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Well, even though I used Dune Stillsuit as an example, the idea I have is nothing related to the recycled water they need, just to generate electricity constantly through their journey to keep them warm or cold.

However, I have two ideas, one that I don't really know if it will work and other that will definitely work, but isn't as cool. And in both cases, I don't really know if it would produce enough energy to anything.

The first one is that the full body suit would be made of fibers, and every couple of centimetres in the clothe, there would be points where the electricity would be absorbed. The electricity would be generate through the friction of these fibers that would move with the body.

The second idea is to simply attach a lot of tiny electrical generators with lines attached to the parts that will be moved. So it would be like the body is making the action of constantly rotating a generator.

And of course, if the both option are possible, the characters in the history could use both methods. Generating even more electricity (requiring more effort to move as a consequence).

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    $\begingroup$ Thermo wear isn't good enough if it is just about cold and warm. What kind of technological level does your setting have. Isn't it easier and more cool u feed stuff your wear with cucumbers or dung and it converts all that in the type of energy a person needs. $\endgroup$ – MolbOrg Apr 17 at 17:48
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    $\begingroup$ I agree with @jamesqf; what is "Duna's Stillsuit"? If you're talking about the Dune stillsuits, they don't generate electricity; their purpose is just to collect water. $\endgroup$ – The Daleks Apr 17 at 18:09
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    $\begingroup$ Keep in mind it takes more effort to walk a mile in an "electricity-generating suit" than in a normal suit, since you have to (a) cover the distance and (b) generate the electricity and (c) carry the suit. It is probably more efficient to wear normal clothes and carry the extra weight of a battery. You still have to (a) cover the distance and (c) carry the battery. But since the plant that made the battery was bigger and more efficient than the suit, the second (c) will be smaller. $\endgroup$ – Daron Apr 17 at 18:37
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    $\begingroup$ Duna? Stillsuit? Mind sees picture of a Kerbal in a stillsuit, exploring the DUNEs of Duna. $\endgroup$ – PcMan Apr 17 at 19:49
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    $\begingroup$ @Daron: As far as heating goes, given sufficent insulation the body can generate more than enough heat to deal with anything short of Antarctic conditions. The problem is more often getting rid of heat - that's why hikers & cross-country skiers dress in layers, and why spacesuits have cooling: en.wikipedia.org/wiki/Liquid_cooling_and_ventilation_garment $\endgroup$ – jamesqf Apr 18 at 1:51
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Electricity by friction: not in usable quantities.

But if your goal is to generate electricity from body movement, there are at least two approaches that work fine.

One way is to use a mechanical inertia-to-motion-to-electricity charger, such as this Ampy Move They work fine, although the power produced is not as great as one could hope for, it is ample to charge a cellphone, for example, faster than the phone discharges even under heavy usage.

Or, if you want to emulate the Dune stillsuit:
I've worked on the cooling vest for a mascot suit. Lots and Lots of little tubes filled with water with little one-way tesla valves, pumped around the torso and upper thighs by the wearer's motion, that circulates cooling water to/from a reservoir.(in a backpack pouch, surrounded by simple cooling packs.)
The pumping action was too effective, and caused pressure in the reservoir to spike if the suit wearer got too involved in the sports. I'm sure one could hook a simple turbine-generator unit to the reservoir inlet, and use this for generating power. Something like this, with a layout where the user's motion provides the pumping, like mine did (before it leaked)

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This is a great question, but let's start with the natural limitation

In keeping with the laws of thermodynamics, the human body cannot generate more energy (for any purpose, including cooling or heat) than it can take in. In fact, since some of the energy it takes in must be used to keep the body alive, there's a substantial limitation to what the body can do. In the short term, it could generate life-saving cooling or heating. An example would be to connect an exercise bike up to an alternator that, in turn, drove a heater or cooler. But every coulomb of energy the body produces comes at the expense of consuming energy that could be used to pump the heart and work the muscles.

In other words, you'll generate all the HVAC (heating, ventilation, and air conditioning) you need until you drop over dead, which will happen at a much earlier age than you would have lived had you been able to use that energy for other purposes.

What does this mean? It means that body movement alone is a poor way to generate energy for any purpose. Not that this matters, because...

Let's talk about literary license

Dune's stillsuits were fascinating when Herbert first released the story. They were an inventive solution to an obvious problem: how do you have a bunch of Bedouin survive a planetary desert? Not a well or an oasis to be found. Herbert's capture of body water is "simple" and realistic: the water from sweat, urine, feces and breath is captured through several layers of undefined [this is important!] cloth such that it is perfectly stored in catch pockets (no or virtually no loss). Here's the kicker, though... pumps were part of the heel of the boot to provide the pumping action needed to move the water around. That's undefined, too! Finally, Herbert never explained how the solids were removed. And I'm not just talking about what's left over in feces once the water is drawn away. I'm talking about the salts from sweat, the nitrates from urine, etc. That's never defined.

