The Johns Hopkins press release is much better https://www.jhuapl.edu/news/news-releases/250521-apl-thermoe...
Oh nifty. These can also be used to generate electricity from body heat. Or presumably any waste heat.
Staying cool without refrigerants: Next-generation Peltier cooling
121–130 of 329 posts
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#122I wonder if this will eventually lead to battery temperature conditioning on cell phones and laptops similar to electric cars.
Not likely without other contributing technologies. These devices just move heat from one side to the other, at the cost of producing more heat. So you still have to dissipate even more heat on the hot end with a fan/heatsink, in addition to draining the battery running the Peltier.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#123For those worried about tiny COPs from these gizmos, trawling through the actual paper -- as well as the PR from JHU APL -- in this HN post [1] shows claims of COPs of ~15 for Delta Ts of 1.3°C. A compressor based cooler gets a COP of about 4 in the real world. I'm pretty sure this is an apples to oranges comparison to an expert (I am not one of those) but a factor of 3+ increase in COP is fairly noteworthy -- if it…
Delta Ts of 1.3°C. Might as well not use a refrigerator if your ambient temperature is that low.
You missed the "delta", meaning change.
One side would have been ~23C and the other 24.3C.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#124For those worried about tiny COPs from these gizmos, trawling through the actual paper -- as well as the PR from JHU APL -- in this HN post [1] shows claims of COPs of ~15 for Delta Ts of 1.3°C. A compressor based cooler gets a COP of about 4 in the real world. I'm pretty sure this is an apples to oranges comparison to an expert (I am not one of those) but a factor of 3+ increase in COP is fairly noteworthy -- if it…
What about a ΔT of say 20°C? I'd reckon most refrigerators and air conditioners are around there (temp difference of refrigerant between evaporator and condenser). Stacking a bunch of these Peltiers to give more temperature difference would give a pretty low CoP. Say, for a 13°C temperature difference you'd have to stack 10 of them and use 10x the power. It's even worse actually as the hotter ones have to also pump t…
Note that a small temperature difference that is sustained very consistently over a long time using a tiny amount of electricity (let's say half of what the parent post cited, so like a COP of 8) could add up to a lot of nearly-free cooling. You'd chill your walls for weeks and when a heat wave comes with hot nights for a week, if you(r home automation) close(s) the blinds during the heat of the day, the more-powerful AC might barely have to do anything
Just an idea of course, but I'd not write new tech off as "ok but just 1.3 degrees who cares" when the claimed COP is so insanely good without first trying it out
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#125Earlier quoted context omitted.
Delta Ts of 1.3°C. Might as well not use a refrigerator if your ambient temperature is that low.
You missed the "delta", meaning change. One side would have been ~23C and the other 24.3C.
That's still a lot hotter than I'd like my refrigerator, to be fair to OP.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#126The Johns Hopkins press release is much better https://www.jhuapl.edu/news/news-releases/250521-apl-thermoe...
Oh nifty. These can also be used to generate electricity from body heat. Or presumably any waste heat.
Only if you have a cold environment into which to dump that heat into. You could maybe trickle charge your phone in the winter, if you don't mind a cold spot where the device sits on your body.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#127Earlier quoted context omitted.
> Normal fridges just let the temperature have a wider swing which is good enough for most needs. These wide swings annoy me. You hear that you shouldn't let your fridge go above 4°C, because that's dangerous. And you obviously don't want your fridge to go below 0°C. But finding a setting where the hottest part of the fridge doesn't go above 4°C (or even 5°C or 6°C) during the hottest part of the cycle and the coldes…
Why should that be dangerous? I have never heard that. I have always had my fridge at 8°C and never had something dangerous happen to me. I have never come across fridges that were way cooler, apart from fridges of friends in Canada and the US. What's the reasoning?
The recommendation I've always heard in the Netherlands is 7°C, it's more recent that I've been seeing 4°C on meat packaging in Germany (where I live now). I doubt anyone's fridge is consistently at or below 4° without freezing things constantly, so I've been assuming this is wishful thinking and/or ass-covering on the manufacturer's part and not what anybody actually does. Your 8°C is close enough that it probably makes little difference, though afaik this is an exponential curve (at 14°C it would last far less than half as long) so I'd not be surprised if things spoil a bit sooner than they otherwise would
Even if your products generally meet their "should be safe at least until" date (Mindesthaltbarkeitsdatum, idk if it's the same as "best before"), you might exceed that longevity more often than you do now and thus have less food waste by setting the fridge colder - if food waste is a thing you have in the first place (I'm the type of person that is hungry all the time, opens the fridge when hungry, and isn't super selective (among what I've bought anyway), so food I buy ~always gets eaten before it spoils, but then when I see food waste numbers, apparently that's not the case for everyone so I'm just throwing this out there)
Edit: trying to fact-check myself, I can't find any trustworthy source in Dutch saying your foodstuffs fridge should be more than 4°C. I measure new fridges when moving in and again at least once during the first summer to make sure they stay at or below 7°C when we had the door open a normal amount of times, so I know they're that (and not much cooler, to not freeze items or waste energy). So far, products meet their minimum shelf life date thingy and almost always exceed it. Strange. Maybe this recommendation I heard predates the internet (showing my age here), or maybe every page on the internet assumes that nobody actually measures it properly and so they recommend a value that's half of what's actually safe?
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#128For those worried about tiny COPs from these gizmos, trawling through the actual paper -- as well as the PR from JHU APL -- in this HN post [1] shows claims of COPs of ~15 for Delta Ts of 1.3°C. A compressor based cooler gets a COP of about 4 in the real world. I'm pretty sure this is an apples to oranges comparison to an expert (I am not one of those) but a factor of 3+ increase in COP is fairly noteworthy -- if it…
COP has to be compared at the same delta T. The COP of a loss less refrigerator is infinite at Delta T = 0 And you dont get to stack Peltiers to increase COP, only to increase delta T. Still, Peltiers are super cool and I have some ideas for their use od they get slightly better. Advances are super welcome.
One can only hope some kind of phonon diode material can exist that a slight voltage can overcome something so inescapable as entropy by providing it only lanes that suit us.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#129I used peltier coolers on K6 processors 1M computer years ago. They worked great and lasted about as long as the PCs did. Not long after I bought mine, they disappeared from cooler offerings. I've wondered what became of the tech.
I remember one objection to Peltier coolers in that application is that could possibly cool the CPU below the dew point and cause water condensation, something a fan can't do.
Anybody who points to dew point issues would be fascinated by
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#130What I want is a silent refrigerator, will this bring that? pray
They already exist! Well, small ones.
A hotel I was staying at had a small bar fridge that used a Peltier. I only know because it stopped working so I checked it and realized it was only a Peltier plus a heat exchanged (a cyclopropane loop).
I presume a full size fridge is outside of reach at this point.