Publikationen

In order to investigate the grid integration of wind turbines (WT) of various scales and designs, a wind turbine emulator (WTE) is being built in Flensburg within the state-funded project GrinSH. The special feature of this WTE is the use of a large gas engine instead of an electric motor to emulate the behavior of a WT. In order to develop the controls of this innovative WTE and to design the upcoming test runs under safe conditions, a software in the loop model (SILM) was applied. This SILM contained a mathematical model of the wind turbine, mathematical models of the gas engine with an integrated controller, and a model of the generator and frequency converter unit, as well as a preventive modulator of the reference signal (PMRS). The PMRS module converts the reference signal of the emulated WT in such a way that the dynamics of the engine components can be calculated and balanced in advance to enable the required behavior of the entire SILM despite the dynamics of the gas engine. It was found that the PMRS module, developed and tested in this work, increased the ability of the WTE, based on a gas engine, to reproduce the dynamics of a WT.

The transition to renewable energy sources to mitigate climate change will require large-scale energy storage to dampen the fluctuating availability of renewable sources and to ensure a stable energy supply. Energy storage in the geological subsurface can provide capacity and support the cycle times required. This study investigates hydrogen storage, methane storage and compressed air energy storage in subsurface porous formations and quantifies potential storage capacities as well as storage rates on a site-specific basis. For part of the North German Basin, used as the study area, potential storage sites are identified, employing a newly developed structural geological model. Energy storage capacities estimated from a volume-based approach are 6510 TWh and 24,544 TWh for hydrogen and methane, respectively. For a consistent comparison of storage capacities including compressed air energy storage, the stored exergy is calculated as 6735 TWh, 25,795 TWh and 358 TWh for hydrogen, methane and compressed air energy storage, respectively. Evaluation of storage deliverability indicates that high deliverability rates are found mainly in two of the three storage formations considered. Even accounting for the uncertainty in geological parameters, the storage potential for the three considered storage technologies is significantly larger than the predicted demand, and suitable storage rates are achievable in all storage formations.

The study at hand elaborates on potential barriers, prerequisites and optimization potentials for the automation of the twistlock handling process in container terminals. A case analysis enlightens latest automation developments of this essential task in container transport. Eight experts from different organizations in maritime logistics and seaport operations were interviewed in a qualitative multiple-case research design. The interviews were evaluated by qualitative-quantitative content analysis with MAXQDA software. Automated twistlock handling systems are hardly implemented, although they represent the missing link between other container handling technology in the automated container transport. The study reveals that most implementation barriers consist of technological issues, followed by economic and strategic barriers. The study identifies implementation strategies and their key success and shows that safety improvements and cost reductions are major benefits of this automation. An innovation framework for this field of automation is conceptualized as scientific contribution. Practical implications include recommendations for relevant stakeholders in container logistics.

As members of the food supply chain, food manufacturers acquire power and hold responsibility for the sustainable transformation of our food systems. Sustainability assessment and reporting frameworks function as instruments to shape sustainable transformation processes. Their suitability for food manufacturing companies and their connectivity with the up- and downstream food supply chain is investigated here. The first section of the study explores the need for holistic, company-based sustainability frameworks in the food manufacturing sector from the literature. The second part compares seven frameworks, in terms of content and supply chain connectivity. Food sector specificity demands the inclusion of topics specific to food systems. Furthermore, none of the investigated frameworks fulfils both food sector specificity and full connectivity with the up- and downstream supply chain. As a limitation to this work, comparison of the frameworks at topic-level instead of indicator-level is considered. The findings call for more harmonised and integrated sustainability assessment throughout the food supply chain. The framework a food manufacturer should apply depends on their motivation behind conducting the sustainability assessment and reporting. Evidence is provided from various perspectives and with regard to key issues such as content, certification and communication. No comparison between sustainability frameworks has been made yet from the supply chain perspective of food manufacturers.