h a l f b a k e r y
Expensive, difficult, slightly dangerous, not particularly effective... I'm on a roll.
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Suppose that you build an underwater power plant which generated electricity from a hydrothermal vent [link].
Instead of sending that power to the shore using long expensive cables, I propose an alternative: Hydrogen balloons.
The method would be as follows:
One would first purify some seawater
using reverse osmosis. No energy would be needed to pressurize the seawater, since it's already at very high pressure due to the depth at which we're working.
We do need to pump the fresh water away from the R.O. membrane, but this shouldn't take much energy.
Once we have pure fresh water, we perform electrolysis on it, producing hydrogen and oxygen. The oxygen is discarded into the ambient sea water. The hydrogen is pumped into a balloon. The balloon's initial state is a flat roll of plastic, taking up relatively little space on board the power plant.
As the H2 balloon fills, we also fill a small secondary balloon with seawater (by preference using some of the brine discharged by the reverse osmosis process, but any seawater will do).
When enough H2 has been put into the first balloon, we seal the two balloons, link them with a tether, and release them.
They float up to the surface, and the water balloon acts as an anchor, to keep the hydrogen balloon from escaping into the atmosphere.
A ship finds the two balloons, aided by the beacon that's on the hydrogen balloon. The crew reels the upper balloon in, and compresses the hydrogen into a storage tank. The crew also takes the lower balloon, first piercing it and discarding the seawater that was within it. Then they set sail for shore.
Geothermal From Hydrothermal
[goldbb, Nov 08 2009]
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||// No energy would be needed to pressurize the seawater// Wah-waaaah.
||What [AWOL] said. Bad physics. It's the differential pressure across an RO mebrane that makes it work - you can have ambient on the intake side but you'll need to drop the pressure on the outlet, by pumping, same as on the surface.
||Releasing oxygen in quantites into the deep ocean is going to seriously disrupt the ecology, which is little understood.
||The change in pressure on the hydrogen balloon as it ascends will be several orders of magnitude, and it will expand proportionately (Apply General Gas Law). Better to pipe both hydrogen and oxygen to the surface in their compressed form.
||goldbb: you need to explain why is it better to make
hydrogen at the bottom of the ocean from desalinated sea
water, than it is to make it from fresh water on the surface,
where most of the likely users are located.
||//Releasing oxygen in quantites into the deep ocean is going to seriously disrupt the ecology, which is little understood.//
||In that case, don't purify the water before electrolysis. No oxygen released then.
||a good halfbaked idea. (aside from the whole RO bit but since that isn't critical to the idea lets explore some other issues.) First issue I would like to broach is the fact that gassious H2 is notoriously "light" (not dense) and thus would require huge balloons for delivering any volume of energy. thousands of balloons.
Then I question the infrastructure efficiency. Piloting a ship of sufficient strength to contain liquified H2 and then having it wait around, and wait, as it is filled by hundreds of thousands of individual balloons. We are talking about a LOT of wasted energy and effort.