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After watching Animatrix I started to wonder if it would be energy efficient to draw power from human "batteries".

Without the Sun there would be no endless - in our time frame - source of power. That would lead to no vegetation, so humans would need to be recycled in order to feed those human batteries. Is there any scenario in which you could use humans as batteries?

I also note that:

The matrix would draw huge amounts of energy to maintain. A machine maintaining human power plants would use energy and there can be no 100% energy-efficient engine.

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closed as off-topic by Ghanima, ckersch, bowlturner, Nick Wilde, HDE 226868 Feb 23 '15 at 19:02

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about worldbuilding, within the scope defined in the help center." – Ghanima, ckersch, bowlturner, Nick Wilde, HDE 226868
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Duplicate: See scifi.stackexchange.com/questions/1263/… $\endgroup$ – guildsbounty Feb 23 '15 at 18:12
  • $\begingroup$ Simply burning humans as fuel would be much more efficient than recycling them to feed other humans and gather energy released by them. $\endgroup$ – Peteris Feb 23 '15 at 20:28
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    $\begingroup$ Don't ask me where, but I somewhere read that an early draft for the Matrix had the machines use the humans in the Matrix as neuroprocessors instead of batteries. That would have been much more scientifically plausible and would have tied in nicely with the virtual reality idea, but was discarded as too inaccessible for a general audience. $\endgroup$ – Philipp Feb 23 '15 at 22:22
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Second Law Of Thermodynamics says every closed system loses energy (technically: the entropy of a closed system can only increase). Recycling Humans (or anything) to feed more Humans will lose energy at each generation. In the case of Humans a lot of energy because Humans are really bad at making electricity.

The Sun obscured by clouds in The Matrix is still heating and warming the Earth, its only the direct solar energy that is blocked. This still leaves several ways of harnessing the Sun's power.

If the Sun were completely gone, there remain many, many reserves of power on the Earth. Vsauce covers this in his video "What If The Sun Disappeared".

  • Geothermal (which will last billions of years)
  • Fission and fusion
  • Chemical (far more than just oil)

What about using a Human as a battery? Humans are very bad at converting calories into electricity and produce less than a volt. But a battery is just an energy storage unit, usually chemical. Humans have lots of chemical energy stored inside them! That's what a calorie measures. You'd be better off using Humans as a source of chemical energy: burn them. You'll get about 75000 Watt-hours out of burning an adult Human which is enough to keep a laptop running for about 1000 hours. At 7 billion humans that's 525 trillion Watt-hours or 1/7th of the electricity produced in the US per year. Use that to produce steam to turn a turbine to generate electricity (which is what we do today). Then whatever you planned on feeding the humans, burn that, too!

Don't get too excited by those numbers, converting power from one form to another is inefficient (again with the Second Law). It depends on how you do the conversion, but theoretical limits are in the 60% to 80% range. Reality is more like 40%.

When it does make sense to use Humans for power is to recapture the waste energy of going about your daily life. From exercise equipment with generators on them, to a self winding watch. In this sense, you are using the chemical energy stored in a Human as a battery, converting it to kinetic energy, and then converting that to electricity. This isn't using Humans to generate energy, it's capturing what would have otherwise been lost by normal Human activity.

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