An impossible promise?
In this time of rising temperatures, more extreme weather and powerful social media, devices for increased comfort can count on a lot of interest. A case in point is the news about ‘The World’s first Ductless Portable Airconditioner [1], (‘WFDPAC’), a product promoted by the firm Morphy Richards. It has attracted an investment of more than €750,000 on Kickstarter.com [2]. It is fascinating that 2,153 people backed a product which cannot be what it purports to be.
Because this device, and what it claims to do, goes against everything we know about cooling, we want to give it the Reden Makes Sense treatment and let the numbers speak. Without numbers, a discussion has no solid base.
[1] Deze airco heeft geen afvoerslang nodig en is een grote hit (bright.nl)
[2] Morphy Richards: First Ductless Portable Air Conditioner by Morphy Richards - Kickstarter
A case of simple thermodynamics
The second law of thermodynamics makes it impossible to cool a room without exhaust; the heat from the room cannot be reduced using electric energy. The opposite, heating, is possible, as proven by an electric heater. Heating and cooling are very different things. The same law makes that it is impossible to convert heat to work without a flow of heat out of the system. This is why cars need a cooling system; the engine converts heat (from burning fuel) to work, propelling the car, but also need to be cooled. The second law has been known since the 1850s.
It is, therefore, impossible to cool a room without expelling the heat outside the room. Is this what Morphy Richards tries to do? Below we argue that Morphy Richards misuses the English language and that the whole product is at best an effective evaporative cooler, and at worst an unnecessarily complicated fan.
Or a case of semantics?
According to Wikipedia, air conditioning is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature. The Encyclopedia Brittannica is less restrictive:
Air-conditioning: the control of temperature, humidity, and motion of air in an enclosed space, independent of outside conditions [1].
The fact that the device has no connection to outside the room (except the wall socket) means that it cannot remove heat from that room, which means that it cannot be an air conditioner in the Wikipedia sense of the word. But because Morphy Richards, in the video on their website, state that “long use in a closed room should increase the ambient humidity and create a not comfortable situation”, the definition of the Britannica also disqualifies it.
There is yet another definition of ‘air conditioner’ by a Morphy Richards spokesperson. To the question: “Is it an air conditioner or evaporative cooler?”, he answered: “okay, it’s very easy to answer, the joint of compressor and refrigerant create air conditioner, so this is an air conditioner” [2].
I think he means to say that it must be an air conditioner because it uses a compressor and refrigerant. This is clearly nonsense, because a refrigerator uses a compressor and refrigerant too, and it is not an air conditioner. If you put a refrigerator in the middle of a room with the door open, the room will get warmer, not cooler.
[1] Air-conditioning | Types, Benefits & Maintenance | Britannica
[2] All Your Questions About Our Ductless AC Answered! | MorphyRichards (youtube.com)
So, it isn’t an air conditioner; what is it?
As far as can be inferred from the available information, the ‘WFDPAC’ has two air flows. The first is from the room to the room via the hot part (condensor) of the internal compressor heat pump (the same system which drives a refrigerator or conventional AC unit). This flow serves to remove water vapour from the heat exchanger. The water vapour is formed as water is sprayed on the condensor. Apparently, the heat from the heat pump is mostly used for evaporating the water, so that the expelled air is not much hotter than the temperature in the room.
The second flow is from the room, via the cold part (evaporator) of the compressor heat pump, to the room. This air is simply cooled, without taking up water.
The system sketch shows three things:
- The ‘WFDPAC’ delivers cold air (directed to the user) as well as moist air, in a different flow.
- It releases water into the room.
- It introduces electric energy into the room.
Now that we have a system, let’s put in some numbers. We consider the system as an air conditioner in the accepted sense of the word (see above). This means that a reduction of the room temperature is the useful output. We know the device uses 300 W and uses up its water in 4 – 8 hours. We do not know how much water the tank holds, so we’ll use a reasonble guess (it is a portable container), say 4 litres. In one second, therefore, the device introduces 300 J of heat (from electricity) into the room, and 1/3600 litre of water. It takes 2.26 MJ to evaporate one kg of water, so per second, 2260000/3600 = 628 J is required to evaporate the water. 300 J is supplied by the electric energy, the rest is delivered by the ambient air. The COP (coefficient of performance) of the system (not counting the cost of the water, or the energy needed to supply it) is (628 - 300)/300 = 1.09. For any cooling system, this is very low, it should be at least 2.
For room cooling, there are much cheaper systems [1], which only require 65 W for the same amount of water, giving an estimated COP of (628 – 65)/65 = 8.7; much better than the ‘WFDPAC’.
However, the ‘WFDPAC’ has one card up its sleeve: it delivers very cold air. In an ambient of 34 °C, its jet of air has a temperature of 13,5 °C at a distance of 2 m. However, given the limited cooling capacity (628 W, or enough to cool 25 litre of air per second), it is only a small cone of air that can be so cold! The ‘WFDPAC’ appears to be useful for one person only.
Finally,since the ‘WFDPAC’ cools by means of evaporation, it is basically the same as transpiration, the method by which we cool or bodies. A highly effective way of boosting transpiration, and keeping the skin dry, is the traditional fan. In particular the ceiling mounted fan does a good job, delivering high air speeds at low noise levels, and low energy consumption [2].
[1] Blokkerluchtkoeler BL - 40001 - 3 snelheidsstranden - incl. koelelementen - wit | Blokker
[2] Vent-AxiaHi-Line plafondventilator wit 15000 m3/h diameter 1400 mm - HL140 | Ventilatieland
Conclusion
The ‘World’s first ductless portable air conditioner’ is a device which uses water to cool air, and electricity to make some air very cold to supply a cooling jet of air. It has a locally refreshing effect. As a room cooler, it is inferior in performance to a fan, an evaporative cooler, and even a real AC system. It looks nice, and is backed by a good sales pitch, but it cannot live up to its claims. It may be very pleasant to have a jet of cold air in your face, and this is what the ‘WFDPAC’ can deliver, but the use of the term ‘air conditioner’ is misplaced.
