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Stopa42 t1_j0bdlvs wrote

Physicist here. To boil 1 litre of water you need 4200 J of energy per degree of Celsius. So to heat water to boiling temperature from room temperature, you need approximately 4200 J/°C * 80°C = 336 kJ of energy. To deliver that amount of energy in 5 seconds means you need to supply power of 336 kJ / 5s = 67.2 kW. With standard 230 V outlet this would be 67.2 kW / 230 V = 290 A of electric current. Using 3phase plug for 360 V would require 186 A. Cables in walls are typically rated for a few tens of Amperes, definitely not hundreds. This is why circuit breakers are typically rated for ~20A. Running such a high current through the cables would literally melt them.

TLDR: You most definitely can have a 5-second kettle but it would set your house on fire.

EDIT: Electric vehicle superchargers are usually rated for 50-100kW, so you could make a kettle that plugs in EV supercharger and boils water in less than 5 seconds.


prescience6631 t1_j0bjzmt wrote

Setting my house on fire for 5-second kettle is a reasonable tradeoff, where do I sign up?

If I nuke my neighborhood can I have 5-second pizza or hot pockets?!


jdbrew t1_j0bqnac wrote

Now there’s a question. At what distance from a nuclear bomb with the heat from the explosion perfectly cook a hot pocket


ThePowderhorn t1_j0cj4vg wrote

I'm content to read the results of that experiment from hundreds of miles away.


Procyon4 t1_j0cr7hf wrote

Drop it right on top of the hot pocket to ensure the proper molten magma temp inside to burn all your taste buds


X2ytUniverse t1_j0cw3i1 wrote

I don't want to say for sure, but I'm pretty sure there was 2014-ish youtube video about that, might've been one of the Vsauce channels or something. Think they determined that its actually impossible.


Dlee8113 t1_j0dkwjl wrote

Yeah, was gonna say I swear I’ve seen a vid on like flash cooking a frozen pizza


[deleted] t1_j0cw4qz wrote

If this isn’t already in one of Randall Munroes books, expect it to be very soon!


alexjaness t1_j0crs49 wrote

yes, but they will still somehow be frozen in the middle


oregonadmin t1_j0fepdg wrote

Your hot pockets will still be cold in the middle.....


F1NNTORIO OP t1_j0bikyk wrote

When shall we rise out of the dark ages and into futuristic housing with supercharged cables and appliances?


Rogermcfarley t1_j0bjhp9 wrote

It's the dark ages to utilise more power. Need to use less power not more wherever possible.


1stdayof t1_j0bneko wrote

Getting the water to boil requires the same amount of energy whether that's completed at 10A or 200A.


Rogermcfarley t1_j0bo475 wrote

It does but it requires an infrastructure change that's arguably unnecessary and I refer you to my previous point on consumerism.


YawnTractor_1756 t1_j0bl34k wrote

I love when people advocate against technologies on the internet and don't even get the irony of it.


Rogermcfarley t1_j0bmgpx wrote

I'm a strong advocate of technology. I'd rather have working fusion technology, machine learning that will help us create better scientific studies and unravel the vast complexity of human biology so we can treat more health issues. Technology that creates sustainable consumerism and technology that eliminates the need to deforest the rain forests, to stop using flourinated gasses and nitrogen based fertilisers. If that means my kettle doesn't boil in 5 seconds that's the sacrifice I'll gladly make.


realstreets t1_j0f18pb wrote

But what is the point of abundant energy from nuclear fusion if we can’t use it to supercharge our household appliances to save us 30 secs each morning?


YawnTractor_1756 t1_j0bn74r wrote

Then why would you advocate against boiling kettle in 5 seconds? Having faster energy delivery does not have any anti-preservational qualities in itself. For what it's worth it the other way around, from charging cars to warming houses, if our power grid could do more we would be able to replace fossils faster.


Tree-farmer2 t1_j0bpmom wrote

The real limitation of electricity replacing fossil fuels is that storage is much more challenging.


YawnTractor_1756 t1_j0c6ns0 wrote

There are many real limitations, and storage is one of them, but many of people are clueless to how much the grid itself and its limitations in power delivery and (!) conversion are a problem. The only difference with storage is that overall we already know how to do it. If storage would be magically solved tomorrow you would still need to upgrade and partially rebuild the whole grid to make things work.


ThePowderhorn t1_j0cll0s wrote

Count me among the clueless. One of the things that's been percolating in my mind as more and more devices run on DC and batteries is when the electric grid as it currently exists will be an anachronism for its then-current (no pun intended) use cases. Your mention of conversions brought this to the fore.

