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Ambivalent? Are you sure?
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Transport hydrogen gas across water in a safety blimp.
The bag(s) are on a long tether, with a small boat on the
other end. The boat, in turn, drags a tether hanging a water
pickup. Water tanks, pumps, fuel cell..
For downwind travel, dump ballast until the boat lifts off and
dragging your tail in the water.
Upwind, suck up ballast until the boat is floating comfortably
and use power from hydrogen fuel cell.
||Surely the only economical way to transport hydrogen is in
liquid form? Or am I wrong?
||Economy of transport is determined by the mode
of transport. Road, airplane, and rail transport are
limited by bulk, so hydrogen is only worthwhile in
compressed form for those modes.
||Gas-filled bags at sea are not limited by bulk. But,
upwind travel would be probably be uneconomic.
||H2 holds about 25 MJ of energy per cubic meter.
Thats about $0.25 worth of natural gas (at ten
bucks a gig) or $70 of electricity (at 10 cents a
kW/hr). Hydrogen is intermediate in value
between natural gas and electricity.. a buck a
cube is a nice round number. A sphere 10 meters
diameter of H2 would be worth about $700. A 30m
sphere: $18,000. I think it would fly.
||EDIT: 25 MJ of electricity is worth 70 cents, not
seventy bucks.. so a buck a cube for H2 is a bit
pricey. Maybe more like 50 cents.
||The exchange rate between fuel gas and
electricity is roughly the efficiency of an "X"-
fueled power plant. Natural gas is burned and
passed through a thermodynamic cycle, so the rule
of Carnot applies. In a hydrogen fuel cell, there's
no such restriction. The efficiency could be as
high as 50cents/70cents
||Bunned. I came up with this idea myself, but didn't post it on Halfbakery. Given that the sphere (or whatever shape you make the bag) would fly, you could also transport other goods along with the hydrogen. Have a small tractor blimp towing a bag of Hydrogen, with cargo hanging from it, then when you reach your target, deflate the bag and unclip the cargo, before rolling the bag up and stowing it in the blimp.