For anyone trying to understand whether dehumidification alone is enough to make them comfortable try the link below - load the 'givoni' comfort overlay and your city's weather chart. If most of the weather is [edit] vertically above the comfort zone or possibly the natural ventilation zone adjacent [/edit i originally wrote in the 'evaporative cooling' zone shown which is wrong] its probably a good choice for you.
It’s a fascinating tool and thanks for the link! But oh my word — I need to find and download a weather station file, then upload it again to the same tool? I don’t spend much time in GIS tools, but this feels almost maliciously opaque :D
These instructions are hidden behind a “Toggle Instructions” button which is hidden in a popup which is hidden in a select control:
> “Once you have found the right weather station, select its indicator and click the 'Download Weather File' link in the popup. This will download the selected file to local storage so you will need to select the 'Load...' button or the 'Load Weather File...' menu item and locate the downloaded file on your system.”
I mean, I UX for a living and I’ve seen some daft shit, but I’ve rarely seen a tool so useful and polished in its presentation which presents a less-clear surface area to the user. I want to put a frame around it somehow, as The Master Antipattern.
You're taking flak for being too harsh, but I'm glad you posted, because without your second sentence I don't think I could have figured it out. It's too counterintuitive to select a file, download it, and then upload it. My mind would have rejected it before even considering it if I hadn't read your comment before I clicked.
It's a neat and interesting visualization, though, once you get past that. I could see it being useful.
Not sure if this is the case here, but lots of weather APIs cost money, so if they tried to integrate the full process themselves they would no longer be providing a free service, and instead losing money. So by outsourcing the download portion to you, each IP may get a few free downloads and then you just provide the data yourself saving the creator money and allowing the tool to be free...
Me neither, but are there any GIS tools, that get it right?
My (limited and possibly outdated) experience with them is kind of horrible. Buttons and information overload and the workflow of experienced users is strictly memorized. I know some people (used to) make their living, just by knowing where to click around in ArcGIS and helping others who do not know the interface structure so well.
Software experts exist for pretty much every piece of complicated software. There is so much you can do in arcgis that only someone who spent a lot of time would know how to use the tool and when to use the tool, but most gis technologists don't need their help as they spend time in the software to learn it too.
Guarantee you that over 50% of people who visit this site turn away in frustration, and over 90%+ of the people who aren't computer scientists on Hacker News lol. Yep this is a beautifully-functional tool but the UX is ridick! Also - Select your city by dragging through the map? Weird chart with blue boxes result one has no idea how to read without digging for further instructions?
You’re welcome to that, of course. There’s prior art: “Don’t look a gift horse in the mouth,” etc. But there is, for one thing, a difference between a personal gift, and publishing something for public use.
Consider that you’re literally contradicting one of the foundations of the Internet — criticism and improvement. How many websites have you or I visited in the last 25 years? If none of us criticized things we got for free, most critique would never occur at all. How would we learn and improve without that? I mean, is creating a bug ticket on a FOSS Github project criticizing something you get for free? It strikes me as an odd position.
Now of course one shouldn’t be an asshole while criticizing, or hurt people deliberately. But I don’t see any of that in my comment.
Not everything on the internet or web is really intended for public consumption, even if it is left open to it. The standard for a personal tool is far different than one intended as a tool for general use.
At my work, in the break room, some people left stuff on the table for anyone to take. A neti pot, an Outback Steakhouse bobblehead figurine, some Christian romance novel.
They stayed on the table for three years, until I threw them away.
Meant for a reply to the adjacent Godel_unicode but the nesting limit (?) precludes that:
No, rude asshole criticism is extremely rude. Well-pitched constructive criticism is a gift, although you'd be right to say that when addressing strangers it's easy to come across as a demanding prick. So if you can provide that feedback for improvement along with sincere praise then criticize away.
the nesting limit is way deeper than this, there's a cooldown timer for replying too fast in a thread. and if you view the page for the comment, you can always reply.
Thanks for the explanation! Since my last comment on anything was a couple of days ago I guess the cooldown gets tripped by something else too (possibly I went back+forward a couple of times so looked like obsessive reloading)
No, you just need to click on the ‘n time ago’ bit which opens that comment which then enables you to reply directly no matter how nested or save/favorite.
I.e. your comment I replied to said ‘2 hours ago’ I clicked there and replied.
As someone who has made free stuff in the past, what's even the point if other people don't engage with it? And does it even count as engagement if its just fluff and not critical engagement? Positive vibes only makes the positive vibes meaningless.
As someone who has made lots of free stuff that tons of people actually use, the internet is full of people who think that they are super insightful and that their scathing indictments of the shade of grey that you picked are incredibly useful. It’s full of people who think that they are entitled to have no social skills because they “know UX”.
It’s orders of magnitude easier to destroy than to create, and our culture is all about supposed experts gate-keeping with their banal comments about UX problems that boil down to personal preference.
To be clear, i definitely agree, the internet is full of crazy people with irrational complaints.
I suppose i consider that part of the price of putting oneself out there. Its hard to imagine getting rid of that without throwing the baby out with the bath water, so to speak.
