04 Fakultät Energie-, Verfahrens- und Biotechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5

Browse

Filters

2021 - 20247

Settings

Author: search.filters.author.Sauer, AlexanderSubject: search.filters.subject.670

Search Results

Now showing 1 - 7 of 7
  • Thumbnail Image
    ItemOpen Access
    Process model and life cycle assessment of biorefinery concept using agricultural and industrial residues for biohydrogen production
    (2024) Gamero, Edgar; Ruppert, Sophia; Miehe, Robert; Sauer, Alexander
    Sustainable waste management strategies are urgently needed due to an increasing global population and increased waste production. In this context, biorefineries have recently emerged as a promising approach to valorize waste streams and supply a broad range of products. This study presents the process model and life cycle assessment (LCA) of a biorefinery concept using a novel biochemical method, a so-called “dark photosynthesis” conversion. This process is coupled to a photo-fermentation using microalgae. Overall, the biorefinery concept can produce hydrogen, lutein, β-carotene, and proteins for animal feed. Apple pomace from apple juice production is used as feedstock for the primary conversion step. A process model was created with the process simulation software Aspen Plus ® using experimental and literature data. Results from this model were then used in an LCA. The environmental impacts of the proposed biorefinery concept are relatively high, showing the need for process optimization in several areas. Energy system integration, stream recycling, and higher hydrogen yields are recognized as especially important for improving the environmental performance of this concept. Despite these findings, the model shows the feasibility of implementing the biochemical conversion technologies in a biorefinery concept for effectively utilizing residue streams.
  • Thumbnail Image
    ItemOpen Access
    Improvement of delivery reliability by an intelligent control loop between supply network and manufacturing
    (2021) Bauer, Dennis; Bauernhansl, Thomas; Sauer, Alexander
    Manufacturing companies operate in an environment characterized as increasingly volatile, uncertain, complex and ambiguous. At the same time, their customer orientation makes it increasingly important to ensure high delivery reliability. Manufacturing sites within a supply network must therefore be resilient against events from the supply network. This requires deeper integration between the supply network and manufacturing control. Therefore, this article presents a concept to connect supply network and manufacturing more closely by integrating events from the supply network into manufacturing control’s decisions. In addition to the requirements, the concept describes the structure of the system as a control loop, a reinforcement learning-based controlling element as the central decision-making component, and the integration into the existing production IT landscape of a company as well as with latest internet of things (IoT) devices and cyber-physical systems. The benefits of the concept were elaborated in expert workshops. In summary, this approach enables an effective and efficient response to events from the supply network through smarter manufacturing control, and thus more resilient manufacturing.
  • Thumbnail Image
    ItemOpen Access
    Defining material compliance : a comprehensive analysis
    (2021) Buckreus, Lorena; Nuffer, Anne-Kathrin; Miehe, Robert; Sauer, Alexander
    The increase in the number of environmental regulations has resulted in great challenges for corporations in the manufacturing industry, especially within the electronic and electrical and the mechanical engineering sector. To address these compliance requirements, specialized management fields such as environmental compliance, substructures and management approaches have been implemented in industry. Recently, adherence to requirements concerning the composition of products and the use of materials and substances within products has become increasingly important and is referred to as material compliance (MC). Although the topic is of increasing importance, there is no generally accepted definition for MC nor a management framework. Corporations are thus unable to systematically address MC, and compliance violations occur frequently. We derived a definition for MC based on extensive literature research, which we subsequently evaluated in a quantitative survey. Our results indicate that MC is commonly understood as the adherence to requirements concerning the composition of a product and the use of substances and materials within products. By proposing a definition for MC, we aim to introduce a common understanding, enable future research to systematically address the topic and develop a framework for the management of MC.
  • Thumbnail Image
    ItemOpen Access
    Complex job shop simulation “CoJoSim” : a reference model for simulating semiconductor manufacturing
    (2023) Bauer, Dennis; Umgelter, Daniel; Schlereth, Andreas; Bauernhansl, Thomas; Sauer, Alexander
