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Item type:Publication, Access status: with files , Effects of vapothermal pretreatment on anaerobic degradability of common reedResidual materials from currently unused plant matter are available locally in abundance and serve as a valuable substrate for biogas production via anaerobic digestion. However, in most cases, a pretreatment is necessary to overcome their recalcitrant behavior. Against this background, earlier ground biomass from Phragmites australis, better known as common reed, is pretreated in a vapothermal atmosphere at temperatures between 122 and 178 °C and residence times between 18 and 102 min. Herein, the influence of such a pretreatment on the specific biogas and methane yield is aimed to be evaluated. In addition, the main causes for changes in degradability are identified by means of accompanying analytics. It is found that vapothermal pretreatment is able to significantly enhance degradation velocity during anaerobic digestion. However, under severe conditions, the biogas and methane yields decrease, which is traced back to an increase in cellulose crystallinity, inaccessibility of pores due to precipitated reaction products, as well as the formation of inhibiting substances and proportional increase in nondegradable lignin.Publicationtype: Journal ArticleScopus© Citations 5 105 224 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Interfacial Thermal Resistance in Magnetocaloric Epoxy-Bonded La-Fe-Co-Si Composites(2018-08); ; ; ; Magnetocaloric composites made from La−Fe−Co−Si particles and an epoxy binder matrix exhibit mechanical stability and good magnetocaloric properties, but also a large characteristic time for thermal transport. Here, the origin of this large time constant is examined by comparing two measurement techniques, direct and contactless, to finite-element simulations based on a tomographic dataset of the sample. The combination of the low thermal conductivity of the epoxy matrix and a thermal resistance at the interface between epoxy and La−Fe−Co−Si is shown to be in good agreement in simulations and experiments. The findings help to disentangle the role of the thermal conductivity and the interfacial thermal resistance for the heat flow in magnetocaloric composites. It is shown that the low thermal conductivity of the epoxy alone cannot explain the large time constant and possibilities for using the interfacial thermal resistance to tailor anisotropic thermal conductivity for directional heat transfer in magnetocaloric composites are presented.Publicationtype: Journal Article193 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Automation of the Storing-In Part of a Hydrogen-Storage System using Liquid Organic Hydrogen Carriers(2018-03-01); ; Accumulating electrical energy in decentralized electrical grids is a demanding task. Preliminary work exists on the charging and discharging of liquid organic hydrogen carriers (LOHCs). These carriers allow the storage of hydrogen by reversible hydrogenation of an aromatic compound. A challenge is that the chemical process has to be conducted within the power-generating infrastructure, and therefore, continuous and fully automated implementation is mandatory. In this work, the fundamentals of controlling and automating LOHC-based energy-storage systems are presented. For this purpose, the identification of the controlled variable is performed before its influence on the reaction dynamics is determined. This results in a fully automated hydrogenation process, whereby the conductibility of the reaction, the performance, and the necessity of applying pressure pulsations to get a stable operation mode are shown. Derived from these results, the investigations help to establish LOHCs as feasible hydrogen carriers, which will be a decisive step to mid- and long-term energy-storage systems suitable to a modern smart-grid infrastructure.Publicationtype: Journal Article195 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Analysis of a two-stage fuel reactor system for the chemical-looping combustion of lignite and bituminous coal(Wiley-VCH, 2016-10-01); ; ; ; Werther, JoachimTo investigate the influence of the fuel characteristics on the conversion behavior in a chemical-looping combustion facility, lignite coal dust (d90,3=233 μm) and two fractions of bituminous coal with different particle sizes (fine fraction d90,3=163 μm, coarse fraction d50,3=707 μm) were used as solid fuel. To improve the conversion performance, a pilot plant with a rated power of 25 kW was constructed with a two-stage fuel reactor. The influence of the fuel composition, particle size, and the presence/absence of elemental oxygen on the conversion in the fuel reactor are presented. The used oxygen carrier was produced by the impregnation of γ-alumina oxide with copper oxide, which is able to release gaseous oxygen, but loses this ability because of deactivation. The lignite dust shows a very good conversion performance and carbon capture efficiencies over 95 % as well as oxygen demands below 2 %. Both bituminous coal fractions have a good performance with regard to fuel conversion and oxygen demand but they suffer from a high carbon slip. Hence the carbon capture efficiency is around 60 % for the fine fraction and 40 % for the coarse one. The performance improvement as a result of the second stage was investigated separately, and we proved that it enhances the overall conversion. In addition, the oxygen carrier generated a favorable reaction environment by releasing elemental oxygen in the second stage of the fuel reactor.Publicationtype: Journal Article94 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Information and communication technology in Energy Lab 2.0 : smart energies system simulation and control center with an open-street-map-based power flow simulation example(Wiley-VCH, 2016); ; ; Isele, JörgIn Energy Lab 2.0, the interplay of different forms of energy on different value chains is investigated. Novel concepts to stabilize the volatile energy supply of renewables by the use of storage systems and mainly by applying to-be-developed tools and algorithms of the information and communication technology sector are sought. Hence, a key element of Energy Lab 2.0 is the smart energies system simulation and control center. This consists of three parts: a power-hardware-in-the-loop experimental field, an energy grid simulation and analysis laboratory, and a control, monitoring, and visualization center. For these three labs, big data technologies, advanced control methods, and reliable, safe, and secure software structures are of equal importance. As an example, a data processing pipeline to create power flow simulation models from raw Open Street Map data, statistical databases, and geodata is presented and discussed.Publicationtype: Journal Article18