Control of fuel cells by Zenith F.

By Zenith F.

This thesis bargains with keep an eye on of gas cells, concentrating on high-temperature protonexchange-membrane gasoline cells. gas cells are units that convert the chemical strength of hydrogen, methanol or different chemicals at once into electrical energy, with no combustion or thermal cycles. they're effective, scalable and silent units that could supply energy to a wide selection of utilities, from moveable electronics to automobiles, to nation-wide electrical grids. while reviews concerning the layout of gas mobilephone structures and the electrochemical homes in their elements abound within the open literature, there was just a minor curiosity, albeit starting to be, in dynamics and regulate of gasoline cells. within the really small physique of obtainable literature, there are a few it appears contradictory statements: occasionally the gradual dynamics of gasoline cells is said to give a keep watch over challenge, while in different articles gas cells are claimed to be effortless to regulate and ready to keep on with references that vary very swiftly. those contradictions are in general brought on by variations within the units of phenomena and dynamics that the authors made up our minds to enquire, and in addition via how they formulated the keep watch over challenge. for example, there's little question that the temperature dynamics of a gasoline mobile could be gradual, yet clients aren't desirous about the cell's temperature: strength output is a way more very important degree of functionality. gasoline cells are very multidisciplinary structures, the place electric engineering, electrochemistry, chemical engineering and fabrics technological know-how are all concerned at a variety of degrees; it's as a result unsurprising that few researchers can grasp all of those branches, and that the majority of them will overlook or misread phenomena they're unusual with.

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Pathapati et al. [5] produced a model that calculated the overvoltage as in Amphlett et al. [6], adding the effects of transients in overvoltage and non-steady-state gas flow. A similar model, with a more detailed modelling of the overvoltage, has been proposed by Lemeš et al. [7]. Shan and Choe [8] presented a fuel-cell model that considered the dynamics of temperature, membrane conductivity, proton concentration in the cathode catalyst layer and reactant concentration. The current, however, was considered the input of the system rather than being determined by the external load.

Kallo et al. [7] performed a series of dynamic tests on a direct methanol fuel cell, identifying three main factors in the dynamic response: the charge double layer’s capacitance, catalyst poisoning and reactant crossover. It has been shown by Rao and Rengaswamy [8] that current does not change stepwise during specific transients, such as when changing the external resistance, but instead follows a certain pattern, which may be described as a step change followed by what appears to be an exponential relaxation.

The cell could be kept at a given temperature by a custom-made external electric heater with a feedback control loop, consisting of a thermocouple and an electronic control unit (West 6400 1/16 DIN profile controller). It should be noted that, whereas the laboratory setup needed make-up heat because of its small size, an application will probably need cooling instead, since the reaction heat will be sufficient to maintain its temperature. 5 % oxygen, both at atmospheric pressure. 5 % H3 PO4 solution, in order to make up for any loss of phosphoric acid in the cell’s membrane.

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