If you spent a lot of time making something useful to a small set of users who already had extensive domain knowledge, but users without extensive domain knowledge found it confusing and couldn't derive value from your product would you prefer A) they tell you about their experience, or B) users just view your product, quietly wonder "what am I looking at?", the silently move on?
I don’t think this is intended to be used in isolation. Cooling dry air is much less energy intensive than cooling dry air + a bunch of water. So, this device efficiently removes the moisture from the air, allowing the ac system to do less work.
AC systems are pretty good at dehumidifying as well. I'm going to be replacing my home AC system soon (it's 13 years old) and was asking our AC maintenance guy about getting an oversized system. In central Texas days approaching 110 seem to be the norm these days. In this weather, my "correctly" sized system can only drop the temperature around 25 degrees different than the outside. He advised against going oversized because apparently a big system cools faster than it removes moisture and you can end up with a block of ice at the exchanger or get condensation and then mold inside.
I was thinking a smarter thermostat should be able to monitor humidity in the air and run the AC at a low level, ramping up as moisture goes down, but that doesn't seem to be a feature in any of them (product idea?).
Maybe a separate dehumidifier like the one in the article combined with an oversized system could work?
I'm in a similar climate and have an oversized unit on the roof of a condominium building . Perfect for us would have been a 1.5 ton unit but the installer put in a 2.5 ton and told us it would be fine. Reality is...
The temperature rises and the AC kicks on. The plenum chamber in the AC unit, which is near the roof and is hot is flushed out to the condo interior. So we get a blast of hot dry air, followed by a blast of cold dry air for a brief period. The large unit quickly cools the condo and then switches off. So on a hot day the unit is cycling all day. This still happens on the hottest days of summer [in contrast, perfect would be a unit that, in the hottest weather, turns on and runs all day, barely keeping up]. To boot, this raises the electrical bill and stresses the AC unit.
So don't get a unit that is too big. Go to the trouble to have the unit sized properly.
The dehumidifier sounds great but it will decrease reliability and be one more thing to fail. It might be worth trying. Definitely don't use it with an oversized system - use it with an undersized system!
I’m no expert, but my understanding is that most residential systems don’t run at variable speeds. In effect, the AC is either on or off. And that’s what makes an oversized system a poor choice: there no way to slow it down.
One exception is Carrier’s Infinity system, which is variable speed. It’s relatively more expensive, still not all that expensive, and may be overkill if you don’t have multiple zones, which it can also handle. Also, you’re stuck with Carrier’s matching thermostats. But it may be a good choice if you’re looking for flexibility.
Depending on where you live, though, actually finding an installer who can do one at a reasonable price can be a serious problem. Like I was quoted about double the price to go from their "standard" system to a variable speed unit when I replaced mine a couple years ago.
Most HVAC companies like to have a "standard" line they do and then charge dearly to deviate from that, because that's where callbacks and problems come from.
I don't think you can get a variable speed system at the same price as a single speed one or even close to that: it's different, more complicated hardware. And, as it is already more expensive, they don't make variable speed versions of the cheapest designs hence they use more expensive materials and processes in the production (sound insulation, fancy finned coils, weather protection and such).
Do you know if a variable speed system will let you oversize and avoid the typical problems from doing so (short cycling, failure to dehumidify, etc...)? I haven't been able to find out a definitive answer. It seems like it wouldn't take a very smart thermostat to measure humidity and cycle times and throttle cooling to ensure that both factors are accounted for.
I don't know, sorry. You better to talk with an HVAC installer. Perhaps your issue is that your system is not sized right from the beginning, did you get a schedule J or got the tonnage from the previous install/square footage?
I have talked to two different HVAC companies and our system is sized correctly. When I complain that when it's 105 out I'm lucky if it can hold 80 they tell me it's working as expected. They say no system can do more than about a 25F drop but I have a hard time believing that. People in hotter climates somehow are able to cool their homes more than 25 degrees and commercial spaces (like stores and offices) somehow manage to cool more than that.
On the other hand, I'm asking them to sell me something that's more expensive and the fact that they don't want to tells me that they have some reason to believe I wouldn't be happy with the result.
It costs money to do a schedule J measurements so it's unlikely you've got it from just talking. What you describe sounds like an undersized system. Max 25 drop is obviously false, I have solid 75 with 115 outside with a residential AC, for example.
The explanation in the article does not make sense to me unless it's talking about window units. Ducted systems do not cool the outside air so the amount of temperature drop in the air passing through is not relevant. As long as it can cool faster than the air is being heated inside it can drop the inside temperature to the temperature of the coil, which is unlikely to be set at 80 degree in your case.
I can't find a single article saying anything else. The 20-25 degree maximum temperature drop seems to be everywhere which leads me to think it must be true but I don't understand why. I'm trying to find out what happens if you go oversized on a variable speed system and can't find any information.
It's not quite peanuts: when I had been replacing my AC system I was quoted the single speed system at $X, dual speed at $1.5X and variable speed at $2X. You need two variable speed motors: in the compressor (which is the most expensive part) and in the air handler (it's low power compared to compressor) and you also probably want a variable furnace, which is can be way more expensive than a fixed power furnace as you cannot just throttle your gas line to get less heat: that will cause condensate in the heat exchange and quick end of the furnace.
