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Safety and legality aside, could you design a phone that never needed to be charged?


nhnifong

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What energy sources are available that would allow an ordinary smartphone to operate without ever needing to be charged?

If you included a 0.5 W radioisotope thermoelectric generator, how big would the phone have to be? How hot would it get? Would it have to use Plutonium 238 or could it use some other fuel?

Correction: I didn't mean "never". Just that it would last as long as you owned it, for like 5 years or something.

Edited by nhnifong
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Phones or anything else that needs no input energy are just as plausible as perpetual motion machines; which are impossible. Even RTGs can run out of fuel; it just happens decades later, depending on the chosen fuel.

We can, however, design one that has enough battery reserve to last its entire service life (typically 1-2 years). Alternatively, they can be made to constantly charge itself, similar to how wristwatches wind their spring using energy from hand movements. Problem is, neither of these technologies have enough power density to be stuffed into a smartphone frame.

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depends what you're asking.

could I?

no

is it possible with todays technology?

possibly with classified / bought out technologies.

is it possible eventually?

sure, I see no reason why tapping into zero point energy shouldn't provide enough energy for all humanities energy requirements.

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design one that has enough battery reserve to last its entire service life (typically 1-2 years).

That's what I was thinking. My inital research indicated that it would be possible with about 1 gram of Pu-238 and some thermocouples.

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Isn't there already a phone in development that runs off bio-electric impulses and body motion, just by being handled or stored in the pocket?

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As shynung mentioned, "never" is a rather long time. So long that you'd need an infinite power source to do so. A more practical idea is to try to cram enough energy into it that it won't need to be charged before you replace it.

You kinda answered your own question though. If correct, a gram of Pu-238 isn't all that much to fit into a smart-phone battery. It could be easily accommodated by removing the battery. So there you go. As long as you don't mind getting just a little bit more irradiated by your phone than the environment, that'd work. The main problem would be disposal, as while sure, you could use it in a phone, you couldn't throw it anywhere. Pu-238 is an extremely powerful alpha emitter, so you sure wouldn't want to eat it or let anyone else ingest any. Bad fuel choice for a phone (or any ubiquitous product).

sure, I see no reason why tapping into zero point energy shouldn't provide enough energy for all humanities energy requirements.

Uhhhhhhhh...how about the slight problem that there isn't even a theoretical basis for turning any of that into useful energy? Nadda. (Unless someone's published some papers on the subject recently that are actually verifiable.)

You could also say "I see no reason why all our energy problems might be solved in the near future because magic might exist and Merlin might come back to give us all free energy."

Edited by phoenix_ca
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thorium might be an option for a radioactive fuel.

lots of output, and the radation can be blocked with aluminum foil.

You can't power a phone using thorium alone. Not oxide, not metallic. It's not a suitable atom like you have in RTGs, where isotope of plutonium alpha-decays like mad and creates heat.

You could use thorium in a chemical battery, but it would be shortlasting. Thorium has similar chemical reactivity like lithium. But nuclear, no. Won't happen.

Also, rays emanating from thorium samples (metal, oxide, chloride, etc.) can't be blocked by an aluminium foil. Thorium and its products emanate gamma-rays. You need few centimetres of lead to attenuate that sufficiently.

So, no thorium phones, no thorium cars. Can't happen.

Isn't there already a phone in development that runs off bio-electric impulses and body motion, just by being handled or stored in the pocket?

I don't know what you mean by those impulses, but there are chargers that use body motion and body heat, but they are used to slow down the battery discharge. They can't power the phone because those energy sources are too weak.

sure, I see no reason why tapping into zero point energy shouldn't provide enough energy for all humanities energy requirements.

I don't think you know what zero point energy is, or in fact how energy behaves. There's a reason why it's called zero point.

Edited by lajoswinkler
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no-ones written a paper on it therefore it's impossible.

:D

That is exactly not what I said. You're seeing a fallacy where there isn't one (or rather making one-up, which is known as a straw-man argument). I said there is no theoretical basis for ever being able to convert zero-point energy into any sort of energy we could put to use. Your assertion that you "see no reason why tapping into zero point energy shouldn't provide enough energy for all humanities energy requirements" is thus an incredible exercise in naivety.

Edited by phoenix_ca
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there are betavoltaics which use tritium to produce a very small amount of power. i dont think they are powerful enough to run a phone though. they were used in pacemakers prior to the invention of lithium ion batteries. i could not find any actual numbers from actual devices, but from what i was able to find is that they usually produce power on the order of tens of microwatts to milliwatts.

i think the main problem is that these kinds of devices depend on isotopes that do not exist in nature, and have to be produced as side products in nuclear reactors. so they are expensive, in limited supply and just not economical. tritium goes for $30000/gram.

Edited by Nuke
micro != nano
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Phone that never needs to be charged

Anyway, it seems more likely that as technology progresses that both batteries and the chips and such that phones use will get better, so a charge might last months or years. Or you'll just lay your phone on a nightstand or something that has an "area" charger to top off what little charge you use.

Or not, because phone makers like that you have to replace batteries often, since so often it results in "meh, might as well just get a new phone"

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I don't know what you mean by those impulses, but there are chargers that use body motion and body heat, but they are used to slow down the battery discharge. They can't power the phone because those energy sources are too weak.

I think the idea was that the phones would become more power efficient, eventually requiring so little energy that it could soak up enough power from the user to keep it running.

