@misc{SakkasRoger, author = {Sakkas, Nikolaos Panagiotis and Roger, Abang}, title = {Thermal load prediction of communal district heating systems by applying data-driven machine learning methods}, series = {Energy Reports}, volume = {8}, journal = {Energy Reports}, issn = {2352-4847}, doi = {10.1016/j.egyr.2021.12.082}, pages = {1883 -- 1895}, abstract = {Load forecasting is an essential part of the operational management of combined heat and electrical power units, since a reliable hour- and day-ahead estimation of their thermal and electrical load can significantly improve their technical and economic performance, as well as their reliability. Among different types of prediction techniques, data-driven machine learning methods appear to be more suitable for load estimation in operational systems, compared to the classical forward approach. Research so far has been concentrated mainly on the magnitude of buildings with single load types. It has only been extended to a limited degree on the level of a district heating network where several end users with different characteristics merge into one bigger scale heat consumer (city or group of communities). In this study, artificial neural networks are utilized, to develop a load prediction model for district heating networks. A segmented analytical multi-phase approach is employed, to gradually optimize the predictor by varying the characteristics of the input variables and the structure of the neural network. The comparison against the load prediction time series generated by a local communal energy supplier using a commercial software reveals that, although the latter is enhanced by manual human corrections, the optimized fully automatic predictors developed in the present study generate a more reliable load forecast.}, language = {en} } @misc{KatzerBabulKlattetal., author = {Katzer, Christian and Babul, Konrad and Klatt, Matthias and Krautz, Hans Joachim}, title = {Quantitative und qualitative relationship between swirl burner operating conditions and pulverized coal flame length}, series = {Fuel Processing Technology}, volume = {156}, journal = {Fuel Processing Technology}, issn = {0378-3820}, doi = {10.1016/j.fuproc.2016.10.013}, pages = {138 -- 155}, language = {en} } @misc{ZiemsTannertKrautz, author = {Ziems, Christian and Tannert, Daniel and Krautz, Hans Joachim}, title = {Project presentation: Design and installation of advanced high pressure alkaline electrolyzer-prototypes}, series = {Energy Procedia}, volume = {29}, journal = {Energy Procedia}, issn = {1876-6102}, doi = {10.1016/j.egypro.2012.09.087}, pages = {744 -- 753}, language = {en} } @misc{KangwanpongpanCorreadaSilvaKrautz, author = {Kangwanpongpan, Tanin and Correa da Silva, Rodrigo and Krautz, Hans Joachim}, title = {Prediction of oxy-coal combustion through an optimized weighted sum of gray gases model}, series = {Energy : the international journal}, volume = {41}, journal = {Energy : the international journal}, number = {1}, issn = {0360-5442}, doi = {10.1016/j.energy.2011.06.010}, pages = {244 -- 251}, language = {en} } @misc{MissagiaGuerreroNarraetal., author = {Missagia, Bruna and Guerrero, Cinthya and Narra, Satyanarayana and Sun, Yaoming and Ay, Peter and Krautz, Hans Joachim}, title = {Physicomechanical properties of rice husk pellets for energy generation}, language = {en} } @misc{AsegehegnSchreiberKrautz, author = {Asegehegn, Teklay Weldeabzgi and Schreiber, Matthias and Krautz, Hans Joachim}, title = {Numerical Study of Bubbling Gas-Solid Fluidized Beds Hydrodynamics: Influence of Immersed Horizontal Tubes and Data Analysis}, language = {en} } @misc{AsegehegnSchreiberKrautz, author = {Asegehegn, Teklay Weldeabzgi and Schreiber, Matthias and Krautz, Hans Joachim}, title = {Numerical simulation and experimental validation of bubble behavior in 2D gas-solid fluidized beds with immersed horizontal tubes}, doi = {http://dx.doi.org/10.1016/j.ces.2011.07.056}, language = {en} } @misc{SchreiberAsegehegnKrautz, author = {Schreiber, Matthias and Asegehegn, Teklay Weldeabzgi and Krautz, Hans Joachim}, title = {Numerical and Experimental Investigation of Bubbling Gas-Solid Fluidized Beds with Dense Immersed Tube Bundles}, language = {en} } @misc{KangwanpongpanFrancaCorreadaSilvaetal., author = {Kangwanpongpan, Tanin and Franca, Francis H. R. and Correa da Silva, Rodrigo and Smith Schneider, Paulo and Krautz, Hans Joachim}, title = {New correlations for the weighted-sum-of-gray-gases model in oxy-fuel conditions based on HITEMP 2010 database}, series = {International Journal of Heat and Mass Transfer}, volume = {55}, journal = {International Journal of Heat and Mass Transfer}, number = {25-26}, issn = {0017-9310}, doi = {10.1016/j.ijheatmasstransfer.2012.07.032}, pages = {7419 -- 7433}, language = {en} } @misc{NimtzKlattWieseetal., author = {Nimtz, Michael and Klatt, Matthias and Wiese, Bernd and K{\"u}hn, Michael and Krautz, Hans Joachim}, title = {Modelling of the CO2 process- and transport chain in CCS systems - Examination of transport and storage processes}, series = {Chemie der Erde - Geochemistry}, volume = {70}, journal = {Chemie der Erde - Geochemistry}, number = {3}, issn = {0009-2819}, doi = {10.1016/j.chemer.2010.05.011}, pages = {185 -- 192}, language = {en} } @misc{AhaFindeisenKrautz, author = {Aha, Ulrich and Findeisen, Alexander and Krautz, Hans Joachim}, title = {Maintenance optimization for large coal-fired power plants}, language = {en} } @misc{AhaFindeisenKrautzetal., author = {Aha, Ulrich and Findeisen, Alexander and Krautz, Hans Joachim and Kahlert, Joachim}, title = {Korrosion und Instandhaltungsoptimierung CO2-armer Braunkohlekraftwerke unter ge{\"a}nderten Prozessbedingungen und -parametern}, language = {de} } @misc{AsegehegnSchreiberKrautz, author = {Asegehegn, Teklay Weldeabzgi and Schreiber, Matthias and Krautz, Hans Joachim}, title = {Investigation of bubble behavior in fluidized beds with and without immersed horizontal tubes using a digital image analysis technique}, doi = {http://dx.doi.org/10.1016/j.powtec.2011.03.025}, language = {en} } @misc{AsegehegnSchreiberKrautz, author = {Asegehegn, Teklay Weldeabzgi and Schreiber, Matthias and Krautz, Hans Joachim}, title = {Influence of two- and three-dimensional simulations on bubble behaviorin gas-solid fluidized beds with and without immersed horizontal tubes}, doi = {10.1016/j.powtec.2011.11.050}, language = {en} } @misc{AbangWeissKrautz, author = {Abang, Roger Atini and Weiß, Sabine and Krautz, Hans Joachim}, title = {Impact of increased power plant cycling on the oxidation and corrosion of coal-fired superheater materials}, series = {Fuel}, volume = {2018}, journal = {Fuel}, number = {220}, issn = {0016-2361}, doi = {10.1016/j.fuel.2018.02.047}, pages = {521 -- 534}, abstract = {As power generation from variable renewable energy sources such as wind and solar power continues to increase in the future, fewer baseload power plants will be needed. As a result, high operational flexibility is becoming a vital requirement for conventional power plants to allow for the smooth integration of the variable renewable energy sources (v-RES) into the grid. To understand the impact of high operational flexibility (increased cycling) for coal-fired power plant materials, five commercial coal boiler superheater and reheater materials were investigated under isothermal and cyclic conditions for 1000 h each. The candidate alloys investigated were: T91, VM12-SHC, TP347-HFG, DMV304 HCu and DMV310 N. The results (weight change kinetics and metallographic analysis) after exposure at a metal surface temperature of 650 °C clearly showed the impact of increased flexibility on the corrosion and oxidation of the materials. Oxide growth (weight gain), metal loss, oxide spallation, and grain boundary attack were found to be more severe under cyclic conditions than under isothermal conditions.}, language = {en} } @misc{MerzschLechnerKrautz, author = {Merzsch, Matthias and Lechner, Stefan and Krautz, Hans Joachim}, title = {Heat-transfer from single horizontal tubes in fluidized beds: Influence of tube diameter, moisture and diameter-definition by Geldart C fines content}, series = {Powder Technology}, journal = {Powder Technology}, issn = {1873-328X}, doi = {10.1016/j.powtec.2012.12.002}, language = {en} } @misc{LechnerMerzschKrautz, author = {Lechner, Stefan and Merzsch, Matthias and Krautz, Hans Joachim}, title = {Heat-transfer from horizontal tube bundles into fluidized beds with Geldart A lignite particles}, series = {Powder Technology}, journal = {Powder Technology}, number = {253}, doi = {10.1016/j.powtec.2013.10.041}, pages = {14 -- 21}, abstract = {This work investigates the heat transfer mechanism in fluidized beds equipped with horizontal heat exchanger surfaces such as single tubes and especially tube bundles. Previous works were performed for varying operating conditions and solids' material properties, leading to a heterogeneous and therefore not applicable spectrum of derived correlations for the influence of tube diameter and tube bundle geometry on heat transfer. Based on a wide range validation of the correlation for the influence of single tube diameter on heat transfer