> Maybe a separate dehumidifier like the one in the article combined with an oversized system could work?
Wouldn't a "right sized" system plus dehumidifier be better? If you oversize the AC to the point it short cycles, it won't be providing as much dehum as you have now, so you'd just be shifting that load to the dehum, not helping overall.
In a lot of the US, getting a variable speed system can actually cost a hell of a premium, even though the wholesale cost of the equipment doesn't vary by much.
My variable speed AC came with humidity control in the thermostat. Perhaps you are looking at the single speed products, which cannot have a "low level"?
My AC guy said that a right sized system in Texas will never be able to pull the temperature down more than about 25 degrees Fahrenheit. This is the limit I’m trying to get around and I know it’s possible because systems in hotter places can do (like in Arizona) and commercial systems in shopping malls and stadiums can do it too.
Just guessing here but “right sized” might be relative to historic temperatures and don’t take into account the extremes?
In Arizona 117 is common enough that you’d expect the AC to handle it with no problem but Texas it probably isn’t that common (guessing). Think the hottest it got since I’ve lived there was 122. People also commonly don’t cool their houses too low because it gets expensive, my sister used to have a McMansion and their AC bill was a lot (something like $400/month) and they were only cooling to around 78 or so.
Your guess is exactly right. There are a couple of standards that are used to calculate the correct size of unit and it shoots for something that will work most of the time. Now that weather is getting more extreme I question if those manuals are still correct.
That’s exactly what I’m trying to figure out. The guy basically told me that they won’t install an incorrectly sized AC and I’m trying to figure out why. The best that I can determine is that they are worried about humidity issues but I don’t see why a smart thermostat and variable speed system couldn’t work around that.
Commercial spaces have giant units that cool much more than I want. What are they doing differently?
Cool! So, you set the Givoni Bioclimatic Chart overlay on?
Grew up in the evaporative zone, and it worked well, except on the hottest of days (which come now more often..). Now I live in a much more humid place, which seems to be in natural ventilation/mass cooling zones (overlap of the boxes is a tad confusing to read.
I'm thinking there is a lot of context here I am missing as a layman. you can shift all the zones (including comfort zone) up and down the chart by adjusting the "mean outdoor temp" slider. people don't really work that way, unless we are assuming that they keep wearing their outdoor clothes inside maybe?
> whether dehumidification alone is enough to make them comfortable ... if most of the weather is in the 'evaporative cooling' zone shown its probably a good choice for you.
That doesn't seem right - the evaporative cooling zone includes conditions like 40C 1% humidity.
What would dehumidification alone do under those conditions?
Sorry my bad brain explosion writing evaporative cooling. Should read 'vertically above the comfort zone' is good for evap cooling. Ive edited the above comment too. Thsnks for pointing out my mistake
I don't understand this. I can't understand how the thermodynamics works to not simply heat the air back up again when you dehumidify. I guess you can somehow have all the latent heat of vaporisation go into the water? Can anyone explain this? Surely an adsorber based system must release that energy at some point.
It works in less arid places too. You can use the humidified cool air to cool incoming air. The now warm air is pumped out. Essentially, you can achieve this by putting a wet filter on the house outflow of an MVHR system, before the heat exchanger. The problem with MVHR is that the flow rates aren't very high. I have an inkling though that with a well designed, efficient house you could maintain a more consistently comfortable temperature with very low energy usage (think a few W and perhaps 1 l/hr water). The psychrometric chart suggests you can get a temperature delta of better than 10 degrees Celsius at 35 degrees with 40% RH.
I don't think so, though I did struggle slightly to understand the schematics. That system still seems to humidify the incoming air, just in two stages. I might have missed something though.
The point is if we don't care about losing the water to the atmosphere (in climates where water is not scarce), we don't need a closed water cycle. For your house outflow air, on the psychrometric chart, you follow the isenthalpic line with evaporative cooling as far as though can (the diagonal lines from bottom right to top left ending in the wet bulb temperature, which is adiabatic in our case since constant pressure). This gives the temperature on the cold input side of the heat exchanger, which cools the incoming air, which will have an increase in RH, but only due to temperature change.
I posit the system would work well to reduce uncomfortable temperatures to be more in normal range in temperate climate extremes.
I just experienced 38 degrees heat with 30% humidity here in Berlin just a few days ago. and then 28 degree heat with 60% humidity. I'll take 38 degrees at 30% humidity every time. It was fine. At 60% humidity, you are sweating non stop and it's uncomfortable because not enough of it evaporates. You feel sticky, hot and miserable. At 30% humidity, sweating cools your body really effectively and while taxing, you recover quickly in the shade. 38 degrees (slightly warmer than you) is no joke. But at that humidity, I prefer it over much cooler temperatures with higher humidity. The combination of high temperatures and humidity is lethal.
I live in south-eastern Canada today it was 35C which is something I've never seen here. And the humidity at one point was 90% which is typical since I am on an island. Thankfully it went to about 70%.
