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The energy industry must change dramatically in order to reduce CO2-emissions and to slow down climate change. Germany, for example, decided to shut down all large nuclear (2022) and fossil thermal power plants by 2038. Power generation will then rely on fluctuating renewables such as wind power and solar. However, thermal power plants will still play a role with respect to waste incineration, biomass, exploitation of geothermal wells, concentrated solar power (CSP), power-to-heat-to-power plants (P2H2P), and of course waste heat recovery (WHR). While the multistage axial turbine has prevailed for the last hundred years in power plants of the several hundred MW class, this architecture is certainly not the appropriate solution for small-scale waste heat recovery below 1 MW or even below 100 kW. Simpler, cost-effective turbo generators are required. Therefore, the authors examine uncommon turbine architectures that are known per se but were abandoned when power plants grew due to their poor efficiency compared to the multistage axial machines. One of these concepts is the so-called Elektra turbine, a velocity compounded radial re-entry turbine. The paper describes the concept of the Elektra turbine in comparison to other turbine concepts, especially other velocity compounded turbines, such as the Curtis type. In the second part, the 1D design and 3D computational fluid dynamics (CFD) optimization of the 5 kW air turbine demonstrator is explained. Finally, experimentally determined efficiency characteristics of various early versions of the Elektra are presented, compared, and critically discussed regarding the originally defined design approach. The unsteady CFD calculation of the final Elektra version promised 49.4% total-to-static isentropic efficiency, whereas the experiments confirmed 44.5%.

Introduction: We aimed to examine whether student teachers’ tendency to test anxiety relates to their later perspective-taking tendency and self-efficacy. The purpose of the presented study was to obtain first insights into the relationship between test anxiety, perspective-taking, and self-efficacy tendencies in student teachers. These tendencies may determine student orientation across different situations. We tested the hypothesis that the test anxiety components emotionality and worry relate to later low perspective-taking and self-efficacy.Methods: We conducted a longitudinal study with 275 student-teachers and analyzed the obtained data using structural equation modeling.Results: The data analysis revealed that only emotionality is related to lower perspective-taking and self-efficacy in later life.Discussion: We conclude that lowering student teachers’ test anxiety emotionality (e.g. through interventions) would result to later increased perspective-taking tendency.Limitations: Participants attended the study voluntarily, so it was a self-selected sample. We employed a correlational design over two measurement times instead of experimental methods.Conclusions: The obtained results give an explanation of why student teachers focused rather on themselves than on school students in classes. The perspective-taking tendency is important for teachers’ student orientation. The role of perspective-taking in different teaching situations might be investigated in further research.

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