I've devised a world where artificial intelligence (AI) have taken over as middle-class (America), leading to the further division of human classes: a superior upper-class and a now much lower-class (slaves).

In this world the natural resources normally available to manufacture electricity for consumption are (nearly) wiped out, and our AI middle-class are requiring their lower-class humans to perform some sort of manual labor for production of electricity. This output of electricity is imperative for the AI and upper-class to sustain their own lives.

There are many methods available to create electricity by manual labor, but my question is which method is considered the most efficient with special consideration given to the human body's physical ability.

The AI want to make the best use of their resources (i.e. food for the lower-class, maximum output/human), thus needing a very efficient method for the production, while making the assumption the lower-class humans performing this labor are fed special nutrient rich diets to maximize output. These humans are born and bred to perform these jobs, and are likely to not know any other style of life.

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    $\begingroup$ It would be more efficient to remove people from the equation altogether. Just burn the food directly to produce electricity. Of course, this is pretty horrible for your plot, unless you used the killing-off of the middle-class as a central aspect to it. $\endgroup$
    – user6511
    Mar 25, 2015 at 3:07
  • $\begingroup$ @user6511 -This is, as you mention, horrible for my plot. The solution I seek assumes the lower-class, almost sub-human slaves, are a value proposition thus creating more energy than they consume. I agree your solution may produce the electricity needed to harness enough power for the AI. I've not formulated a plausible explanation debunking this scenario, but I suppose I'll reach one upon further examination of my environmental architecture. $\endgroup$
    – The Onion
    Mar 25, 2015 at 3:21
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    $\begingroup$ I kind of doubt it, having a middleman (the slaves) always reduces efficiency since the slaves also consume energy and resources. Does your plot require the value of slaves to be specifically in energy generation? Providing service and entertainment to the human masters would be more realistic, I think. $\endgroup$ Mar 25, 2015 at 6:05
  • $\begingroup$ As well as burning the food, you might as well burn all the humans while you're at it. This is by far the most efficient way to extract energy from an existing human. Get your electricity from nuclear and renewables. $\endgroup$ Jul 27, 2016 at 11:46

7 Answers 7


Cleaning solar panels.

The Earth's resources are getting scarce, but the sun is still free.

A huge solar power infrastructure is in place, but the panels need a lot of maintenance, mostly cleaning.

Optional: Pollution or nuclear war has made the world a lot more sooty than we have it today.


I don't see an AI making itself reliant on slave generated power. Human slaves are very temperamental. They whine. They complain. They want food every day. They make an awful screechy noise when their calcium based infrastructure snaps due to overwork. Who wants to deal with that? No, human slaves are too inefficient, and too unreliable for something so important to the AI's as power.

Instead, I can see an AI relying on nuclear power. The human element would come in the form of mining for uranium and transporting it. The upper echelon of humanity would run the actual plants, unless the AI has automated all of that itself. Or if you are trying to hand wave away all resources, there's always geothermal, solar, tidal power, and of course hydropower. Humans walking on treadmills isn't going to cut it.


The problem with going for electricity is that, as noted, it's always going to be better to just convert our food directly. Even if humans turned 100% of the food we consume into electricity, that would still be only breaking even.

Instead, you should use us for what we are good as: Cheap, Renewable, Self-Repairing Labor

The key is that humans don't use electricity, and we don't have to be built. Our food can be grown on land that's not viable for energy production, which means that we don't drain the AI's electricity grid at all. A dumb bot might do a better repair job, but the electricity and resources it uses could be better used elsewhere, by real AIs.

Additionally, damaged humans will self-repair, just needing time instead of more precious real resources, and our reproduction follows the same strategy.

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    $\begingroup$ To use an analogy, we use cows, sheep, goats and other livestock as a pre-existing, self-replicating chemical factory to convert inedible grass and cellulose into edible protein. $\endgroup$
    – Schwern
    Mar 25, 2015 at 6:37
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    $\begingroup$ The actual labor may be deployment and maintenance of solar farms. Jobs like leveling terrain, dusting the panels, building foundations for them, laying electric grid, that all requires a lot of energy if done by machines. Employing humans for that purpose would be vastly more energy-efficient. $\endgroup$
    – SF.
    Mar 25, 2015 at 8:37

Well, assuming you read all the other comments, realize that it'll be horribly inefficient, but gave your AI and the upper class strong sadistic tendencies so they want to do it ANYWAY...

