Living with a single hose portable air conditioner in the city
schleiss.ioAuthor here, I just had to get some thoughts out and complain how bad these portable air conditioners are.
I just don't understand why the appliances space attracts so little innovation or startups. Even though they are at least 400€ a piece and could generate lots of revenue on mass.
On Friday I listened to the newest Macrovoices episode with Philip Verleger [1] where they argued that America has far too few engineering students to even create a green energy revolution in America. The expertise was transferred primarily to software engineering jobs.
Dr. Verleger apparently was one of the key players in created the oil futures markets, so he probably knows a thing about this space.
[1] https://www.macrovoices.com/983-macrovoices-276-philip-verle...
>My portable air conditioner uses about 1200kW/h according to my 10€ energy consumption meter.
JFYI, 1200 kW/h sounds a tad bit too much to me...
Oh, you are right. A typo. Thank you.
Yep, now it's much better, 1200 W/h sounds like "normal" for a small portable unit.
About the channeling of the hot air inside: >The other day I modified my air conditioner to channel the hot outside heat right back at the compressor to heat up the outside air instead of the cooler inside heat. Compared to last year, I don't really see a difference. Last year I didn't have this system and couldn't get below 22C/72F either. So I probably wasted my time optimizing my air conditioner.
Having the conditioner be fed continuously the hotter air should be less efficient.
A house (normally) is not air tight if you suck air out of a room, pumping it outside, the same amount of air will re-enter the room by all the leaks of windows, doors, etc. (if this was not the case, think of bathrooms without windows with an aerator, people don't die in those bathrooms because of the vacuum).
Let's say that your portable conditioner can treat a given amount of air (let us assume 1 m3/min) and that temperature lowering is linear (it isn't) i.e. that unit can lower the temperature 20° C.
If the room you have the thingy installed is 3x4 mt and 3 mt high, it contains 36 m3 of air.
If the air was treated "sequentially" (i.e. imagine a square pipe 1m x 1m 36 m long) it would take 36 minutes to lower the whole amount from 40° C to 20° C at full power.
In the meantime (assuming that your house has a minimum of insulation from the outside) there will be only a partial re-heating of the air, so that each of the 36 m3 of air (still imagine the sequential treating) is at a slightly different temperature, 1st m3 will be (say) at almost the same outside temperature, but still lower, 35° C, last one (the one just treated) will be at 20 °C.
Now, if you re-enter the "loop", that 1st cubic meter temperature can be lowered to 15 ° C, so the loop is a "virtuous one".
In reality, if you expel the hot air from a room, the same amount of hot air will re-enter the room from the leaks, what you are doing is using the volume of the room to act as a cache of sorts, i.e. the air that enters (at 40 ° C) will be "diluted" and in theory that will contribute only to 40/36=1,11 degrees warmer air.
BUT, and here is the nice part, the hotter air will go towards the ceiling, and since you are not 3 m tall, you will be living in the cooler 2/3 of the room, and the air that the conditioner treats will be cooler (assuming the unit is on the floor and not suspended), and as such it can be made even more cool with less energy.
Yes, I realized that too, therefore I put the machine on the desk to suck in the air of the middle of the room instead of the coldest air on the bottom of the room.
But how come the room doesn't get colder overall? Is it sized too small? My apartment here is about 36m2 with 2.7m tall rooms. The unit has 14000BTU which is one of the largest portable air conditioner that you can get. Even if I were to close the doors to the other rooms, it would only be able to cool the room by 1 degree during the day (8 hour span). In the night it does its job well by lowering the temperature to the outside temperature but it won't go beneath it.
1200W/h is still moderately nonsensical. The unit is 1200W, or 1200Wh/h if you want to put it that way.