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Nicosia, Cyprus

Koultoukis E.D.,Z Energy | Koultoukis E.D.,Greek National Center For Scientific Research | Koultoukis E.D.,Aristotle University of Thessaloniki | Gkanas E.I.,Greek National Center For Scientific Research | And 7 more authors.
International Journal of Energy Research | Year: 2014

SUMMARY: A reliable process for compressing hydrogen and for removing all contaminants is that of the metal hydride thermal compression. The use of metal hydride technology in hydrogen compression applications, though, requires thorough structural characterization of the alloys and investigation of their sorption properties. The samples have been synthesized by induction - levitation melting and characterized by Rietveld analysis of the X-ray diffraction patterns. Volumetric pressure-composition isotherm measurements have been conducted at 20, 60 and 90 °C, in order to investigate the maximum pressure that can be reached from the selected alloys using water of 90°C. Experimental evidence shows that the maximum hydrogen uptake is low since all the alloys are consisted of Laves phases, but it is of minor importance if they have fast kinetics, given a constant volumetric hydrogen flow. Hysteresis is almost absent while all the alloys release nearly all the absorbed hydrogen during desorption. Due to hardware restrictions, the maximum hydrogen pressure for the measurements was limited at 100 bars. Practically, the maximum pressure that can be reached from the last alloy is more than 150 bars. © 2014 John Wiley & Sons, Ltd.

Zitko R.,Jozef Stefan Institute | Van Midden H.J.P.,Jozef Stefan Institute | Zupanic E.,Jozef Stefan Institute | Prodan A.,Jozef Stefan Institute | And 4 more authors.
International Journal of Hydrogen Energy | Year: 2011

Titanium borates show promising hydrogen storage characteristics. Structural relaxation around individual hydrogen atoms and the binding energies are studied by means of the density functional theory methods for a number of hydrogenated TiB2, TiB and Ti2B structures. Starting with the possible symmetric hydrogen sites a random structure searching has been performed, in addition to locate all energetically stable adsorption sites. It is shown that for the three bulk compounds considered, the lowest binding energies are obtained for TiB2 (in the 0.3-1.8 eV range), the largest for Ti2B (in the 3.9-4.7 eV range), while for TiB they are intermediate (in the 2.8-3.5 eV range). Calculations performed on hydrogenated Ti2B result in two energetically stable sites for two different starting environments, suggesting a possible soft mode solution. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Odysseos M.,Hystore Technologies Ltd. | De Rango P.,CNRS Neel Institute | Christodoulou C.N.,Hystore Technologies Ltd. | Hlil E.K.,CNRS Neel Institute | And 9 more authors.
Journal of Alloys and Compounds | Year: 2013

The present work has been aiming at the synthesis and study of a series of La1-xCexNi5 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8) alloys in an attempt to investigate possible alterations of the hydrogen absorption/desorption properties The alloys were prepared by induction melting of the constituent elements. The systematic characterization of all new compounds by means of XRD and hydrogen sorption measurements revealed the effect of the partial substitution of La with Ce on the crystal structure and the final hydrogen storage properties of the alloys. Extensive absorption/desorption experiments (Van't Hoff diagrams) have shown that such alloys can be used to build a metal hydride compressor (MHC), compressing H 2 gas from 0.2 MPa to 4.2 MPa using cold (20 C) and hot (80 C) water. © 2013 Elsevier B.V. All rights reserved.

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