A potato battery can light up a room for over a month (2013) | Hacker News Reader

A potato battery can light up a room for over a month (2013)

smithsonianmag.com

71 pointsmiles69 comments

Just use salt water?

It's even cheaper and more shelf-stable than potato, and there's quite a lot of it on the planet.

Or just use a solar panel. I'm sure with a battery, a single panel could light up my room perpetually.

A solar panel may not be economically possible for many people in say Africa.

A single solar panel should last you at least 10 years. How much does a 10 year supply of copper and zinc plates cost? I think you would have to stretch to insane lengths to find any case where this kind of power source is economical, sustainable or logical.

I have friends who live in shanty towns in Zambia. I can guarantee you that they will be unable to shell out for a solar panel — even if it lasts for 10 years. I don't know about zinc, but copper is plentiful (in fact, they both live in the Copperbelt Province) and they don't have to pay for all 10 years of copper and zinc in one instalment.

Article is complete faff. The potato is not the battery, it is not an energy source, and the article says nothing about the economics of the two plates which are the actual energy source. Don't waste your time.

Also, does the article include in their equation the amount of energy needed to boil the potatoes for 8 minutes?

If you’d read the article, you’d know that it explains that the potato is just acting as the electrolyte, and it does mention that replacing the zinc electrode is cheap.

As another comment explains, it is merely getting back some of the energy expended in extracting metallic zinc and copper from their ores.

Also such potato batteries have been a school science projects for long.

I'm not defending potato batteries, I'm just pointing out that the article already explains all of this.

... as would a bucket of salt water. Or piss.

Yes, but the headline says it's a potato battery. It's not. It's a battery with a potato in it.

But that's what all potato batteries are.

That’s what they want you to think.

Lmao (if I delete this it’s bc I don’t like getting downvotes)

Nooo I can’t delete!!!!

That’s what they want you to think.

It is a potato battery—that's what it's called when you use a potato as the electrolyte for a battery.

https://www.youtube.com/watch?v=36hzlFVgVa8 seems to be the video (didn't play for me at the link).

It's really a zinc and copper plate battery. Apparently boiling the potatoes can improve the power output.

You'd have to factor in the resource usage of producing zinc and copper plates before even considering using this as a real solution.

I think this because an enormous amount of energy was use to smelt the metal from ore. Oxidizing it slowly for electricity is possibly just a weak and inefficient battery.

Is it viable? We know industrials get power at cheaper rate in some counties, is there any arbitrage possible by making huge batteries like this for residential and commercial use?

2010. (posted article from 2013).

https://www.researchgate.net/profile/Boris-Rubinsky/publicat...

> To be clear, the potato is not, in and of itself, an energy source. What the potato does is simply help conduct electricity by acting as what’s called a salt-bridge between the the two metals, allowing the electron current to move freely across the wire to create electricity. Numerous fruits rich in electrolytes like bananas and strawberries can also form this chemical reaction. They're basically nature’s version of battery acid.

That doesn't sound so exciting to me.

Isn't that a bit like saying

"The sun is not a light source, it's just very hot, which causes hydrogen to go into nuclear fusion, which releases energy in form of electromagnetic radiation"?

Or is my comparison flawed?

The energy is coming from metals rather than the potato. The potato simply links them allowing their ions to react and create an electric potential.

Iwish the article described the cost, size, and rarity of the two metals, but instead it focused only on the potato

The actual paper does: https://www.researchgate.net/publication/239391768_ZnCu-vege...

If you want a deeper dive, the chemistry here is actually really simple and (IMO) very cool.

I'm drawing on some really dusty knowledge here but TL;DR the cells can be modeled as two reactions, oxidation and reduction. One is gaining an ion and the other is shedding one. This is typically shown in the equation as some number of "e-".

Because there are two reactions, each one is described as a half cell and there are tables[1] of all the voltages that these half cells create. Therefore you can mix and match to create batteries of arbitrary voltages, though whether they're practical is another issue.

If you look at the table, you'll notice that some common battery chemistries stand out, like:

Li+ + e− ⇌ Li(s) −3.0401

for lithium Ion batteries (the other reaction adding the last ~.7v to reach the nominal 3.7 cell voltage you're used to). Similarly you can find the half cells that make up a 1.5v alkaline battery[2].