I felt tired it wears you out even 35C is OK but any humidity over 60% is terrible. My entire childhood up until ten years ago a 30C day here was a very hot day that came maybe once per summer but most years never.
So that 10C difference only feels like 2C difference, but comes with the complications of being all sticky, which might make you feel more miserable overall despite being technically cooler.
Also, I don't know enough about wet bulb, but would it be possible that if humidity is higher, that sweat evaporates more slowly, and accumulates rather than just evaporating? If sweat drips off your body rather than evaporating off, do you still get the cooling effect (is it the releasing of sweat, or the evaporating that cools you?). Walking through a park on a summer day and a lab environment are going to be a bit different.
Basically, my question is, does wet bulb temperature accurately represent the human body, or is this a spherical cow moment?
Less evaporation happening is exactly the mechanism by which the wet bulb temperature is higher the more humidity there is. Sweat dripping off doesn't invalidate the model because heat is still being pulled away at the maximum rate, it's just that the body is expressing more moisture than actually needed.
I was more thinking of things like surface area. At a certain point, once the sweat starts pooling, the sweat to evaporation ratio goes down (since it can only evaporate at the surface, which is further away from the skin, so now sweat is also insulating).
And the point of evaporative cooling isn't that sweat is taking heat away from the body through contact heat transfer. Evaporation actually uses heat for the phase change, which means that a single drop of sweat will pull heat out of your body through standard heat transfer. And if it drips. then it has just pulled that heat away. If it evaporates, it will actively pull even more heat away. Which is why wet-bulb temps can be below ambient. If the sweat drips, you don't get the evaporation benefits. So if you sweat to the point that you are dripping, I would have to believe that you wouldn't hit the ideal wet-bulb temps, and would thus be hotter.
I grew up in Berlin as well and never minded the heat, because it was usually dry. But in the last decade or so we seem to have more of these hot and humid days, which makes me wonder…
why doesn’t this startup target consumer dehumidifiers first, it would seem like an easier market when u have some newfangled technology with magical properties. Unless it’s really expensive.
Contains a "novel desiccant material that has exceptional adsorption properties."
But no mention of how much the material costs and how long it lasts. Is this another one of those new surface chemistry materials that doesn't last long, like the ultra-black material, the ultra water repellant material, and the exotic salt water desalination membranes?
That's not the novel part, the novel part is thermally connecting the regenerating and saturating sides. I think the tldr is that the regenerating side is evaporating and thus cooling? The work input into the system (aside from fans) is the vacuum pump.
They're using vacuum to dry the desiccant; the mechanism to seal the two chambers well enough to pull a vacuum seems like a high failure point.
The vacuum may pull the shutters against seals during the regen. So the shutters would move freely with the vacuum off, then seal tightly during the dry cycle. You would need filtration to protect the seals, but compliant seals assisted by vacuum draw would probably be okay.
Ah! They are using vacuum thus inputting energy to move the regen and sat sides around otherwise this would have a distinct whiff of ‘perpetual motion’ about it.
You could probably build something similar using zeolite (if that's not already what they've using). The form factor undoubtedly matters but there are existing water absorptive materials that are long lasting and effective.
I'm not qualified to evaluate how plausible this is, but if it does actually work out it could be a huge boost in multiple ways. Air conditioning accounts for somewhere around 10% of US energy usage [1] and probably more in southern areas. Cutting that by a third is a lot. Not to mention the potential range extension for BEVs - in some of my BEV testing earlier this year, HVAC cut range by around 20% (note this wouldn't necessarily help much for heating, which is usually a bigger range impact).
I'm not qualified either, however, we can see from [1] that in southern states summer energy use jumps like crazy--almost all because of AC--peaking when solar production drops to about half around 6pm [2]. Given that humidity affects both the efficiency of AC, and personal comfort (sometimes I run the AC just to dehumidify), and the fact that it's only going to get hotter with GW, and more humid (because warmer air can hold more water), targeting AC efficiency is a BFD.
I posted to here because (a) government lab, so has some credibility, and (b) getting feedback from the HN community who might have informed opinions about it.
Your second citation does not show AC peaking at 6, it shows Solar and Wind use averages over time of day.
I don’t know when AC use peaks but total use tends to peak before 6PM while residential use peaks in the morning and evening [1]. Solar does fall off around then and rather suddenly for any given longitude. But what you see with the duck curve (slouching midday prices with a 6PM peak) in California is reduced grid demand. Grid demand is not the same as energy use because of behind the meter generation (e.g., rooftop solar). The duck curve shape is caused by replacement energy use from solar not reduced energy use.
Thank you. My second citation was to show that solar availability in summer drops by about 6. My assertion about peak AC was based on your citation. Actually, I thought that I had linked to it in my post. My intention was to link to the other two and that one; somehow that got lost; a case of too many tabs, maybe.
I recently got back from a few hundred mile road trip in >100F temperatures in an EV with decently high (40%+) humidity. Climate was <5% of the energy usage as reported by the car. Even when driving around town in 114F weather, its rarely been >15% of my overall energy usage.
