Thermoelectric cooling is pretty inefficient, because the materials need to balance competing requirements:
- Good thermal insulator
- Good electrical conductor
- Good semiconductor
This is because the hot & cold sides are sandwiched closely together as a PN junction, so once you move heat from one side to the other, it just leaks right back. Mechanical cooling doesn't have this problem, because the hot & cold sides are separated by thin bits of tubing. This makes the thermal leakage a "minor annoyance" in a mechanical system as opposed to "literally the whole problem we're trying to solve" as it is with thermoelectrics.
One work-around is to stack lots & lots of thermoelectric coolers on top of each other. That reduces the temperature difference at each individual PN junction, which in turn lowers the leakage. That's what this team is doing, but using layers that are only a few nanometers thick, so they can fit dozens or hundreds of junctions in a single package.
They claimed 55% Carnot efficiency based on a 30-100 angstrom gap maintained by piezoelectric controllers, and a method to construct large electrodes with matched surfaces so that the gap could be maintained over a large area. It all sounded plausible but never went anywhere as far as I know.
Thermoelectric cooling needs as much research as possible. Mechanical cooling is extraordinarily space consuming. CHESS has the potential over the next 10 years to largely replace vapor compression in most systems other than the most extreme gradients or scales. They are small enough to incorporate into most devices and would allow smaller devices more thermal load. In some ways I think efficient TEC like CHESS could be more useful than room temperature super conductors.
Nah. Heat pumps are ~10-100x more efficient than thermoelectric. Thermoelectric is just inefficient mechanism and is inherently difficult to scale up as the more electricity gets generated so does more heat which inhibits the temperature gradient you’re trying to utilize. There’s a reason water cooling is preferred instead of peltier to ferry heat away from electronic.
Magnetocaloric is super interesting though as an alternative to heat pumps. Likely the next big revolution in this space.
Further to that, have a look at the refrigeration units on chest type portable fridges. They’re really not very big, compressor smaller than a roast chicken, small low speed fan similar to an auxiliary cooling fan in a PC, a controller board, and a few meters of metal tubing.
They typically consume around the 50 to 80 watts while the compressor and fan are running, and generate two to four times that in cooling capacity.
Surely people have adapted these in to PC cooling units?
> Mechanical cooling is extraordinarily space consuming.
You'd wind up taking up even more space with a TEC solution at these efficiencies. To replace a 5-ton condensing unit you'd have to reject on the order of 50-100kW of heat.
> the APL team achieved nearly 100% improvement in efficiency over traditional thermoelectric materials at room temperature
Peltier effect refrigeration has very low efficiencies (5%) so while this is an amazing accomplishment it will not replace other more mechanical cooling methods.
But efficiency is extremely important in this context, not just for saving energy, but because the inefficiency manifests as heat generated, which undermines the intended refrigeration. So as far as Peltiers go, a doubling of efficiency is like a 3x ~ 4x improvement in effectiveness. Peltiers are already used for cooling in some contexts (eg. cooling CCDs) and this greatly grows the envelope for where they can be effectively employed.
Under low-heat-pumping, with minimal role of parasitics, TFTEC modules offer four times the Coefficient of Performance (CoP) advantage over bulk devices. As an example, system-level CoP with a 16-couple TFTEC module is ~ 15 for small temperature differentials of 2 °C, pumping about 1.2 W heat load using 80 mW of electric power. Such small-scale high-CoP cooling is relevant for distributed refrigeration or compartmentalized refrigeration as well as for use in future electronic thermal management
They also note that the maximum cooling power density depends inversely on thickness, and this is where the thin-film TECs like this gets most of their improvements from, compared to millimeter thick regular TECs.
Just a quick scan before going to bed, but looks interesting for certain applications.
No, they turn a temperature gradient into electricity. If one side is heated and the other cooled, you can get current flow on the two leads. And as with many electrical devices, it can also be run in reverse: if you put a voltage across the leads then one side will get hot and the other side will get cold.
So it's a better Peltier element? The article only seems to compare it to existing thermoelectric devices and not standard refrigeration units so I'm going to assume they haven't gotten even close to that efficiency. If they had I would assume they wouldn't shut up about the fact.
Also one of the biggest if not the biggest downside of these chips is, unlike a split refrigeration circuit, the front gets cold while the back gets hot which means you can't move the heat very far.
