[HN Gopher] Efficient dehumidifier makes air conditioning a breeze
___________________________________________________________________
Efficient dehumidifier makes air conditioning a breeze
Author : jonnycomputer
Score : 250 points
Date : 2022-07-23 16:07 UTC (6 hours ago)
(HTM) web link (www.pnnl.gov)
(TXT) w3m dump (www.pnnl.gov)
| Maursault wrote:
| 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.
| abstract_put wrote:
| Is this an actual construction technique in real life (beyond
| DIY-ers)? Is there a name for it?
| Maursault wrote:
| I'm not aware of any installs or of any official name for
| this, but I like to call it _wet roof._
| cjalmeida wrote:
| An even simpler method is painting your rooftop white/light
| gray.
| freemint wrote:
| 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?
| space_fountain wrote:
| 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
| calvinmorrison wrote:
| So is the concept basically to pump air over a very hydrophilic
| mesh and suck that water out? i don't really get it honestly
| jillesvangurp wrote:
| 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.
| ant6n wrote:
| 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.
| acchow wrote:
| Curiously, if you do the wet bulb conversion:
|
| 38C@30% humidity = 24.4C
|
| 28C@60% humidity = 22.2C
| DannyBee wrote:
| 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)
| jonnycomputer wrote:
| Here is their patent submission:
|
| 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...
| DannyBee wrote:
| 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.
| jonnycomputer wrote:
| 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).
| CorrectHorseBat wrote:
| >(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?
| dzhiurgis wrote:
| IIRC there are some dew points where you wanna be using both AC
| and heat in a vehicle.
|
| 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.
| Animats wrote:
| 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?
| trebligdivad wrote:
| The video talks about a metal-oxide framework; no idea of the
| lifetime of them but they seem to be the cool new tech used in
| everything at the moment.
| dgacmu wrote:
| 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.
| grigri907 wrote:
| This sounds like a retooling of the dessicant air dryers [0]
| that have been used for years in industrial compressed air
| systems.
|
| [0]
| https://en.m.wikipedia.org/wiki/Compressed_air_dryer#Desicca...
| KennyBlanken wrote:
| 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.
| trebligdivad wrote:
| Would this work for clothes drying?
| [deleted]
| atemerev wrote:
| I can't handle dry air, my nose immediately becomes blocked. So I
| hope it won't become obligatory in every AC unit.
| jhugo wrote:
| 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.
| pfdietz wrote:
| 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).
| colechristensen wrote:
| Air brought down to ~50% humidity is quite a lot more
| comfortable and not at all dry.
| kube-system wrote:
| 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.
| amluto wrote:
| 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.
| bbarnett wrote:
| Sadly, this is seldom the case for heat in Ottawa. Often it
| can be 32C, 35C, with 80%, even much higher humidity.
|
| 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.
| Traubenfuchs wrote:
| 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.
| jonnycomputer wrote:
| 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.
| bilsbie wrote:
| I wonder if cooling without dehumidifying is possible. A lot of
| times I want it cooler in the house but it starts getting
| uncomfortably dry.
| amluto wrote:
| 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.
|
| 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.
| lazide wrote:
| They operate below the dew point because;
|
| 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.
| amluto wrote:
| > 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.)
| washadjeffmad wrote:
| 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.
| dymk wrote:
| You could run a humidifier at the same time
| hgomersall wrote:
| That's easy, just aerosolise a load of water in your house.
| verall wrote:
| Use a swamp cooler
| More-nitors wrote:
| ditto this
|
| efficient dehumidifier+AC will do wonders on wet+hot regions
| (south-east asia)
| influxmoment wrote:
| You are noticing a change in relative humidity even tho the
| cooling did not change the absolute humidity
| [deleted]
| lukevp wrote:
| 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.
| bbarnett wrote:
| If that was the case, it would be more humid, not less.
| SoftTalker wrote:
| 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.
| bbarnett wrote:
| Not sure why you're replying to me, read upthread in more
| detail.
| jonnycomputer wrote:
| Use an evaporative cooler instead, then, if you live in a place
| that is arid enough.
|
| https://en.wikipedia.org/wiki/Evaporative_cooler
|
| Or use a humidifier, I guess.
| jonnycomputer wrote:
| I believe this is a link to the submitted patent:
|
| https://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2...
| udev wrote:
| From what I can see this is a patent application for the
| dehumidification part only, which can be added to a pre-
| existing HVAC system.
|
| The website claims the system can eliminate the compressor and
| refrigerant completely.
|
| Not sure if they have a separate patent for that.
| [deleted]
| mannykannot wrote:
| 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.
| Terretta wrote:
| Incidentally, staying on a beach island last 3 summers, and this
| summer the AC isn't working right, only "cooling" about 1C.
|
| 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.
| WaitWaitWha wrote:
| An evaporative cooling solution by "Tech Ingredients" seems to be
| more efficient (correct me if I am wrong)
|
| [0]https://www.youtube.com/watch?v=7w4rg3UcsgI
| Bloating wrote:
| evap cooling doesn't work (well) in humid climates
| twelvechairs wrote:
| 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.
|
| https://drajmarsh.bitbucket.io/psychro-chart2d.html
| Terretta wrote:
| Incredibly cool (ahem) resource, though it seems to prefer
| temps about 5C higher than those preferred by people who like
| AC.
