> I am still wondering where the energy will come from to heat the sugar?
Sucrose (and several other sugars) is C12H22O11
In combustion of sugar the end products are water and CO2
You can think of this being 11 x H2O + 12 x C
or 22H + incomplete CO2 needing extra Oxygen.
Energetic concerns and structure (crudely put) govern what actually happens.
From the above you can see that the claim in the web page cited
europe.cnn.com/2002/TECH/science/08/28/sugar.cars.reut/index.html
is, at best, incomplete as more Oxygen is need to make CO2
viz
"The research, to be published Thursday in the science journal Nature, found
that heating the sugar solution to 392 degrees Fahrenheit and passing it
over a platinum-based catalyst broke it down into hydrogen and carbon
dioxide."
[[392F = 200C]]
It requires more Oxygen to get CO2 plus Hydrogen.
The conversion described is probably catalytic with respect to the Platinum
and probably adds Oxygen with a net energy output to drive the process. The
overall result is probably LESS energy from the Hydrogen combustion than
from Sugar combustion BUT having pure Hydrogen is useful. I haven't heard of
a fuel cell that runs on sugar yet :-).
The conversion process can probably provide process heat for some other
activity.
Sugar makes a respectable rocket fuel but is not as "good" (energetic) as
the pure Hydrocarbon "rubbers" in use in rocket fuels (eg PBAN in the Space
Shuttle boosters or the slightly superior HTPB which is similar to the
rubber in car tyres.).
The "probably" watchdog is going to bite me if he reads all the foregoing
:-)
> I am still wondering where the energy will come from to heat the sugar?
From the article:
"Our goal in a perfect situation would be to achieve a process where
25 percent of the hydrogen would be used to heat the solution with the
remaining 75 percent free to be used as fuel," Dumesic said. "But we
are a long way from that."
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You caught me... I didn't read the article. Though it seems to imply
something along the lines of perpetual energy as long as you are stuffing
sugar in the tank. Maybe I am oversimplifying it.
{Original Message removed}
> You caught me... I didn't read the article. Though it seems to imply
> something along the lines of perpetual energy as long as you are stuffing
> sugar in the tank. Maybe I am oversimplifying it.
Yeah, that is a bit oversiplified. You neglected the fuel input. That's
like claiming your car gives you perpetual thermal energy because the heater
will keep producing heat as long as you keep putting gas into the gas tank.
Actually, a car is a very good analogy for this situation. The flywheel
keeps the engine turning as long as there is more gas being input
(neglecting stalls, and yes, this is a simplified case), but a starter is
required to start the engine turning. Equally, the some of the output
hydrogen will keep the decomposition chamber hot, while more sugar gets
input, but to start the process it requires another heat source, since there
isn't any hydrogen yet.
Regards,
--Brendan
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>I am still wondering where the energy will come from to heat the sugar?
They are saying in the article that they are at the point where 50% of the
extracted energy is used to heat the sugar. They want to get to 25% for
heating.
Peter
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>Peter L. Peres wrote:
>
>> www.cnn.com/2002/TECH/science/08/28/sugar.cars.reut/index.html
>>
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>Begs the question,
> If x amount of sugar can produce y amount of energy , how much energy z
>did it take to produce and refine the sugar?
The real question is, will machines compete with people for food ?
The sugar they use is glucose, and that is not so 'refined'.
sugar/fructose syrup, aka molasses when concentrated, is what you get when
extract sugar from beets or cane. This is done by crushing them in a mill
and then boiling them in water. This is a simplistic description of the
process but everything else has got to do with hygiene and increasing
yield. Check the price of refined sugar vs. fuel (mass for mass although
comparing by energy content would be better).
Peter
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> > > I am still wondering where the energy will come from to heat the
sugar?
> >
> > From the article:
> > "Our goal in a perfect situation would be to achieve a process where
> > 25 percent of the hydrogen would be used to heat the solution with the
> > remaining 75 percent free to be used as fuel," Dumesic said. "But we
> > are a long way from that."
> >
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> >
> >
>
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>
>
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