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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?
Yeah, it's all underwater. See post about editors on crack.
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. =])
Lithium in particular doesn't play well with water. To tell the truth, right now it looks like I'll probably just be using 3 or 4 alkalike D-cells (Duracell says they should be ok for years, especially at 50 degrees F) and sealing it all up with epoxy. The only opening in the pipe will be for the LED, which will be epoxied in place. Hopefully the lens can take immersion in salt water.
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.
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
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.