Also in the article, it is implied that there is no chance to replace mechanical compressors for great thermal powers, but for small thermal powers, from a few watt to a few hundred watt, thermoelectric devices may become preferable, due to small size, simplicity and reliability
Heat pipes (as in CPU heatsinks) can passively move the heat up to a feet away. Far enough to allow effective insulation between cold and hot side. From there you can move the heat further away with a fan.
Heat pipes only reduce the thermal resistance between 2 points. They cannot cool something below ambient temperature.
Thermoelectric coolers do not compete with heat pipes. They are useful only when you want to obtain a temperature lower than the ambient temperature. Otherwise, heat pipes or liquid flow cooling are the right solutions.
You could have heat pipe filled with liquid that evaporates at 5 degrees. This way it would draw heat from ambient level temperature and lead it to peltier device that would cool it below 5 deg and liquefy it back again. This way you could have peltier in the middle of your thick insulation layer with heat pipes drawing the heat into it from the cooled space and drawing the heat from the other side of it outside (using traditional heat pipes this time).
>system-level coefficient-of-performance is ~15 for temperature differentials of 1.3 °C.
There's a long way to go. As far as I know, the leader in condensed-phase refrigeration cycles is still the sodium iodide ionocaloric method, which blew past all of the competing methods (magnetocaloric, elastocaloric, thermoelectric) when it was announced in 2022:
Thermoelectric cooling is pretty inefficient, because the materials need to balance competing requirements:
- Good thermal insulator - Good electrical conductor - Good semiconductor
This is because the hot & cold sides are sandwiched closely together as a PN junction, so once you move heat from one side to the other, it just leaks right back. Mechanical cooling doesn't have this problem, because the hot & cold sides are separated by thin bits of tubing. This makes the thermal leakage a "minor annoyance" in a mechanical system as opposed to "literally the whole problem we're trying to solve" as it is with thermoelectrics.
One work-around is to stack lots & lots of thermoelectric coolers on top of each other. That reduces the temperature difference at each individual PN junction, which in turn lowers the leakage. That's what this team is doing, but using layers that are only a few nanometers thick, so they can fit dozens or hundreds of junctions in a single package.
Twenty years ago there was a company trying to commercialise thermoelectric cooling based on a vacuum gap: https://web.archive.org/web/20031213235132/http://www.coolch...
They claimed 55% Carnot efficiency based on a 30-100 angstrom gap maintained by piezoelectric controllers, and a method to construct large electrodes with matched surfaces so that the gap could be maintained over a large area. It all sounded plausible but never went anywhere as far as I know.
Thermoelectric cooling needs as much research as possible. Mechanical cooling is extraordinarily space consuming. CHESS has the potential over the next 10 years to largely replace vapor compression in most systems other than the most extreme gradients or scales. They are small enough to incorporate into most devices and would allow smaller devices more thermal load. In some ways I think efficient TEC like CHESS could be more useful than room temperature super conductors.
Nah. Heat pumps are ~10-100x more efficient than thermoelectric. Thermoelectric is just inefficient mechanism and is inherently difficult to scale up as the more electricity gets generated so does more heat which inhibits the temperature gradient you’re trying to utilize. There’s a reason water cooling is preferred instead of peltier to ferry heat away from electronic.
Magnetocaloric is super interesting though as an alternative to heat pumps. Likely the next big revolution in this space.
Further to that, have a look at the refrigeration units on chest type portable fridges. They’re really not very big, compressor smaller than a roast chicken, small low speed fan similar to an auxiliary cooling fan in a PC, a controller board, and a few meters of metal tubing.
They typically consume around the 50 to 80 watts while the compressor and fan are running, and generate two to four times that in cooling capacity.
Surely people have adapted these in to PC cooling units?
>Heat pumps are ~10-100x more efficient than thermoelectric.
Peltier junctions are a type of heat pump.
Mechanical heat pumps are 10x-100x more effective than peltier heat pumps.
> Mechanical cooling is extraordinarily space consuming.
You'd wind up taking up even more space with a TEC solution at these efficiencies. To replace a 5-ton condensing unit you'd have to reject on the order of 50-100kW of heat.
> the APL team achieved nearly 100% improvement in efficiency over traditional thermoelectric materials at room temperature
Peltier effect refrigeration has very low efficiencies (5%) so while this is an amazing accomplishment it will not replace other more mechanical cooling methods.
For sure this doesn't replace mechanical cooling.
