[ExI] Fwd: Cheap fuel from coal and solar

Keith Henson hkeithhenson at gmail.com
Wed Oct 18 17:41:11 UTC 2023

--------- Forwarded message ---------
From: Keith Henson <hkeithhenson at gmail.com>
Date: Mon, Oct 16, 2023 at 2:17 PM
Subject: Cheap fuel from coal and sola

We are going to need fuel for a considerable time.

>From the dawn of the industrial revolution,

H2O + C → H2 + CO (ΔH = +131 kJ/mol)

The reaction is endothermic, so the fuel must be continually re-heated
to maintain the reaction. (Wikipedia)

Carbon is 12 gm/mol. 83 mol/kg and a kg would soak up 10900 kJ. A
metric ton of carbon evaporated in steam would need 10900000 kJ or
3.03 MW hours.

This would produce 1/6th of a ton of hydrogen with a combustion energy
content of 50 MWh/ton, about 8.3 MWh. CO combustion is 10.1 MJ/kg. We
have 2800 kg or about 7.85 MWh. So we make about 16 MWh of gas from a
ton of coal and 3 MWh of renewable electric power. Most of the energy
in the gas is from the coal.

A few years ago a 900 MW solar PV project in the Mideast signed a
power purchase for 1.35 cents per kWh so I think $20/MWh works for a
rough economic analysis.

Following a ton of coal, the syngas from a ton would cost ~$20 for the
coal (plus shipping) and $60 or less for the intermittent power.  Call
it ~$80/ton.

Half a ton of carbon would be pulled out in the water gas shift
reaction to get the hydrogen ratio up to where you need it for F/T
input.  500 kg of carbon and 1/6 of that in hydrogen should show up in
the product.  The F/T energy loss is about 25%, not sure about the
material loss or where it might go.  .583 ton x 7.3 bbl/ton is 4.26
bbl. or $18.80 /bbl.

That's down near or below the production cost for oil.  Of course, the
F/T capital cost has to be added to this plus the completely unknown
cost of the arc gasifiers.  The Orxy plant cost is ~$8/bbl (ten-year
write-off) but that was in 2007 dollars.  What comes out of an Oryx
plant is a refined product rather than crude oil making it more
valuable than crude

Most big energy projects when you analyze them are just silly.  This
is not something you can reject out of hand.

This does not help with the build-up of carbon in the atmosphere, but
we will have to do air capture anyway.

Please check the math.  Age is making this harder and harder.


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