Now, it's true that amazing gains are being made in the efficiency of internal combustion engines, both gas and diesel: direct injection, cylinder deactivation, stop-start, eco-mode throttle mapping, to name a few of the recent applied technologies.
"We really and truly expect that fuel cells are going to double the fuel efficiency of the best internal combustion engines and in some cases triple it, " Roan said.
Technologies such as internal combustion engines and gas turbines will continue to improve gradually in efficiency but they are familiar and developed.