I get that pretty much everything short of solar is turbine-driven, which if I recall correctly is why we have an AC grid (high-school physics was a while ago, so I don't remember why). Since solar is the only residential-scale generation option, at what point does it start making sense to keep small-scale (say, neighbourhood level) DC needs separate from the AC that industry is designed around? I can't imagine there's anything to be gained from DC-AC-DC conversion.

edit: typo


PM_ME_YOUR_WOLOLO t1_j0cuuq8 wrote

I had to look this up because I didn't remember why either,transmitting%20electricity%20over%20long%20distances. but apparently it's more efficient (less energy loss in most circumstances)


PsikoticWanderer t1_j0duw2u wrote

I am an electronics engineer. AC current travels long distances on a conductor while losing very little energy. DC current loses energy in the form of heat as it travels on a conductor. Centralized power grids liked we have today based on DC are not possible.

When AC shorts to ground a local thermal event occurs causing localized damage. When DC+ shorts to DC- it heats the whole conductor path from the point of contact back to the source and damages or destroys all conductors in that circuit. In the event of a short AC repairs will be much cheaper.

Google Edison Tesla, they had a years-long feud over AC vs DC power grid. An elephant may have been involved.


PM_ME_YOUR_WOLOLO t1_j0dv3kp wrote

Thank you for the explanation! Yeah I do recall learning about Edison and Teslas feud over AC vs. DC. I’m a software engineer so this isn’t my wheelhouse at all


PsikoticWanderer t1_j0e7gap wrote

I do software too. Test dev for an automotive manufacturer so I get to build test stands and program them. Fun stuff.


Tree-farmer2 t1_j0egvx8 wrote

Didn't DC motors at the time cause sparks and AC solved this?


YawnTractor_1756 t1_j0dc6g6 wrote

All renewables require a DC-AC conversion. And we would need tons of them. And they use rare metals.

Broadly conversion also means voltage transformation. If you want to run more current (because we make more electricity, because we need more electricity, because we charge cars and shift from cooking with gas to electric etc etc) then you either need more wires (and more towers, and transformers) or you need better wires and better transformers.

There is additional problem with maintaining electric frequency. Currently it is done via fossil generators, nuclear is not suitable for that purpose because of how it's generation is used. Renewables are expensive at that. In future of renewable energy it has to be done with storage. If storage is used for it then storage would not just be a 'backup battery' now, it would become a grid forming part, with added requirements.

I googled a good article about that, here:


ThePowderhorn t1_j0ddzp1 wrote

Thanks for the link! Usually I have a distance excuse to not do further research, but given that I get my power from Austin Energy, learning more should be rather doable.


A_Slovakian t1_j0c9r18 wrote

The current grid could never support everyone having a 5 second boil kettles or a 10kW PC or what have you. It would cost billions to upgrade the grid to support that and doing such a massive infrastructure project would release millions of tons of CO2 into the atmosphere.


swiminpool t1_j0bm49q wrote

What, he’s gonna write you a fuckin letter or something? Lol


ReaperofFish t1_j0c77et wrote

When we have individual fusion generators with superconductor wiring in our homes.


Nyrk333 t1_j0chkpj wrote

Why accept the limitations of the house wiring? You don't need to *source* 336 Kj of energy in 5 seconds, you need to *deliver* that much energy to the water in 5 seconds...

If your kettle had a large capacitor that charged up over, say 30 minutes, and maintained that charge. You could pour water into it, retreat to a minimum safe distance, and trigger the kettle remotely with an app on your phone....


jawshoeaw t1_j0cgntr wrote

I believe the national ignition facility may be interested in your above grant proposal.


pab_guy t1_j0bipge wrote

Nah just use a supercapacitor it's fine.


thefarstrider t1_j0dco4h wrote

> EDIT: Electric vehicle superchargers are usually rated for 50-100kW, so
you could make a kettle that plugs in EV supercharger and boils water in
less than 5 seconds.

Patent that shit my friend. Brits would install the chargers even without owning an EV.


VukKiller t1_j0bk7he wrote

Now make it wireless.


protoman888 t1_j0bqggn wrote

and integrate AI into it which knows when I want my cup of tea


rixtil41 t1_j0dar5w wrote

Instantly vaporized if someone walks in front of it.


timelesssmidgen t1_j0c11bs wrote

How about with a big old capacitor inside the kettle which trickle charges in between use?


timbe3 t1_j0ccj9t wrote

For the amount of energy needed... Wouldn't that requires a capacitor bank the size of a car?


timelesssmidgen t1_j0cez2w wrote

Wikipedia tells me super capacitor energy densities are around 0.01 MJ/kg (no idea if that's reasonable for consumer grade stuff) So to store 336 kJ you'd need 34 kg of super capacitor. Not nothin' but if you really want that cuppa right now you might go in for it. Electrolytic capacitors are more like 0.00001 MJ/kg, requiring 34 thousand kg. So... I won't be installing that under my sink.


ryan__fm t1_j0bqaio wrote

That's assuming the liter of water is in a kettle-shaped container, right? If a coffee machine can constantly get cold water to very high temperatures very quickly because it's a small amount at a time, wouldn't it be possible to design a kettle so that more of the water's surface area is in contact with the heating elements? So essentially instead of boiling 1 liter of water in a pot, you're boiling something like 1/10 of a liter of water in 10 smaller pots?