coefficient, tube bundles with different tube diameters and horizontal and vertical spacings and alignments were investigated. Experiments were carried out using electrical heat transfer probes in a 0.15 m2 fluidized bed test facility at ambient conditions. Geldart A lignite and Geldart D solids were used in order to distinguish between predominant particle-convective and gas-convective heat transfer mechanisms. The tube bundle reduction factor on heat transfer coefficient was derived as a key parameter based on dimensionless geometric numbers. This factor predicts the reduction of the heat transfer coefficient compared to that of the single tube due to the particle and gas flow disturbances caused by the immersed tubes. Tube diameter as well as tube bundle geometry were successfully implemented into useful correlations for predicting tube bundles' heat transfer of gas-solid fluidized bed systems operating with fine particles.}, language = {en} } @misc{HorsfieldScheckWenderothKrautzetal., author = {Horsfield, B. and Scheck-Wenderoth, Magdalena and Krautz, Hans Joachim and Mutti, M.}, title = {Geoenergy: From visions to solutions}, doi = {http://dx.doi.org/10.1016/j.chemer.2010.06.002}, language = {en} } @misc{KrautzNimtz, author = {Krautz, Hans Joachim and Nimtz, Michael}, title = {Flexible Operation of CCS Power Plants to Match Variable Renewable Energies}, series = {Energy Procedia}, volume = {2013}, journal = {Energy Procedia}, number = {40}, issn = {1876-6102}, doi = {10.1016/j.egypro.2013.08.034}, pages = {294 -- 303}, abstract = {The German Energiewende is resulting in high grid load changes caused by renewable energies. Therefore flexibility of power plants is getting more and more important. Future CCS power plants are usually equipped with more components than conventional power plants, resulting in a more complex and inert reaction on changes in power output. Additionally, due to the change in price structures and higher fixed and operational costs for CCS power plants, it is harder for them to be economically efficient. This study will show different options to increase the flexibility of CCS power plants and evaluate their benefits.}, language = {en} } @misc{KrautzCorreadaSilvaKangwanpongpan, author = {Krautz, Hans Joachim and Corr{\^e}a da Silva, Rodrigo and Kangwanpongpan, Tanin}, title = {Flame pattern, temperatures and stability limits of pulverized oxy-coal combustion}, series = {Fuel : the science and technology of fuel and energy}, journal = {Fuel : the science and technology of fuel and energy}, number = {Vol. 115}, issn = {0016-2361}, doi = {10.1016/j.fuel.2013.07.049}, pages = {507 -- 520}, abstract = {The challenges in maintaining a stable oxy-coal flame have been reported in the open literature. In case of pulverized coal combustion, narrower flammable regimes arise not only of differences in the feed gas composition, but also due to changes in the flow dynamics because of reduced volume flow rate through the burners to match similar temperatures and radiative heat transfer within the furnace. The present work focuses on the study of flame structure and stability of pre-dried lignite fired by a staged feed-gas burner. Experimental runs were carried out in a 0.40 MWth laboratory facility, with the objective of investigating the effects of swirl strength and feed gas distribution in the burner registers. To assess the experimental data, a numerical study of the non-reacting flow in the near burner region is performed. Predicted flow pattern and flame images show that the primary fuel jet penetrates the internal recirculation zone, forming an annular doughnut reverse flow region for both firing conditions and resembling a type-1 flame pattern. Temperature measurements indicate that the feed gas distribution among the burner registers control the flame temperature in parallel with the swirl number in both air-fired and oxy-fired environments. The oxy-fuel cases exhibite markedly reduced temperatures on the flame axis. This difference in the core arises not just from the more pronounced penetration depth of the primary jet, but also due to reaction mechanisms including pyrolysis and gasification reactions at the higher concentrations of CO2 and water vapor. Flame stabilization is shown to be strongly dependent on an appropriate distribution of the feed gas and strength of swirling flow in the burner front. The results correlated in terms of swirl number, secondary/tertiary flow ratio and secondary/primary axial momentum point to similarities in the stability limits between air-firing and oxy-firing.}, language = {en} }