Aren't most big military ships nuclear powered? Submarines were diesel/electric hybrids until nuclear came into the picture there.
Fighter jets all use gas turbine engines that produce astronomical amounts of thrust (burning an equally astronomical amount of kerosene) and weight reduction is of the utmost importance. A battery and electric motor that could produce a tiny fraction the power would weigh more than the whole rest of the plane. Besides, military and efficiency are oxymorons.
More important for fuel efficiency is probably the ability to wait until there is really a load for the engine before running it. At low power levels combustion engines - especially otto cycle engines - are very inefficient. Darned Carnot ratio. Diesels are better about that.
You're very right about the storage size for regeneration/acceleration. For passenger vehicles the gross weight is a design number, and choosing a target top speed gives the amount of energy needed for that mission. I think that's why Honda went with ultracapacitors for their concept car; if you don't need massive storage and the ability to hold it a long time, the high charge/discharge rates of capacitors are very attractive.
I think Toyota is working on that for the European market.
Go figure... 95% of the diesels we get over here are crap.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.