495 research outputs found

    Passing ship effect in shallow and confined waters, a systematic model test study of moored containership at quay

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    Conference Proceedings published: https://waterbouwkundiglaboratorium.paddlecms.net/sites/default/files/2022-05/6th%20MASHCON_Proceedings.zip /// Password = MASHCO

    Passing ship effect in shallow and confined waters, a sytematic model test study of moored containership at quay

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    Conference Proceedings published: https://waterbouwkundiglaboratorium.paddlecms.net/sites/default/files/2022-05/6th%20MASHCON_Proceedings.zip /// Password = MASHCO

    Tricarboxylic Acid Cycle Activity Measured by 13C Magnetic Resonance Spectroscopy in Rats Subjected to the Kaolin Model of Obstructed Hydrocephalus

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    Evaluating early changes in cerebral metabolism in hydrocephalus can help in the decision making and the timing of surgical intervention. This study was aimed at examining the tricarboxylic acid (TCA) cycle rate and 13C label incorporation into neurotransmitter amino acids and other compounds 2 weeks after rats were subjected to kaolin-induced progressive hydrocephalus. In vivo and ex vivo magnetic resonance spectroscopy (MRS), combined with the infusion of [1,6-13C]glucose, was used to monitor the time courses of 13C label incorporation into the different carbon positions of glutamate in the forebrains of rats with hydrocephalus as well as in those of controls. Metabolic rates were determined by fitting the measured data into a one-compartment metabolic model. The TCA cycle rate was 1.3 ± 0.2 Όmoles/gram/minute in the controls and 0.8 ± 0.4 Όmoles/gram/minute in the acute hydrocephalus group, the exchange rate between α-ketoglutarate and glutamate was 4.1 ± 2.5 Όmoles/gram/minute in the controls and 2.7 ± 2.6 Όmoles/gram/minute in the hydrocephalus group calculated from in vivo MRS. There were no statistically significant differences between these rates. Hydrocephalus caused a decrease in the amounts of glutamate, alanine and taurine. In addition, the concentration of the neuronal marker N-acetyl aspartate was decreased. 13C Labelling of most amino acids derived from [1,6-13C]glucose was unchanged 2 weeks after hydrocephalus induction. The only indication of astrocyte impairment was the decreased 13C enrichment in glutamine C-2. This study shows that hydrocephalus causes subtle but significant alterations in neuronal metabolism already early in the course of the disease. These sub-lethal changes, however, if maintained and if ongoing might explain the delayed and programmed neuronal damage as seen in chronic hydrocephalus

    Towards positive energy districts: assessing the contribution of virtual power plants and energy communities

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    The concept of positive energy districts (PED) encompasses a range of policies and strategies in response to climate protection targets in urban areas. Due to the limited potential of renewable energy in urban neighborhoods, broader definitions of PED are proposed that allow for energy exchange through the grid infrastructure. This study evaluates demand side management in combination with a virtual power plant (VPP) to assess the impact on the design of PED. In particular, the optimal customer behavior in response to flexible electricity tariffs is analyzed. A techno-economic energy system model is proposed for an urban area in Germany that optimizes the customer cost and the VPP’s margin. This includes electrical energy generation, storage, demand, and access to the short-term electricity market. Based on economic analysis, a dynamic market-based tariff allows the VPP to maximize profit margins. Consumers benefit when the local balances of renewable energy supply and demand are integrated into the dynamic tariff

    Challenges and Barriers for Net‐Zero/Positive Energy Buildings and Districts—Empirical Evidence from the Smart City Project SPARCS

