This invention provides a reversible hydrogen loading and discharging system and a reversible method for loading and discharging hydrogen. The system and the methods of this invention comprise ethylene glycol as a liquid organic hydrogen carrier and at least one transition metal. By reacting ethylene glycol with at least one transition metal; at least one hydrogen molecule and at least one oligoester of ethylene glycol are formed (hydrogen releasing)⋅, and by reacting at least one oligoester of ethylene glycol with at least one transition metal and at least one hydrogen molecule, at least one ethylene glycol is formed (hydrogen loading).