    The manufacturing industry is facing increasing volatility, uncertainty, complexity, and ambiguity, while still requiring high delivery reliability to meet customer demands. This is especially challenging for complex job shops in the semiconductor industry, where the manufacturing process is highly intricate, making it difficult to predict the consequences of changes. Although simulation has proven to be an effective tool for optimizing manufacturing processes, reference data sets and models often produce disparate and incomparable results. CoJoSim is introduced in this article as a reference model for semiconductor manufacturing, along with an associated reference implementation that accelerates the implementation and application of the reference model. CoJoSim can serve as a testbed and gold standard for other implementations. Using CoJoSim, different dispatching rules are evaluated to demonstrate an improvement of almost 15 percentage points in adherence to delivery dates compared to the reference. Findings emphasize the importance of optimizing setup time, particularly in products with high variance, as it significantly impacts adherence to delivery dates and throughput. Moving forward, future applications of CoJoSim will evaluate additional dispatching rules and use cases. Combining CoJoSim with dispatching methods that integrate manufacturing and supply networks to optimize production planning and control through reinforcement-learning-based agents is also planned. In conclusion, CoJoSim provides a reliable and effective tool for optimizing semiconductor manufacturing and can serve as a benchmark for future implementations.
  • Thumbnail Image
    ItemOpen Access
    Comparative life cycle sustainability assessment of mono- vs. bivalent operation of a crucible melting furnace
    (2022) Schutzbach, Maximilian; Kiemel, Steffen; Miehe, Robert; Köse, Ekrem; Mages, Alexander; Sauer, Alexander
    The benefits of energy flexibility measures have not yet been conclusively assessed from an ecological, economic, and social perspective. Until now, analysis has focused on the influence of changes in the energy system and the ecological and economic benefits of these. Therefore, the objective of this study was to perform a life cycle sustainability assessment of energy flexibility measures on the use case of a bivalent crucible melting furnace in comparison with a monovalent one for aluminum light metal die casting. The system boundary was based on a cradle-to-gate approach in Germany and includes the production of the necessary process technologies and energy infrastructure and the utilization phase of the crucible melting furnaces in non-ferrous metallurgy. The LCSA is performed for different economic and environmental scenarios over a 25-year lifetime to account for potential adjustments in the energy system and volatile energy prices. In summary, it can be said that over the entire service life, no complete ecological, economic, and social advantage of energy flexibility measures through a bivalent system can be demonstrated. Only a temporarily better life cycle sustainability performance of the bivalent furnace can be shown. All results must be considered with the caveat that the bivalent crucible melting furnace has not yet been investigated in actual operation and the calculations of the utilization phase are based on the monovalent crucible melting furnace. To further sharpen the results, more research is needed and the use of actual data for bivalent operation.
  • Thumbnail Image
    ItemOpen Access
    How do german manufacturers react to the increasing societal pressure for decarbonisation?
    (2022) Buettner, Stefan M.; Schneider, Christian; König, Werner; Mac Nulty, Hannes; Piccolroaz, Chiara; Sauer, Alexander
    From the perspective of manufacturing companies, the political, media and economic discourse on decarbonisation in the recent years manifests itself as an increasing social expectation of action. In Germany, in particular, this discourse is also being driven forward by powerful companies, respectively sectors, most notably the automotive industry. Against this background, the present paper examines how German manufacturing companies react to rising societal pressure and emerging policies. It examines which measures the companies have taken or plan to take to reduce their carbon footprint, which aspirations are associated with this and the structural characteristics (company size, energy intensity, and sector) by which these are influenced. A mix methods approach is applied, utilising data gathered from approx. 900 companies in context of the Energy Efficiency Index of German Industry (EEI), along with media research focusing on the announced decarbonisation plans and initiatives. We demonstrate that one-size-serves-all approaches are not suitable to decarbonise industry, as the situation and ambitions differ considerably depending on size, energy intensity and sector. Even though the levels of ambition and urgency are high, micro and energy intensive companies, in particular, are challenged. The present research uncovers a series of questions that call for attention to materialise the ambitions and address the challenges outlined.
  • Thumbnail Image
    ItemOpen Access
    A conceptual framework for biointelligent production : calling for systemic life cycle thinking in cellular units
    (2021) Miehe, Robert; Buckreus, Lorena; Kiemel, Steffen; Sauer, Alexander; Bauernhansl, Thomas
    A sustainable design of production systems is essential for the future viability of the economy. In this context, biointelligent production systems (BIS) are currently considered one of the most innovative paths for a comprehensive reorientation of existing industrial patterns. BIS are intended to enable a highly localized on-demand production of personalized goods via stand-alone non-expert systems. Recent studies in this field have primarily adopted a technical perspective; this paper addresses the larger picture by discussing the essential issues of integrated production system design. Following a normative logic, we introduce the basic principle of systemic life cycle thinking in cellular units as the foundation of a management framework for BIS. Thereupon, we develop a coherent theoretical model of a future decentralized production system and derive perspectives for future research and development in key areas of management.