Underwater Power Generation? 62
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?
I'd love to help you... (Score:3, Funny)
Re:I'd love to help you... (Score:3, Funny)
And stay off the lawn, damnit!
Dangerous (Score:2, Funny)
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.
Re:Dangerous (Score:3, Funny)
You sure about that, eh?
Re:Dangerous (Score:2)
Seriously, all power generation has some sort of negative effect. (You down with entropy? [mchawking.com]) Even (large) wind farms have been shown to (slightly) increase the level and duration of frost down wind.
Re:Dangerous (Score:1)
why dont we ban slinging ourselves around planets too, because that slows them down.
puhleaze
Re:Dangerous (Score:2)
Re:Dangerous (Score:1)
Re:Dangerous (Score:1)
Bubbles? (Score:2, Funny)
Re:Bubbles? (Score:1)
Yeah, split the "fart atoms" for a remarkable source of power. Especially after burrito night!
Re:Bubbles? (Score:2)
Re:Bubbles? (Score:1)
Or would that be a job for the illegal imigrants?
And would it pay minimum wage or would it be hazzard pay ?
April Fools (Score:1)
Great Writeup! (Score:1, Offtopic)
late breaking news: ...! more on that at 11 (Score:1)
Piezo electric rods... (Score:4, Insightful)
Re:Piezo electric rods... (Score:2)
Skip the science. Focus on phonics.
Re:Piezo electric rods... (Score:1)
Channels (Score:4, Insightful)
6 watt hours per year. (Score:4, Insightful)
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.
Re:6 watt hours per year. (Score:5, Informative)
Ok, so I've gotten into this geocaching [geocaching.com] thing lately, and while working on a cache to be hidden in about 60 feet of water off the coast, it occured to me that a blinking LED might make it easier for divers to spot. No problem, whip up a blinker circuit with an LM3909 [national.com] and a super-bright green LED [lumex.com] and we're set. But what about power? Sure, four D-cells [duracell.com] would let it run for close to a decade, but where's the fun in that? The undersea environment is quite dynamic, and there's got to be some power down there that can be harnessed. What I need are some ideas on how to do that.
We keep seeing stories here about tidal power [slashdot.org], 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. 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:
The generator need not fit inside the 4-inch cache tube, but it shouldn't be huge, either. It needs to be practical to build, and not terribly expensive. Above all it's got to be reliable and enduring. Any ideas?
Re:6 watt hours per year. (Score:2)
So the requirements are something that lights up, is nifty, not too expensive, non-hazardous, and works most of the time.
So something that went dark during periods of unusual calm would be ok.
I doubt anything will outperform a lithium cell in any respect except for being more nifty.
Most of the devices I can think of, will stop working if they get coated with living stuff. How long does stuff stay clean 60 feet down?
Re:6 watt hours per year. (Score:2)
Storm tossing? (Score:2)
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
You aren't giving us very much info... (Score:2)
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
Re:You aren't giving us very much info... (Score:2)
Re:You aren't giving us very much info... (Score:1)
There's two other problems that you need to consider then:
Buy yourself a small tupperware container. Put your electronics in. Drill a hole for any cables to come out of, and seal it up with silicone sealent, from any good hardware store. Put silicone sealent around the top of the tupperware box, and place it on.
Allow the sealent so set and voilia, one long-life sealed container.
Michael
Re:You aren't giving us very much info... (Score:1)
Re:You aren't giving us very much info... (Score:2)
It is true that a battery subject to adverse conditions will leak, but that goes again toward engineering a good battery compartment, and buying good batteries that are suited to low drain applications.
I still say that it'd be far better than any generator scheme he could come up with. There are reasons he might not want to use batteries, but the ones you mention are cop-outs to cover incapable engineers.
-Adam
Re:You aren't giving us very much info... (Score:3, Insightful)
Watertight I've no doubt of. Survive ocean submersion for the decade or more he seems to want it for is more difficult. Maybe cast the whole thing in silicone and without air pockets. Frankly, he'll be putting it in an environment that most plastics and metals fair poorly in, and probably changing it's ambient pressure constantly.
Further, comparing the difficulty of a battery compartment to the difficulty of a generator is disingenuous, I think. What I'm cautioning against is not the difficulty (which I think is about the same, and made quite arduous by the proposed lifetime and environment); I'm concerned about the consequences of an engineering failure.
If almost any of the generation ideas he proposes goes south, worst case is that the device stops working. If a battery compartment leaks, the battery leaks alkalines or lithium compounds into the surrounding seawater.
That's my two cents.
Re:You aren't giving us very much info... (Score:3, Interesting)
I thought about pressurizing the pipe to help counteract the outside pressure, but I just recently had a bad experience with pressurized ABS (spudgun experiment) and I'm wary of trying it again. The window replacement alone cost me $25 last time...
Yeah, batteries are the easiest way to go, but I just like the idea of trying to make an ultra low-power circuit run indefinitely (until component failure) unattented, without access to solar power.
Re:You aren't giving us very much info... (Score:2)
Differentials (Score:4, Informative)
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.
Re:Differentials (Score:2)
Re:Differentials (Score:2)
Unless you're doing all this underwater, which wouldn't make sense given the examples you put forth.
Re:Differentials (Score:4, Interesting)
There can still be a considerable amount of surge at depth. I remember finding one roughly 1-meter hole in a rock wall near Anacapa that funneled the surge through it with enough force to knock me around and almost tear the regulator from my mouth, and then suck me through and spit me out the other side. It'd be able to generate tons of power, but it'd be way to heavily travelled a spot for my purposes. (See post about underwater lair. =])
Re:Get over yourself! (Score:2)
Use wave motion as previously discussed (Score:1)
make a fan (Score:3, Interesting)
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.
I agree with those that say use batteries... (Score:3, Insightful)
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...
Re:spud/lemon - battery (Score:1)
Seiko Kinetic Watch (Score:2)
Get yourself a seiko [seikousa.com] 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 :-)
Longevity problem (Score:1, Interesting)