A sane solution would be a mug with a small resistive heating element in the base that would work off a Qi wireless charging pad. Could even have thermostatic control to maintain precisely your preferred temperature.
Actually, this seems so obvious that I bet this product already exists.
Maybe you could get a variation on this sane, practical idea.
Surely, but it is just something else to be charged. More cables, reduced performance over time. Batteries just lack that engineering elegance of a decaying isotope.
We are stardust, man! We got to get ourselve back to the Garden!
I take it the OP wants a closed container, and not an actual open-topped cup?
No, just a coffee cup. Though a travel cup that doesn’t spill would be a boon to humanity. Let’s do that too, while we’re at it.
Coffee is made up of water and ground coffee beans. Even if you found a safe and simple way to keep the coffee at a constant hot temperature, you still have the problem of steam escaping and turning what is left to sludge.
Why? It just needs to be kept “warm” or to “hot”. This happens to take 52 seconds on my microwave. I then drink it. The coffee isn’t permanent, the heat would be, or near enough.
Can we make control rods small enough? Maybe a Teapot that could be nuclear powered. Or coffee pot. That would be useful. Hammacher-Schlemmer - “World’s Best Nuclear Powered Coffee Pot”! (Can be found on pg. 42)
Getting it hot is not the problem. What happens if you keep it hot is the actual problem.
Have you considered a geothermal solution?
Nuclear is geothermal, kinda.
In what way?
Wait. My Daddy had something like that. It was electric but I could see it being wireless, solar, or nuclear. I suppose.
He sat his mug on it at his desk. I guess it worked. He never complained.
I imagine he got it at Harriet Carter. Neiman Marcus wasn’t in his mindset.
Maybe one of those airline catalogs.
Hey, the airline cup rears it’s head again. Nice.
Admittedly that sounds dangerous. The old “FiestaWare” was mildly hot on a geiger counter. We can name the new line “SiestaWare” - permanent, that is.
No, not something that can be charged. Something with a heating element driven directly by the charging pad. Build the charging pad into your desktop or whatever and Bob’s your uncle.
Beck may be a lot of things, but a dude she ain’t.
Beck is Dudette.
Getting back to the OP after the recent unpleasantness …
In the real world there are electric coffee cup keeper-hotters that’re essentially a hotplate sized for a standard ceramic mug. I’ve had one for each desk for years. They don’t put out enough energy to heat coffee from room temp, but they reduce the cooling rate to near zero. Yes, it very slowly cooks your coffee. But it keeps a standard cup drinkably warm much longer than you’re likely to be interested in it.
Here’s a typical example of the breed; they are legion: Amazon.com: Coffee Mug Warmer. My point is not that the OP should buy one. It’s that now we have access to the specs, so we can size our RTG, dilithium crystal, flux capacitor, anti-matter annhilator or whatever.
This warmer runs on 18W. A few others I checked have similar specs. A resistive heating element is nearly 100% efficient. So what we need is a) an 18W radioactive heat source, and b) (ref @Chronos above) a way to turn the heat off, or dissipate it safely so the empty cup doesn’t self heat to the point of singing your desk or thermally burning your hand.
Google informs me Strontium-90 puts out 0.95W/g. So we need about 20g of pure Strontium-90. That’s a lump of metal about the size of 4 or 5 US 5 cent coins. So the volume is not a problem. The half-life is ~29 years, so it seems we could count on decent coffee warming performance for 5, maybe 10 years.
The hard part is turning it off. I suppose we could deliver it with a heat-sink / scrub brush like thing that you put into the empty cup that has enough surface area to passively radiate and conduct 18W into room temp air indefinitely while maintaining the cup at a safe-to-touch temperature. Whew, that was kinda easy.
These nice folks will sell you some. Really: Radioactive Sources; Isotopes (imagesco.com). It’s $90 per 0.1 microcurie, and I was unable to locate a good conversion factor so I can’t say how many of these little beauties you’ll need per cup. Anyone?
The nice thing about Strontium-90 is it’s a beta emitter. So it should be practical to keep the radiation inside the cup structure, net of whatever daughter rays are created as the ceramic absorbs the betas. As mentioned above, gamma would be environmentally unfortunate.
I have not had good luck with those USB-powered coffee warmers; however, if you get one that is not a cheap piece of shit, or, better, one where the cup itself contains a heating element, then it should do what you want.
My wife has an Ember self-heating mug for her tea. Expensive as shit but works as advertised.
In the early 1960s, dude became prominent in surfer culture as a synonym of guy or fella. The female equivalent was “dudette” or “dudess”, but these have both fallen into disuse and “dude” is now also used as a unisex term.