Earlier quoted context omitted.
What's even AI about it?
Much like a hybrid vehicle, this system intelligently switches between the two cooling methods depending on what best suits the situation.
So...it has a microcontroller. Impressive! /s
Staying cool without refrigerants: Next-generation Peltier cooling
111–120 of 329 posts
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#112For 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.
The idea was just so astonishing that I ordered some from American Science and Surplus. I connected the leads to a battery and poof, one side got hot and the other got cold. Blew my mind.
I didn't actually have a use for it. It was just neat that it actually worked.
I understand the basic physics of it perfectly well. It's just one of those things where you expect basic physics to be overwhelmed by friction or something.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#113For 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…
>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.
Real life refrigeration usually isn't very interested in a difference of 1.3 C. The Carnot COP for this temperature drop near ambient conditions is, I believe, around 200. When you consider a cooling technology relative to the Carnot efficiency (or COP) you get a better idea of what the efficiency means in practice. For an AC unit blowing 10 C air on a 40 C day, the Carnot COP is about 10, while real units get less than half that. But I think that's still better than the Peltier effect getting less than 10% performance relative to Carnot limits.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#114Earlier quoted context omitted.
> You hear that you shouldn't let your fridge go above 4°C Really? My fridge says 8°C, I think?
8 degrees or just 8 on the 1-10 scale that many of them use? (I always remember the recommended fridge temperature as 40F, which avoids the confusion.)
I suspect it's that. Most inexpensive refrigerators don't have thermostats. Which seems insane; it cannot add that much to the price.
8C is a perfectly fine temperature for a wine fridge. And they usually have thermostats because a wine fridge is a luxury item. As opposed to keeping people from getting foodborne illness.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#115Earlier quoted context omitted.
The article says they have made peltiers 75% more efficient than existing ones.
OK, a typical Peltier device has 3.5% coefficient of performance, that is, it produces 35 W of cooling per 1 kW consumed. Fine, let's expect that the new tech doubles the efficiency, to 7%. Still, to my mind, pretty wasteful, on par with a steam railway engine. A Peltier element is good in cases where you can afford a large heat removal device, but need precise temperature control and no moving parts. For a home frid…
That is wrong, COP is expressed as a ratio, not a percentage (efficiency is expressed as a percentage, which is COP * 100). And as others have said, both efficiency and COP are dependent on ΔT both in refrigeration and thermoelectric cooling.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#116What I want is a silent refrigerator, will this bring that? pray
My wine fridge uses Peltier and is super quiet. It's the perfect application for this because wine doesn't need to be as cold as a normal fridge, and noise is a consideration.
It's not completely silent though, there's a small PC-like fan but it's way less loud than a compressor.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#117Earlier quoted context omitted.
OK, a typical Peltier device has 3.5% coefficient of performance, that is, it produces 35 W of cooling per 1 kW consumed. Fine, let's expect that the new tech doubles the efficiency, to 7%. Still, to my mind, pretty wasteful, on par with a steam railway engine. A Peltier element is good in cases where you can afford a large heat removal device, but need precise temperature control and no moving parts. For a home frid…
While Peltier cooling have low efficiency wouldn't it be ideal in some cases like: - energy source is solar, DC already and abundant. - cold climate so the fridge can contribute to heating the room Anyway good to know those small electric cooler with Peltier effect must be consuming a lot electricity.
A common use case: coolers. You don't want a whole compressor, but you do want to keep your hot dogs safe and your beer drinkable. It's not very efficient but it's enough for short periods.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#118For 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…
The ΔT between evaporator (typically 2-6°C while cooling) and condenser (often 40-50°C in cooling mode) is much higher than 20°C. The condenser is often almost 20°C above ambient outside temperature.
The design ΔT of ~10°C is the typical return-to-supply air ΔT.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#119Earlier quoted context omitted.
I've been thinking about what it would look like to convert my GE fridge into a minisplit (i.e., move the compressor, condensing coil & fan outside). You can buy R600a on Amazon right now. One $60 can will charge the system ~5 times.
With home HVAC, fridges, water heaters, and dryers all using now able to use of dependent on heat pumps I wonder how long it be before we see modular appliances that connect to coolant lines where the temperature differential is supplied by a central high efficiency heat pump. Cars already have heat scavenging that can move heat from where it's being created through losses to places where it's valuable, like the cabi…
There's some commercial options for this, but it's not common. Usually, these devices just have their own compressors, because they all pale in comparison to the heat pump(s) used for climate control. For example, I have a HP water heater, and its heat pump is about 1/3 of a ton, whereas most homes need 3+ tons for climate control. Fridges are a fraction of that.
For HP clothes dryers, there's no efficiency to steal from somewhere else, because they use both the hot and cold coils - similar to (the same, really) dehumidifiers.
The tradeoff would also be running high-pressure refrigerant lines everywhere. That would require EPA certification (in the US, anyway) to connect/disconnect an appliance, and it would probably be less reliable. These sealed-system units are generally pretty reliable, because the refrigerant is installed at the factory under ideal conditions, and there's no connections that are made later that may be done poorly.
Re: Staying cool without refrigerants: Next-generation Peltier cooling
#120I wonder if this will eventually lead to battery temperature conditioning on cell phones and laptops similar to electric cars.