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Impact of renewable energies on the operation and economicsituation of coal fired power stations： Actual situation of coalfired power stations in Germany

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Frontiers in Energy 2017年第2期11卷 119-125页

作者： Hans-Joachim KRAUTZ Alexander LISK Joachim POSSELT Christian KATZER Department for Power Plant technology Brandenburg University of Technology Cottbus-Senftenberg 03046 Cottbus Gemany

Due to the fluctuating character of the renewable energy sources the demand of conventional power plants for flexibility is increasing. In the recent years, in Germany there has been a fast rise of production capacity of renewable energies, especially from wind turbines, photovoltaic installations, and biomass plants. The installed nominal power of wind turbines is actually (December 2016) 42 GW and of photovoltaic installations 40?GW. The renewable electric energy production in Germany is about 190?TWh/a, which represents a share of 33% of the yearly demand. The increased need for flexibility affects both the power gradients as well as the minimum load of conventional power plants. Due to this flexibility behaviour, conventional power plants are faced with problems concerning the durability of power plant components, corrosion, more maintenance effort and consequently the overall life expectancy. Another consequence of the increasing share of renewable energies is the decreasing full load operating hours, especially of coal fired and gas power plants. Along with decreasing revenues from the energy exchange market, coal fired power plants are faced with new economically challenges.

关键词： flexible load operation minimal load power gradients power plant maintenance corrosion life expectancy

Eigenvalue sensitivity analysis based on the transfer matrix method

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International Journal of Mechanical System Dynamics 2021年第1期1卷 96-107页

作者： Dieter Bestle Engineering Mechanics and Vehicle Dynamics Brandenburg University of Technology Cottbus‐SenftenbergCottbusGermany

For linear mechanical systems,the transfer matrix method is one of the most efficient modeling and analysis ***,in contrast to classical mod-eling strategies,the final eigenvalue problem is based on a matrix which is a highly nonlinear function of the ***,classical strategies for sensitivity analysis of eigenvalues *** parameters cannot be *** paper develops two specific strategies for this situation,a direct differentiation strategy and an adjoint variable method,where especially the latter is easy to use and applicable to arbitrarily complex chain or branched multibody *** the system analysis itself,it is able to break down the sensitivity analysis of the overall system to analytically determinable derivatives of element transfer matrices and recursive formula which can be applied along the transfer path of the topology *** examples of different complexity validate the proposed approach by comparing results to analytical calculations and numerical *** obtained procedure may support gradient‐based optimization and robust design by delivering exact sensitivities.

关键词： adjoint variable method direct differentiation sensitivity analysis transfer matrix method

Will Germany move into a situation with unsecured power supply?

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Frontiers in Energy 2019年第3期13卷 551-570页

作者： Harald SCHWARZ Energy Distribution and High Voltage Engineering Faculty 3Brandenburg University of TechnologyCottbus-Senftenberg 03013Germany

Together with a huge number of other countries, Germany signed the Paris Agreements in 2015 to prevent global temperature increase above 2℃. Within this agreement, all countries defined their own national contributions to CO2 reduction. Since that, it was visible that CO2 emissions in Germany decreased, but not so fast than proposed in this German nationally determined contribution to the Paris Agreement. Due to increasing traffic, CO2 emissions from this mobility sector increased and CO2 emission from German power generation is nearly constant for the past 20 years, even a renewable generation capacity of 112 GW was built up in 2017, which is much higher than the peak load of 84 GW in Germany. That is why the German National Government has implemented a commission (often called "The German Coal Commission") to propose a time line: how Germany can move out of coal-fired power stations. This "Coal Commission" started its work in the late spring of 2018 and handed over its final report with 336 pages to the government on January 26th, 2019. Within this report the following proposals were made:①Until 2022: Due to a former decision of the German Government, the actual remaining nuclear power generation capacity of about 10 GW has to be switched off in 2022. Besides, the "Coal Commission" proposed to switch off additionally in total 12.5 GW of both, hard coal and lignite-fired power plants, so that Germany should reduce its conventional generation capacity by 22.5 GW in 2022.②Until 2030: Another 13 GW of German hard coal or lignite-fired power plants should be switched off.③Until 2038:The final 17 GW of German hard coal or lignitefired power plants should be switched off until 2038 latest. Unfortunately the "Coal Commission" has not investigated the relevant technical parameter to ensure a secured electric power supply, based on German's own national resources. Because German Energy Revolution mainly is based on wind energy and photovoltaic, this paper will describe the

