| Author: | Xia, Lingchao |
| Title: | Modelling and optimization of high temperature proton exchange membrane fuel cell |
| Advisors: | Ni, Meng (BRE) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Fuel cells Proton exchange membrane fuel cells Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Building and Real Estate |
| Pages: | xiii, 92 pages : color illustrations |
| Language: | English |
| Abstract: | Clean and renewable energy have been given high expectations to overcome the energy crisis raised in last century. High temperature proton exchange membrane fuel cell (HT-PEMFC) is one of the most promising power sources, but its commercialization has been hindered by high fabrication costs relative to its cell performance. Of the components that make up HT-PEMFC, the bipolar plates (BPs), gas diffusion layers (GDLs), and catalyst layers (CLs) are critical for reactant supply, reaction kinetics and electron transfer. Therefore, there is a pressing need to further reduce fabrication cost while improving cell performance. For the bipolar plates and GDL, both components are key factors that would affect the cell performance. A three-dimensional, non-isothermal model was developed in chapter 3 and 4 to investigate the effect of related parameters on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. Results indicated that a channel to rib ratio of 1 led to a peak power density of 0.428 W cm-2. Optimal GDL thicknesses for the anode and cathode are 80-120 μm and 140-170 μm, respectively, with an optimal GDL porosity of 35-45%. The study on GDL optimization demonstrates that carefully controlling the thickness and porosity of GDL can result in a performance increment by 7.7%. For the CLs, both percolation model and reconstruction model are developed respectively in chapter 5 and 6. Then, they are integrated with macro model for further investigation. The effective reaction thicknesses (ERT) of both anode and cathode are identified. The ERT was found to depend on the ratio of activation loss and concentration loss ηact+conc to ohmic loss ηohmic. The working voltage and the cathode flow rate have opposite influence on the ERT of the two electrodes. Regarding microstructure analysis, the reconstruction model offers an advantage over the percolation model which assumes all ionomer particles are spherical. The results showed that a considerable number of Pt particles are partially covered by the ionomer, making it inappropriate to assume that all catalysts are completely covered. Both Pt/C ratio and I/C ratio significantly affect the composition and microstructure of CL. While increasing Pt loading can enhance cell performance, the improvement rate is relatively small at a high platinum loading, and the cost of performance increases linearly with Pt loading. Therefore, when designing the CL for high temperature proton exchange membrane fuel cell, both cell performance and cost must be considered. Overall, a peak power density of 0.467 W cm-2 can be achieved by carefully controlling the aforementioned parameters. This value represents a 12.53% improvement in cell performance compared to the previous data of 0.415 W cm-2. Additionally, the catalyst cost can be significantly reduced by 56% through the implementation of a thinner catalyst layer (22 μm), in comparison to the previous thickness of 50 μm. Future work will focus on durability and stack scale modeling, as the results of single channel and single cell models may differ from those of stack scale. |
| Rights: | All rights reserved |
| Access: | open access |
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