Do you have any data on air conditioning and EV range? I find nothing helps as much as going 110kmph (~70mph) rather than speeding at 130kmph (~80mph).
Presuming that the AC condensor gets airflow from the car moving through the air, it is going to be more efficient if the car is moving faster. However after a point, the air resistance will be hurting range more than anything.
My Aircon uses about 4kw (3 to 4 is typical) plus several 100s W for the fan. So ev usage time times that is the reduced power available and thus reduced range. It is just as noticeable on a petrol car especially on lower power compact versions, it won't have too much impact on gas guzzling engines since they are already inefficient and usually more powerful so it is less noticeable, though the added consumption will be more of course.
Kona EV has a page on power consumption, which at 30C ambient temperature and a long drive said I used about 4% on AC. Same amount goes to "electronics" which I find surprising.
“There’s a huge opportunity in electric vehicles (EVs) and particularly electric buses because integration of our dehumidifiers in their air conditioning systems can extend their driving ranges by up to 75 percent,” said Matt Jore, CEO of Montana Technologies.
__extend their driving ranges by up to 75 percent__
> In the winter humidify the air for more efficient heating?
I'm rusty too, but the more mass you have, (or things that takes heat) the more energy you need to heat up. But then you have inertia. That's why people put bricks around simple wooden stove - so after the wood has burned out, those bricks still give you heat.
Why not just use a regular humidifier? Evaporative humidifiers are just a fan with a special filter that's good at absorbing water and has a very high surface area so it also evaporates quickly.
daikin had this premium residential series called ururu sarara 7 which does this. albeit with some performance upper bounds to keep costs sane. somewhat complicated setup, and i think it would be a brilliant unit if your local weather is within the designed performance envelope
The mechanism they describe is exactly how desiccant compressed air dryers already work.
It is hard to believe that they really have come up with some super novel desiccant. If they did, it would be instantly useful in this already existing commercial application and trivial to integrate.
In practice, we already have good rechargeable desiccants that work well for a very long time (ie 10+ years at constant duty cycles)
Yeah, this reads like a standard dessicant dryer applied to HVAC. I can believe that it costs less to run the dessicant dryer and then cool the air than a standard AC. This is often very true in compressed air, because you are trying to compress air, and if your air is saturated with water, you are producing a much smaller volume of compressed air vs using dry incoming air. Water is relatively incompressible, so it's actually somewhat remarkable how true this is (IE what volume of air you get out of 80% humidity intake air vs 30% humidity intake air)
The main issue they are likely (IMHO) to hit is contamination. Compressed air is filtered before being dessicant dried to avoid getting oil/dust/etc on the dessicant, because it will reduce efficiency and destroy adsorption capability over time.
Compared to compressed air, residential HVAC systems are not that well filtered (commercial can be). There are lots of people using nothing or random low-MERV fiberglass filters. That will destroy dessicant capability very quickly.
So i have to imagine they are starting commercial first.
Yeah, this is pretty far out of my expertise (so appreciate your commentary). Your point about contamination might explain their market choice (which others have questioned in these threads).
>(IE what volume of air you get out of 80% humidity intake air vs 30% humidity intake air)
A quick Google gives me that both are in the order of ~10 g/kg (or g/m3 at standard pressure), so I'd say both will be about the same? What am I missing?
HVAC industry is such a huge market primed to be disrupted. The way they wanted to "size" your room properly is really used to calculate cooling/heating capacity to achieve a comfortable relative humidity. But back in the days they didn't have DC inverter, units were either on 100% full power or shut off at 0%. Nowadays with linear inverter units cooling/heating can be ramped up and down, but we also have a lot more requirements now like greenhouse potential etc.
Ignoring all that, it is in theory possible with 3rd party sensors + algorithm to coordinate all assets to achieve a satisfying outcome. Chug in vent control then you'd have a pretty decent solution.
So if you only have AC units, it'd cool from one end with shade and fan the hot end. If you have humidifier units, then it can coerce air to be dried first before being conditioned etc. Just by turning on/off vents and units and learning from sensor data.
This. IANAP (...Not A Physicist), but condensing water vapor releases a whole lotta heat. If you could do that "free" - well, setting up a heat engine between your hot condenser and the evaporation-cooled spot where you let the water vaporize again becomes a classic perpetual motion machine.
(Yes, I see that the article claims their system is a mere 10 to 30 times more energy efficient than conventional dehumidifiers. That still sounds far too good to be true.)
Conventional AC and dehumidifiers remove water from air by cooling both until the cooled water drops out of solution. This is supposedly using chemical means to remove hot water from the air so that you don't have to cool it.
Fuel cells and electric motors are vastly more efficient at turning propane into motion than a combustion engine. Its possible they found a dessicant that is particularly easy to reverse at stp. Theymention the absorbing dessicant is exothermic which is unusual I think? And they pump that heat over to regenerate the other dessicant under a slight vacuum. Sounds a bit like the oxygen generators people use for lung conditions, or to weld with.
My understanding is heat from first chamber + external vacuum is used to dry out a second chamber and then the system is reversed when the first chamber is saturated.
