Testing setup for automatic cycling of metal hydride composites

In a future hydrogen community, metal hydrides can be used in several new applications. The most common application is as hydrogen storage material for stationary or mobile applications. However, there exist plenty of other applications like heat storage systems, thermal compressors, air conditioning systems, hydrogen purifying systems, etc. For all of these applications cycling stability is a major issue as it determines operational strategies as well as overall lifecycle cost. For pure materials, there exist studies on several thousands of cycles as these materials can be tested in very low quantity and accordingly in small apparatus. However, due to the low thermal conductivity of the powder as well as the low powder density, it is very common to press these powder materials into pellets, and add e.g. expanded natural graphite to improve the thermal conductivity. For these kind of composites it is not only required to determine the stability of the absorbed amount of hydrogen, but also to determine e.g., the geometric stability or the stability of the thermal conductivity. The present setup, that has been built in the framework of a German BMBf Project “HD-HGV” (grant number 03EK3020), is able to test the geometric stability of such pellets in a fully automatic manner up to 1000s of cycles. The hydrogen uptake (of up to 1.8 g of H2) is measured by the Sieverts method and it is possible to measure up to 4 different pellets in parallel. The temperature of the materials can be varied between -20 °C and 330 °C and the pressures between 101 … 107 Pa. So far with this setup hydride-graphite composites of the following materials have been tested: Hydralloy C5 [1], MgH2 and NaAlH4

Numerical Investigations of a Counter-Current Moving Bed Reactor for Thermochemical Energy Storage at High Temperatures

High temperature storage is a key factor for compensating the fluctuating energy supply of solar thermal power plants, and thus enables renewable base load power. In thermochemical energy storage, the thermal energy is stored as the reaction enthalpy of a chemically reversible gas-solid reaction. Metal oxides are suitable candidates for thermochemical energy storage for solar thermal power plants, due to their high reaction temperatures and use of oxygen as a gaseous reaction partner. However, it is crucial to extract both sensible and thermochemical energy at these elevated temperatures to boost the overall system efficiency. Therefore, this study focuses on the combined extraction of thermochemical and sensible energy from a metal oxide and its effects on thermal power and energy density during discharging. A counter-current moving bed, based on manganese-iron-oxide, was investigated with a transient, one-dimensional model using the finite element method. A nearly isothermal temperature distribution along the bed height was formed, as long as the gas flow did not exceed a tipping point. A maximal energy density of 933 kJ/kg was achieved, when (Mn,Fe)3O4 was oxidized and cooled from 1050 °C to 300 °C. However, reaction kinetics can limit the thermal power and energy density. To avoid this drawback, a moving bed reactor based on the investigated manganese-iron oxide should combine direct and indirect heat transfer to overcome kinetic limitations

Feasibility analysis of a novel solid-state H2 storage reactor concept based on thermochemical heat storage: MgH2 and Mg(OH)2 as reference materials

This paper discusses the feasibility of a novel adiabatic magnesium hydride (MgH2) reactor concept based on thermochemical heat storage. In such a concept, the heat of reaction released during the absorption of hydrogen is stored by a thermochemical material in order to be reused in a subsequent desorption stage. Magnesium hydroxide (Mg(OH)2) has been selected as the suitable material for integration into the MgH2 storage system due to its thermodynamic properties. An analytical formulation of hydrogen absorption time is used to determine the range of the geometrical characteristics of the two storage media, their properties and their operating conditions. The advantage of the proposed new concept is the possibility to reduce the mass of the heat storage media by a factor of 4 compared to phase change material, improving then the gravimetric system capacity as well as its total cost. The second advantage is an improved flexibility of the operating pressure conditions for MgH2 absorption reaction and Mg(OH)2 dehydration reaction that enables shorter hydrogen absorption times by ensuring larger temperature gradients between the two storage media

Aggregation-resistant alpha-synuclein tetramers are reduced in the blood of Parkinson's patients

Synucleinopathies such as Parkinson's disease (PD) are defined by the accumulation and aggregation of the α-synuclein protein in neurons, glia and other tissues. We have previously shown that destabilization of α-synuclein tetramers is associated with familial PD due to SNCA mutations and demonstrated brain-region specific alterations of α-synuclein multimers in sporadic PD patients following the classical Braak spreading theory. In this study, we assessed relative levels of disordered and higher-ordered multimeric forms of cytosolic α-synuclein in blood from familial PD with G51D mutations and sporadic PD patients. We used an adapted in vitro-cross-linking protocol for human EDTA-whole blood. The relative levels of higher-ordered α-synuclein tetramers were diminished in blood from familial PD and sporadic PD patients compared to controls. Interestingly, the relative amount of α-synuclein tetramers was already decreased in asymptomatic G51D carriers, supporting the hypothesis that α-synuclein multimer destabilization precedes the development of clinical PD. Our data, therefore suggest that measuring α-synuclein tetramers in blood may have potential as a facile biomarker assay for early detection and quantitative tracking of PD progression.</p

