Many years back, I learnt about how air-conditioning works. It basically works by transferring heat through conduction from the cooling fins to the air outside of the room/house/unit that it is supposed to cool.
Outside air < — Cooling fins <— metal tubes <— freon gas <— internal air (from room etc)
In the process, some heat is generated. This heat generated is due to inefficiency of the compressor, electronics etc found in air-conditioning units. This inefficiency is common in practically *all* electrical devices, where some electrical power is converted into actual intended work, while others are lost, either as heat, sound or kinetic energy or a combination of them all.
In a sense, air-conditioners do not create “coolness”. “Cold” cannot be created. Only heat can be created. Coldness appears to exist only in contrast to the lack or relative differences in heat. So while a heater generates heat, a cooler (eg air-con) does not actually create cold. It merely displaces it. Coldness itself is also empty of inherent characteristics.
Further to that, heaters do not actually generate or create heat as well. They merely release the potential energy “trapped” or “stored” in the fuel, or convert energy from one form to another, eg convert electrical energy to heat energy. In the process, most heaters “lose” some energy through ambient heating (ie, heating up the appliant itself in an unintended manner), unintended lighting, sound etc. We can perhaps say that heat itself is dependent arising, that it is also inherently empty.
Now consider a fridge placed in a small enclosed room. Most if not all fridges contain warnings about using fridges where heaters are placed or about using them in an enclosed area. A fridge works more or less in the same way as a air-conditioner. The fridge itself is the room and the
cooling system cools the ‘room’ in the fridge. If a fridge is used in a small enclosed room, the room would inevitably over time heat up until the heat loss of the room due to its walls with the outside world matches the heat generated by the fridge. If the fridge merely displaces heat and produces no heat of its own, an equilibrium would be reached pretty fast. However, a fridge also produce heat of its own. You get the drift.
Now consider earth, with its atmosphere as the ‘Room’. The rooms we are cooling are akin to tiny little fridges in this big Room. Owing to heat loss to space, the whole earth cools off at night. But in the day itself, the reverse is true. Heat from sunlight is warming up the surface of earth and the air, while these little fridges are doing their part to displace heat, and inevitably adding on ambient heat to the environment. Simply put, air-cons do not just ‘cool’ the rooms, they also heat up the environment.
There are many variables left out in the simplistic analysis above. Amongst them, the contents in these little fridges play a key role. In actual fridges, food items do not generate heat of their own and hence lose heat to the surrounding air in the fridge until an equilibrium is maintained, depending on the preset temperature. Now consider the little fridges. While the air-cons try to cool down the room, our body tries to compensate the heat loss through our skin and maintain our bodily temperature by generating heat. Besides that, the other appliances we use in these little fridges are all generating heat as a by-product. Ever wondered where the heat in your notebook goes to? Yes, it heats up the room. How about the ac adapters, TVs, hifis, hair-dryer, washer etc? They all do their part in generating more heat. These all add up and require a constant regulation of the temperature by the little fridges, adding more to the heat displaced to the environment.
The heat transfer statement becomes:
Outside air <— Cooling fins <— metal tubes (+ byproduct heat from air-con) <— freon gas <— internal air (from room etc) <— heat from us + all appliances running
Granted, air-conditioning has done much in increasing productivity and comfort for modern living, but we have to wonder, at what cost. While we chase after big numbers and gun down fossil fuel usage, cutting down of trees etc and blame them for global warming, or the hot weather, perhaps we should relook something closer to our everyday life: Air-conditioning.