Energy is being put into the system but it is less than the AC unit cooling humid air on its own so is a net gain relatively speaking.
From what I understand, the desiccant releases water under slight pressure from vacuum pump, which presumably is less than the energy saved by using the desiccant in the first place.
The release of water from the desiccant occurs at a lower pressure than its absorption. Energy is consumed in maintaining that lower pressure by pumping away the water vapor as it is released (presumably, it is vented outdoors.)
From the patent:
[The vacuum pump] is used to provide modest compression to raise the vapor pressure sufficiently to condense to liquid water. Because the compression work is only done on the water vapor, this minimizes the energy consumption. Lastly, the condensate is pumped up to atmospheric pressure for discharge to a storage vessel (this consumes a trivial amount of additional energy).
Update: The patent also implies that the high efficiency of any given device of this type may only obtain over a limited range of operating conditions:
Sorbents optimized for a 43.degree. C., 60% RH condition are likely to perform poorly and result in much higher power consumption at the more challenging 27.degree. C., 10% RH humidity condition and vice versa.
Being mold sensitive and living in the pacific nw we have two dehumidifiers just to keep our house from mold growth. This would save us a lot of money if it works out.
Check out mini-splits and ducted mini-splits. The latter can be setup to look like traditional forced air systems. These include heat pump system (cooling/heating) and ability to dehumidify. Zoning the home is also very easy, you do need to ensure you have a competent contractor to properly set these up if you go with the more complex/feature rich systems.
Depends on what you are comparing to - if a dedicated whole house system, then possibly (depends on ducting and such). Any portable systems are likely to be less efficient when compared on throughput.
The major win for me is that it all just works. The units already have drains and they balance everything as they cool. No separate system to worry about or maintain.
If you are west of the Cascade mountains, that sounds like an air flow or drainage issue. The humidity is already pretty low, so moisture evaporates pretty quickly, in my experience.
And their bathrooms. Major party foul to take a shower in Seattle and not turn on the bathroom fan. If you’re lucky you will get lectured by your host. If not they will just silently judge you.
Where I am near the Puget Sound, I generally get around 50-60% relative humidity at outside temperatures. Which isn't really very humid. But my basement sits at 5-10 degrees cooler than outside temperature, and the same water content in the air, but 5-10 degrees cooler is a recipie for puddles in the basement. Running the ground floor A/C makes it worse, as the air handler is in the basement and cools the utility room through convection of the vents (better design of HVAC would help, but it'd hard to retrofit without tearing up a lot of stuff). Running a dehumidifier helps, but a more efficient dehumidifier might be nice.
Indoor humidity, especially in winter, can still be low. Even when dealing with saturated outdoor air, by the time you heat it up indoors it can be borderline to a bit too dry for comfort.
Of course, anything outside your heat envelope/moisture barrier is pretty damp.
But I notice surfaces get dry very quickly, even though it is cloudy. It can rain and drizzle for hours between 4am and 10AM, and then by noon everything is dry.
That’s because it doesn’t actually rain that much in Seattle. A quarter inch of rain dries quickly no matter where you are.
Everyone thinks it rains tons in Seattle. It rains constantly, but it doesn’t rain tons.
The north end of Vancouver Island gets 3.5x as much rain per year as Seattle. The temperate rainforest plants do fine in Seattle because it only dries out in the summer. The rest of the year it’s just damp all the time.
That said, given the market, I would expect about a year of analysis to get the design win, then another year or two to get first products from design into production. I find their idea of going after electric busses "first" as a stretch since a) all e-busses are currently made in China so the technology transfer would be challenging, and b) there aren't that enough municipalities committed to e-busses yet to make a viable market for Montana Energy (if they capture 100% of the E-bus market they sell about 1000 units this year, probably not enough to sustain a company).
That makes me wonder about the company.
If it is run by scientists who insist on going for the most efficient implementation rather than by engineers who understand getting the value of having anything on the market, the company will fail.
Comparing their system to the top Energy Star performers [0], and taking their performance (20 L/kWh) at face value, they win by over 8x. If nothing else, they should be selling dehumidifiers! A quick web search suggests that the US dehumidifier market is between $1bn and $2bn per year. If they’re anywhere near as good as they claim, they should be able to capture essentially the entire market, especially if they are competent at marketing. They could, in addition, attempt to integrate with the high end heat pump makers (Mitsubishi, Daikin, etc) and target the high end HVAC market.
I would be willing to believe that electric busses are a decent market (lots of time spent with doors open), but the EV car market seems like a poor target (lots of solar heating, doors and windows mostly closed in hot or humid weather, size and weight of equipment are constrained).
A long time ago I had an opportunity to interact with the highest levels of a company called "Plastic Logic" who had created a flexible e-paper display that was much more durable than the glass covered displays. They presented their business plan where they were going to market with the "Plastic Reader", basically doing the entire product and software in house. I urged and pleaded with them. I said, "You guys are brilliant at displays, you've got a killer product here. Sell it to people who make readers! You start making money right away and you get better and better at making displays. Let your customers take the market risk of getting the form factor and software right, just start by making money!"
