Vol.5 No.4 2013
Research paper : Evaluating Uncertainty for the Standardization of Single Cell/Stack Power Generation Performance Tests for SOFC (A. Momma et al.)−261−Synthesiology - English edition Vol.5 No.4 (2013) Yohei TanakaCompleted the doctoral program of the Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering of Kyoto University in 2005 and joined AIST in the same year. Currently senior research scientist at the Fuel Cell System Group of the Energy Technology Research Institute. His areas of specialization include catalyst chemistry, fuel cell performance evaluation, and energy engineering. For this paper, he was responsible for preparing the gas supply methods and the uncertainty evaluation methods for the draft standard. Tohru KatoCompleted the graduate program at Tohoku University and earned a doctorate degree in engineering in 1991. In 1992, joined the Electrotechnical Laboratory Japan of the Agency of Industrial Science and Technology of MITI, where he conducted research on the technology for high temperature electrolysis. Currently serves as Industrial Science and Technology General Director for the Research and Development Division under the Industrial Science and Technology Policy and Environment Bureau of METI. For the preparation of this paper, he was responsible for the establishment and operation of the national committee, preparation and editing of the draft standard, the proposal for the concept of cell stack/assembly unit, and the oversight of the research project as a whole. Discussions with Reviewers1 Justification of the parameters chosen for uncertainty evaluationQuestion (Hiroshi Tateishi, AIST)In “3.2 Description of uncertainty evaluation in the draft standard,” it is stated, “Because uncertainty evaluations of some of these tests were likely to be very difficult or troublesome, our proposed draft standard only mandated that the uncertainty evaluation be conducted on the results of the rated power tests.” The reasoning for omitting the “difficult or troublesome” evaluations is not clear. If these omitted steps had a major impact on uncertainty, wouldn’t the entire process lose its credibility?Answer (Akihiko Momma)What we meant by this is that we made uncertainty evaluation mandatory only for the results of the rated power test in the draft standard. For other test results, the users themselves were to judge the reliability of data from the information on measurement instruments, which must be included in the test report according to the draft standard. Therefore, it is not that the uncertainty of the rated power test depends on the results of those other tests that the draft standard did not make it mandatory to perform uncertainty evaluation, as you suggested. Uncertainty evaluation was in fact difficult for some tests other than the rated power test. For others, we actually did not know what to do, and decided not to require them. We judged that imposing an excessive burden on test operators for uncertainty evaluation would go against the view of the committee by being not consistent with its overall goal to make the standard as user friendly and accessible as possible.2 If uncertainty evaluation is not feasibleQuestion (Hiroshi Tateishi)At the end of “4.3 Relationship between measurand and input quantity (measurement of sensitivity coefficients),” it says, “When gas is supplied using a mixture gas cylinder, for example, it is virtually impossible to independently change the concentration of one component gas of the gas mixture to measure its sensitivity coefficient, thus making it impossible to evaluate the impact of the uncertainty of a component gas on the voltage.” Wouldn’t the fact that it is “impossible to evaluate” the impact of uncertainty present a problem?Answer (Akihiko Momma)In the draft standard, a number of scenarios were considered to establish the methods of supplying fuel gas. When a mixed gas cylinder is used to supply fuel, we judged that it was practically impossible to conduct uncertainty evaluation. In this case, users would determine the reliability of data by referring to the test conditions and gas composition analysis table, which the standard requires to be included in the test report. We had no choice but to resort to this difficult decision even though there is no doubt that it is problematic.