And this is an incredibly important lesson for a new author. You don't need to explain every little detail. In fact, you don't want to explain every little detail. Remember those laws of thermodynamics I mentioned? If you applied them to "the pumping action" of Herbert's stillsuits, what you'd have is an impractical to use (if not impossible to use) solution because the few centimeters of pumping due to the fall of a foot (children's and adult's, female and male, lots-o-variation there) aren't actually enough to do what Herbert envisioned. My point is, literary license doesn't require you to explain anything. And that's valuable, because sometimes what you want to do can't actually be explained.

Having said that...

How the body and/or the suit can pull energy from the environment

  1. The suit can be made out of a solar-absorbing material. Remember that black is the absence of reflected light. If you had a 100% efficient solar material, it would be black. Would it be enough for your needs? Literary license — it does by definition.1

  2. The suit is made up of miles upon miles of flexible-but-virtually-indestructible insulated micro wire, which ends up in a battery. Your world either has a strong magnetosphere or an incredibly high percentage of highly magnetic minerals such that wandering around in that suit charges the battery (the suit becomes a passive generator).

  3. In the same way that a potato creates a salt-bridge between copper and zinc elements to cause electricity to flow (cool article here), the composition of the suit is such that it creates a similar bridge between the atmosphere and the body, from which electron flow can be tapped and stored. The suit, like the potato, is consumed in the process (a useful trait for any story, the suit becomes a commodity or a resource limitation).

You'll notice I did not explain how any of that could work. It doesn't matter. The question is can any of it be used such that a reader is willing to suspend their disbelief and enjoy your story. To that end, your friction solution works, too.

  1. The suit is designed to maximize the heat generated through friction between body parts. Thermoelectric generators sourced between the suit and the outside air temperature are used to generate electricity.

1There are a lot of science purists on this site who believe, for reasons I literally cannot understand, that all science fiction must be based on the science fact that we understand today. We understand so little about science today that it makes angels weep — but that doesn't seem to stop some from chastising others for not adhering to it. Humbug. Good science fiction is as much about imagining the possible, even if it doesn't conform to whatever nonsense we believe we understand today, as it is about using what we understand today. 1, 2

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    $\begingroup$ It might actually be enough energy, humans waste a lot of energy bobbing up and down while we walk. piezoelectric shoes can generate a surprising amount of power despite low efficiency,(they have a lot of other problems however) But I agree there is a such a thing as too much explanation in fiction. If you try to explain every tiny detail you have probably bored your audience. $\endgroup$ – John Apr 17 at 21:39
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    $\begingroup$ @John or, worse, your imperfection gets noticed (paragraph #3, good for Niven for being a good sport about it). $\endgroup$ – JBH Apr 17 at 21:51
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    $\begingroup$ @John worth looking at newscientist.com/article/… if you're interested in how to capture "waste" energy from human motion. I'm not entirely convinced that I'd want to run a long way with one of these but it offers a vaguely plausible grounding for technobabble about generating useful amounts of electrical power. $\endgroup$ – KerrAvon2055 Apr 18 at 1:31
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    $\begingroup$ " pumps were part of the heel of the boot to provide the pumping action needed to move the water around. That's undefined, too! " that may be undefined but it's also very very plausible relatively low level tech that most with even the most rudimentary engineering background could visualise without further detail, it didn't need further defining because that description adequately defines it for most, "heal pumps & valves" is all any engineer would need to hear to be able to go away & design that element of the suit. $\endgroup$ – Pelinore Apr 18 at 2:14
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    $\begingroup$ Having spent a little time as a sorta intern in the water industry - there's plausible ways that a foot pump might be used to turn salty post consumer water into drinking water - possibly a foot powered RO filteration system.... $\endgroup$ – Journeyman Geek Apr 18 at 8:03
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Every morning I take the bike for a ride, and every morning I wear a jacket made of synthetic material. Every time that I place the key in the slot to open the door and get out I see a spark.

The spark happens because while I wear the jacket the friction between the jacket and my clothes produces electrostatic charges which then get to ground once the metallic key touches the key-slot.

This is what you are looking for: static electricity.

A static electric charge can be created whenever two surfaces contact and have worn and separated, and at least one of the surfaces has a high resistance to electric current (and is therefore an electrical insulator).

The energy released in a static electricity discharge may vary over a wide range. The energy in joules can be calculated from the capacitance (C) of the object and the static potential V in volts (V) by the formula E = ½CV2. One experimenter estimates the capacitance of the human body as high as 400 picofarads, and a charge of 50,000 volts, discharged e.g. during touching a charged car, creating a spark with energy of 500 millijoules. Another estimate is 100–300 pF and 20,000 volts, producing a maximum energy of 60 mJ.

With those level of available energy you don't really have much juice to do anything serious besides setting some gas on flame.

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  • $\begingroup$ 500 mJ is enough energy to run a 1W LED night light for 1/2 second. $\endgroup$ – Wayne Conrad Apr 18 at 15:07

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