Half a croissant, on a plate, with a sign in front of it saying '50c'
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Vacuum Energy

No no, not what you think
  (+5, -9)
(+5, -9)
  [vote for,

This is actually a method of providing energy to deep-sea habitats. A large steel container, having floats attached and ballasted with sand, is evacuated and dropped to the habitat on the sea floor.

Opening a valve allows water to enter the container to turn a turbine connected to a generator. Quite a lot of juice can be generated because of the large head of the water column, although the volume is naturally limited. Dumping the sand allows the filled but still buoyant container to float back to the surface.


CIP – 1

Dispense with the habitat. A mother ship makes a great circuit, continuously dropping off thousands of cylinders and picking them up. At the bottom, the generated electrical energy is used to split water into hydrogen and oxygen, which are stored under the high pressure of the seabed for later harvesting by the mother ship. The cylinders do not initially have to be evacuated of air, and the fuel source is simply the gravitational energy derived from sending the sand (or rock) ballast to the bottom.

ldischler, Oct 21 2002

Pop the cork http://www.hypacc.com/
No good, not enough bang/smoke/fire [lurch, Oct 22 2002]

Ocean Power ocean_20power
This relic from 2001 is essentially the same thing [ldischer] posted in 2002. [bungston, Dec 01 2006]


       Are you sure this generates more energy than it takes to construct and operate?
snarfyguy, Oct 21 2002

       I should probably delete the first idea and go only with the CIP, but then history would lose an invaluable example of the creative mind at work. Yes, snarfyguy, this scheme is over-unity, the major energy source being only the gravitational potential energy in rock and sand, cheaply obtained from your local beach. The drawback: over a very long time, our Morlock descendents could send entire continents into the deep.
ldischler, Oct 21 2002

       Your limit on energy return is limited by mgh (mass x strength of gravity at the surface of the earth x height change). You could use either the pressure vessel approach as you describe, or a tethered weight that you unwind against a dynamo then haul back the empty cable.   

       Either way your energy return is limited by mgh, so your upper limit is 10000J for every kilogram (kg) you drop by a kilometer (km). Say you have 5% efficiency (not too unusual) you'd get 500J (per kg per km).   

       That's about enough to run a light bulb for about nine seconds.
st3f, Oct 21 2002

       [st3f] I'm calculating an energy density ratio for the 1km gravitational energy of sand to the heating value of fuel oil of about 1/5000 -- or 1/500 for the deepest part of the ocean. If I'm not way off base here, it seems this side of feasible. And remember – Morlocks don’t require much light.
ldischler, Oct 21 2002

       No, but they do require more keys.
bristolz, Oct 21 2002

       [st3f], In this age running a *light bulb for nine seconds* is enough to get to the next new idea...
hollajam, Oct 22 2002

       bris: ouch.   

       ld: Wrong in so many ways. You'll be lucky just to recoup the energy expended cycling the cylinders.
DrCurry, Oct 22 2002

       DrCurry, I'm still waiting for your elaboration on "Wrong in so many ways". (Back of the envelope calculations will suffice.) Government sponsored fusion research is "wrong in so many ways", but they still get hundreds of millions to burn. And their equipment turns radioactive besides. Even if idiotic, my idea is at least harmless – and if it doesn’t work, the containers will be useful for stashing radioactive waste.
ldischler, Oct 22 2002

       It doesn't sound like this will work to provide a net gain in energy (perhaps you could mathematically prove this guess incorrect for us?), but it might work economically. See the Ben Cruachan hydro plant in Scotland - run the turbines to generate electricity during peak price times, reverse them and refill the reservoir during off-peak times. You could drop this thing at peak hours, and worry about recovery and recreating the vacuum during off peak hours.
namaste, Oct 22 2002

       Yes, [namaste], there is a net gain. The question is whether hidden issues of complexity make the concept impractical. I contend that this very impracticability is what makes it appropriate. That is, at the halfbakery. On the other hand, I will need several hundred million tax dollars to actually prove whether it is impractical but appropriate, or inappropriate but practical.
ldischler, Oct 22 2002

       namaste: There is a net gain. It is taken out of the potential energy of the ballast that starts at the surface of the ocean and ends up on the sea floor.
st3f, Oct 22 2002

       The possibility of getting the energy out of this fairly rapidly is another consideration. Some think that the stored energy can be utilized *very* rapidly (see link).
lurch, Oct 22 2002

       Replace the word 'sand' with 'garbage'. You won't get any more votes, but it'll sound a little more HalfBaked and you can claim you're killing two birds with one stone.
phoenix, Oct 22 2002

       Replace the word "garbage" with "nuclear waste", and I'd agree. To be practical, the ballast has to be a lot denser than your average garbage.
ldischler, Oct 22 2002

       This sounds very similar to a design for a perpetual motion machine i saw once. I can't remember exactly what it was that stopped it working so can someone help? It was a continuous belt with lots of containers attached with the ends sealed with rubber and weights. when the end faces upwards the weight drops into the jar and compresses the stuff inside. The opposite happens on the other side and so when you put it in the water one side rises and the other falls.   

