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This paper presents the relationship between electric current fluctuation and energy efficiency of a laboratory scale alkaline electrolyzer, combinedwith a novel rectifier system. Electrochemical impedance spectroscopy of the electrolysis cell provides information on the ohmic resistances, the double layer capacity between electrodes and the electrolyte as well as the frequency dependency of these parameters. Thus, it enables the generation of specific current profiles in order to reduce ohmic resistance from polarization as well as bubble evolution. The measurement results show a connection of the energy efficiency on the provided current profiles as well as on the periodical pulse duration. A pulsed current profile, based on the results from the impedance spectroscopy, is able to reduce polarization and bubble resistance losses, while consuming additional electrical energy. [ABSTRACT FROM AUTHOR]

A sustainable energy economy implies high shares of volatile renewable energy sources and requires the use of energy storage technologies. Hydrogen is a very flexible energy carrier and can be employed as a large-scale energy storage in electric grids. This paper focuses on the integration of hydrogen production, conversion and storage options in a smart grid environment. A process current source (PCS) that functions as a rectifier for an alkaline electrolysis system and is compared to a conventional rectifier structure that is not specifically designed for dynamic operation. All components of the smart grid are scaled using a staggered algorithm that combines a pattern search algorithm and a genetic algorithm. This smart optimization tool shows high flexibility, accuracy and low computing times. The required computing time has been reduced by 56% in contrast to genetic algorithms without the pattern search method. Furthermore, the energy system optimization reduced the alkaline electrolysis below 30% of the initial scale in order to yield lower costs. Therefore, the difference in rectifier performance was reduced to a minor contribution.