The hitch in this case is that if we ever see such a car, Daimler's R&D chief believes 2020 or 2025 would be the window for its appearance. The technologies aren't concept-only, or as out-there as using thorium for power, but scaling up to passenger car sizes and standards might be a decade or more out. The return: an S-Class with an emissions-free range of 621-miles.
That might sound like overkill, but as of now only one S-Class undercuts the European average for vehicular CO2 emissions. With the noose tightening in 2015 and even tighter strictures in 2020 and 2025, Mercedes (and plenty of other automakers) will need to position itself for 2025 and beyond.