But efficiency is extremely important in this context, not just for saving energy, but because the inefficiency manifests as heat generated, which undermines the intended refrigeration. So as far as Peltiers go, a doubling of efficiency is like a 3x ~ 4x improvement in effectiveness. Peltiers are already used for cooling in some contexts (eg. cooling CCDs) and this greatly grows the envelope for where they can be effectively employed.
IIRC there is an application in solar panels where thermo electric cooling could play a role if we could get the efficiency just slightly higher.
The paper[1] has some actual details, like this:
Under low-heat-pumping, with minimal role of parasitics, TFTEC modules offer four times the Coefficient of Performance (CoP) advantage over bulk devices. As an example, system-level CoP with a 16-couple TFTEC module is ~ 15 for small temperature differentials of 2 °C, pumping about 1.2 W heat load using 80 mW of electric power. Such small-scale high-CoP cooling is relevant for distributed refrigeration or compartmentalized refrigeration as well as for use in future electronic thermal management
They also note that the maximum cooling power density depends inversely on thickness, and this is where the thin-film TECs like this gets most of their improvements from, compared to millimeter thick regular TECs.
Just a quick scan before going to bed, but looks interesting for certain applications.
[1]: https://www.nature.com/articles/s41467-025-59698-y
I need this for my compact compost freezer [1]
[1] https://www.envirofreezely.com/
I’ll watch your video later when I get home. Mostly leaving a comment so I can find it easier later.
Freezing food waste prior to composting it results in much faster breakdown in the compost.
So, these devices.... turn heat into electricity? Where does the electricity go, back into the system it's powering?
> turn heat into electricity?
No, they turn a temperature gradient into electricity. If one side is heated and the other cooled, you can get current flow on the two leads. And as with many electrical devices, it can also be run in reverse: if you put a voltage across the leads then one side will get hot and the other side will get cold.
Most IR cameras use Peltier cooling so better coolers should lead to better cameras.
Presumably night vision on drones and missiles and things suddenly gets a lot smaller and deadlier?
Obligatory video on the inefficiencies of thermoelectric cooling/Peltier elements from Techonology Connections: https://www.youtube.com/watch?v=CnMRePtHMZY
Down the heat pump rant rabbit hole we go.
So it's a better Peltier element? The article only seems to compare it to existing thermoelectric devices and not standard refrigeration units so I'm going to assume they haven't gotten even close to that efficiency. If they had I would assume they wouldn't shut up about the fact.
Also one of the biggest if not the biggest downside of these chips is, unlike a split refrigeration circuit, the front gets cold while the back gets hot which means you can't move the heat very far.
One step at a time... it would be astonishing if any thermoelectric device can leapfrog mechanical compressors.
Also in the article, it is implied that there is no chance to replace mechanical compressors for great thermal powers, but for small thermal powers, from a few watt to a few hundred watt, thermoelectric devices may become preferable, due to small size, simplicity and reliability
just noting that household fridge/freezers are in that power range...
Yeah but, household freezers are typically capable of freezing many tens of kilograms of material down to -18 to -24 degrees C / 0 to -10 F
Peltier coolers aren’t anywhere near this.
> can't move the heat very far.
Heat pipes (as in CPU heatsinks) can passively move the heat up to a feet away. Far enough to allow effective insulation between cold and hot side. From there you can move the heat further away with a fan.
Heat pipes only reduce the thermal resistance between 2 points. They cannot cool something below ambient temperature.
Thermoelectric coolers do not compete with heat pipes. They are useful only when you want to obtain a temperature lower than the ambient temperature. Otherwise, heat pipes or liquid flow cooling are the right solutions.
You could have heat pipe filled with liquid that evaporates at 5 degrees. This way it would draw heat from ambient level temperature and lead it to peltier device that would cool it below 5 deg and liquefy it back again. This way you could have peltier in the middle of your thick insulation layer with heat pipes drawing the heat into it from the cooled space and drawing the heat from the other side of it outside (using traditional heat pipes this time).
I think you may have just reinvented absorption refrigeration, previously invented by Ferdinand Carré in 1858.
https://en.wikipedia.org/wiki/Absorption_refrigerator
From the abstract:
>system-level coefficient-of-performance is ~15 for temperature differentials of 1.3 °C.
There's a long way to go. As far as I know, the leader in condensed-phase refrigeration cycles is still the sodium iodide ionocaloric method, which blew past all of the competing methods (magnetocaloric, elastocaloric, thermoelectric) when it was announced in 2022:
https://www.science.org/doi/10.1126/science.ade1696
...but the temperature drop of 25 C is just barely practical for air conditioning in warm (but not desert) climates.
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