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    Without decarbonizing cities energy and climate objectives cannot be achieved as cities account for approximately two thirds of energy consumption and emissions. This goal of decarbonizing cities has to be facilitated by promoting net-zero/positive energy buildings and districts and replicating them, driving cities towards sustainability goals. Many projects in smart cities demonstrate novel and groundbreaking low-carbon solutions in demonstration and lighthouse projects. However, as the historical, geographic, political, social and economic context of urban areas vary greatly, it is not always easy to repeat the solution in another city or even district. It is therefore important to look for the opportunities to scale up or repeat successful pilots. The purpose of this paper is to explore common trends in technologies and replication strategies for positive energy buildings or districts in smart city projects, based on the practical experience from a case study in Leipzig—one of the lighthouse cities in the project SPARCS. One of the key findings the paper has proven is the necessity of a profound replication modelling to deepen the understanding of upscaling processes. Three models analyzed in this article are able to provide a multidimensional representation of the solution to be replicated

    Ökonomische Bewertung von innovativen Speichertechnologien in Energiesystemen mit einem hohen Anteil erneuerbarer Energien

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    Diese Arbeit geht der Frage nach, ob sich durch die stattfindende Transformation zu einem kohlenstoffarmen Energiesystem in Deutschland auch Marktchancen fĂŒr innovative Marktteilnehmer, insbesondere fĂŒr Speicherbetreiber, herausbilden. Die ökonomischen Effekte, die in Energiesystemen mit hohen Anteilen an variablen erneuerbaren Energien (vEE) auftreten, können durch deren Integrationskosten gemessen werden. Die wissenschaftlichen Untersuchungen in Bezug auf den zusĂ€tzlichen Speicher- bzw. FlexibilitĂ€tsbedarf fĂŒr ein solches Energiesystem setzen hĂ€ufig bei den Ungleichgewichten in der Systembilanz an. Den jeweiligen Methoden liegen jedoch unterschiedliche Annahmen und Rahmenbedingungen zu Grunde, sodass die Ergebnisse nur eingeschrĂ€nkt miteinander verglichen werden können. Der stĂŒndlich schwankende Großhandelspreis an der Strombörse ist ein wichtiger Indikator, um den FlexibilitĂ€tsbedarf zu signalisieren. Viele Analysen legen historische oder auch prognostizierte Preiszeitreihen fĂŒr eine Bewertung von Speicheroptionen zu Grunde. Jedoch wird dabei die RĂŒckkopplung der Betriebsweise eines Energiespeichers auf die Marktpreise außen vor gelassen. In dieser Arbeit wird deshalb eine Methode entwickelt, um den Einfluss eines steigenden Marktvolumens an Speichern und anderen FlexibilitĂ€tsoptionen auf die Spotmarktpreise abzuschĂ€tzen. Untersucht wird der Einfluss des Speichereinsatzes auf die Stromnachfrage und die Spotmarktpreise in 2020 sowie 2030. Die hierfĂŒr zu definierenden Szenarien fĂŒr den Strommarkt werden modellgestĂŒtzt abgebildet und ausgewertet. FĂŒr die Beantwortung der Fragestellung werden techno-ökonomische Modelle, z.B. das Strommarktmodell MICOES zur Kraftwerkseinsatzplanung, das Modell DeSiflex zur GlĂ€ttung der Residuallast durch integrierte FlexibilitĂ€tsoptionen sowie das Modell Arturflex zur AbschĂ€tzung der Arbitragegewinne durch Einsatz von FlexibilitĂ€tsoptionen am Spotmarkt, herangezogen

    Economic potential of demand side management based on smart metering of youth hostels in Germany

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    Additional electricity meters behind the grid access point can improve understanding of energy consumption patterns and thus, adjust consumption behavior. For this study, smart meters were installed in three hostels, out of which two are analyzed further in this paper. Starting from an onsite inspection, all appliances were assigned to reasonable groups for sub-metering. Based on data for the year 2021, the sites are characterized according to the sub-metering concept. In addition, load profiles for type-days are derived, which allows to establish a baseload during COVID lockdown and compare it to consumption patterns for normal occupation. In the prescriptive part, the demand profiles are analyzed regarding their economic potential for load shifting. Consumption data for one week with normal occupation is used as input for techno-economic modeling. The mixed-integer model minimizes electricity purchasing costs for different scenarios including dynamic tariffs and onsite generation from photovoltaics
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