Efficient dehumidifier makes air conditioning a breeze (2014)
pnnl.gov
pnnl.gov
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 think it depends on you and what you're comfortable with.
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.
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.
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.
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.
I.e. your comment I replied to said ‘2 hours ago’ I clicked there and replied.
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.
They stayed on the table for three years, until I threw them away.
It's a neat and interesting visualization, though, once you get past that. I could see it being useful.
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.
Its one of those cases where you need some techincal knowledge and its not going to make money so gets missed despite its importance.
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?
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.
Commercial spaces have giant units that cool much more than I want. What are they doing differently?
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.
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.
Any reason why? I would naively think that putting in a variable speed motor with a dial would be peanuts on the total cost?
Or just get a variable-speed heat pump to handle cooling and heating.
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.
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.
The max 25 drop does seem to be a widely reported thing. For example, my first search result for "max ac drop" is this:
https://www.jerrykelly.com/blog/how-many-degrees-cooler-can-...
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!
That doesn't seem right - the evaporative cooling zone includes conditions like 40C 1% humidity.
What would dehumidification alone do under those conditions?
Dehumidification after evap cooling would make sense.
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 found one company that supplies exactly what I'm talking about: https://www.homevap.nl/en/overzicht-koude-bevochtiging/homev... though I'm tempted to try something homebrew using a piezo water mister.
It’s endlessly fascinating how different we can all be.
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.
38C@30% humidity = 24.4C
28C@60% humidity = 22.2C
> Wet-bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only
> Our bodies sweat to cool off, but, because water evaporates slower in more humid conditions, we cool down a lot slower in humid conditions.
Basically, "what is the absolute coolest you can get from evaporative cooling via sweat."
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?
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 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.
Dew point determines how much body cooling you can achieve through sweating.
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?
[0] https://en.m.wikipedia.org/wiki/Compressed_air_dryer#Desicca...
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.
I was skeptical but had missed that bit!
https://cdn.shopify.com/s/files/1/0196/5170/files/model_s100...
“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__
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.
[1] https://www.eia.gov/todayinenergy/detail.php?id=36692
[2] https://jrenewables.springeropen.com/articles/10.1186/s40807...
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.
In the summer dehumidify air for more efficient cooling.
In the winter humidify the air for more efficient heating?
This would be a win-win-win because where I live summers a hot and humid, and winters are dry, and my heat-pump dries the air even more.
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.
Set system to de-humidify instead, and air to room is 5C-7C lower temp than air at return. (As measured by a laser temp sensor.)
Note that ambient humidity is above 80% so there’s plenty dehumidifying available.
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)
https://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2...
Not sure which desiccant they're using. They have several papers on their site, e.g. https://www.pnnl.gov/publications/graphene-oxide-membranes-h...
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.
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?
https://www.air-compressor-guide.com/articles/water-in-compr... has a reasonable view.
The short version essentially amounts to you will end up with a lot of water to deal with.
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.
(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.)
I recommend you look up how heat-pumps work: https://www.nrcan.gc.ca/energy-efficiency/energy-star-canada...
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.
Why would it be a problem to do just the middle one instead of all three?
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.
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.
https://komonews.com/weather/faq/why-doesnt-our-humid-air-fe...
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.
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.
Of course, anything outside your heat envelope/moisture barrier is pretty damp.
I was probably mistaken about it not being humid. This article clarified that it is a combination of dew point and humidity that affects how we feel.
https://komonews.com/weather/faq/why-doesnt-our-humid-air-fe...
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.
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).
So I agree, they’re doing this wrong.
[0] https://www.energystar.gov/most-efficient/me-certified-dehum...
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.
Trying to integrate with electric buses seems extremely unwise.
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)
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.
efficient dehumidifier+AC will do wonders on wet+hot regions (south-east asia)
https://en.wikipedia.org/wiki/Evaporative_cooler
Or use a humidifier, I guess.
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.
This is a notable exception:
https://www.chiltrix.com/chiller-controller/
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.
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.)
https://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2...
The website claims the system can eliminate the compressor and refrigerant completely.
Not sure if they have a separate patent for that.
On an EV you'd have to use resistive heater since you just can't flip the valve while AC is running and turn it into heat pump instantly.
> 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)
so its a scam then, ok
At the other end of the spectrum, most radiant cooling systems cannot safely dehumidify.
Seeing as it was -30C a mere 6 months ago, and many Canucks think 15C with sun is a nice temp, comfort comes at close to 20C.
Which of course, with the sun pounding on the house, means you need the return air to be 10C or some such.