Abstract: A power converter for a bioelectrochemical system includes first converters each including a direct current terminal for supplying electric current via electrodes of the bioelectrochemical system, and a second converter for supplying energy to the first converters from an external electric power grid. Each first converter includes an electric element for receiving energy from the second converter and a circuitry for converting voltage of the electric element into electrolysis voltage suitable for the bioelectrochemical system. The electric element can be a secondary winding of a transformer or a direct voltage energy storage. Each first converter is galvanically isolated from the other first converters at least when the first mentioned first converter supplies energy to the bioelectrochemical system. Thus, each first converter drives its own electrode pair without disturbing the other first converters.

Abstract: An apparatus for estimating electrical properties of an electrolyzer includes a data processing system for estimating electrical values, for example a membrane resistance, of the electrolyzer based on a difference voltage, a current, and an initial value and an attenuation time constant of a double-layer capacitance voltage of the electrolyzer during a shutdown of the electrolyzer. The difference voltage is a difference between a voltage of the electrolyzer and a total reversible voltage of the electrolyzer. The initial value and the attenuation time constant of the double-layer capacitance voltage are estimated based on values of the difference voltage when the current is zero and thus the difference voltage equals the double-layer capacitance voltage. The electrical values can be estimated even if a stepwise interruption of the current of the electrolyzer is not possible.

Abstract: A system for alkaline water electrolysis includes electrolysis cells, a hydrogen separator tank, a first piping from the electrolysis cells to the hydrogen separator tank, an oxygen separator tank, a second piping from the electrolysis cells to the oxygen separator tank, and a third piping for conducting liquid electrolyte from the hydrogen separator tank and from the oxygen separator tank back to the electrolysis cells. The system includes an ultrasound source for applying ultrasound on the liquid electrolyte contained by the first piping. The ultrasound enhances the separation of dissolved hydrogen gas from the liquid electrolyte contained by the first piping, and thus energy efficiency of the alkaline water electrolysis is improved. Furthermore, a safe control range of the alkaline water electrolysis is broadened because crossover of hydrogen gas to an oxygen side of the system is reduced.

Abstract: A system for an electrochemical process includes an electrochemical reactor, a converter bridge for supplying direct current to electrodes of the electrochemical reactor, and serial inductors connected to alternating voltage terminals of the converter bridge. The converter bridge includes bi-directional controllable switches between the alternating voltage terminals and direct voltage terminals of the converter bridge. Forced commutation of the bi-directional controllable switches enables reduction of current ripple in the direct current supplied to the electrochemical reactor. The forced commutation enables also to control a power factor of an alternating voltage supply of the system.

Abstract: A power converter for a bioelectrochemical system includes first converters each including a direct current terminal for supplying electric current via electrodes of the bioelectrochemical system, and a second converter for supplying energy to the first converters from an external electric power grid. Each first converter includes an electric element for receiving energy from the second converter and a circuitry for converting voltage of the electric element into electrolysis voltage suitable for the bioelectrochemical system. The electric element can be a secondary winding of a transformer or a direct voltage energy storage. Each first converter is galvanically isolated from the other first converters at least when the first mentioned first converter supplies energy to the bioelectrochemical system. Thus, each first converter drives its own electrode pair without disturbing the other first converters.