Would heating a space up to 50c require the same amount of energy as cooling it down to -50?

473 views

Lets assume we have a 0.5 square meter box, sitting in an envoirement that is 0c.

Would it take the same amount of energy to heat the box up to 50c as it would take to cool that box down to -50c?

Assuming the exact same box is in the exact same location with the exact same surroundings

In: 6

5 Answers

Anonymous 0 Comments

No.

To cool a box, you must pump its heat elsewhere, and this process consumes energy.

To heat a box, you can either dump energy directly into it, or pump heat into it, and for the sake of comparing apples to apples we’ll compare pumping heat into it. This consumes less energy than pumping heat out, because the energy consumed also winds up as heat inside of the box.

Anonymous 0 Comments

That short answer is No and is as easy as this.

Anything and everything we do produces heat. In the case of heating a space this heat is good and helps. In the case of cooling a space that heat is an inefficiency that means some amount of energy input isn’t going into cooling a space, it’s becoming heat. The difference between those two examples means that cooling will always take more energy than heating.

Anonymous 0 Comments

[deleted]

Anonymous 0 Comments

Contrary to the other answers here, cooling a space down by 50C would in general require less energy then heating the same space by 50C. This is because a heat pump normally operates at 200-300% efficiency, that is, a Joule of energy spent on operating a heat pump allows to pump away about 2-3 Joules of heat away. Conversely, there is no such efficiency shortcut for heating – you have to provide every Joule of added heat. Unless, of course, the heating is also performed by a heat pump, then it’s roughly the same situation as cooling. Such heating systems aren’t very widespread, but they are available.

Anonymous 0 Comments

No, and I’ll explain from a different standpoint than the other current answers.

0°C is a highly relevant temperature to us humans, being the freezing point of water, but it’s not particularly special from a physics perspective. The Kelvin scale is used to measure temperature from an absolute standpoint, and is much more applicable to this kind of question. 0°C is 273.15°K.

[Thermal Conductivity] is a property of matter that indicates its ability to transfer heat energy within its internal structure. Higher thermal conductivity allows for faster heat transfer from a heat source to a heat sink, whereas lower thermal conductivity causes the opposite. Notably, Thermal Conductivity of materials varies (usually non-linearly) with the current temperature of the material.

[Thermal Conductivity]: https://en.wikipedia.org/wiki/Thermal_conductivity

Thermal Conductivity is usually expressed as a function of the temperature of the material in Kelvin, as the absolute scale makes the math much simpler.

All of this is background to say the following:

For every unit of heat you pump into a material, the next unit of heat costs an additional amount of energy to pump in. For every unit of heat you pump _out_ of a material, the next unit costs _less_ energy to pump out.

This is all before you get into the efficiency of the actual heat pump mechanism itself, which has its own issues. Pumping heat into a material inherently costs less energy overall as you only have to supply the heat itself and a small amount of overage to cover the material of the heating element, whereas pumping heat out of a material requires you to perform the same transfer of energy, but then dump it somewhere that is isolated from the target material, which an additional energy expenditure, and a waste of the dumped heat energy.

As to which is more efficient, it depends upon specifics, but it’s definitely not a 1:1.