An innovative, efficient and large hydrogen liquefier is described. Innovations lie in the fact that (i) the feed, 10kgs(-1), is refrigerated in heat exchangers catalytically promoting the ortho-para conversion (ii) down to the low temperature of 20.5 K and at the high pressure of 60 bar at which it is available and (iii) lastly expanded to the storage conditions of 1.5 bar and 20K through a liquid-phase turbomachine; (iv) refrigeration is via four helium recuperative Joule-Brayton cycles arranged so that the refrigerant follows the cooling curve of hydrogen and the volume flow rates in compression and expansion processes are typical of axial-flow high-efficiency turbomachines; (v) compression is accomplished in 15 intercooled 8-stage devices derived from gas turbine technology. Heat exchangers require specific surfaces comparable to current state-of-the-art liquefiers. Nevertheless, the predicted work of approximately 18 MJ kg(-1) is half as much as the requirement of those liquefiers and corresponds to a second-law efficiency of almost 48%. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.