Plasma extracellular vesicle tau and TDP-43 as diagnostic biomarkers in FTD and ALS

Minimally invasive biomarkers are urgently needed to detect molecular pathology in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Here, we show that plasma extracellular vesicles (EVs) contain quantifiable amounts of TDP-43 and full-length tau, which allow the quantification of 3-repeat (3R) and 4-repeat (4R) tau isoforms. Plasma EV TDP-43 levels and EV 3R/4R tau ratios were determined in a cohort of 704 patients, including 37 genetically and 31 neuropathologically proven cases. Diagnostic groups comprised patients with TDP-43 proteinopathy ALS, 4R tauopathy progressive supranuclear palsy, behavior variant FTD (bvFTD) as a group with either tau or TDP-43 pathology, and healthy controls. EV tau ratios were low in progressive supranuclear palsy and high in bvFTD with tau pathology. EV TDP-43 levels were high in ALS and in bvFTD with TDP-43 pathology. Both markers discriminated between the diagnostic groups with area under the curve values &gt;0.9, and between TDP-43 and tau pathology in bvFTD. Both markers strongly correlated with neurodegeneration, and clinical and neuropsychological markers of disease severity. Findings were replicated in an independent validation cohort of 292 patients including 34 genetically confirmed cases. Taken together, the combination of EV TDP-43 levels and EV 3R/4R tau ratios may aid the molecular diagnosis of FTD, FTD spectrum disorders and ALS, providing a potential biomarker to monitor disease progression and target engagement in clinical trials.</p

Numerical investigation of hydrogen charging performance for a combination reactor with embedded metal hydride and coolant tubes

A two-dimensional model investigating the hydrogen charging process in a combination reactor filled with both LaNi4.3Al0.4Mn0.3 and 2LiNH2-1.1MgH2-0.1LiBH4-3 wt.%ZrCoH3 materials has been developed. The selected configuration is a cylindrical reactor of 32 cm of diameter where the MeH is filled in annular tubes separated from the complex hydride bed by a gas permeable layer. The diffusion of hydrogen towards the two storage media is ensured by filters embedded in the middle of the MeH tubes whereas the coolant tubes are placed in the centre of their triangular arrangement. Simulation results have shown that the charging process depends on the MeH reaction heat required for the initiation of the CxH reaction as well as the heat management once the complex hydride starts to store hydrogen. High hydrogen storage rates and short refueling times can be obtained by increasing the number of MeH and coolant tubes and ensuring an efficient heat removal at the peripheral area of the CxH media. A refueling time of 3 min is achieved for an optimum configuration of 49 MeH tubes and 96 coolant tubes while increasing the thermal conductivity of the CxH media to 3.5 W/(m K). Such a result could make the identified optimum configuration as a suitable hydrogen storage system for fuel cell forklift trucks since it meets the requirements of this application in terms of weight and size