关键词： CO2 reduction mobility sector renewable generation coal commission secured power generation capacity reliable power supply power-to-gas power-to-heat

Are Ni/and Ni5Fe1/biochar catalysts suitable for synthetic natural gas production?A comparison with g-Al2O3 supported catalysts

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Green Energy & Environment 2023年第3期8卷 744-756页

作者： M.Gonzalez-Castano C.Morales J.C.Navarro de Miguel J.H.Boelte O.Klepel J.I.Flege H.Arellano-García Department of Process and Plant technology Brandenburg University of Technology(BTU)Cottbus-SenftenbergPlatz der Deutschen 1Cottbus03046Germany Applied Physics and Semiconductor Spectroscopy Brandenburg University of Technology Cottbus-SenftenbergKonrad-Zuse-Strasse 1Cottbus03046Germany Department of Inorganic Chemistry Institute of Materials Science of SevilleConsejo Superior de Investigaciones Cientificas(CSIC)Universidad de Sevilla(US)Avenida Americo Vespucio 49Seville41092Spain Institute of Materials Chemistry Brandenburg University of Technology Cottbus–SenftenbergUniversitatsplatz 1SenftenbergD-01968Germany

Among challenges implicit in the transition to the post-fossil fuel energetic model,the finite amount of resources available for the technological implementation of CO_(2) revalorizing processes arises as a central *** development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular *** Ni and NiFe catalysts supported over g-Al_(2)O_(3) oxide as reference materials,this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO_(2) *** development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst *** lower Turn Over Frequencies than Ni/Al catalyst,the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst *** NiFe catalysts,analogous Ni_(5)Fe_(1) alloys were constituted over both alumina and biochar *** highest specific activity of the catalyst series,exhibited by the NiFe/C catalyst,was related to the development of surface basic sites along with weaker NiFe-C interactions,which resulted in increased Ni0:NiO surface populations under reaction *** summary,the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.

关键词： Biochar catalysts Carbon catalysts Ni catalysts NiFe alloy Bimetallic catalysts Synthetic natural gas CO_(2)methanation

Influence of increasing numbers of RE-inverters on the powerquality in the distribution grids： A PQ case study of arepresentative wind turbine and photovoltaic system

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Frontiers in Energy 2017年第2期11卷 155-167页

作者： Przemyslaw JANIK Grzegorz KOSOBUDZKI Harald SCHWARZ brandenburg university of technology 01968 Cottbus-SenflenbergGermany Department of Electrical Engineering Wroclaw University of Scienceand Technology 50-370 Wroclaw Poland Department for Energy Distribution and High Voltage Engineering Brandenburg University of Technology 01968 Cottbus-SenftenbergGermany

This paper presents the selected power quality (PQ) indicia of a wind generator and a photovoltaic installation considered to be the representative of medium voltage and low voltage distribution grids. The analysis of measured values suggests that the decrease in PQ is a case of specific combination of distributed generation, grid parameters and load behaviour. Modern generators have a limited impact on PQ. On the other hand, fluctuations in power generation are regarded as an emerging PQ indicator. The growing number of distributed renewable installations causes stochastic, variable, and hardly predictable power flows in the distribution grid. The nature of fluctuations in wind and solar generation is different. In both cases, new indexes for the quantification of fluctuations are needed and are yet not standardised. Proper assessment of these fluctuations enables definition of useful fluctuation limits and rules for optimal storage system integration.

