3 ms·

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 condense

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 the waste heat from the cooler ones.

sokoloff 1y ago
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.
lucb1e 1y ago
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
- Dylan16807 1y ago
  Chill for weeks? What kind of thermal mass are you thinking of there? A brick wall is on the heavy side and you'd be able to store a whopping 1/8 of a ton of AC in ten feet of brick wall. It'd save about 0.1kWh of AC power use. A whole house will have many lengths of wall but also multiple tons of cooling requirements, so that doesn't help much. And how are you going to distribute those small temperature differences without wasting a ton of power? And that's after you figure out how to trap a temperature difference in your walls for more than a day.

sokoloff 1y ago

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.

lucb1e 1y ago

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

Dylan16807 1y ago
Chill for weeks? What kind of thermal mass are you thinking of there? A brick wall is on the heavy side and you'd be able to store a whopping 1/8 of a ton of AC in ten feet of brick wall. It'd save about 0.1kWh of AC power use. A whole house will have many lengths of wall but also multiple tons of cooling requirements, so that doesn't help much. And how are you going to distribute those small temperature differences without wasting a ton of power? And that's after you figure out how to trap a temperature difference in your walls for more than a day.