conditions, a polarization curve (V–I curve) was performed. A semi-empirical and macroscopic (0D) model of the fuel cell voltage was established in steady state conditions in order to model some of these experimental data. The proposed parameterization approach for this model (called here the “multi-VI” approach) is based on the sensitivity to the operating conditions specific to each involved physicochemical phenomenon. According to this method, only one set of parameters is used in order to model all the experimental curves (optimization is performed simultaneously on all curves). A model depending on air over-stoichiometry was developed. The main objective is to validate a simple (0D) and fast-running model that considers the impact of air over-stoichiometry on cell voltage regarding all commercially available MEAs. The obtained results are satisfying with AdventPBI MEA and Danish Power Systems MEA: an average error less than 1.5% and a maximum error around 15% between modelled and measured voltages with only nine parameters to identify. However, the model was not as adapted to Advent TPS® MEA: average error and maximum error around 4% and 21%, respectively. Most of the obtained parameters appear consistent regardless of the OCs. The predictability of the model was also validated in the explored domain during the sensibility study with an interesting accuracy for 27 OCs after being trained on only nine curves. This is attractive for industrial application, since it reduces the number of experiments, hence the cost of model development, and is potentially applicable to all commercial HT-PEMFC MEAs.
... This identification gives a global error of 3.38 % and a maximum error (for one ) of 8.02 %. The parameter = 2.93 is different from the values found in the literature for LT and HT-PEMFCs, but in the same order of magnitude: 1.75 [45], 1.5 [44,46], and 1.73 to 2.07 [47] (p. 67). ...
In this work, a commercially available membrane electrode assembly from Advent Technology Inc., developed for use in high-temperature proton exchange membrane fuel cells, was tested under various operating conditions (OCs) according to a sensibility study with three OCs varying on three levels: hydrogen gas over-stoichiometry (1.05, 1.2, 1.35), air gas over-stoichiometry (1.5, 2, 2.5), and temperature (140 °C, 160 °C, 180 °C). A polarization curve (V-I curve) was performed for each set of operating conditions (27 V-I curves in total). A semi-empirical and macroscopic (0D) model of the cell voltage was developed in steady-state conditions to model these experimental data. With the proposed parameterization approach, only one set of parameters is used in order to model all the experimental curves (simultaneous optimization with 27 curves). Thus, an air over-stoichiometry-dependent model was developed. The obtained results are promising between 0.2 and 0.8 A.cm−2: an average error less than 1.5% and a maximum error around 7% between modeled and measured voltages with only 9 parameters to identify. The obtained parameters appear consistent, regardless of the OCs. The proposed approach with only one set of parameters seems to be an interesting way to converge towards the uniqueness of consistent parameters.
... The work focused on a cell-level degradation, and therefore, possible deviations due to stack behavior were not considered. The following assumptions were used throughout this paper [43]: ...
... The exchange current density was a function of temperature and acid concentration. The implementation was done according to [43], where the acid concentration was expressed as the mole fraction of phosphorous pentoxide (P 2 O 5 ) as shown in Equation (5). It increases with increasing temperature and decreasing acid concentration. ...
... Even though the charge transfer coefficient depends on temperature [49], in the current work it was considered as a constant at 0.5 due to inconsistent literature data where it varied between 0.2 and 0.8 under similar conditions [29,50]. Generally, a high disagreement for both exchange current density and charge transfer coefficient can be noticed in the literature [34,43,46,49]. The exchange current density was defined as follows [43]: 15 373.15 (5) where y P 2 O 5 is the molar fraction of P 2 O 5 , and a and b are coefficients for exchange current density, given by a 0 = 6.8462 × 10 −5 , a 1 = −2.2910 ...
In this paper, the performance of a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) was modeled using literature data. The paper attempted to combine different sources from the literature to find trends in the degradation mechanisms of HT-PEMFCs. The model focused on the activation and ohmic losses. The activation losses were defined as a function of both Pt agglomeration and loss of catalyst material. The simulations revealed that the loss of electrochemical active surface area (ECSA) was a major contributor to the total voltage loss. The ohmic losses were defined as a function of changes of acid doping level in time. The loss of conductivity increased significantly on a percentage basis over time, but its impact on the overall voltage degradation was fairly low. It was found that the evaporation of phosphoric acid caused the ohmic overpotential to increase, especially at temperatures above 180 °C. Therefore, higher temperatures can lead to shorter lifetimes but increase the average power output over the lifetime of the fuel cell owing to a higher performance at higher temperatures. The lifetime prognosis was also made at different operating temperatures. It was shown that while the fuel cell performance increased linearly with increasing temperature at the beginning of its life, the voltage decay rate increased exponentially with an increasing temperature. Based on an analysis of the voltage decay rate and lifetime prognosis, the operating temperature range between 160 °C and 170 °C could be said to be optimal, as there was a significant increase in performance compared to lower operating temperatures without too much penalty in terms of lifetime.
... Better tolerance to CO, which permits, for example, an easier use with H 2 directly from hydrocarbon steam reforming (95% of the current world production) or biomethane [12][13][14]; • Use with dry gases (it is not necessary to use a gas humidification system when operating with air) [14,15]; • Simplified thermal management (easier cooling at higher ambient temperatures, which could be a real advantage for an aircraft on the airport tarmac in an arid zone). • Moreover, compared to the LT-PEMFC, its main drawbacks are: • Its longer start-up time (the fuel cell must be preheated to avoid the presence of liquid water harmful to the electrolyte) [13]; • ...
The operating conditions can have uncontrolled effects on the voltage of a High-Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC). For instance, the HT-PEMFC can be used at ambient pressure, i.e., without having a back pressure regulator. In this case, the variation in the atmospheric pressure directly affects pressures inside the fuel cell, which induces voltage variation. Moreover, in transient phases, several coupled phenomena can have an uncontrolled effect on the voltage. For example, following a change in the current operating point, thermal conditions in the fuel cell can vary, and the temperature stabilization then leads to a voltage variation. This article introduces a readjustment method for the fuel cell voltage to compensate for the effects of the pressure and temperature variations that are undergone and to decouple their effects. This methodology is based on the realization of a design of experiments to characterize the voltage sensitivity to pressure ([1; 1.5 bar]) and temperature ([120; 180 °C]) between 0.2 and 1 A/cm2 of an Advent PBI MEA (formerly BASF Celtec®-P 1100 W). The data obtained allowed identifying an empirical model that takes into account the aging caused by the experiment. Finally, the methodology is criticized before proposing an alternative method.
... Better tolerance to CO, which permits, for example, an easier use with H 2 directly from hydrocarbon steam reforming (95% of the current world production) or biomethane [12][13][14]; • Use with dry gases (it is not necessary to use a gas humidification system when operating with air) [14,15]; • Simplified thermal management (easier cooling at higher ambient temperatures, which could be a real advantage for an aircraft on the airport tarmac in an arid zone). • Moreover, compared to the LT-PEMFC, its main drawbacks are: • Its longer start-up time (the fuel cell must be preheated to avoid the presence of liquid water harmful to the electrolyte) [13]; • ...
