The substitution of the high-purity and expensive raw materials vanadium (V) and titanium (Ti) by their low-cost, low-purity alternatives ferrovanadium (FeV) and Ti sponge in Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5 was investigated and the microstructural, thermodynamic and cyclic properties were tested of these compounds. Four different samples were prepared and studied: one material
In view of hydrogen based backup power systems or small-scale power2gas units, hydrogen storages based on metal hydrides offer a safe and reliable solution. By using Hydralloy C5 as suitable hydride forming alloy, the present tank design guarantees very simple operating conditions: pressures between 4 bar and 30 bar, temperatures between 15 °C and 40 °C and minimal efforts for thermal management in combination with fast and constant charging and discharging capabilities. The modular tank consists of 4 layers with 5 reactor tubes each that are filled with metal hydride-graphite composites of a diameter of 21 mm. Experiments show that each layer of this tank is able to desorb the desired amount of hydrogen for a fuel cell operation at electrical power of 160 Wel for 100 min reaching a utilization factor of 93% of the stored hydrogen at RC. Furthermore, the experimental results of modularity, increasing loads and the electric air ventilation are presented
Recently, metal hydride composites (MHC) have been proposed which consist of a hydride forming metal alloy and a highly heat conduction secondary phase such as expanded natural graphite (ENG) in order to improve the thermal conductivity of metal hydride powder beds. However, only little data is available in the literature on the effects of extensive cycling on technically relevant properties of MHC. In this paper, hydrogenation characteristics, thermal conductivity and geometrical stability of Hydralloy (R) C5-based MHC were thoroughly investigated over 1000 cycles. The obtained results suggest that the MHC under study did not significantly alter their hydrogen uptake characteristics throughout cycling, despite the fact that their thermal conductivity decreased during the first 250 cycles but remained constant thereafter. Although the cylindrical MHC maintained their geometrical stability, radial cracks were detected after cycling. Based on these results, MHC are suitable for high-dynamic applications such as hydrogen storage or thermochemical devices
Abstract:The German Aerospace Center has merged a wide range of technological research and development for future cars in a project called "Next Generation Car". Within this large research project, three vehicle concepts for different applications (urban, regional and interurban) and with different powertrains (fuel-cell, battery and hybrid) will be developed. Research questions on different levels from conceptual question about vehicle modularity down to detailed technological aspects like combining hydrogen storage with cabin climatization and a systematic investigation of different thermal energy storage systems for electric vehicles concepts are covered by this project. To the latter, the contribution shows an overview about three thermal storage technologies-sensible solid media, metallic latent and thermochemical thermal energy storage systems-and details about the development of an electrically heated (power-to-heat) solid media storage system to achieve high storage densities and to allow flexible thermal discharging values. Central works target the identification of suitable thermal management solutions in future electric vehicle concepts to increase range, efficiency and flexibility.
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