[1] https://en.wikipedia.org/wiki/Standard_electrode_potential_(...

[2] https://en.wikipedia.org/wiki/Alkaline_battery

I don't know why - but this comment makes me laugh

It can’t be quite that simple. I’m not at all an expert in electrochemistry, but you can put pure zinc and pure copper together in a sealed container with nothing else except ideal electrodes until the cows come home, and you will not end up with copper oxides, zinc oxides, or any useful energy output.

I mean, just some salty water will do the trick

Not the OP, but now I got it, thanks.

What it means is that the potato is just working as a media to connect two metal plate and not as a power source. Actual voltage and current is created by the metal plates corroding and melting into potato.

So it’ll be like saying “the atmosphere is not an energy source, it just blows between the sun and solar panels” without understanding what that means.

No, the potato is basically acting as a salt bath here. It would be more like thinking the empty space the sun's light travels through is the light source, not the sun.

See also this bit of Internet history: https://web.archive.org/web/20000815202656/http://world.std....

Discussed a little bit here:

Potato-powered web server - https://news.ycombinator.com/item?id=3346741 - Dec 2011 (10 comments)

Spud, potato powered web server - https://news.ycombinator.com/item?id=887160 - Oct 2009 (6 comments)

Doesn't this require the degradation of the zinc and copper plates that are required for it to work?

Yes, conversion of the metallic copper and zinc into ionic salts is where the energy comes from.

Read the paper:

https://www.researchgate.net/publication/239391768_ZnCu-vege...

The zinc is consumed. The copper is not.

Yes, but the plates could be cleaned and used multiple times.

For plates of reasonable size, simple abrasion would be enough.

I assume I'm just being dense, but if you have to boil the potato, surely that takes a bunch of energy? Or do you burn wood to do that in this scenario

Yes. The question to ask in these approaches, from an appropriate technology standpoint, is the locality around creating energy storage and what it would take to maintain the storage device, not just conversion efficiency.

For example, one may argue in a given situation one should use an induction cooktop from an efficiency standpoint (and also particulates reduction). Another may argue in a given situation one should use a woodstove if they can source the wood in a sustainable manner and can create maintain the woodstove itself locally. Not asserting a right answer here, just outlining some tradeoffs.

Would the potato be safe to eat afterwards?

If widely deployed, I would imagine that a non-negligible number of potatoes would be eaten after being exhausted as a battery.

Many copper compounds are toxic, I wouldn't even think about it.

zinc ain't no cakewalk either

Then why is it used to carry drinking water

Drinking water isn't a corrosive / reactive media the same way a battery is.

You dont want metal salts in your potatoes

You dont want to want to eat a cooked potato that is 40 days old either.

The potato doesn't provide the energy; the two metals do.

The implicit development is the improvement of LED efficiency.

Sorry for being glib, but I'm reminded of this comic:

https://www.smbc-comics.com/comic/energy

Obligatory portal 2 snippet:

https://m.youtube.com/watch?v=0S3_YJC6OFs

Might I suggest the name:

Spud-U-Light?

I can't believe the level of disconnect some people on HN have with the "other" worlds.

Poor people don't need LEDs? LEDs are the cheapest light source in the long run. The electricity/batteries to run it might be expensive or impossible to get in some places.

Check out this gravity-run light source which is "essentially free" and being used in many places.

https://youtu.be/Jsc-pQIMxt8

They now sell “NowLight”, which you pull on for a minute and it generates enough electricity for 15 minutes of talk time on a mobile phone (or 2 hours of light)

https://deciwatt.global/nowlight

That gizmo doesn’t exist any more.

Even if it did, the physics don’t really work. A high end bright LED light draws a few watts. Let’s say the LED uses 1 watt, and the gears are perfectly efficient. One watt-hour is 2655 foot-pounds. Assume the weight is 265 pounds with a 10:1 pulley to lift it. You’d have to pull the rope attached to the pulley 100 feet to charge the light to run for one hour, and the device would need to be 10 foot tall. Figure in mechanical losses, and a more realisitic LED, and you end up multiplying the weight, and pully ratio by ten. Now, the weight is similar to a small car, and you pull the rope 0.2 miles for a one hour charge. Make it 5 foot tall, and the weight and rope double again.

I first heard about it here! Glad it’s still a thing, it’s neat.

https://news.ycombinator.com/item?id=9981745

This is wrong on so many levels it's hard to know where to begin.

