Vol.5 No.1 2012

Research paper : Durable polymer electrolyte fuel cells (PEFC) for residential co-generation application (K. Tanimoto et al.)−64−Synthesiology - English edition Vol.5 No.1 (2012) Tetsuhiko KobayashiJoined the Osaka National Research Institute, Agency of Industrial Science and Technology in 1984. Director of the Special Division for Green Life Technology, AIST in 2001. Director of the Research Institute for Ubiquitous Energy Devices, AIST in 2004. At the commencement of the Project for Fundamental Research of Degradation of PEFC Stacks described in this paper, was the research liaison for various organizations including the Ministry of Economics, Trade and industry, NEDO, fuel cell system companies, energy supply companies, and universities.Discussion with Reviewers1 Difference between “product” and “commercial product”Question (Kazuo Igarashi, Institute of National Colleges of Technology, Japan)In the text, you use the two terms “product” and “commercial product.” There are places where you make the distinction between the two and places where you don’t. I think it is important to separate the two, so please review the use of these terms.Answer (Kazumi Tanimoto)In this paper, the “product” is the device that incorporates the fuel cell such as the fuel cell cogeneration system and fuel cell automobile. “Commercial product” is the product that has been commercialized such as the residential cogeneration system “ENE-FARM.” When the “product” is commercialized, the cost is added to the functions such as performance and durability to be acceptable in society, and this becomes the “commercial product.”As you indicated, there were two places in “Chapter 6 Conclusion” where the terms were interchanged, and this was corrected.2 Molten carbonate fuel cell (MCFC)Question (Kazuo Igarashi)In paragraph 2, chapter 2, you write “… there seemed to be opportunities for trials ... due to the characteristic of the product.” What do you mean by this trial?Answer (Kazumi Tanimoto)This was a reference to the molten carbonate fuel cell (MCFC) that is one of the distributed fuel cell generation technology. In Japan, the Marubeni Corporation attempted to market the technology developed by FuelCell Energy of the USA as a distributed generation system. Marubeni established the Nihon Nenryo Denchi Hatsuden K.K. and conducted several demonstration tests, but the venture company was terminated in December 2011 and it was never launched in Japan. I regret this course of event, because I was involved in this technological development for 20 years. I think it has superior performance compared to other fuel cells. The demonstration trials are done in other countries as part of the investigation of the process for its commercialization. I added this description since I hope for the revival of this technology.3 Degradation pattern of the polymer electrolyte fuel cell (PEFC)Question (Kazuo Igarashi)In paragraph 1, subchapter 4.1, you write, “the accelerated degradation pattern of (c) ... was determined to be most fatal for the cogeneration system.” Can you describe in detail why you say so?Answer (Kazumi Tanimoto)This is based on the empirical data of the manufacturers and the energy companies. The individual system designs are different in terms of the flexibility and adaptability of the system control in the cogeneration units. Fatal degradation is judged on the degree of damage.4 Scenario toward the practical use of fuel cellQuestion (Norimitsu Murayama, Advanced Manufacturing Research Institute, AIST)You write at the beginning of paragraph 2, “Chapter 2 For the practical application of fuel cell,” “in the fuel cell technology… lower the hurdle of technological issues….” Specifically, what were the technological issues and how were the hurdles lowered?Answer (Kazumi Tanimoto)One of the technological issues for the fuel cells was to scale up when it was introduced as the distributed power source. There is the issue of cost due to scale up. Scaling up the assemblies also brings new processing development for manufacturing components and unifying systems. For the application to small sized cells, the manufacturing technology will be an extension of the laboratory level, and I used the expression “lowering the hurdle” in that sense.5 Degradation mechanism of the polymer electrolyte fuel cellQuestion(Norimitsu Murayama)Isn’t it more straightforward if you say that the “decrease of gas diffusion by enhanced flooding at the electrode” and the “decrease of CO poisoning resistance” are accelerated by the gas switching method? Assuming this statement, in paragraph 3, “Subchapter 4.1 Degradation factors of the actual cell/stack and the accelerated aging method,” I think you should explain the mechanism by which the CO poisoning resistance decreases by the gas switching test.Answer (Kazumi Tanimoto)In the project, the two factors of degradation were selected and investigated, and as described in the text, we were unable to sufficiently control the factor that accelerated the “decrease in CO poisoning resistance.” As you indicated, if the two factors are presented in this text, I should follow them logically, but I write from the perspective of showing the efforts and processes of the research method. Also, seeing the “decrease of CO poisoning resistance,” we specifically considered the accelerated aging method of adjusting the CO content of the fuel to change the degree of degradation. However, we could not obtain the expected results within several thousand hours, and therefore, it is as written in the paper.6 Standardization of the accelerated aging test of the polymer electrolyte fuel cellQuestion(Norimitsu Murayama)Is the introduced gas switching test standardized?Answer (Kazumi Tanimoto)To be established as the actual accelerated test protocol, I think it is necessary to calculate the acceleration coefficient by comparing the developed accelerated test protocol with the tests conducted under standard conditions. Since there are not many tests conducted in real time, it is necessary to collect sufficient data including the text conducted by the accelerated aging method.


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