Fuel cells are definitely an important part of the mix.  For cars batteries are fine in the city but they do not have the range for other things.  Even for ones in research energy density is a problem.  Hydrogen fuel cells are being used and catalysts and electrodes are improving in efficiency, durability while getting much less expensive. Ethanol fuel cells are being tested in Brazil that has a large ethanol fuel system.  Ethanol is easier to handle than hydrogen and there is a process the takes CO2 +energy to produce ethanol so no bioethanol necessary but rather a temporary  CO2 sequestration.