Engineers harvest clean, continuous energy from air • Hacker News Board

Re: Engineers harvest clean, continuous energy from air

#51

Post by pdonis » Fri, Dec 15, 2023, 1:08 AM UTC

BobaFloutist wrote: post #42

pdonis wrote: post #29

Earlier quoted context omitted.

> by converting air moisture to liquid water using a compressor, the dehumidifier is releasing the latent energy of water vapor The latent heat does get released, but the question is, where does it go? In an air conditioner, which also condenses water vapor from the air, the heat released goes into the refrigerant, which means it ultimately gets put into the atmosphere outside from the condenser. A dehumidifier is ba…

I guess it's like a reverse swamp-cooler?

Sort of, if you think of a swamp cooler as something like a "rehumidifier".

Re: Engineers harvest clean, continuous energy from air

#52

Post by AnimalMuppet » Fri, Dec 15, 2023, 2:52 AM UTC

pdonis wrote: post #41

AnimalMuppet wrote: post #34

Earlier quoted context omitted.

Good explanation on the warm. I still disagree on the cold. The cold in the midwest cuts through you in a way that it doesn't in the dry. Air temperature's the same, but the difference is noticeable. Why is that? If not humidity, then what is it?

See my response to the sibling post to yours. My experience in the Midwest (and elsewhere) on colder days is that the biggest factor is wind. Even a relatively light wind on a cold day can make a big difference in draining heat from your body. Convection makes a big difference in the heat transfer properties of air. Btw, you say "in the dry", but have you ever been in the desert on a cold night? I think you might rec…

> Btw, you say "in the dry", but have you ever been in the desert on a cold night? I think you might reconsider just how cold "dry cold" can feel.

Lived in Salt Lake City for 60 years, so yes. And I would say that, to me, the cold in the Midwest is worse than the cold in the West, even at the same temperature and wind.

But after reading your response, another variable has occurred to me. The west isn't just dry, it's high and dry. Higher elevation means lower air pressure. Lower air pressure means fewer molecules hitting each square inch each second, carrying off heat. Is lower air pressure part of why the cold doesn't cut through you as much out west?

Re: Engineers harvest clean, continuous energy from air

#53

Post by wlesieutre » Fri, Dec 15, 2023, 4:35 PM UTC

jrockway wrote: post #16

wlesieutre wrote: post #10

Earlier quoted context omitted.

Watts are a rate of one joule per second. If you want to talk about a quantity of energy rather than a rate of energy production/consumption, the units would be either kilowatt hours or joules (1 kWh = 3,600,000 joules).

Yup, kilowatt hours are a cursed unit that simply reduces to joules (a nice and easy to remember 3.6 million of them).

Yeah I have to work that out every time

Re: Engineers harvest clean, continuous energy from air

#54

Post by pdonis » Fri, Dec 15, 2023, 5:32 PM UTC

AnimalMuppet wrote: post #52

pdonis wrote: post #41

Earlier quoted context omitted.

See my response to the sibling post to yours. My experience in the Midwest (and elsewhere) on colder days is that the biggest factor is wind. Even a relatively light wind on a cold day can make a big difference in draining heat from your body. Convection makes a big difference in the heat transfer properties of air. Btw, you say "in the dry", but have you ever been in the desert on a cold night? I think you might rec…

> Btw, you say "in the dry", but have you ever been in the desert on a cold night? I think you might reconsider just how cold "dry cold" can feel. Lived in Salt Lake City for 60 years, so yes. And I would say that, to me, the cold in the Midwest is worse than the cold in the West, even at the same temperature and wind. But after reading your response, another variable has occurred to me. The west isn't just dry, it's…

> Is lower air pressure part of why the cold doesn't cut through you as much out west?

Could be, yes. The lower air pressure means less heat transfer out of your body, as you say.

Re: Engineers harvest clean, continuous energy from air

#55

Post by qqqwerty » Fri, Dec 15, 2023, 6:40 PM UTC

raphaelj wrote: post #18

Something similar happened when I put a dehumidifier in my bedroom. Basically, I noticed that the room was heating significantly when I turned it on. Way faster than what you should expect from its power usage (about 250W avg.). Correct me if I'm wrong, but by converting air moisture to liquid water using a compressor, the dehumidifier is releasing the latent energy of water vapor (0.627Wh/L) in addition to its own e…

Interesting. I am surprised this doesn't seem to be more widely known. We have an ancient gas wall heater in our living room and due to a cat with CKD, we need to keep the bedroom doors closed. We have some small electric heaters, but those are not safe to leave on in our toddlers bedroom and are expensive to operate. I have been looking into getting some window mounted heat pumps, but they are expensive, bulky, and don't really work with our windows.

We live by the coast, so we have a few small dehumidifiers for mold prevention but have not been using them much. I am going to test this out and see if it works. I don't particularly mind bundling up, but the toddler can't make it through the night with the blankets on. So if this does work, seems like it would be the perfect solution.