If you wanted to set up a process to harness power from electric eels what would be the biggest hurdle to surmount.
Assume that money for the project is not an issue and there wont be animal rights groups creating barriers to setting up vast electric eel farms.
So whats the dope on harnessing electricity from electric eels.
There are aquariums that light up Christmas trees with electric eels, so it’s possible.
The problem is scaling up to a useful power output. If you have unlimited funding and don’t care about efficiency, the next problem would be getting enough eels. Eels are currently impossible to breed in captivity. Farmed eel (the kind we put on sushi) are raised from elvers (young eels) caught in the wild.
Electric eels are not related to true eels at all, they just look a bit like them; they’re classed as a species of knifefish.
Admittedly, there are no reliable records of electric eels having been bred in captivity either, but not many people have tried. It wouldn’t involve the same problems as breeding true eels, which migrate between salt and fresh water as part of their reproduction.
Electric eels don’t emit electricity all the time (at least, not at a relevant level), it’s for defence and killing prey, and they can’t keep it up for all that long. You’d need to have most of your fish ‘recharging’ most of the time, while your fish that were actively producing power would need to be poked with something non-conductive, or otherwise annoyed or startled into discharging electricity.
The other issue is that they require high quality soft water, at tropical temperatures; unless you have an appropriate tropical stream to feed your setup, you’d be using more energy on running heaters and pumps to keep the fish alive than you’d stand a chance of getting back from the fish.
Some youtube videos showing electric eels killing alligators and other large animals was in dirty brackish water. So dont think they will need very good water quality as long as the pH is right.
Reading the details on that article, the eel does not actually power the tree. The tree is conventionally powered; there are just sensors in the tank that detect the frequent low-power shocks the eel produces and uses the output of those sensors to control the lights. It does say that they were able to get power from the eel directly, but only for super-low-voltage lights which presumably weren’t very visually interesting.
Electric eels produce two levels of shocks. The low level shocks are used for navigation and prey sensing. The high level shocks can stun prey, but also hurt the eel a bit. The eel can also use the high level shocks for defense.
As Chronos noted, they aren’t actually using the shocks to power the Christmas lights, presumably because the amount of energy is small enough that the low voltage lights they managed to illuminate were rather underwhelming. Instead, they use the shocks to trigger other circuitry that causes the lights on the tree to go on. Basically, they are cheating to make the eels look more impressive at generating electricity than they really are.
In a way, the low level shocks are kinda like lemon batteries. Yes, they make electricity, but it’s really not practical to power anything from them. You’d need an entire table top of lemon batteries to power anything useful, and you’d need an awful lot of eels to generate a useful amount of electricity as well.
Also, lemon batteries, while weak, are at least constant. Electric eel discharges aren’t constant. They are very spotty and are of very short duration. Any practical electric eel power harvesting system would probably require storage capacitors or batteries of some sort that the eels would charge. A system like this would be theoretically possible, but would be very difficult to create in the real world. And, as noted upthread, you’d probably spend more energy maintaining the eels than you would get in useful electricity.
The high level shocks produce a lot more power, several hundred volts and about an amp or so of current (for comparison, the low level shocks are maybe half a dozen to a dozen volts, with a current measured in milliamps). But again, the eels don’t use this high level electrical discharge very often, and while the voltage and current levels are both pretty impressive, the duration of the shock is mere milliseconds. It’s more than enough to jolt the bejeezus out of you and get your attention, but the total energy is fairly small.
The shock organs in electric eels are basically weak chemical batteries. The reason they are so powerful is that there’s an awful lot of them stacked in series, which adds up the voltage between all of the individual electrical cells. If usable electricity is your end goal, there are definitely easier ways of constructing batteries and harnessing energy from them.
But, as a thought exercise, I think your biggest challenge will be keeping the eels alive. And you’re going to need a lot of eels. No, more than that. No, even more than that. I’m talking a LOT of eels.
Hamster wheels connected to mini-generators are probably a better choice.
They can also leap out of the water and kill horses.
E_c_g speaks truth. He knows that’s why “hamster wheel” won out over “tank o’ eels” in the trade study to decide how to power this message board. 
Yeah, you might want to consider powering your house with a giant baking soda-vinegar reactor instead.
Water clarity has nothing to do with water quality from a fishkeeping perspective. Mud in the water is irrelevant to many fish, it’s invisible stuff like dissolved ammonia (which fish produce as a waste product) and hardness that can kill fish. While I’ve never kept electric eels, I have kept other knifefish, and they’rel notoriously sensitive to water quality. You cannot tell water quality from a youtube video, you’d need to actually test the water.
Incidentally, according to a fishkeeping magazine I used to get, a German water company experimented with another member of the knifefish family (which all produce electricity to some extent) as part of their water monitoring, back when monitoring equipment was more expensive. They fed their water supply, prior to chlorine addition, through a tank containing a knifefish, then monitored its electrical output; when there was an unexplained spike in electricity from the fish, they tested the water properly.
Or lighting it with jars of fireflies.
We do have a tank o’ eels, but we use it for troll control.
Is the thought that “This would be cool”, or “This would be used as a source of energy”?
If it is the latter, you are always going to spend vastly more energy keeping the eels alive than you will ever gain from them.
True, but not necessarily relevant. There are plenty of “power generating” facilities that are net power consumers, like Dinorwig.
Even at the age of seven I remember thinking “what a colossal waste of money; they must be using more power to pump the water back up than it generates on the way down.” And I was right. What I didn’t understand is that power grids need the ability to generate a lot of power quickly, even if it’s at a net loss, as well as net power generators.
Pshaw! Next, you will be saying that the power supplies on The Matrix are implausible!