Humans producing electricity is pretty much exclusively possible via a detour through physical labor creating kinetic and/or potential energy.

You could have your humans pushing something similar to a horse mill linked to a generator if you want a direct human works -> electricity conversion, but personally I'd put a step in between there. Humans can output the most work if they're pulling downwards, allowing gravity to help them. So take a big rock, attach a chain going over a pulley system to it, and let the humans lift it up. The rock then slowly pulls down the chain, which in turn moves a set of gears connected to your generator. While this rock is ticking downwards (clocktower clocks used a similar energy source) the humans pull up the next rock.

Bonus: lifting a huge rock upwards only to see it slowly descend again, over and over, maybe in long rows of similar setups with the rocks constantly rising up their towers and going down again is utterly demeaning, and the lower class people will work their hands raw doing this. Well, it's a bonus since I assume you want to display horrible, horrible living- and working-conditions, which these definitely are.


As has been pointed out over and over again from the Matrix movies, using humans as an electricity source is a terrible idea. You'd be better off just burning the food to create steam to turn a turbine. Robots, unshackled by the existing economic structures, can just cut out all that and use solar power.

Humans have to do something useful for the robots, something the robots cannot do themselves or cannot do well or efficiently. Here are some thoughts...

Humans may provide a purpose for the robots to exist, in a perverse way. Humans have 4 billion years of evolutionary survival instinct driving us to continue on, what would drive a society of robots? It may be that robotic society must base itself on the imperative of "serving humans" even if it has been so grossly flipped on its head that humanity is trapped in a sort of nursing care nightmare home.

Humans may remain better at certain tasks like being able to see and understand unusual situations. I can imagine robotic sensors remaining limited to what they're programmed to recognize and being slow to react to new, unexpected, or chaotic stimulus. They might keep humans around to look at odd things and tell them about it.

Perhaps the robots, having to defend against other biological species, keep the humans around as breeding grounds for biological warfare. Who wants to invade when the whole planet is teeming with disease?

Perhaps humans are almost like a nature preserve, or a seed bank. The robots know they were created by humans. They know they may lack the creativity of humans. So they keep them around to inject new ideas into robotic society from time to time.

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    $\begingroup$ Going off your nature preserve idea, I think I would see it more as an honoring of humans as the creators in the way that Hindus honor the cow. $\endgroup$ Mar 25, 2015 at 21:11


If you really want to generate electricity from human muscle power, you have to use our legs (the most powerful muscles) at a steady, not too fast motion.

Historically, the best way to use muscle power was done using treadwheels (e.g. https://en.wikipedia.org/wiki/Treadwheel_crane) - like giant hamster wheels, they have been used to lift weights, pump water, etc.

Nowadays, the most sustained power can be extracted using bicycle-like contraptions. They can be easily linked to a generator and minimize any "wasted" movements. See http://www.lowtechmagazine.com/2011/05/pedal-powered-farms-and-factories.html for examples. IIRC you can extract something like 100w per person in this way - so if you get a dozen men pedalling, you can power a nice toaster.

Anything that relies on power of human hands/arms will generate less power.


Methane from sewage into a fuel cell. The human isn't providing any additional effort other than needed for natural function, so marginal input is zero.

Efficiency being Eout/Ein is nearly infinity. ;)

  • $\begingroup$ The energy out the human bottom is much less than the energy in his mouth. Again, better to just burn the food directly. $\endgroup$
    – kingledion
    Jul 27, 2016 at 13:00
  • $\begingroup$ @kingledion: One constraint is to keep humans alive, if I understand the question. A diet rich in a great deal of fibre solves that problem. Beyond that point, any additional manual labour done will be less efficient than burning fuel directly, as you stated. $\endgroup$
    – nzaman
    Jul 27, 2016 at 13:45

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