For now fossil fuels are hard to replace and no real technological leaps in the near future. Look at fuel cells, they have yet to deliver on promises. Batteries are getting better (more abuse tolerant), but still power or energy density remains low by comparison to fuel.
Hybrids are good for stop and go, but VW diesel actually gets better mileage at highway speeds then Prius or it did a few years ago. What was discussed earlier is a “series hybrid” the train locomotive example which does better at low speeds. At mid to high speeds parallel hybrids do better, that is in which both electric motor and internal combustion engine share load, or electric motor handles getting it moving and engine augments power as required and also charges battery. At high speed say 80+ MPH a well designed engine is best.
I guess from a “fun” standpoint a series hybrid would be the way to go. Motor in each wheel hub and it could turn on a dime like a tank (wheels turn opposite to each other and it almost spins in place). Perhaps 2 gen sets (engine generator combination) giving it some redundancy while being able to be economical when needed or serve as power station for small community. Diesels will run on vegetable or reasonably easily derived oils, so that would be fuel of choice I would guess.
The advantage to electric motor in wheel hub would be that it is more efficient then all 8 wheels mechanically coupled. The inverters could be set up to deliver torque as required or send power to the wheel that is not spinning. Then there are also active handling possibilities, but beyond the scope of conversation here.
Battery pack size, that’s a tough one. Perhaps treat it like city bus and use it for initial acceleration and store some regenerative braking energy. Also have a small quiet range in which truck is almost silent, because it is running on batteries only. But remember your discharger to charge ratio, usually 5:1 or you can discharge battery 5x faster than charge. You mentioned super-capacitors, those are still very unproven at high energy levels that would be required for 8x8 (never mind the size).
As far as diesel noise, not sure if have heard new Volvo truck, when that turbocharger gets spooled up it sounds more like a turbine than anything else, it surprised me first time I heard it.
Now if you want to go out on the fringe, Purdue has shown aluminum with something added (can’t remember details) will split water into hydrogen and oxygen which can be burned. The aluminum gets reduced to an oxide when done… But I wouldn’t go there.
Not sure what if anything was added, so sorry if this got dragged off topic.
