[Beowulf] Re: "hobbyists" still OT

Robert G. Brown rgb at phy.duke.edu
Thu Jun 26 03:30:17 EDT 2008


On Thu, 26 Jun 2008, Jon Aquilina wrote:

> taking this thread off on another tangent here though. using bio fules might
> be good for now but is actually creating lots of problems. the end all
> solution would to be to use hydrogen as the fuel source. put water in the
> car gets broken down through hydrolysis and the water which is exhaust is
> recycled back into the system. no need for fueling stations because a
> convenient source of water would be your outside your door

I'm trying to let the thread die because it is way OT and because I'm
packing to leave for my "teach at the beach" summer.  But note well --
the fundamental issue isn't really "burn this" or "burn that" sythetic
fuel (defined quite loosely as a fuel that is manufactured or assembled
by humans out of parts that are not themselves fuel, e.g. hydrogen
(fuel) produced out of water.

The issue is what is the source of free energy that will be used to do
the synthesis, put the energy INTO the fuel.  It takes energy to
electrolyze water.  It takes energy to grow corn and turn it into
alcohol.  It takes energy to grow oilseed crops and turn them into
biodiesel.  The free energy source might be the sun, it might be fossil
fuels (indirectly the sun), it might be plants (the sun), wind (the
sun), hydroelectric (the sun) -- hmmm, with the exception of geothermal
and nuclear, looks like nearly everything is the sun.

Stored sunlight is in finite supply in fossil fuels.  Plants grow slowly
and require more than JUST sunlight to produce energy, so a fair bit of
energy yield has to be turned right back into fertilizer, fuel for
tractors or oxen, humans to grown and transport it, the refining or
extraction process.  Using THIS fuel to produce hydrogen would simply
layer inefficiency on inefficiency, as one would throw maybe 70% of it
away in the process, and then throw a fair bit of what remained away in
the final stage of energy release as work.  The laws of thermodynamics
cannot be broken, not really.

This suggests that in the long run, the only free energy sources likely
to be able to keep up with human demand are the sun, implemented as
DIRECT conversion through solar cells, concentrators, turbines, and
perhaps thermonuclear fusion (not fission).  The deuterium or helium
supply of the planet is relatively inexhaustible compared to other
fossil fuels, and more could be mined from other planets in the solar
system if need be.

So sure, hydrogen is great, once you have the free energy source.  But
FIRST you need that, as hydrogen doesn't WANT to come out of water
molecules.  You have to make it come off.

   rgb

>
> On Wed, Jun 25, 2008 at 6:04 PM, Mike Davis <jmdavis1 at vcu.edu> wrote:
>
>> Vincent Diepeveen wrote:
>>
>>>
>>> Some 3d world country managers are begging to adress this issue: "My
>>> nations people die,
>>> as your bio fuel raises our food prices, the poor are so poor here, they
>>> use that stuff as food
>>> and cannot afford it now".
>>>
>>> USA nor Europe can *never* produce that stuff as cheap as 3d world
>>> countries can.
>>>
>>> Since my uncle held a patent on an Alcohol Fuel still, and my grandfather
>> grew corn, I have a somewhat different view. I'm not sure where your
>> information is coming from. According to http://www.earth-policy.org/, the
>> US produced 414 Million tons of grain last year. Of that total 81 Million
>> tons were used for fuel and 106 Million tons were exported. While it might
>> be less expensive to produce grain in the 3rd world, the top exporter of
>> Corn, Rice and Wheat for the world is the US.
>> http://www.earth-policy.org/Updates/2008/Update69_data.htm#table10
>>
>>
>> http://www.earth-policy.org/Updates/2008/Update69_data.htm#table9
>>
>> Now since corn prices have been rather stagnant until recently for almost
>> 30 years and since I know farmers that have burned corn for heat rather than
>> sell at a loss. I see the increase in grain prices as neutral. Yes, there
>> are bad results for the third world. But those farmers growing grain deserve
>> a fair price for the work and uncertainty of agriculture.
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>
>
>
>

-- 
Robert G. Brown                            Phone(cell): 1-919-280-8443
Duke University Physics Dept, Box 90305
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Web: http://www.phy.duke.edu/~rgb
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