Browsing by Author "Linder, Marc"

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Open Access
Automotive cooling systems based on metal hydrides
(2010) Linder, Marc; Laurien, Eckart (Prof. Dr.-Ing.)
The present work focuses on metal hydride sorption systems as an alternative technology for automotive air-conditioning systems. Although this technology offers the possibility to increase the energy efficiency of a car (by utilising waste heat) and consequently reduces the CO2 emissions, its weight specific cooling power has so far been the main obstacle for an automotive application. Based on investigations of various metal hydrides, two alloys (LmNi4.91Sn0.15 and Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5) were chosen for further investigations on different laboratory test benches. A capillary tube bundle reaction bed was applied due to its large heat transfer surface and consequently expected short cycle times. The experimental investigations were carried out systematically starting with material characterisation of each individual metal hydride (Pressure-concentration isotherm measurements, intrinsic absorption/desorption kinetics), followed by the measurement of individual reaction bed dynamics (for both alloys) and the analysis of the coupled metal hydrides (sorption system). One important result obtained from the measurements of individual reaction bed dynamics is the limitation of the fast metal hydride sorption system due to slow intrinsic desorption kinetics of the alloy working at low temperatures (cooling temperature). Therefore, the very fast AB2-type alloy (Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5) was applied at the high-pressure side (low temperatures) which allows half-cycle times of the sorption system in the range of 100 to 120 s. The corresponding specific cooling power of the sorption system is therefore around 640 W/kg related to the desorbing alloy. In comparison to the state of the art metal hydride based cooling system, the specific power of the sorption system is more than tripled which leads to a clearly reduced necessary mass of metal hydride. Based on the experimental investigations, two different metal hydride sorption systems for automotive cooling were investigated: The thermally driven sorption system (closed system) and an open system for hydrogen-fueled cars that is conceptually proposed in this work. This new metal hydride sorption system utilizes the hydrogen pressure difference between a high-pressure storage tank and the fuel cell or combustion engine. Its main advantage in comparison to the closed sorption system is the clearly reduced system complexity that is especially necessary for automotive cooling.
Open Access
Gas-solid reactions for energy storage and conversion
(2022) Linder, Marc; Thess, André (Prof. Dr.)
Reversible gas-solid reactions could offer relevant technological contributions to an energy system predominantly based on renewable energy. However, our current understanding of this technology is mainly based on fundamental material research and generic application concepts. Therefore, the first part of this work summarizes the current state of knowledge in order to identify unique advantages that could arise from reversible gas-solid reactions for energy storage and conversion. Starting with a technological differentiation between various reversible processes used for energy storage, a classification of different reactor designs and a generic approach for thermal integration and necessary reaction gas supply, three main directions are derived that currently seem most promising to transfer the specific properties of gas-solid reactions to technical systems: (1) open configurations to reduce system complexity, (2) utilization of available pressure differences to adjust the reaction temperature and (3) combination of abundant materials with the intrinsic possibility of lossless storage. Based on these considerations, the second part of this work summarizes our approach to transfer material properties to technical systems, e.g. by developing storages that utilize oxygen from air, by taking advantage of the pressure dependency of the reaction temperature of metal hydrides and salt hydrates or by combining the long-term energy storage possibility with abundant and costefficient reactants such as calcium oxide and water.