Hard to say now, it was one of those things I read in an article about an awesome new breakthrough in development, that you never hear another peep about until another ten years have passed. Though, I might be mixing human body energy with other bio-tech I read about for the same purpose, such as batteries 'powered' by microorganisms.

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Or not, because phone makers like that you have to replace batteries often, since so often it results in "meh, might as well just get a new phone"

Not really. Phone manufacturers have a vested interest in reducing the footprint of the energy supply. Most of the space and weight of a phone now is taken-up by the battery. Reducing the size of the battery and increasing it's energy capacity are actually great things for manufacturers because it allows smaller devices, or similarly sized devices with far more computing power.

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I don't think you know what zero point energy is, or in fact how energy behaves. There's a reason why it's called zero point.

Yes, hydro electrical plants get their energy from the potential energy in the water higher up the river.

the water in the ocean still contains lot of potential energy relative to earth core but that energy is hard to tap.

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One of the interesting concepts is powering some electronics by harvesting the man-made electromagnetic fluctuations, emitted by cell phone transmitters, WiFi routers and just power cables.

The problems are:

a) can it ever have enough power to maintain outgoing signal that won't get lost in this electromagnetic noise? It could be OK for text messages and even maybe for internet (it usually requires much less output than input, but heavy uploads might be a problem), but for phonecalls it's questionable.

B) can overuse of this technology create too much interference for the communications?

c) it probably won't work outside the cities

So, for simple electronics yes, for phones most likely no.

As for radioactive, I'd say betavoltaics with low heat output are the option. RTG works by getting hot and requires rather good cooling, and I don't want to have something hot like this in my pocket, even if it's shielded.

Thorium reactor? Are you serious? The fact it's less active on its own than U-235 does nothing with other issues, like fission products. And shielding from neutron radiation is not as easy. Besides it's still thermal-based

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Just to put some numbers on it, assuming your phone uses about 1W, to get five years of life out of it you're looking at about 45kWh (160-ish MJ). If you limit yourself to about 100g for your storage system you need something with an energy density of about 1600MJ kg-1. Power is low enough we don't need to worry about power density. Looking at tables of energy densities (such as this and this) then all battery technologies and all known liquid fuels are out the window.

You'd need to either radically reduce power consumption or you're looking at nuclear fuels to hit your energy density target, and miniaturising those seems a bit implausible.

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Fun ways to build devices that never require recharging: hook up a fuel cell to your bloodstream.

Now obviously this technology doesn't have the power density to handle smartphones either, but it can handle things like pacemakers which are implanted into the body in such a way that changing the batteries is really, really inconvenient yet critically important. By instead using a fuel cell that can process glucose to produce electricity, the pacemaker can run for as long as the heart that it keeps pumping lives.

Future visions for this technology include wireless touchscreen skin implants, which could bring us somewhere in the vicinity of smartphones again :P

Edited by Streetwind
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Cell phone batteries these days are about 2.5Ah at 3.7V. That's about 35kJ. And a charge lasts about a day at moderate use. That's under 65MJ over 5 years. Most people change their phones at least that often. That's less than a microgram of mass defect energy. You can get that from a few milligrams of nuclear fuel. If you are stuck with efficiency of an RTG, that's still under a gram of fuel all in all. So yes, the answer is that you positively can build a phone that you will never need to recharge within its intended 5 year life span.

And now for practical considerations. The nuclear fuel would have to be extremely unstable. The half-life would have to be on the order of a decade. That means, no naturally occurring isotope will do. This would have to be something you intentionally breed in a reactor. Expensive as hell and not even remotely environmentally friendly. Next, we go to power output. RTGs are not efficient, and you are not building a more efficient reactor on that scale. You'd be lucky to get 5% out of it, which means the reactor will be dumping almost 10W of heat constantly. You know how hot your phone gets after a long conversation? Picture that all the time.

And now, the elephant in the room. Radiation. Most of the energy released by such a device is going to be in form of ionizing radiation. Unshielded, this power output would result in you taking a lethal dose in under a minute. Naturally, the very idea of making RTG is in absorbing radiation, but there are no materials that will absorb it efficiently enough on the scale of a cell phone. There is simply no way. Enough radiation will escape to make it a serious health hazard. At best, this thing might be safe enough for a quick phone call, and I wouldn't even bet on that. Maybe, there is sense of keeping something like this in a led-lined safe for emergencies, but I could think of a number of much safer and cheaper ways of getting power for one phone call.

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Thorium reactor? Are you serious? The fact it's less active on its own than U-235 does nothing with other issues, like fission products. And shielding from neutron radiation is not as easy. Besides it's still thermal-based

You're missing a point. You can't have a nuclear reactor the size of a smartphone battery. You need a pile of the fissionable material, or else you have no criticality.

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And now, the elephant in the room. Radiation. Most of the energy released by such a device is going to be in form of ionizing radiation. Unshielded, this power output would result in you taking a lethal dose in under a minute.

Not really. It all depends on the fuel. Pu-238 would be the obvious choice if you can make an RTG efficient enough to cram it into a phone, as the alpha particles emitted by it are just normal alpha particles (5.593MeV), and thus have low penetration (skin is enough to block them, easily; the metals in the phone would further reduce their penetration potential).

The heat issue...yeah that'd be more of an issue and far more annoying than the radiation.

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