The guy with the most sway in the company was the scientist who had actually come up with the way to make transistors on plastic and integrate them into a display. He was (and still is) a brilliant guy. But he was so smart that he felt "the display is the hard bit, everything else is practically off the shelf. Why should we give up our margin and our advantage to people who can't currently get a display with these properties. When we start shipping all other e-readers will become obsolete overnight!" (Not an exact quote but close enough from memory.)
I tried to explain how risk didn't care how good your display was, adding to existing risks of getting the displays reliably produced, the rest of the stack put dozens of other ways your product could get stalled on its way to market and the "other guys" were investing like crazy. They couldn't possibly match the software and design engineering talent people that already had a reader on the market had right now. I told the CEO straight up, I said, "This path leads to failure, it always leads to failure."
Of course they totally failed and sold off their assets a few times to various hedge funds and guess what, their display never ever made it to mass production because the brilliant guy who designed it in the first place didn't focus on that.
I'm still sad they chose that route, it could have been epic.
By this analogy, I suppose they could sell to, say, Aprilaire. On the other hand, it’s not particularly hard to stick a nice blower on their device and sell a self contained unit. Plenty of vendors will gladly sell them excellent ECM blowers.
Trying to integrate with electric buses seems extremely unwise.
They might be approaching the E-Bus market because their device needs to vent outside, and an airhandling device has easy access to vent outside, whereas a home dehumidifier often wouldn't have easy access to outside air.
In addition, an E-bus has an acute need for energy efficiency; reducing the need for energy for climate control lets you go more miles on the same battery and range on a large, heavy, EV is hard to increase. It makes sense for liquid fueled busses too, but liquid fuel allows for a pretty long range anyway.
Getting a design win on a new(ish) transportation category could have a bigger impact than competing in an existing market; although if the E-bus market is really 1000 units, they better find other applications soon. (Although if works for E-busses, it should work for any vehicle where dehumidification is happening)
They'll probably sit on the patent so it can't be used and we'll see the tech on the market after expiry in 10 years. Seems to be what happens with patents
I am kinda struggling with the thermodynamics of that mechanism. Can someone explain where the energy saving comes from using Thermodynamic Integration or comparing the (almost) cyclic processes of this one with a conventional air conditioners cycle?
I think this is similar to the difference between a heat pump and a heater. Normally to dehumidify we strip the humidity out of the air and turn it into water, but all the embedded energy in the water vapor needs to go somewhere and it ends up heating up the house. Here instead they have a device that on net pumps humid air out of a structure. It doesn’t try to pull it all out of the air, just to move it from one bit of air to another so it doesn’t have to pay the full price of removing it
A traditional dehumidifier is more or less an air conditioner, where you run inside air over the cool side, so that humidity condenses and is collected, then the air exits over the warm side and into the room.
This device uses two chambers with a dessicant and alternates between running inside air through the chamber to adsorb humidity from the air into the dessicant and then using a vaccum to pull water vapor from the dessicant and pump it into the outside air.
There's no energy intensive phase change of the refrigerant, and if I understand it correctly, the adsorbtion and deadsorbtion of the water vapor into and out of the dessicant isn't very energy intensive either. Note that this system doesn't work without access to outside air to vent the water vapor, whereas a traditional dehumidifier runs within a space, although the condesate may drain to outside.
The effectiveness will likely depend on the humidity and temperature and the properties of the cooling system this device is paired with. An air conditioner will generally provide some dehumidificiation anyway (unless the cold side doesn't reach the dew point...) and maybe that's enough, in which case additional dehumidification isn't helpful. In some places, temperature reduction isn't needed and just dehumidification, this system could help reduce humidity without providing cooling.
Yes, easily: just operate the evaporator (or other heat exchanger) above the dew point.
Sadly, most air conditioners are not capable of doing this. As far as I can tell, this is a weakness in the software or control system and is not a hardware limitation, although it might cause some systems to have to operate off their most efficient point or to require more airflow than the design supports well to get enough cooling.
In principle, any hydronic cooling system could be adapted to do that trick, by adding a mixing valve, an air temperature and humidity sensor, and a little computer. AFAICT the Chiltrix device works by adjusting the air-to-water heat pump’s supplied water temperature directly.
1 - drier air feels cooler, and has other advantages (reduced condensation on surfaces, etc).
2 - it’s more efficient for them to do so, considering heat exchanger surface area, the phase change temperature of the refrigerant, etc.
For the most part, those are the priorities people have. Subtle things like ‘not drying out the air too much’ are less noticeable and not generally a competitive advantage.
> 1 - drier air feels cooler, and has other advantages (reduced condensation on surfaces, etc).
This is the cargo cult problem. When it’s too humid, dry air feels better. So HVAC engineers pick a nominal coil temperature based on some design climate and use it everywhere. Dryer does not feel better in hot, dry places.
> 2 - it’s more efficient for them to do so, considering heat exchanger surface area, the phase change temperature of the refrigerant, etc.
I have not gone through all the math, but I’m willing to bet that this follows from #1. Engineers picked a coil temperature and designed from there. There are multiple refrigerants on the market, the operating pressure of a system can be controlled at least a little bit, and it’s even possible to operate the coil warmer than the refrigerant with no fundamental change in COP. (Hydronic systems do the latter regularly by recirculating some of their working fluid.)
