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With the growing share of renewable energies in the electricity supply, transmission and distribution grids have to be adapted. A profound understanding of the structural characteristics of distribution grids is essential to define suitable strategies for grid expansion. Many countries have a large number of distribution system operators (DSOs) whose standards vary widely, which contributes to coordination problems during peak load hours. This study contributes to targeted distribution grid development by classifying DSOs according to their remuneration requirement. To examine the amendment potential, structural and grid development data from 109 distribution grids in South-Western Germany, are collected, referring to publications of the respective DSOs. The resulting data base is assessed statistically to identify clusters of DSOs according to the fit of demographic requirements and grid-construction status and thus identify development needs to enable a broader use of regenerative energy resources. Three alternative algorithms are explored to manage this task. The study finds the novel Gauss-Newton algorithm optimal to analyse the fit of grid conditions to regional requirements and successfully identifies grids with remuneration needs. It is superior to the so far used K-Means algorithm. The method developed here is transferable to other areas for grid analysis and targeted, cost-efficient development.
The energy supply of Offenburg University of Applied Sciences (HS OG) was changed from separate generation to trigeneration in 2007/2008. Trigeneration was installed for supplying heat, cooling and electrical power at HS OG. In this paper, trigeneration process and its modes of operation along with the layout of the energy facility at HS OG were described. Special emphasis was given to the operation schemes and control strategies of the operation modes: winter mode, transition mode and summer mode. The components used in the energy facility were also outlined. Monitoring and data analysis of the energy system was carried out after the commissioning of trigeneration in the period from 2008 to 2011. Thus, valuable performance data was obtained.
The aim of this research work was to develop a boiler model with few parameters required for energy planning. The showcase considered for this work was the boiler system of the energy center at Offenburg University of Applied Sciences. A grey box model of the boiler was developed systematically starting from model abstraction, simplification, model break-down and to the use of empirical correlations wherever necessary to describe the intermediate effects along with the use of information from manufacturer’s specification in order to reduce parameters. This strategy had resulted in a boiler model with only 6 parameters, namely, nominal burner capacity, water gallery capacity, air ratio, heat capacity of wall, thermal conductance on flue gas and hot water side. Most of these parameters can be obtained through the information available in the spec sheets and thus an energy planner will be able to parameterize the model with low effort. The model was validated with the monitored data of the showcase. It was tested for the start-up, shut-down behavior and the effect of storage.
The aim of the paper was to investigate the energy saved in the shift from separate generation of thermal and electrical energy to trigeneration at the energy facility in Offenburg University of Applied Sciences (HS OG). The energy facility at HS OG used a traditional heating system and electricity from grid until 2007 afterwhich they installed a trigeneration system to meet its continuously changing dynamic thermal and electrical demands. This paper highlights the methodology that had been derived to analyze and study the effect of this shift based on the energy consumption data available from 2004 to 2011, which were scarce due to the limited monitoring. From the energy analysis, we concluded that 8 % primary energy was saved in this shift at the energy facility of HS OG. And from economical perspective 5 % useful thermal energy and 39 % useful electrical energy was saved in this shift at the energy facility of HS OG. Nevertheless, the term energy saving, in general, is very relative and complex to define in such a changeover.
Micro gas turbines (MGTs) are regarded as combined heat and power (CHP) units which offer high fuel utilization and low emissions. They are applied in decentralized energy neration.
To facilitate the planning process of energy systems, namely in the context of the increasing application of optimization techniques, there is a need for easy-to-parametrize component models with sufficient accuracy which allow a fast computation. In this paper, a model is proposed where the non-linear part load characteristics of the MGT are linearized by means of physical insight of the working principles of turbomachinery. Further, it is shown that the model can be parametrized by the data usually available in spec sheets. With this model a uniform description of MGTs from several manufacturers
covering an electrical power range from 30kW to 333kW can be obtained. The MGT model was
implemented by means of Modelica/Dymola. The resulting MGT system model, comprising further heat exchangers and hydraulic components, was validated using the experimental data of a 65kW MGT from a trigeneration energy system.
Innovative combined heat, cold and power (Trigeneration) at Offenburg University of Applied Sciences
(2013)
During the coronavirus crisis, labs had to be offered in digital form in mechanical engineering at short notice. For this purpose, digital twins of more complex test benches in the field of fluid energy machines were used in the mechanical engineering course, with which the students were able to interact remotely to obtain measurement data. The concept of the respective lab was revised with regard to its implementation as a remote laboratory. Fortunately, real-world labs were able to be fully replaced by remote labs. Student perceptions of remote labs were mostly positive. This paper explains the concept and design of the digital twins and the lab as well as the layout, procedure, and finally the results of the accompanying evaluation. However, the implementation of the digital twins to date does not yet include features which address the tactile experience of working in real-world labs.
Zum ersten Mal gibt es mit dem kooperativen Promotionskolleg über „Kleinskalige erneuerbare Energiesysteme – KleE“ für hochqualifizierte Absolventen der Hochschule Offenburg die Möglichkeit zur Promotion innerhalb des engen wissenschaftlichen Austauschs eines Doktorandenkollegs. Betreut werden sie gemeinsam von je einem Universitätsprofessor und einem Hochschulprofessor. In Zusammenarbeit mit der Albert-Ludwigs-Universität Freiburg, dem Zentrum für Erneuerbare Energien (ZEE), und den Fraunhofer-Instituten für Solare Energiesysteme (ISE) sowie für Physikalische Messtechnik (IPM) forschen 15 Doktorandinnen und Doktoranden im Promotionskolleg KleE an interdisziplinären Forschungsthemen.
Radiation is an important means of heat transfer inside an electric arc furnace (EAF).
To gain insight into the complex processes of heat transfer inside the EAF vessel, not only radiation from the surfaces but also emission and absorption of the gas phase and the dust cloud need to be considered.
Furthermore, the radiative heat exchange depends on the geometrical configuration which is continuously changing throughout the process.
The present paper introduces a system model of the EAF which takes into account the radiative heat transfer between the surfaces
and the participating medium. This is attained by the development of a simplified geometrical model,
the use of a weighted-sum-of-gray-gases model, and a simplified consideration of dust radiation.
The simulation results were compared with the data of real EAF plants available in literature.