Hydrogen fuel cell technology is one of the key focus areas to facilitate the transition from carbon-based fuels to more sustainable solutions in the transportation and mobile power sectors. Transient voltage fluctuations due to load changes and even operation of fuel cells with DC/DC and DC/AC converters are detrimental to the lifetime and this paper proposes a method to deal with these fluctuations. Adding electric field modifier (EFM) electrodes made of gold to the membrane of a fuel cell was proposed elsewhere as a way to influence the short term flux of charge carriers through the membrane. While electrochemical impedance spectroscopy shows a limited capacitance of such electrodes, experiments using square wave excitation of the system in the kHz frequency range show a promising reaction of the cell to this treatment. More in-depth analysis of the used electrode material reveals the need to insulate future EFM electrodes in order to prevent oxidative dissolution. However, this work shows that the principle of using EFM electrodes to manipulate transient oscillations is physically sound.

Using fuel cells in energy generation makes it possible to provide clean energy in line with the demand. Fuel cells offer a major advantage over other renewable energy sources whose generation is dependent on external influences. However, fuel cells cannot compete economically with conventional energy generation systems such as diesel generators. Such an economical constraint is partly due to the higher energy requirements of hydrogen storage. Metal hydride storage systems offer the possibility of reducing the energy intensity of storage due to low storage pressures. Heat is also required to operate such storage systems, which can be provided from the fuel cell's waste heat. To extract the heat from the fuel cell, a novel cooling circuit structure for large-scale applications is presented and simulated, considering the requirements of the metal hydride storage system regarding temperature (60°C) and mass flow (60 kg/min). The architecture of the cooling concept consists of a primary and a secondary circuit, whereby the primary circuit is responsible for cooling the fuel cell and the secondary circuit for extracting the heat. Finally, simulation data are presented, which show the system behaviour in the event of changes in the fuel cell's electrical load and the heat consumer's thermal load. This coupling strategy shows that the cooling system is suitable for extracting the waste heat and keeping all essential parameters constant.

In a future renewable energy system, electrolyzer, as coupling elements between power and gas systems, convert renewable electricity into storable hydrogen, which can be used in further consumption sectors. The general scope of this investigation is a controlled proton exchange membrane electrolyzer at a low voltage grid. For this, the proton exchange membrane electrolyzer as well as the power electronics for grid connection are developed as components for the "Extended Node Method" based on electrical equivalent circuit diagrams. It is shown how these components are especially defined for this method, how their topology affects the node definitions and how the AC/DC and DC/DC transitions are realized. As a study case, a sample model of a 40 kW stack is considered. The setpoints for electrolyzer current as well as reactive power are adjusted and transient calculations are carried out. The results are compared with models in Simulink/Simscape and show general agreement.

Hydrogen fuel cells have become one of the most viable power sources for electric aircraft. Models representing the electrical behavior of the fuel cell stack over the full dynamic operation region are essential for the development of power electronic energy systems powered by fuel cell stacks. This work presents an electrical equivalent circuit model for PEM fuel cell stacks representing the static and dynamic electrical behavior of the fuel cell stack under pulsed loads up to frequencies of 10 kHz. Dynamic phenomena on time scales slower than the considered timescale of power-electronic switching, such as reactant flow, membrane hydration, and temperature effects, are considered stationary. The parame-terization method proposed is developed on measured data from a 110 W PEM fuel cell stack and validated with a set of measured data from a 2 kW stack. The time-domain simulated behavior of the parameterized model shows an accurate representation of the measured behavior: the parameterized model reproduces both the static polarization behavior and the behavior under high-frequency pulsed loading with errors of less than 1% with respect to the nominal stack voltage. The model is suitable for dynamic simulation of power electronic systems directly connected to fuel cell stacks and can be parameterized without special electrochemical impedance spectroscopy measurements. (c) 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

The dynamic controllability of the fuel cell could be improved by the addition of an electric field modifier (EFM), to selectively boost or attenuate the flux of protons through the membrane and, thereby, influence cell performance. This approach follows the commonly accepted idea of the potential gradient across the membrane being the main driving force behind the proton transport in the membrane. To evaluate the applicability of the idea, a simulation model for a membrane with an integrated EFM is developed to study the effects on the membrane behaviour. First, a modified Poisson-Boltzmann-Model (1D) is developed to characterise the capacitive behaviour of the double layer at the EFM. The approach considers steric restrictions in the membrane pores to estimate the double layer capacitance and the range of the effect at the EFM. Second, the characteristic behaviour of the capacitance is implemented in a secondary current distribution model (2D) as a variable capacitance. In transient simulations, boost of the cell current by up to 82% and attenuation up to a complete reversal of the direction compared to the stationary operation are achieved. Thus, it was possible to show the potential of EFMs to influence the characteristics of fuel cells and electrolysers during transient operation.

