Re:New ‘mirror’ fabric can cool wearers by nearly 5°C
by dragontamer on Friday July 09, 2021 @02:36PM
(#27786944)
The only device that gets that small is a Peltier cooler, and those have far less efficiency than a proper Air Conditioner / Refrigerant based pump.
You can experiment with Peltiers yourself: they're widely available on Digikey and are extremely small and effective at "air conditioning" like tasks (moving heat to the hot side, while cooling the cold side).
But due to their lack of efficiency, they can never properly compete against a large scale central air conditioner: be it a proper dehumidifier, refrigerator, or actual AC / HVAC unit.
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A 100W Peltier might be able to move 50W (meaning the hot-side is 150W of heat, while the cold side is -50W of cooling). Perfect efficiency (50W heat hot side / -50W of cooling cold side) is impossible, much like perpetual motion machines.
In contrast, a proper air conditioner might be closer to 100W of power delivering 300W of cooling (Emit 400W of heat on the hot side, and provide -300W cooling on the cold side).
Furthermore, the temperature difference from a Peltier is small, maybe 10C or 20C (and the bigger the delta, the less efficient a Peltier gets). A proper compressor / refrigerator can handle much larger temperature differences at much higher efficiency.
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So the key for Peltier is to find low temperature differences (maybe keep it to 10C to minimize the efficiency loss), at low-wattages (so that the inefficiency won't generate too much heat). Maybe 10W to provide -5W of cooling (cold side) and 15W of heating (hot side) which won't raise the temperature of the room too much, and still provide some degree of comfort to the people wearing the jacket.
But its clear to me that "air conditioning" is one of those "bigger is better" deals. You'd rather more centralize the hot-side vs cold-side (ex: make sure the hot side is outside, rather than having many hot-sides inside fighting each other, raising the temperature of the room you're working in)
You can experiment with Peltiers yourself: they're widely available on Digikey and are extremely small and effective at "air conditioning" like tasks (moving heat to the hot side, while cooling the cold side).
But due to their lack of efficiency, they can never properly compete against a large scale central air conditioner: be it a proper dehumidifier, refrigerator, or actual AC / HVAC unit.
-------
A 100W Peltier might be able to move 50W (meaning the hot-side is 150W of heat, while the cold side is -50W of cooling). Perfect efficiency (50W heat hot side / -50W of cooling cold side) is impossible, much like perpetual motion machines.
In contrast, a proper air conditioner might be closer to 100W of power delivering 300W of cooling (Emit 400W of heat on the hot side, and provide -300W cooling on the cold side).
Furthermore, the temperature difference from a Peltier is small, maybe 10C or 20C (and the bigger the delta, the less efficient a Peltier gets). A proper compressor / refrigerator can handle much larger temperature differences at much higher efficiency.
-------
So the key for Peltier is to find low temperature differences (maybe keep it to 10C to minimize the efficiency loss), at low-wattages (so that the inefficiency won't generate too much heat). Maybe 10W to provide -5W of cooling (cold side) and 15W of heating (hot side) which won't raise the temperature of the room too much, and still provide some degree of comfort to the people wearing the jacket.
But its clear to me that "air conditioning" is one of those "bigger is better" deals. You'd rather more centralize the hot-side vs cold-side (ex: make sure the hot side is outside, rather than having many hot-sides inside fighting each other, raising the temperature of the room you're working in)