The development and preliminary tests of a 5 kg Mg2FeH6 heat storage system which is useable for short and long-term storage applications at temperatures around 500 degrees C are described. The heat transfer for the heat storage process (dehydrogenation of the hydride Mg2FeH6) and heat release (hydrogenation of the hydride precursor 2Mg-Fe) is done by the flow of molten salt in appropriate heat exchangers serving as heat source or heat sink. The construction of the tube bundle reactor as a heat storage tank is presented. 1.6 kWh of heat could be released and 1.5 kWh of heat could be stored during the first experimental tests. Difficulties, which occured during the preliminary tests, are described. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.