As far as I can tell, there is no market for an air conditioner with better humidity control because no one has created a market — everyone expects that air conditioned air is unpleasant, and no one has marketed their superior system well.
(Lots of people in very humid climates think that comfortable air conditioned air is too cold — they have to set thermostats to 70 or even lower to be comfortable. This is because of inadequate dehumidification. Lots of people in hot, dry climates think that air conditioned air is too dry. These people aren’t wrong.)
Ideally, add more mass to your home. We're most sensitive not to absolute temperatures but to the characteristics of radiant heating and cooling in our environments. In-floor heating or cooling would do a lot more to stabilize your comfort than blowing around conditioned air.
Relative humidity rises for the same volume of water/air as temperature decreases. The dryness of an A/C is because of the condensation accumulating from the air passed across the evaporator, it is dehumidifying at the same time it’s cooling.
The air tempertature at the evaporator is cold -- maybe 40 degrees or so? The relative humidity is about 100% (as evidenced by liquid water condensing on it). But the house itself never gets that cold, heat moves in from outside by radiation, the air temperature is higher, maybe 70-80 degrees, which results in a lower relative humidity.
As far as I can tell, the article does not claim (or no longer claims) that this device can eliminate the compressor and refrigerant from an A/C system. It does claim that it can eliminate condensation on the evaporator, which is plausible, and it does eliminate the compressor and refrigerant used in conventional heat-pump dehumidifiers.
> Traditional dehumidifiers are too large and too energy intensive to install in vehicles, but AirJoule’s compact size and zero net energy penalty makes dehumidifying air before cooling it in a vehicle not only possible but creates huge energy savings.
Uh, what? Pretty sure most vehicles have AC, which functions the same as a traditional dehumidifier. The only difference is the cooled air AC would output is run back across the "exhaust" pipes to reheat it, instead of ejecting the heat outside.
(No comment on the energy saving aspect, just the first part caught my eye)
Few years ago I was in Phoenix,AZ when it was 40 most of the day with I'm guessing 0%-10% humidity. As our hotel had a pool I went for a dive and returned back to the shade and to my surprise I started shaking from being cold as evaporative cooling effect was so intense.
Similar to other HN user, I would prefer this kind of heat aka 40 degC with 0-10% humidity than what we have in Denmark during few summer days with 28 degC and 70% humidity.
>“There’s a huge opportunity in electric vehicles (EVs) and particularly electric buses because integration of our dehumidifiers in their air conditioning systems can extend their driving ranges by up to 75 percent,”
You know what else would make cooling your home energy efficient? If your home was not absorbing as much heat from the sun. Most roofs are black petroleum product, because oil everything! For not a whole lot of money, the cost of some digging, running pipes, and a pump, one could encase their home inside a closed loop 5mm tall waterfall during summer, which would drop their energy bill significantly. The idea is a little water runs over all outside surfaces of your home, taking whatever heat the surface of the home has with it (but also taking heat through evaporation) back down under the ground surface where it exchanges the heat. Add water as it is lost through evaporation. Really, if civil engineers and builders had made everything a water wonderland instead of heat absorbing black top, it would be a lot fn cooler.
energy efficient but not water efficient. Also unless you're in an area with plentiful soft water you're gonna create some impressive mineral deposits. You're better off painting things white and insulating the house better (which helps with both heating and cooling it).
Dehumidification is already obligatory in AC units by the nature of how they work. When you cool air down it can’t hold as much water and so that water condenses and leaves the air. The current way that we handle this is we just let that water condense on your AC evaporator coil, then expel the cool water as waste. But it’s more efficient if your AC unit spends its time cooling air instead of water.
If you cool air to a temperature comfortably above the dew point, there is absolutely no reason that dehumidification is obligatory. There are two reasons for dehumidification: running the coils at a temperature cargo-culted from a standardized guideline that doesn’t take the local climate into account and running the coils at a temperature such that adequate cooling capacity can be achieved at a low-enough airflow.
At the other end of the spectrum, most radiant cooling systems cannot safely dehumidify.
If it reduces the humidity to just the point where condensation would form in the A/C coils, you won't see any change (except to reduce the load on the A/C).
Not sure where you are located, but most people have low toleration for overly dry air. Running an air conditioner in a dry place like Arizona or California will only make it drier. Running it in a humid place like Florida or Virginia makes the humidity level tolerable. When I lived in California, we used an evaporative cooler most times of the year. Only the hottest days did we turn to AC. But here in the east coast, the evaporative coolers would probably be mostly useless.
It's not a binary "dry/wet" thing. If you live in a humid place, you can probably remove quite a bit of moisture from the air before you encounter those symptoms.
Yes, this getting used in offices or public transport and the air there getting even drier sounds extremely scary and horrifying to me. With a humidity under 40% I feel pain and under 30% I develop severe inflammation in my whole pharynx and become unable to function from pain.
https://drajmarsh.bitbucket.io/psychro-chart2d.html