New fuel from seawater?

[simmo]

Picked this up from another forum relating to motorbikes and found it pretty interesting. The science to it is pretty groundbreaking would have to say. I wonder if it was one of those experiments where someone joked well why don't you try seawater ha ha... And low and behold.

http://newenergyandfuel.com/http:/newenergyandfuel/com/2014/04/09/us-navy-making-hydrocarbon-fuel-from-seawater/

http://digitaljournal.com/news/politics/usa-navy-s-ability-to-make-fuel-from-seawater-a-game-changer/article/379930#ixzz302D72Lii

Happy reading
Simmo ;)

[Rob P]

And some more from the IFLS website http://www.iflscience.com/technology/using-seawater-create-jet-fuel

[Astro_Bot]

Very interesting. And there's the added benefit of removing dissolved CO2 from seawater. :thumbsup:

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But IFLS mention something odd:


They missed an important point: all USN aircraft carriers are already nuclear powered. There's really only one other type of ship that uses a large amount of jet fuel, and that's a large amphibious ship with a substantial air wing. It is indeed not too much of a stretch to build future classes of these very large ships with a nuclear powerplant, at least for the USN.

But solar?

Perhaps it's an interesting diversion to find out if either or both of these sources can feasibly supply the required energy, and since I had some spare time ...

To give an idea of the size of solar or nuclear installation needed to generate the daily jet fuel requirement of a USN aircraft carrier, just look at the energy density of jet fuel, the estimated amount used per day (in wartime) and the efficiency of 92% given:

Typical fighter fuel load: 10000 litres (assume all fuel used)
Wartime sorties per day: 160 per day for 30+ days
Energy density of JP5/F44/AVCAT: ~35MJ/L

Therefore we need 56 million MJ daily, or 56 x 10^12 Joules per day.

With efficiency of the onboard fuel generation process at 92%, required electric power output is therefore: 1/0.92 x 56 x 10^12 / (24 x 60 x 60) Watts = 7.05 x 10^8 W = 705 MW.

Nuclear: The A1B model fitted to new USN carriers (CVN 78/Gerald R. Ford class) is, in aggregate, in the 500+ MW class, so it's not too much of a stretch to provide this power from a nuclear source - just double the nuclear power plant in new build ships, and you're pretty much there - and since the new reactors are smaller and less maintenance intensive, that's not too hard. So, this does seem feasible for a modern nuclear-powered carrier.

Solar: Full sunlight at noon is around 1100W/m2, but not all of that light reaches the solar cell - haze, sun at an angle, dust/salt on cell surface, night, rain/fog, etc. will reduce the incident light reaching the cell, so the average is in fact only ~164W/m2 over any given 24-hour day (around the world).

Solar cells are rated by efficiency - how much incident light energy is converted to electric power. The best lab result for efficiency, with the newest technology in perfect conditions, is 44%. We'll assume these cells are used, so to get 705 MW, we need 4.3 x 10^6 m2. But, only one side of the ship can face the sun, and there are many practical restrictions on where solar cells could go (in sub-optimal generating conditions), so the capacity installed needs to be much greater - I'll assume by a factor of 2. So, to get that 705 MW, you actually need 8.6 x 10^6 m2, or roughly 9 square kilometres!!

So, solar generated jet fuel on a carrier? Err, no! ;)

[simmo]

Nice pickup there astro bot and we'll researched.

Perhaps the solar would be for land based supply facilities for aircraft carriers and land based aircraft. Once away from land the ships go it alone and supply reserves to stay away for some time till they eventually come back to stock for consumables like food,y dunny rolls etc.

I take it the process would be somewhat like desal plants and perhaps this is where they got the idea from?