关键词： power quality harmonics sags photovoltaic(PV) system doubly feed induction generator (DFIG) inverters

Belowground Tritrophic Food Chain Modulates Soil Respiration in Grasslands

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Pedosphere 2018年第1期28卷 114-123页

作者： Andrey S.ZAITSEV Klaus BIRKHOFER Klemens EKSCHMITT Volkmar WOLTERS Institute of Animal Ecology Justus-Liebig-University of Giessen Department of Ecology Brandenburg University of Technology Cottbus-Senftenberg

Edaphic biota significantly affects several essential ecological functions such as C-storage, nutrient turnover, and ***, it is not completely understood how belowground animal contribution to these functions changes in grasslands subject to different land use types. A microcosm experiment was carried out to test the effect of a tritrophic food chain on CO_2 release from grassland soils. Soil was collected from three differently managed grassland systems(meadow, pasture, and mown pasture) located in three distinct German regions that cover a north-south gradient of approximately 500 km. The tritrophic food chain comprised natural edaphic microflora, nematodes, and predatory gamasid mites. The experimental design involved a full factorial combination of the presence and absence of nematodes and gamasid mites. Nematodes significantly increased the CO_2 emissions in most treatments,but the extent of this effect varied with land use type. The fact that grazing by nematodes stimulated the metabolic activity of the edaphic microflora over a wide range of grassland soils highlighted the critical impact of the microfauna on ecosystem services associated with soil organic matter dynamics. Gamasids slightly amplified the effect of nematodes on microbial metabolic activity,but only in the pastures. This effect was most probably due to the control of nematode abundance. The fact that gamasid addition also augmented the impact of environmental conditions on nematode-induced modulation of soil respiration highlighted the need for including land use differences while evaluating soil fauna contribution to soil processes. To conclude, the differential response of the investigated tritrophic food chain to different grassland management systems suggests that adverse effects of land use intensification on important soil processes such as atmospheric C-release could potentially be reduced by using management methods that preserve essential features of the belowground fo

关键词： CO_2 emission land use microcosm nematodes predatory mites soil fauna soil food webs

Concept and proof for an all-silicon MEMS micro speaker utilizing air chambers

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Microsystems & Nanoengineering 2019年第1期5卷 196-206页

作者： Bert Kaiser Sergiu Langa Lutz Ehrig Michael Stolz Hermann Schenk Holger Conrad Harald Schenk Klaus Schimmanz David Schuffenhauer Fraunhofer-Institute for Photonic Microsystems 01109 DresdenGermany Chair of Micro and Nano Systems Brandenburg University of Technology Cottbus-Senftenberg03013 CottbusGermany

MEMS-based micro speakers are attractive candidates as sound transducers for smart devices,particularly wearables and *** such devices,high sound pressure levels,low harmonic distortion and low power consumption are required for industrial,consumer and medical *** ability to integrate with microelectronic circuitry,as well as scalable batch production to enable low unit costs,are the key factors benchmarking a *** Nanoscopic Electrostatic Drive based,novel micro speaker concept presented in this work essentially comprises inplane,electrostatic bending actuators,and uses the chip volume rather than the its surface for sound *** describe the principle,design,fabrication,and first characterization *** design options and governing equations are given and *** a standard acoustical test setup(ear simulator),a MEMS micro speaker generated a sound pressure level of 69 dB at 500 Hz with a total harmonic distortion of 4.4%,thus proving the *** potential on sound pressure as well as linearity improvement is *** expect that the described methods can be used to enhance and design other MEMS devices and foster modeling and simulation approaches.

