Quote:
Originally Posted by DracoFelis
2) BUT the laws of physics state that you will always be BEHIND in the energy equation, when you are using energy to make the hydrogen (vs say getting it in tanks of hydrogen gas you fill up from some other source). i.e. the laws of physics require that the energy used to make the hydrogen fuel (in the car, from the water) will ALWAYS BE GREATER than the energy you get from burning it.

That's true, but what you've gotta look at is where it comes from and where it goes. For instance at standard temperature and pressure, 20% or so of the energy required to separate O from H2 comes from environmental heat. Stick it in a warm engine bay and you could be up to only needing 60% in electrical power for the energy the H2 is worth. Then where does the energy go when you burn it? When burning gasoline, in an efficient engine only around 30% goes to developing cylinder pressure, the rest goes out in heat through the tailpipe and radiator. When you burn pure H2 in an IC motor, that maximum is somewhere around 50% going to cylinder pressure, with a theoretical maximum much higher than that, the efficiency there is basically restricted by the mass of the pistons and the reciprocating nature of the engine. If you burn a portion of H2 in a gasoline mixture it's possible that H2 comes much nearer it's theoretical efficiency, with the gasoline mixture kind of acting as a buffer, so it's probable that a given BTU quantity of H2 is "worth" twice to several times the equivalent BTU in gasoline... then there's synergistic efficiencies possible in the H2 which has a very low ignition concentration limit, increasing the efficiency of the gasoline burn through speeding the flame front and allowing less heat to escape, and more pressure to be generated.
Now this still doesn't seem right, because if you burn 33,000 BTU of gas to get 10,000 BTU of mechanical energy, you get 6,000 BTU of electrical energy out of the alternator, which is about what you get if you convert it to hydrogen, you typically get a minimum 20% extra free from thermal inputs, so it makes the actual 80% electrolysis conversion efficiency look like 100% (or more if your engine bay/cell gets toasty) So it takes 5.6 BTU worth of gasoline to make 1 BTU of HHO... if all your trying to do is make HHO
However, we're not running a motor to make HHO, we're running a motor to move us down the road....
So being fuel economy enthusiasts all our cars have 25HP motors that run at 55mph on the highway when your foot is pressed flat to the floorboards right? Fully open throttle, minimal pumping loss, thrashing along at peak efficiency using gas by the teaspoon.....
Ummm no actually, we have horrendously oversized motors that are considered "small" or barely adequate by your typical adrenalin fried motor journalist at 100HP outputs. So, barely cracked throttle, huge pumping loss, purring along at minimal efficiency using gallons.
So you put your 33,000 BTU worth of gas through the first motor and it takes you 5 miles, you put your 33,000 BTU through the second and you're delighted when you do half that. What gives? Well #1 put 23,000 BTU in to heating the atmosphere going down the road and #2 used about 28,000 of it doing that.
So all I need to do is go WOT and drive faster? Um no. If air resistance increased linearly with speed, this would indeed be an (unsafe) option.
So I can install really tall gears and slog along at 1000 RPM with the throttle wide open? Wellll you could.. you've reduced pumping loss, but the efficiency of the motor is both a function of RPM and load, you'd heat the atmosphere with 27,000 BTUs instead.
So can I load the motor in a way such that I gain efficiency? Yes make HHO.
But you just said it takes 5.6 BTU of gas to make 1 BTU of HHO??? Yep at peak efficiency it does.
WHAT? It takes MORE than 5.6 BTU to make 1BTU at low output???
Sure does.
So how in any way shape or form can that be more efficient???
Because you're using 33,000 BTU to do 5,000 BTUs worth of actual useful work in moving the car. (Overcoming drag) and because we're going to load the motor more and increase efficiency by doing so.
That will just burn through my 33,000 BTU quicker!
It might, but what say we save some of it.
Save it?
Sort of, we'll make HHO with it.
Aaaargh there you go again with the HHO.
Calm down, so, if we increase load by 5%
You mean you're just wasting 5% of my BTUs.
Gah, okay, we're "wasting" 5%
BUT efficiency has gone up to 18% you now do 5940 BTU worth of work in moving the car..
Less the wasted 5%
5643
WHA??? That's MORE. Why can't I just go faster again?
Because the energy to overcome drag increases exponentially, you'll not get a proportional increase in ground covered, you'll just heat more air.
Ah.
Yup. NOW do you wanna see what happens to the other 297 BTUs
Hum, I guess.
Okay so we take 297 BTUs of mechanical output, put it through the alternator and get 178 BTU of electricity, which gives us about 178 BTU worth of HHO
Big deal.
Yes but we expect to burn them in the motor at 50% efficiency, since gasoline is only at 18% efficiency at the moment, that makes that 178 worth 2.77X it's BTUage in gas... or about 500 BTU. So we put that in the motor...
And now I'm getting 6143 worth of BTUs worth of moving the car out of 33,000?
That's right, that's actually a 22% gain over what you were getting without claiming unsettlingly large efficiencies for burning hydrogen, or taking into account combustion enhancing aspects.
Right, but I'm still burning 33,000 BTU to get less than a fifth back in moving me, so even though I've gone from 30mpg to 36 mpg it still sucks.
That's right, TANSTAAFL and this isn't it, it's using more of what you already paid for instead of heating the atmosphere.
So tell me about the ArvinMerritor and MIT research that says that hydrogen can reduce the lean burn limit to 26:1, so I can crack the throttle wider and get closer to using 3040% of the go in my dino juice.
Next time young Padouin, the basics learn you must.