Poor people don't need small LED lights and it obviously won't charge a phone. Not sure what the whole "the potato is not, in and of itself, an energy source" is rambling on about. Boiling a potato takes a lot of energy, obviously way more than a battery/potato can deliver.

Here's the rat attractant battery - https://www.researchgate.net/figure/Potato-battery-basic-com...

But jumping to the mathematics I simply don't believe it would be cheaper than a battery

I do believe a potato has a lot of energy, I'd assume much much more than a D Cell, but to turn that to usable electrical energy cheaper than a battery I'd be very surprised. I doubt this, but are unsure.

[edit] Here's someone who ran their clock for 6 months on a potato (Still not proving either way which is cheaper) - https://www.amazon.com/ask/questions/Tx3AUA83YPS7DMP/

>Poor people don't need small LED lights

Huh? Reliable light is one of the best things to provide impoverished areas with, after clean water/food/medicine/sewage.

It's one of those things that we really take for granted, but if someone dropped you in the middle of the woods, I bet a headlamp and power source would be one of the first conveniences that you'd ask for.

Anyways, like others have pointed out, the energy comes from charge carriers moving between the metals stuck in the potato, not the potato itself. That particular misconception comes up surprisingly often, to the point that it's kind of a running joke in its own right. Portal 2 had a pretty tongue-in-cheek take on the gag.

You'll find in practice they can afford a cheap led light and battery what they need is a charger for their phone (And clean water/micro-nutrients/medicine/sewage~=clean water)

And wow, potato batteries are a scam. Fool I am.

So boiling them won't release more energy to electricity... I guess... I'll need to sit down and work it out. I don't get why a cheaper fluid that doesn't rot won't work ok then.

Why is there no web page explaining this Sci Fair scam. Why a potato over salty water? Or a steak. Or a lump of dirt. What's the relationship between a potato having energy and the fact it's used in potato batteries.

Oh, it's not a science fair scam - it's a great way for kids to learn about electricity! Compare it to sticking similar nails in a few other objects, and you've got yourself a poster.

But it's also not as simple as growing a field of lumpy batteries.

aaron695 says:>Poor people don't need small LED lights... <

I commonly find myself asking for a flashlight when helping friends or acquaintances with everyday fixes. I wish I had a potato for every time they offered me their (dim, unwieldy and dysfunctional) cellphone with flashlight app.

In the old days, everyone had these widgets called "flashlights" in their homes. These flashlights worked well and had backup batteries. Today we have a bunch of morons groping in the dark with cellphones.

Fun time watching the cellphones die out during the Texas Freeze event weeks ago. "Anyone got a flashlight?" I now know the proper response is "Nope, but we've plenty of potatoes!"

I can recommend this type of small “everyday carry” style torch: https://www.olightstore.com/i3t-eos.html having got one for my Mum so she could check the time on her watch during the night. Small, single AAA, single end-cap button / two modes - defaults to dim, second quick press for bright.

implements says >"having got one for my Mum so she could check the time on her watch during the night."<

$39 is stiff for a AAA flashlight! How about $3:

https://www.walmart.com/ip/Rayovac-LED-3-lumens-Flashlight/1...

This one has a laser and costs only $6:

https://www.walmart.com/ip/Rayovac-LED-Laser-Pointer-Flashli...

How about a candle and a box of matches? Or this for $1.50:

https://www.walmart.com/ip/BIC-Classic-Pocket-Lighter-Assort...

In my defence, I did say “this type of” - but the equivalents you found looked good.

Not sure about the proposed ‘fire + mother’ combination, though.

Sure, in energy rich nations! But in lots of parts of the world people do not have access to much electricity for lighting.

I've visited people who live on less than $1.90 a day. They generally have power to run any led lights that might run off a potato. They often had access to a motorcycle and access to a cell phone.

One example for electricity is to rent car batteries for the night to charge their phones and run TV's, both vital to help people escape poverty.

They don't want solar lights or bicycles. They need mobility and information flow on their own terms. Give them eBay not Wikipedia / a book with a light.

https://www.researchgate.net/publication/315719288_Can_Solar...

Those minority who don't even have a led light have some pretty big issues. Night time lighting is low on the list, you could just give them a torch and battery not a complicated potato device if it mattered.

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