[ExI] Sandia and energy

[Keith Henson]

On Sun, Dec 20, 2009 at 4:00 AM,  BillK <pharos at gmail.com> wrote:

> On 12/19/09, Keith Henson wrote:
>>  Bill, for basic science reasons that's nonsense.
>>
>>  It would take more energy than a power station is making to convert
>>  the CO2 it puts out into liquid fuel.  So a coal plant would have to
>>  be surrounded by square miles of solar collectors.
>>
>>  It's only when you have solved and oversolved the energy source
>>  problem that making liquid fuels from CO2 makes sense.  The energy
>>  source is what's important, not the well understood chemistry of
>>  making liquid fuels.
>>
>
> You didn't read their press release, did you?

I did, and further I understood it, unlike the funding agency.

> They are not using miles of solar collectors. They intend to use
> parabolic dishes to make a solar furnace to get the thermal energy
> required.

Bill, parabolic mirror concentrators will make a small area very hot,
but they do not increase the collected energy.   They are not magic.
If you need a GW of power to drive the chemical reaction, then (at 100
W/m^2 time average) you need 10E9W10E2W/m^2 or 10,000,000m^2 or ten
square km.

> But this is only a proof of concept plant at present.

No kidding.

> That's why they estimate 10-15 years to improve efficiency and for the
> price of oil to increase and greater need to extract CO2 from the
> atmosphere.

They are *not* going to increase the efficiency beyond the theoretical
limit for the energy it takes to break chemical bonds.  Or rather, if
they do, we will be living in a magical world where where the laws of
termodynamics have been repealed.

And it is not hard to pull CO2 out of the atmosphere,
http://people.ucalgary.ca/~keith/AirCapture.html  100 kWh/ton will do
it. That's a small part (2%) of the energy you need to make the CO2
into hydrocarbons.

> From: Eugen Leitl <eugen at leitl.org>
>
> Energy is a given, but you need good scrubbers, mild conditions,
> preferrably electrochemistry or photochemistry to drive the
> water+carbon dioxide reaction, catalysts and such. And of course
> if you make, say methanol, you need stable, cheap catalysts for
> the inverse reaction. There are certainly encouraging noises
> being heard in that direction, but it's all pure research for now.

Hardly.  Sasol has a 34,000 bbl/day plant in Qatar and there are a
number of other such plants around the world.  The plant in Qatar cost
a billion dollars.  It is being fed with partially oxidized natural
gas, but would run just the same on hydrogen and CO2 from the air.

> The problem with practical processes and plants out there doing
> them is plenty of time and money. We don't really have the time
> anymore, and we pissed away the money as well. Nevermind the skills,
> good chemistry people are extremely scarce now as the discipline
> has gone out of fashion.

The particular chemistry needed has been around since the Germans were
making liquid fuels our of coal in WWI.

http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process

Keith