The hydrogen economy – Vision or reality? 1 1This paper is also published as Chapter 11 ‘The hydrogen economy – vision or reality?’ in Compendium of Hydrogen Energy Volume 4: Hydrogen Use, Safety and the Hydrogen Economy, Edited by Michael Ball, Angelo Basile and T. Nejat Veziroglu, published by Elsevier in 2015, ISBN: 978-1-78242-364-5. For further details see: http://www.elsevier.com/books/compendium-of-hydrogen-energy/ball/978-1-78242-364-5.