Investigation of a New Reactor Concept for Hydrogen Storage in Complex Hydrides

In der vorliegenden Arbeit wird ein neuartiges Reaktorkonzept für die Wasserstoffspeicherung in Metallhydriden im Hinblick auf automobile Anwendungen untersucht. Der Schwerpunkt der Arbeit liegt darauf, den Einsatz von komplexen Hydriden (CxH) zu ermöglichen. Diese weisen sehr hohe Speicherdichten auf, ihre Reaktionsgeschwindigkeit ist jedoch unter automobilen Randbedingungen sehr gering. In dem vorgestellten Konzept wird diese Limitierung aufgehoben, indem einem reinen CxH Reaktor ein Metallhydrid (MeH) in einem räumlich getrennten Bereich zugegeben wird. Ein solcher Kombinationsreaktor ist in der Lage große Mengen an Wasserstoff zu speichern und weist gleichzeitig eine ausreichend schnelle Dynamik der Sorptionsreaktion auf. Als CxH Referenzmaterial wird 2LiNH2 1.1MgH2 0.1LiBH4 3wt.%ZrCoH2 (Li‐Mg‐N‐H) verwendet und zunächst hinsichtlich der physikalischen Eigenschaften untersucht. Zudem werden zum ersten Mal Gleichungen für die Reaktionsgeschwindigkeit dieses Materials ermittelt. Auf Grund von thermodynamischen Überlegungen wird LaNi4.3Al0.4Mn0.3 als passendes Metallhydrid für den Kombinationsreaktor gewählt. Die ermittelten Stoffwerte werden dann verwendet um ein 2D Modell für die Reaktorsimulation aufzustellen. Zusätzlich zur Materialcharakterisierung werden in einem Laborreaktor Absorptionsexperimente mit einem reinen Li‐Mg‐N‐H Reaktor und einem Kombinationsreaktor durchgeführt. Anhand dieser Experimente werden die Modellgleichungen validiert. Das validierte Modell kann für zukünftige Reaktorauslegungen verwendet werden. Abschließend werden in dem Laborreaktor Desorptionsexperimente durchgeführt und durch Simulationen ergänzt. Letztere zeigen insbesondere das Zusammenspiel der beiden Materialien. Die im Rahmen dieser Arbeit durchgeführten Experimente und Simulationen zeigen, dass die Beladungszeit von 10 Minuten im reinen Li‐Mg‐N‐H Reaktor auf 2 – 3 Minuten im Kombinationsreaktor reduziert werden kann. Zudem wird während des Desorptionsvorgangs die Dynamik des Reaktors verbessert und die Ausnutzung der H2 Speicherungkapazität des Li‐Mg‐N‐H Materials erhöht. Im vorliegenden Referenzsystem wird die Gesamtspeicherdichte von 3.2 Gew.% für das reine Li‐Mg‐N‐H Material auf 2 Gew.% reduziert. Allerdings ist eine Beladung und Entladung unter Randbedingungen im Automobil nur mit dem Kombinationsreaktor möglich. Somit verringert der Kombinationsreaktor deutlich die reaktionskinetischen Anforderungen, die an neue Materialien mit hoher Speicherdichte gestellt werden

Considerations on the H2 desorption process for a combination reactor based on metal and complex hydrides

Hydrogen storage systems based on the combination reactor concept are promising for application of future complex hydride materials with high storage capacities and low reaction kinetics at moderate operating temperatures. In such reactors, a fast reacting metal hydride is added to a complex hydride material in a separate compartment of the tank combining the advantages of the high storage capacity of the complex hydride with the high reaction rate of the metal hydride. In the present publication, three issues regarding the desorption performance of such a reactor are discussed based on analytical considerations and 1D simulations. First, it is studied whether the optimal reactor design based on a tubular geometry that has been previously determined for the absorption reaction also enables satisfying desorption performances. It can be concluded from the corresponding simulations that based on the properties of the present reference materials LaNi4.3Al0.4Mn0.7 and 2 LiNH2–1.1 MgH2–0.1LiBH4–3 wt.% ZrCoH3, the hydrogen desorption performance of the materials in this reaction geometry is good. Second, it is shown that besides the geometry of the reactor, also its module size is important, as it can be crucial for the thermal management during the desorption. A methodology was developed that allows to analytically determine a first estimate for the best minimum module size configuration – only based on the desorption rate of the basic material. This approach is confirmed by time dependent 1D simulations applying a validated model for the reference materials. Third, the influence of a realistic periodic desorption load on the performance of a combination reactor is studied. The results clearly show that since the addition of a MeH material enables much smaller module sizes, it is advantageous for the thermal management of complex hydride based reactors and increases their flexibility

Preheating fuel cells at -20°C with metal hydrides using the pressure difference between tank and stack

*: [email protected] Fuel cells in vehicles have to be preheated in winter in order to expand service time and prevent ice formation. Metal hydrides can be used as solution to this challenge, as they can transform the pressure difference between hydrogen tank and fuel cell into heat. Until now, this potential energy stored in the high pressure hydrogen is throttled and lost. The working principle of a metal hydride pre-heater is the following: absorption of hydrogen at higher pressure into a metal hydride produces heat even at low ambient temperatures to preheat the fuel cell. Then, the lower pressure level of the fuel cell as well as waste heat enable desorption of the hydrogen from the metal hydride and the conversion in the fuel cell into electricity. At our institute a reactor designed to investigate the preheating application for fuel cell vehicles was developed. LaNi4.85Al0.15 was used as heat producing material inside a tube bundle heat exchanger to reach high thermal power. Vehicle temperature conditions were simulated via a thermostatic bath considering a thermal regeneration at 130°C against ambient pressure. Hydrogen was provided to the material in a temperature range between -20 and 20°C and a pressure range between 1 and 10 bar, and the thermal power transferred into the heat transfer fluid was measured. The study could verify high thermal power of metal hydrides at low ambient temperature suitable for automotive applications. The experiments showed that the 960 g of material could transfer a thermal power of up to 5 kWpeak at -20°C into the heat transfer fluid. Different influence factors on the thermal power were investigated, such as ambient temperature, hydrogen pressure and mass flow rate of the heat transfer fluid. The biggest influence on the thermal power showed the hydrogen pressure as can be seen in Figure 1