Book/Dissertation / PhD Thesis

FZJ-2018-05691

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Alterungs- und fehlertolerante optimale Betriebsführung eines Direktmethanol-Brennstoffzellensystems

Keller, R. (Corresponding author)FZJ*

2018
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-355-6

Please use a persistent id in citations: http://hdl.handle.net/2128/19899  urn:nbn:de:0001-2018120607

Abstract: To achieve the climate goals of the German government and the resulting reduction in CO$_{2}$ emissions, it is important to develop efficient energy converters. Here, an electrochemical energy conversion using direct methanol fuel cells (DMFCs) offers significant potential, since these cells’ ease of use and their low exhaust emissions are significant advantages over commercial diesel engines. However, to further increase the competitiveness of DMFCs, there must be a significant increase in stack efficiency and long-term stability. The present study deals with operational management strategies for DMFC systems, and their development focus is on maximizing the efficiency of the stack and increasing the long term stability of the system. In the context of a long-term stability increase, the effects of sensor faults and cell aging on critical operating ranges are considered, since they cause a deterioration of the maximum stack efficiency and an increased aging of DMFCs. To develop a basic operational management concept, a DMFC overall model is created that takes characteristic properties into account. Based on this, a model-based predictive control is designed, that has the basic stability criteria of operating areas and the provision of the required output power. The concept of maximum stack efficiency is realized through a static economic optimization, which uses the characteristic models generated in the work. In practice, the methods developed demonstrate that a significant increase in stack efficienc yby 7 percentage points is possible, and that the required stability criteria are met at each time of operation. To extend the model in terms of long-term stability and associated aging phenomena, the measurement data of a 25,000-hour DMFC experiment is analyzed to generate an age dependent model. The initial model of a DMFC is retained in this context, and it is expanded by the characteristic aspect of the degree of aging. By means of this age-dependent model, a simulative evaluation of the aging and possible sensor faults takes place on the previously defined operational management aspects. It demonstrates that without active intervention, a significant reduction in efficiency and long-term stability occurs. Based on these results, the design of active fault- and aging-tolerant operational management takes place. First, a fault diagnosis is developed that unambiguously identifies existing sensor faults and the degree of aging. As a result, depending on the identified fault or degree of aging, a reconfiguration of the operation’s management takes place to continue to meet the maximum efficiency and required long-term stability criteria. In practical applications, the developed operational management shows – at an aging of about 660 hours – it’s effectivity with an increase instack efficiency by 1.5 percentage points. The long-term stability – with a focus on the achievable cell voltage – is experimentally demonstrated by an increase of Δ𝑈4_{cell} = 67 mV at most.

Note: Universität Duisburg, Diss., 2018

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Contributing Institute(s):

1. Elektrochemische Verfahrenstechnik (IEK-3)

Research Program(s):

1. 135 - Fuel Cells (POF3-135) (POF3-135)

Appears in the scientific report 2018

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