Portable AC thoughts

[justinblaber]

Just read your portable AC hacks page. Very impressed.

One thing, midea just released a dual hose inverter model:

https://www.midea.com/us/Air-Conditioners/Portable-Air-Conditioners/Midea-DUO-Smart-Inverter-Portable-Air-Conditioner-MAP12S1TBL

I just bought the toshiba version from
home depot. It's better but it's still far from being optimal. One issue with variable speed compressor is when it winds down when it reaches temp, the dehumidifying component of it doesnt work as well, so theres a sound/dehumifying trade off. Another thing too is the hotter it is outside, the less efficient dual hose becomes, but I think the negative pressure trade off is still worth it.

I think there's a big opportunity for innovation, like you said, big cities like Boston, Seattle, SF have lots of condos where window units arent allowed and without central hvac since climate is usually cold, but have lots of engineers with $$ to spend on these units and lack of housing means more units with poor hvac and extreme weather events will increase demand. But getting financing for something like this will be difficult since it's not software... And all the good engineers go into software since the pay is high.

I think fundamentally the compressor should be in a sound/heat insulated environment right up against the window. This effectively makes the compressor a "part of the outside", even though its technically inside the window. That would dramatically reduce noise and heat. All you need are little holes in the insulated box for coolant lines to come out. Almost like a minisplit but the compressor is still technically inside the window. The blower can be inside no problem since its not super loud and the noise is less bothersome (lower frequency) than compressor noise.

Another issue is how to dehumidify on days where temps are low but humidity is high. You'd need a way to heat the cold dehumidified air, and also if the air is nice and dehumidified outside, but warm inside it makes more sense to just channel in filtered air from the outside inside directly.

So basically theres a good amount of innovation left and a decent market opportunity. I think all it would take is a single good design and then you can have a company like midea mass produce it. I also think fundamentally you just need a single efficient low noise compressor and if you have that theres a lot you can do.

Overall it is shocking how there isnt a single good design out there. These condos cost 300k, 400k and I'd be willing to spend $2k easily for a single good hvac solution (less than 1% of total cost of unit) to solve all the above issues. Even $4k would be worth it for a really, really good design that's super efficient IMO since its a tiny fraction of the overall home cost and improves the livability dramatically. I've also noticed units with good hvac are often substantially higher in cost, like $100k more, so a $4k solution would dramatically increase the value of the housing unit.

It's actually a really interesting problem that requires a multitude of engineering disciplines to solve (thermodynamics, acoustics, aerodynamics, electrical engineering, programming, etc...) and would produce a useful and necessary innovation for society. Definitely a worthwhile problem to tackle.

[pmarks-net]

Midea's huge hose and wide panels strike me as less usable than a traditional dual-hose design, but it's nice to see that manufacturers haven't entirely given up.

[justinblaber]

Yea the hose in hose thing seems like kind of a gimmick. I thought it might be some kind of clever counter current exchange thing but that would just make it less efficient i think... Not sure what the intended purpose was tbh.