关键词： sound utilizing distortion

Impact of crystalline and amorphous iron-and aluminum hydroxides on mechanisms of phosphate adsorption and desorption

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Journal of Environmental Sciences 2018年第8期30卷 175-189页

作者： Stella Gypser Florian Hirsch Anja M.Schleicher Dirk Freese brandenburg university of technology cottbus-senftenberg Faculty of Environment Process Engineering Biotechnology and Chemistry Department of Soil Protection and Recultivation brandenburg university of technology cottbus-senftenberg Faculty of Environment Process Engineering Biotechnology and Chemistry Department of Geopedology and Landscape Development German Research Centre for Geosciences Section 3.1 Inorganic and Isotope Geochchemistry

Fourier-transform infrared（FT-IR） spectroscopic experiments were carried out during phosphate adsorption on highly crystalline gibbsite, poorly crystalline 2-line-ferrihydrite and amorphous iron–aluminum–hydroxide mixtures in the molar ratio 1：0, 10：1, 5：1, 1：1, 1：5, 1：10 and 0：1. The OH stretching vibrational bands were utilized to analyze changes in structural and surface OH groups during adsorption, because the position of characteristic P／O vibrational bands can shift depending on reaction conditions, pH or adsorbed phosphate *** and desorption kinetics were studied at pH6 and different initial phosphate concentrations to achieve varying phosphate coverage on the mineral surfaces. For gibbsite the formation of AlHPO4 and Al2HPO4 can be assumed, while for ferrihydrite, a FeHPO4 or Fe2PO4 complex and the precipitation of FePO4 with longer equilibration time were ***2HPO4 or a Fe2PO4 surface complex was deduced for Fe-hydroxides, an AlH2PO4 surface complex was identified for Al-hydroxide, and both displayed either hydrogen bonds to neighboring hydroxyl groups or hydrogen bonds to outer-sphere complexes. Fe：Al-hydroxide mixtures with high Al ratios showed a low phosphate desorption rate, while ferrihydrite and the Fe：Al-hydroxide mixtures with high Fe ratios had almost negligible desorption rates. It was concluded that within the weakly associated amorphous FeO（OH） materials, FePO4 precipitated, which was bound by outer-sphere hydrogen bonds. With high Al ratios, desorption increased, which indicated weaker phosphate binding of both inner-sphere and outer-sphere complexes and hence, either no or minor quantities of precipitate. Ferrihydrite showed a more rigid structure and a lower extent of precipitation compared to amorphous Fe-hydroxide.

关键词： Phosphate Adsorption Desorption Surface complexation Precipitation FT-IR

Coulomb-actuated microbeams revisited: experimental and numerical modal decomposition of the saddle-node bifurcation

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Microsystems & Nanoengineering 2021年第3期7卷 111-123页

作者： Anton Melnikov Hermann A.G.Schenk Jorge M.Monsalve Franziska Wall Michael Stolz Andreas Mrosk Sergiu Langa Bert Kaiser Fraunhofer Institute for Photonic Microsystems IPMS Dresden 01109Germany Arioso Systems GmbH Dresden 01109Germany brandenburg university of technology cottbus-senftenberg Cottbus 03046Germany

Electrostatic micromechanical actuators have numerous applicati ons in scie nee and *** many applications,they are operated in a narrow frequency range close to resonanee and at a drive voltage of low ***,new applications,such as microelectromechanical systems(MEMS)microspeakers(μSpeakers),have emerged that require operation over a wide frequency and dynamic *** the dynamic performance under such circumstances is still highly ***-of-the-art finite element analysis struggles with pull-in instability and does not deliver the necessary in formation about un stable equilibrium states *** lumped-parameter models amenable to direct physical interpretation are *** inhibits the in dispensable in-depth analysis of the dynamic stability of such *** this paper,we take a major step towards mending the *** combining the finite element method(FEM)with an arc-length solver,we obtain the full bifurcation diagram for electrostatic actuators based on prismatic Euler-Bernoulli beams.A subsequent modal analysis then shows that within very narrow error margins,it is exclusively the lowest Euler-Bernoulli eigenmode that dominates the beam physics over the entire relevant drive voltage *** experiment directly recording the deflection profile of a MEMS microbeam is performed and confirms the numerical findings with astonishing *** enables modeling the system using a single spatial degree of freedom.

关键词： bifurcation modal narrow