The emerging energy web M. Ajmone-Marsan, D. Arrowsmith, W. Breymann, O. Fritz, M. Masera, A. Mengolini and A. Carbone Eur. Phys. J. Special Topics, 214 (2012) 547-569 Published online: 05 December 2012 DOI: 10.1140/epjst/e2012-01705-1