edit: I think I get it... I suppose what I'm describing would be possible if you could supply that much power to it that quickly. Coffee machines use a lot of power but over a longer period of time


jrp55262 t1_j0c1cwb wrote

What you describe is basically an electric tankless water heater. Here are some specs from one manufacturer. The beefiest one they've got requires a 150A electrical connection and it still only raises the input water temperature by 98F; assuming that the incoming cold water is about 55F that gets you up to 153F... which might steep a cup of tea but is still well shy of boiling.


lewisc1985 t1_j0c2g5i wrote

That’s 98 degree delta at 2.5gpm, mind you. If you lower how many gallons are going through it, it can get much warmer. I have a 18kw unit that can do 70-80 degree delta with three 20 amp breakers at a much lower gpm.


timbe3 t1_j0ccfim wrote

New start-up, KTL enters the chat


badumtussssss t1_j0cf5s6 wrote

A tangential question.... How about instant charging of phones and small electronics?


monkeynotes303 t1_j0cp1j6 wrote

On demand hot water boilers are a thing, but not boiling and not 5 seconds. OP needs to up his electrical, it's possible to do, but sounds like you need a new electrical panel, more copper in your walls, an engineer, and a word with the utility company.


stellarblackhole1 t1_j0cuz7y wrote

Would it be cheaper and more efficient to lower the atmosphere of the kettle in order to induce boiling at that point?


Stopa42 t1_j0czn91 wrote

I'm not sure if vacuum pumps are exactly cheaper and more efficient at making water boil (evaporate in full volume instead of just surface) but it would be quite pointless. It's not the vapour bubbles that cook your pasta or brew your tea, it's the water temperature. That's why Papin's pressure pot is a thing, the high pressure increases the temperature limit and allows you to cook watery food at temperatures above 100°C.


jeffbloke t1_j0dg81j wrote

so basically, we can already do it but having the equipment available to do it is a massive, constant, ongoing death hazard. sweet.


p1mrx t1_j0dn03n wrote

Electric vehicle batteries regularly deliver 150+ kW, so it might be more practical to design a superkettle into the car's electrical system.


bcredeur97 t1_j0e07i0 wrote

Is it not possible to charge a bank of batteries or supercapacitors using lower current overnight and then blast it in 5 seconds from the batteries in the morning?


Jetm0t0 t1_j0eb902 wrote

How much energy/heat loss is there from the boiling reaction? I am taking physics soon and couldn't find an answer yet.


epSos-DE t1_j0ee39d wrote

ADDitionally energy state intertia is hard to break.


Acceetation requires more energy than the steady system of incremental steps.


Fast heat-up does requiere additional acceleration effort of the process.


Slow build-up and then a faster heating up could work and maybe shorten the total time by about 25%-30%


Like a boost at 60°C to 80% is much easier than working with cold water.


MrWigggles t1_j0eghn1 wrote

Can water actually heat in 5 seconds? Water can only absorb so much heat in a given amount of time.


boonepii t1_j0eo3ad wrote

How does induction work then? I hear it boils water in seconds.


Half-timeHero t1_j0f2qvs wrote

Additional potential problems:

Besides the power wires you would also need to consider heat transfer and the durability of the heating elements. Transfering that much energy into water within 5 seconds likely isn't even possible as the heating elements would need to be so hot it would flash boil the water immediately next to them, forming a protective layer of vapor, killing your heat transfer and probably melting the heating elements.


Stopa42 t1_j0fmtk7 wrote

That's just a technical issue though. A kettle with a resistive heating element running through the whole body of water you would not even create that high of a temperature. Think about it as several standard kettles connected in parallel.


hgq567 t1_j0fh9ja wrote

Could you use a capacity+battery bastard to trickle charge when you aren’t using it?


KindaSortaGood t1_j0fr60p wrote

Sounds like the entire UK power grid would implode if a 5 second kettle were invented.

Either that or we would have major advancements in adoption of electric vehicle charging tech.


yyytobyyy t1_j0fw75r wrote

Just an electrical correction.

Combined voltage in 3 phased circuit for 230V phase voltage is 400V. For old 220V circuits it's 380V. 360V never existed.

Current in 3 phase circuit can't be just added together when using combined voltage.

However, with resistive AND balanced load (implying perfect 3 phase kettle), you can just calculate single phase current and divide by 3. So the current for 67.2kW in 3 phase circuit would be ~97A per phase.


Stopa42 t1_j0gsnzn wrote

You are of course right. It is 230 V * sqrt(3) ~ 400 V. I don't know how I came up with the 360 V. I don't use these values very often so they are not really imprinted well in my memory. The point stays the same, although circuit breakers rated close to that value are actually commercially available so we're not that far away I think.