Optimized integration of fuel cells into grids or on-board power supplies is necessary to facilitate replacement of conventional energy producers by a reliable and plannable power generation technology. Due to the interdependency between fuel cell current and voltage, integration of fuel cells requires a power conditioning system, which increases integration weight and cost. For this reason, integration of electric field modifier electrodes into the setup of proton exchange membrane fuel cells is a new approach to control the output voltage in order to minimize the subsequent power conditioning system. This approach considers the physics of proton transport through the electrolyte membrane and could offer a lever to control the ohmic resistance. In this paper, a fuel cell model is implemented in MATLAB and extended by electric field modifier electrodes, allowing control of the ohmic resistance through an externally applied voltage. The concept of boosting and attenuating fuel cell voltage is presented along with different setups to enable this behavior. Furthermore, an electrical equivalent circuit for electrically controllable fuel cells is developed and implemented in MATLAB/Simulink. A method to parameterize the developed MATLAB and Simulink models by first experimental results is presented.

The reduction of greenhouse gas and pollutant emissions is a major issue in modern society. Therefore, environmentally friendly technologies like fuel cells should replace conventional energy generation plants. Today, fuel cells are used in households for CHP (combined heat and power) applications, for emergency power supply in many stationary applications and for the power supply of cars, buses and ships and emergency power supply of aircrafts. A significant challenge is the optimal electrical grid integration and selection of the appropriate grid protection mechanism for fuel cell applications. For this, the short circuit capability and behavior needs to be known. This paper gives a mathematical estimation of the short circuit behavior of fuel cells. Five main transient and dynamic phenomena are investigated. The impact of the main transient effect for the provision of additional short circuit energy is simulated, and the simulation is experimentally validated. For this purpose, a 25 c m 2 single cell consisting of a NafionTM 212 membrane and carbon cloth electrodes with a catalyst loading of 0 . 5 m g / c m 2 Pt is analyzed. The magnitude of the transient short circuit current depends on the operating point right before the short circuit occurs, whereas the stationary short circuit current of fuel cells is invariably about twice the operational current. Based on these results, a novel fuel cell model for the estimation of the short circuit behavior is proposed.

The encoding of high-resolution energy profile datasets from end-users generated by smart electricity meters while maintaining the fidelity of relevant information seems to be one of the backbones of smart electrical markets. In the end-user sphere of smart grids, specific load curves of households can easily be utilized to aggregate detailed information about customer’s daily activities, which would be attractive for cyber attacks. Based on a dataset measured by a smart meter installed in a German household, this paper integrates two complementary approaches to encrypt load profile datasets. On the one hand, the paper explains an integration of a lossy compression and classification technique, which is usable for individual energy consumption profiles of households. On the other hand, a perturbation approach with the Gaussian distribution is used to enhance the safety of a large amount of privacy profiles. By this complete workflow, involving the compression and perturbation, the developed framework sufficiently cut off the chance of de-noising attacks on private data and implement an additional, easy-to-handle layer of data security.

With increasing interest in clean energy generation in the transportation sector, increasing attention has been given to polymer-electrolyte-membrane fuel cells as viable power sources. One issue, the widespread application of this technology faces, is the insufficient knowledge regarding the transient behaviour of fuel cells, for instance, following a short-circuit event. In this paper, an agglomerate model is presented and validated, which enables the transient simulation of short-circuit events to predict the resulting peak current and discharge of the double layer capacity. The model allows for the incorporation of detailed morphological and compositional information regarding all fuel cell components. This information is used to calculate the reaction rate, diffusional and convectional species transfer, and the momentum transport. It can be shown that the charge in the double layer capacitance of the fuel cell is key to predicting the peak current and its charge is dependent on the operating conditions of the fuel cell. Further, the effects of the magnitude of the double layer capacity, current rise time and stoichiometry on the dynamic behaviour of the fuel cell are investigated. It can be shown that the discharge of the double layer capacity proceeds from the membrane through the catalyst layer to the gas diffusion layer and that the stoichiometry of the gas supply does not significantly change the absolute peak value of the short-circuit current.

