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Underwater Power Generation?
An anonymous reader writes:
"We keep seeing stories here about tidal power, and that's cool, but I don't see how it can be done without a column rising all the way to the surface. So here are the ideas I've got right now." Read on for some interesting thoughts on the subject...
"Keep in mind that the device will probably be housed in a length of 4-inch PVC or ABS pipe, and it needs about 0.5 ma at 1.5 volts:
- Surge power. Put a couple of funnels back-to-back with a CPU cooling fan-sized turbine and generator in the middle, and run the output through a rectifier and capacitor. But how reliable will those moving parts be after years underwater?
- Self-winding watch concept. Float the thing tethered to the bottom and install some sort of pendulum inside with a magnet on it, moving through a coil. The moving parts are protected, but will it be enough power?
- Yank the chain. Again, tether it, but use the varying tension on the tether to drive a dynamo of some sort. Not sure how this would work.
- Magnetohydrodynamic generator. Like the surge power thing, but using the flow of cunductive seawater through a magnetic field to generate a current. I have no idea how much power this would generate, if any, or how to deal with ion accumulation at the electrodes.
- Nukes. Anyone got a spare radioisotope thermoelectric generator? Any idea how many smoke detectors I'd need to cannibalize to get enough Americium-241?
Do cold fusion in the sea. It's easy.
But first you need to tell us who you are and why you want and underwater lair.
You do realise that by extracting energy from the sea you will be affecting the currents and temperature gradients, and this will have a knock on effect on the weather?
You may think 0.5mA is not much, but just wait until Canada turns into a barren desert and then you'll be sorry.
0xB
How about harnessing the power of underwater fart bubble? ;-)
Wasnt that yesterday?
Wonderful to finally see Slashdot authors manage to put up a story with no spelling or grammar errors on the front page!
Jordan Bettis
this comment is just as insightful and funny as the empty blurb on the main page. so in *theory* this should boost my karma. why are my theories always wrong?
piezo electric rods placed along the coast to capture the energy of wave motion and tidal effects. Unstable airfoils could be placed on top to "play" the rod even during relativly calm periods. In vast mumbers, They would provide two benifits: Act as bariers to coastline erosion because they would absorb the energy of coastal wave action and The generation of electricity of course.
If voting were effective, it would be illegal by now.
The currents through some channels are well known and steady. Put underwater "windmills" in the channel and sit back and collect the "juice". This is similar to sailboats that tow small electric generators or put magnets on the propeller shaft to trickle charge the batteries.
I've hit Karma 50 and gotten a Score:5, Troll... I win!
If your circuit could tolerate voltage droop, a single D-cell would run it for a few years. But voltage droop is probably annoying, so put in a few D-cells and a voltage regulator.
Alkaline batteries aren't rated to last more than 8 years or so, so use lithium batteries if you need something good for decades.
We need to know how many years this should work to give you more precise advise.
I can think of lots of ways to produce 0.75 milliwatts, just none of them will be more reliable than a lithium battery.
You are giving us very little information. But here's what I'll do for you: I'll answer your problem and make it quick, easy, and (most important) CHEAP.
Use a D cell. Yep, your common flashlight battery will supply you with 3.8 years of power at your requirements, and best of all no moving parts!!! If your device lasts half that long underwater then I'll officially be surprised. Need longer time? Use two cells! More power? Go lithium!
Of course, there could be legitimate reasons to not use the cheap, widely available chemical power you can buy at your grocery store (maybe your gov't grant requires you to buy $400 hammers as well or something), but if you posted info relevant to the question, and why painfully obvious solutions have been thrown out then we could get somewhere.
If these are home built one-off projects, I'd definitely ditch the generator concept. It's far too problematic, and will not last anywhere as long as a lantern battery, and probably not as long as the D cell quoted above. If these are research devices, I'd ditch it unless it was actually the whole point of the research (which I suspect). If this is part of your report/dissertation/homework/etc then do your own work. If this is a commercial product, tell us your market, price range, longevity, and what it's actually powering.
