

What happens when coal is gone? - froggy
http://www.scientificamerican.com/blog/post.cfm?id=what-happens-when-coal-is-gone-2010-06-29

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AngryParsley
_"It’s fundamentally impossible to improve on jet fuel because it would break
the laws of physics", pronounced Laughlin. "You can’t have airplanes unless
you make hydrocarbon fuel."_

If electrical energy was cheap but hydrocarbons were expensive, it would be
cost-effective to electrolyze water into hydrogen and oxygen. By mass,
hydrogen is the most efficient way to store chemical energy. By volume, it's
not so efficient, and currently storage is difficult. Still, 200 years from
now I think materials technology will have advanced a little.

Another option is nuclear-powered aircraft.
(<http://en.wikipedia.org/wiki/Nuclear_aircraft>)

Yet another pie-in-the-sky option would be to beam power to the airplane
(either from satellites or ground stations).

I'm no physicist, but I think I just listed three ways airplanes can exist
without hydrocarbons.

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lutorm
You can run jet engines on ethanol, too. It's slightly less efficient by
volume than kerosene, but surely it beats hydrogen.

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anthonyb
Ethanol is basically a hydrocarbon anyway.

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nevinera
>"It’s fundamentally impossible to improve on jet fuel because it would break
the laws of physics", pronounced Laughlin. "You can’t have airplanes unless
you make hydrocarbon fuel."

This guy's a physicist? The claim is absurd, unless he's rolling economics
into the bucket - especially as he's talking decades or centuries from now.

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lutorm
By the time we've burned all coal, global warming will be way out of control
unless CCS systems are ubiquitous. All studies I've seen point to coal
reserves being far, far larger than the atmosphere can handle.

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rdl
The challenge is definitely liquid fuels for transportation, especially
aviation. Stationary applications can easily go electric, and conceivably
maritime transport could go to electric powered by nuclear or bulky non-
hydrocarbon fuels, but aviation is weight and volume limited.

The US Air Force has a goal of qualifying all of their aircraft to fly on
biofuels by 2011; they've flown B-52s and other aircraft on 50-100% biofuel
mixtures. Currently, most biofuels for aviation use cost several times what
petrochemicals cost, but I could definitely see this changing. It's actually
pretty easy to get a jet turbine to run on anything, but the difficulty is
more with qualifying the entire storage/supply chain to be stable, and
stability at temperature extremes. If the Air Force can transition to
biofuels, it will be relatively easy for scheduled commercial flights to
transition.

Given relatively cheap electricity to input, there are plenty of processes to
make liquid hydrocarbon fuels -- algae biodiesel, some forms of intensive
agriculture, and CO2 sequestration from the air, as are pointed out in the
article. These would be "carbon neutral" in terms of atmospheric CO2 as well.

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philwelch
Nuclear-powered maritime transport been a solved problem for decades. (It's a
fairly easy solution, too. Conventional steamships have boilers which generate
steam from seawater, which through a significant amount of gearing turns the
ship's propeller, and through a turbine-generator system generates the ship's
electricity. Nuclear powered ships replace the boiler with a nuclear reactor,
but are otherwise identical.)

The only reason not all US Navy ships are nuclear is because you can get
better performance for frequently-resupplied, less-than-supercarrier-size
vessels with gas turbine engines (literally off-the-shelf jet engines
exhausting underwater). The fuel is even the exact same as aviation fuel, so
you only need your resupply ships to carry one type of fuel.

~~~
rdl
The unsolved issue in nuclear maritime is making it cost effective, including
all life-cycle costs. The US actually had a couple commercial transports which
were nuclear powered (NS Savannah being the main one,
<http://en.wikipedia.org/wiki/NS_Savannah>) , and the USSR built a few
icebreakers and supply vessels, a few of which are still in operation.

~~~
philwelch
Cost-effective is comparative. If there was a severe shortage of other
maritime fuel, we'd be stuck between nuke and sail.

~~~
rdl
True; and according to NS Savannah's reports, it actually would have been
viable during the 1970s.

I wonder if there would be a business in either operating nuclear civilian
ships, or outsourced reactor build and management. The irony being that some
of the best prospects would be nuclear Very Large Crude Carriers.

The other reason the Navy doesn't want 100% nuclear (and kept ships like the
Kitty Hawk around) was some countries are weird about nuclear warships
specifically transiting their waters; some are anti civilian nuclear too, but
are generally more anti-nuclear warship.

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theprodigy
I think coal will last us for a while and we should over time be diversify our
energy sources. Which America is looking to do more now. For instance, some of
the power generated from coal should be generated with nuclear, solar, etc.
This should bring down the rate of coal consumption and allow us to extend our
usage of coal in producing energy for a longer period of time.

So I think energy diversification is the key.

Also, I think nuclear is a great alternative to coal,but for it to be a global
option there has to be a lot of stuff done foreign policy wise and in the
global security space.

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redrobot5050
Next gen nuclear reactors could use liquid thorium or some other isotope.
While there would be a possibility of a foreign nation developing 'dirty
bombs' its a much safer way than dealing with the possibility of something
that could be refined into weapons-grade nuclear materials.

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patrickgzill
There are huge seams of coal in China that have been burning for hundreds of
years. In Centralia, PA there is still a lot of coal around even though the
coal fire there has been burning for some 40 years. We are not going to run
out of coal for hundreds of years...

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MrRage
But are these coal seams burning as fast as if you mined them and burned it
for heat, electricity, etc?