Optimized grid integration of proton exchange membrane fuel cells in various possible applications requires a suitable protection system. For this reason, this paper examines the transient behavior of a fuel cell stack after an external electrical shortening. In order to show the influence of operating parameters on the short-circuit behavior, various experiments with changed anode and cathode humidity, cell temperature and anode and cathode stoichiometry are carried out. With this, manufacturers can estimate the short-circuit magnitude of their stacks and recommend a suitable plant protection system. It could be shown that the peak short-circuit current depends on the operating point as well as the operating conditions. For the steady-state short-circuit current, the gas stoichiometry has an impact on the deliverable current. For all other operating conditions the steady-state short-circuit current is approximately twice the recommended maximum operating current. Furthermore, a method to estimate the effective fuel cell stack capacity out of the transient short-circuit current is presented.

This contribution describes the layout of a flexible protection system for electrical systems, that are supplied by a source with limited short-circuit current capacity. This system consists of a primary analogue under voltage protection device for AC voltages, programmable solid-state power controllers and a central control logic. Possible application scenarios are described for the protection system. An initial single phase prototype is presented, which is used to test the basic protection features.

Common controlling strategies of fuel cells regulate parameters like the flow rates, pressures, temperatures, and relative humidities of the supplied gases. These strategies have a slow control effect on the fuel cell output voltage, especially at high dynamic loads, which is why fuel cell voltage and power drops for several seconds to minutes after a load step. Today, an oversizing of fuel cell systems is necessary to meet the requirements of dynamic load profiles. This paper deals with the design and implementation of an electric field modifier (EFM) control unit into fuel cells to enable the regulation of an additional control parameter, which is considerably faster than the common parameters. The EFM control unit consists of EFM electrodes that are placed directly on or in the membrane of polymer exchange membrane fuel cells and are connected to an external controllable voltage source. Possible electrical connections and actuating signals are presented. Deduced advantages include a better dynamic fuel cell system voltage behavior, a cost- and weight-optimized on-board grid integration, and a prolonged membrane durability.

Today's external fuel cell control by regulation of flow rates, pressures and relative humidities of the used gases has a slow control effect on the fuel cell output voltage. At high dynamic loads these common control strategies lead to voltage and power drops of several seconds to minutes, depending on the fuel cell system size. Therefore, system oversizing is necessary to meet the requirements of dynamic load profiles. In this paper a new approach of an internal electrical fuel cell membrane control with an electric field modifier (EFM) is proposed. The EFM control unit consists of EFM electrodes that are placed directly on or in the membrane of polymer exchange membrane fuel cells and are connected to an external controllable voltage source. Deduced advantages include a better dynamic fuel cell system voltage behavior, a cost-and weight-optimized on-board grid integration, and a prolonged membrane durability.

The aviation industry pursues the integration of fuel cells (FCs) to reduce pollutant emissions. Their connection to the on-board power supply leads to new requirements for electrical grid protection. The limited short-circuit current of a weight-optimized FC system cannot trip a standard fuse. Hence, in this paper, a new protection device is developed as an under/overvoltage primary protection. The proposed device consists of three basic elements: relay; differential amplifier; and current source. This paper includes a detailed description of the protections design process, which includes a requirement analysis, a detailed robustness consideration, and an experimental validation of a developed prototype.

This contribution describes the layout of a novel protection system for electrical systems, that are supplied by a source with limited short-circuit current capacity. This system consists of a primary analogue under voltage protection device for ac voltages, programmable solid-state power controllers and a central control logic. Possible application scenarios are described for the protection system. An initial single phase prototype is presented, which is used to test the basic protection features.

The city of Hamburg will fully electrify the public bus service in the coming years, starting from 2018. The transformation process from diesel to electric mobility will have a significant impact on the electrical infrastructure. Due to this, it is of high interest for both distribution system operators and public transport service companies to quantify the electric power demands and the impacts on the local grid infrastructure. In the following study, bus depots of the Hamburg Hochbahn AG (HOCHBAHN) were investigated. Real data from the field was used to model the bus service trips of a whole week, calculate load profiles, predict yearly energy consumption and identify additional parameters for future bus operation, such as required charging power, battery capacity and effects on the buses’ standing time. The results show that the bus depots’ peak power demand of up to 15 MW might be critical for a 10 kV medium voltage grid that has a power limitation of about 14 MW. Furthermore it was found that the chosen charging algorithm has a major impact on the peak power demand. Mostly, the charging power of 150 kW per bus is sufficient, however in some cases, articulated buses find it hard to get enough standing and recharging time before starting their next service. The results initially quantify the impacts on the distribution grid when whole conventional bus fleets are transformed into fully electric bus fleets. The broad data basis allows to estimate the actual power demands of future bus depots. Hence, this allows improving long-term development of local distribution grid structures.