-Adam
The idea would be to use the temperature differential (which can be significant - 10 degrees Faranheit isn't unusual) to generate current. A decent thermocouple would be able to do this without too much difficulty.
The difficulty, of course, is getting the thermocouple on either side of the thermocline. If the device can be of sufficient length (describing it as housed in a pipe suggests as much) this shouldn't be an issue. However, remaining on the thermocline could be difficult. Perhaps some sort of diaphram that would maintain position at the boundary? Tricky.
IP is just rude.
Is there any torture so subl
I can't believe the arrogance of this poster! There is so much work that is being done in this area, and this geek thinks he can just solve all the problems while goofing off at work? Before you or anyone wastes any more time, please take a look at a small sample of the good info that is already out there: Tons of info!,DOE's Hydro Porgram, The old shut down coean thermal program, and a good survey from the CA energy commission.
"The old forget, the young don't know" --Japanese Proverb
A few weeks back there was a story about Wave Motion power plants. There were links there to other experiments with power generation from wave/tidal foreces.
Requires:
1 large weight for the base
piezeoelectric device
1 foot by 1 foot flapper of suitable material
LED
some silicone goop
case of some sort
Build the flapper with one corner attached to a short arm and the arm to the piezo device. Wire PD to the LED. Fit circuitry, everything except flapper and half of the arm into the case. Anchor non-flapper-arm side of PD to case. Fill with goop. Take a dive and anchor the device on the bottom with the flapper aligned to wave surge and you're done.
LED will pulse when wave surge pushes flapper. 2 LEDs will allow for pulses both in and out.
Good judgement comes from experience, and experience comes from bad judgement.
- W. Wriston, former Citibank CEO
Coupled with resin or silicone potting (as others have suggested), it seems the best, most reliable, and cheapest way to go.
But, there is another option, though it probably won't last as long - think seawater and different types of metal...
That's right - akin to a "spud/lemon - battery" - if such a thing could power a small watch, then it could be scaled up a bit to power an LED...
Reason is the Path to God - Anon
Get yourself a seiko kinetic watch, which generates power by movement, and stores it in a very efficiënt capacitor. Throw out the clock, and use the mechanism (or a couple of mechanisms, either parallel, in series or a combination of boh depending on the power requirements) to power your blinkenlight.
Seal aforesaid device in a package with enough air so that it floats. Attach a large weight with a thether to it, dump it in the surf and hope that it works :-)
Okay... I'll do the stupid things first, then you shy people follow.
[Zappa]
...is using the simple solution, even when it's not the sexiest. You're trying to invent the automobile when all you need is a pair of round logs. I hate to tell you this, but the most perfect special-purpose dry-cell batteries for your needs can be ordered for under $100. Your waterproofing solution (which should be a milspec box and some RTD silicone) will cost about that much, too. You *may* be able to put pairs of electrodes through the wall and use the water as your electrolyte, but good electrodes that won't corrode will cost you more than batteries. I guess the real point here is that every solution other than internal batteries is going to be four or five times more expensive than the most top-of-the-line batteries you can get. Unless money is truly no object, then you should stick to batteries.
If you're thinking long life (greater than 10 years), wouldn't various forms of life become problematic? (i.e. coral, seaweed, algae, sponge, etc.) Even if your moving parts aren't all gunked-up, who's going to see an LED covered in coral? Are there any low-power GPS type devices? Since you're assuming someone will be close enough to see an LED, wouldn't a hand-held unit communicating with a BlueTooth-type device be adequate? Using a capacitor-charging system, you could give pulses as infrequent as every minute or so, if needed.
I've seen what storms on the gulf coast of Florida can do to underwater rock structures, so I have to wonder how you are going to keep your geocache from getting dislodged during rough seas?
-Chris
-- This sig is only a test. If this were a real sig it would say something witty. --
The spud/lemon battery is a fairly simple device, but the electrodes will suffer from corrosion quite easily. The metal oxides, the algae and other living creatures on the electode surface will decrease the current quite significantly.