What happens when coal is gone? | Hacker News Reader

What happens when coal is gone?

scientificamerican.com

24 pointsfroggy18 comments

"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.

Here's a fourth : Blimps.

Blimps are slow. Also blimps are not planes.

And for about $200 a barrel, you can use nuclear power to make that same hydrocarbon fuel out of thin air.

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

Ethanol is basically a hydrocarbon anyway.

None of those options seem particularly viable, even given advanced technology:

* Nuclear has trouble with radiation shielding - not good for passenger planes unless you make enormous planes with a couple of thousand passengers.

* Beaming power is going to cook birds along the route

* If you're going to the trouble of making hydrogen, which is notoriously hard to store, you might as well just make jet fuel instead.

>"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.

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.

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.

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.

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.

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

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.

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.

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.

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...

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

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