NEIS 2023 - Conference on Sustainable Energy Supply and Energy Storage Systems

To increase the service life or durability of PEM fuel cells, no-load operation at open circuit voltage has to be avoided to reduce destructive electrochemical effects. This paper shows two approaches to realize a regulated base-load with a fuel cell protection unit for application in aircraft multi-powertrain-concepts. Firstly, a clocked MOSFET in the form of a chopper circuit, and secondly, a MOSFET in linear operation as current source. This contribution describes the design concept of both approaches and the validation of prototypes in a laboratory pHiL-environment. Both approaches are proven to be viable solutions, with the current source approach resulting in smoother operation.

The importance of electrifying buses in public transportation is increasing massively during the last few years. This owes to the health detrimental emissions of diesel buses and their effect on the climate changes. Correspondingly, the two transportation companies in Hamburg, the Hamburger Hochbahn AG and Verkehrsbetriebe Hamburg-Holstein GmbH (VHH), decided to electrify their bus depots. This ambitious goal is combined with many challenges concerning the design and operation of the charging infrastructure at the minimum costs. Among others also load management, grid impact, power quality. The aim of implementing the presented model is to search for possible usage of flexibility of electric bus depots in the energy market. This is realized by considering the bus depot as an aggregator of positive or negative flexibility. The offering of this flexibility is based on the predefined atypical grid usage in Germany. This enables electricity customers with an annual energy consumption of more than 100,000 kWh to save in grid fees for their load regulation in coordination with grid operators. Nevertheless, the operation of the bus depot has the highest priority in this study to guarantee the ability of buses to travel their routes. This paper analyses three different scenarios for atypical grid usage: the role of load management, the role of a second-life stationary battery and the combination of both cases. As a result, the required supplying periods and capacities of the stationary battery are calculated. Finally, a combined scenario between the supply from the stationary battery and the supply from the grid is presented.

The coupling of the three energy grids electric power, gas and heat, via sector coupling devices such as fuel cells or electrolyzers enables the increase of the share of renewable energies in consumption beyond the electricity sector. Correct modeling is crucial for the physically correct description of the behavior of fuel cells and effects on the energy grids, especially regarding transients caused by switching processes or during plant faults. In the paper presented here, the proton exchange membrane fuel cell is introduced as a component for its use in the “Extended Node Method”. It allows a suitable integration into the grid-based energy systems electricity, gas and heat based on node equations. For this purpose, the fuel cell is described as a multi-energy component. Also, for gas and heating grids, electrical analogies are used. The associated systems of equations are constructed in such a way that they can be applied to different topologies. Exemplary operating points are shown for a sample configuration. The results are partly compared with other calculation methods and software and discussed.