[Vwdiesel] negative aspects of burning water

[Roger Brown]

James Hansen wrote:
> Terry Briggs wrote:
>  > the advantage of a diesel-electric hybrid, thats an easy one, you can
>  > use a much less powerful diesel engine and still have the torque of an
>  > engine 3 times the size of what you are using and still get great
>  > mileage {comparatively}. It's being used now for that very reason
>  >
> 
> Is it really an easy one?
> 
> Have you considered the efficiency losses Terry?  If you can't do 100mpg 
> with a hybrid, it really isn't worth the extra energy footprint to make 
> assemble and carry around all the stuff to have the hybrid.  A lupo does 
> in the 90's with a simple 3 cylinder tdi, so a diesel hybrid better do 
> more than that, or you're just chasing your tail.
> 
> Diesels only use as much fuel as needed to make the power required at 
> the time, unlike a gas engine.  To expound on that, cause it seems to be 
> falling on deaf ears at present... all the air going through a gas 
> engine has to be at stoich mix fuel to air ratio, or the motor grenades 
> eventually.  Diesels have no such constraint, so they will run very 
> efficiently throughout the range of power requirements and rpm.  If you 
> run a diesel at low power requirements, you essentially HAVE a much less 
> powerful motor, until you stomp on it- if you design a car to need 10hp 
> at 60mph, your diesel motor will be making 10hp, and using a 
> corresponding amount of fuel. The only loss in a diesel over a gas is 
> the pumping losses of moving the unthrottled air through the motor.
>   A gas motor cannot run at much less than stoich mix, hence the 
> tremendous gains in efficiency in running it at a constant speed at max 
> efficiency to generate power a la hybrid.
> 
> Trick is, each step in the hybrid train has efficiency losses. 
> Generation, storage, regulation, transmission, usage, do not have 100% 
> efficiency.
> 
> I'm curious if anyone has run the numbers in this.  Roger, you're a 
> clever fellow.  If you're following along, do you have any top of the 
> head guestimates on losses in each of the steps a hybrid goes through 
> with it's energy production, regulation, storage, sharge control, etc?
> 
> thanks
> -james
> 
> 

I saw one overall number that stated the regenerative braking -> battery storage overall 
efficiency is about 75%.  Probably looking at a 5%-10% loss through each stage of the system.

I wonder what you could do with a highly optimized diesel engine built to run at a single, 
constant speed feeding an alternator similarly designed.  Then have that feed an electric 
motor and batteries.  Size the engine to just have enough power for highway cruising.

-- 

   Roger