       If it turns out that it actually would work i want a patent
Alphaman, Oct 22 2002

       ldischler: my original annotation ran to more than five long paragraphs, so rather than bore everyone, one small way this is wrong: the heavy duty cylinder you need for this will not bob back to the surface after the ballast is released.
DrCurry, Oct 22 2002

       That won't do, as the original scenario reads "A large steel container, having floats attached and ballasted with sand...” The floats make the water filled container buoyant. Enough ballast has to be added to send the empty cylinder plus floats to the bottom.
ldischler, Oct 22 2002

       While you're going to all the trouble to run heavy-duty cables and all that down to the bottom of the ocean to lower these containers, I should point out that it is possible to "provide energy to deep-sea habitats" using some of those new-fangled "wires", and some "electricity".
hippo, Oct 23 2002

       [hippo] Ah, but no cables are used. Also, in the CIP, I've sunk the habitat, changing the idea to a form of gravitational energy harvesting, which, come to think of it, would have been a better header name, probably garnering me fewer fishbones.
ldischler, Oct 23 2002

       Idisch: I don't really like the idea but you get my flotation croissant for standing firm and not losing your cool among such negativity and possibly lack of understanding.   

       The idea is a simple one:
1) Load a buoyant container with heavy stuff that you don't mind ending up on the sea bed. The container and contents is now heavier than the surrounding water.
2) Let it go.
3) When it gets to the bottom, dump the heavy stuff. The container is now lighter than the water surrounding it.
4) Let the container float to the top.

       In steps 2 and 4 use your preferred energy generation technique (turbine, fan, large elastic band) to capture some of the energy and slowing the ascent/descent.   

       There's no magic, no free energy. You're simply moving stuff from high up to low down and taking advantage of the fact that you can generate energy doing that (much like a waterwheel can make energy out of a waterfall).
st3f, Oct 23 2002

       // the ballast has to be a lot denser than your average garbage //   

       Fill them with 1/2B annos ....
8th of 7, Oct 23 2002

       Lose my cool? Never. In fact, I've prepared some nifty gifts for everyone who has so kindly helped by kicking the shit out of this idea. I have discovered your addresses, and the packages are on the way...   

       Let me simply the visuals:   

       Drop thingy in water.   

       Thingy goes down for a while.   

       Thingy comes up. It COMES UP! [UnaBubba]   

       Pick up thingy and lo, pressurized O2 and H2.   

       But to send it down, you had to add sand (or UnaBubba!)   

       No free energy. See.
ldischler, Oct 23 2002

       // the heat generated in the brain tissues of the people here //   

       Not sure about that. Room temperature IQ's, mostly. MOSTLY.   

       NB - Centigrade scale.
8th of 7, Oct 23 2002

       ld: It will so do. Please describe the construction of a float that can survive the crushing pressures at the bottom of the sea and not be prohibitively expensive. This is in every way a really bad idea. You have my fishbone: don't expect any more words.
DrCurry, Oct 23 2002

       Ah, now [UnaBubba] wants to send me to the deep. Well, you could be right, perhaps burning 6 billion white hats would generate more energy than the concept at hand. Perhaps burning the tax dollars that I propose to waste on it would be a superior plan. <stalling for time, trying to think of a comeback, oh well…>   

       Yes, my statement about the gases to be returned to the mother ship was not clear: they are stored on the thingy and return to the surface with the thingy.   

       [DrCurry] The thingy floats! I’m sorry I said float, as it must call polystyrene to mind. All I need is buoyancy. This can be achieved by the simple expedient of not filling the thingy completely with seawater at the bottom. This head space (along with the generated gases) sends it back up upon release of the ballast.
ldischler, Oct 23 2002

       "The barrel..."
egbert, Jun 06 2006

       I think 2002 was a good year for physics on the HB.   

       I am looking at [st3f]'s math. Assume 1 km down. We drop an old shipping container with a volume of 70 cubic meters. With 1000 liters/cubic meter that is 70,000 liters (at 1 kg/liter for water). Assuming the 5% efficiency producing 500 J /kg/km: 500 * 70,000 = 35,000,000 J. This runs the lightbulb for 3645 days. You would probably need to change it a few times during that period.   

       The shipping container need not be evacuated, because the volume of air at sea level is trivial,and will be compressed down to nearly nothing at sea bottom.   

       It would be neat if the energy could be generated regardless of where on the container the water entered. I imagine that as described there would be some sort of turbine at the point of entry. But old shipping containers, while cheap, might be leaky and it would be good if point of entry didn't matter.   

       Last: hydrogen, oxygen - bah. Just float the thing back up and generate more energy off the pressurized water within. Producing a float which will stay buoyant at the bottom of the sea will be tricky though...
bungston, Jul 10 2006

       Airtight logic there, [bungston].
methinksnot, Jul 10 2006


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