In Part A of this manuscript which consists of two parts, the experimental investigations pertaining to the absorption of hydrogen in an LmNi(4.91)Sn(0.15) based solid state hydrogen storage device with embedded cooling tubes (ECT) are presented. Two metal hydride based hydrogen storage devices with 36 and 60 ECT filled with 2.75 kg of LmNi(4.91)Sn(0.)15 were fabricated. Performances of the hydrogen storage devices in terms of hydrogen absorption rate and amount of hydrogen absorbed are reported for different supply pressures (10-35 bar), absorption temperatures (20-30 degrees C) and cooling fluid flow rates (2.2-30 l/min). At any given absorption temperature, the rate of hydrogen absorption and the amount of hydrogen absorbed are found to increase with hydrogen supply pressure up to about 35 bar. At the supply condition of 35 bar hydrogen pressure and 30 degrees C absorption temperature, with oil as a heat transfer fluid at a flow rate of 3.2 l/min, the maximum amount of hydrogen absorbed are approximate to 1.18 wt% in 10 min for 36 ECT, and 8 min for 60 ECT. At the absorption condition of 25 bar supply pressure, 30 l/min water flow rate and 30 degrees C absorption temperature, the absorption time of the reactor with 60 ECT was reduced to 5 mm. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.