| joshspankit wrote:
| I prefer temps about 3.5C lower. My ideal indoor work temp is
| 17.5C +-1. At 23, my brain is noticeably groggy.
|
| It's endlessly fascinating how different we can all be.
| antisthenes wrote:
| Are you overweight?
| jonnycomputer wrote:
| 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.
| sonofhans wrote:
| 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.
| GenerocUsername wrote:
| 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...
| eastbound wrote:
| Except you need CORS permissions and therefore, the website
| knows the domain name.
| ac29 wrote:
| The download weather link is just pulling a precomputed
| file from an S3 bucket.
| dkarl wrote:
| 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.
| hutzlibu wrote:
| "I don't spend much time in GIS tools"
|
| 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.
| LegitShady wrote:
| 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.
| jonnycomputer wrote:
| I don't like to criticize things I get for free.
| otikik wrote:
| Was that not a piece of free UX feedback?
| jonnycomputer wrote:
| Sometimes free still costs too much. (:
| bequanna wrote:
| Fair enough, but I think most people appreciate
| _constructive_ criticism with good faith, specific
| suggestions on how to improve.
| bicijay wrote:
| I mean... Why not?
| Godel_unicode wrote:
| It's extremely rude, and a great way to convince people
| who make useful free stuff that the world is composed of
| assholes and that it's not worth it.
| thombat wrote:
| 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.
| yababa_y wrote:
| > but the nesting limit (?) precludes that
|
| 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.
| thombat wrote:
| 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)
| sonofhans wrote:
| 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.
| jonnycomputer wrote:
| 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.
| tiahura wrote:
| 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.
| criddell wrote:
| 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?
| istjohn wrote:
| If you dehumidify first, you it'll be much easier for your
| existing system to cool the air.
| lostapathy wrote:
| > 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.
| andrewmg wrote:
| 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.
| leereeves wrote:
| > 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?
| jonnycomputer wrote:
| Evaporative cooling is where you blow a fan through a wet
| filter, which cools the air. Works in very arid places; it
| humidifies the air.
| hgomersall wrote:
| 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.
| jonnycomputer wrote:
| Interesting. Something like this:
| https://www.researchgate.net/publication/281902445_Two-
| stage...
| leereeves wrote:
| I know, but I think twelvechairs said "dehumidification
| alone" (with neither AC nor evap cooling) was a good choice
| under similar conditions.
|
| Dehumidification after evap cooling would make sense.
| jonnycomputer wrote:
| Oh, could be. The humidity is a comfort issue all by
| itself (and with drier air we can cool ourselves with
| sweat).
| hgomersall wrote:
| 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.
| twelvechairs wrote:
| 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
| bilsbie wrote:
| This sounds like free energy. The desiccant absorbs water and
| then dries out from the heat of absorbing water?
| mannykannot wrote:
| 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._
| bell-cot wrote:
| 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.)
| galangalalgol wrote:
| 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.
| CorrectHorseBat wrote:
| It's been a while since I've studied thermodynamics, but as
| far as I understand it that sounds like a violation of the
| second law of thermodynamics.
| bell-cot wrote:
| Hydrophilic chemicals are a perfectly legal way to
| dehumidify. You pay the price (energy) when you pry the
| water & chemicals back apart.
| CorrectHorseBat wrote:
| Of course, but as far as I understand this device does
| exactly that?
| Dylan16807 wrote:
| There's energy to cool the water, there's energy to
| condense the water, and there's energy to cool the rest
| of the air.
|
| Why would it be a problem to do just the middle one
| instead of all three?
| andbberger wrote:
| it's perfectly legal
| Bloating wrote:
| Congress changed the law
| udev wrote:
| Sounds like the notion of a condenser coil (a very real
| device) violates your understanding of thermodynamics.
|
| I recommend you look up how heat-pumps work:
| https://www.nrcan.gc.ca/energy-efficiency/energy-star-
| canada...
| CorrectHorseBat wrote:
| Not at all, doing it 30x more efficient than that is what
| I have issues with.
| udev wrote:
| 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.
| thunkle wrote:
| 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.
| sologoub wrote:
| 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.
| lotsofpulp wrote:
| 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.
| tatersolid wrote:
| Humidity is low in Seattle?
| thunkle wrote:
| Nope https://weather-and-climate.com/average-monthly-
| Humidity-per...
| lotsofpulp wrote:
| Yes, I guess I was wrong to describe it as low humidity.
| It is a combination of humidity changing during the day
| and lower dew points:
|
| 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.
| cududa wrote:
| You're aware that in the Pacific Northwest it's so humid/
| most people have to paint their roofs with zinc every few
| years to prevent mold growth, yes?
| lotsofpulp wrote:
| Yes, but I also know it feels much less humid than the
| Midwest and eastern US.
|
| 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...
| ezoe wrote:
| Prove it that it will work in a very humid environment or this
| product just make dry air from already dry air.
| jimmar wrote:
| Published 13 months ago. Is this technology in use, yet?
| ChuckMcM wrote:
| Signs point to no. But their web site is pretty complete.
| (https://www.mt.energy/wattair)
|
| 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.
| amluto wrote:
| 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).
|
| So I agree, they're doing this wrong.
|
| [0] https://www.energystar.gov/most-efficient/me-certified-
| dehum...
| ChuckMcM wrote:
| This exactly.
|
| 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.
| amluto wrote:
| 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.
| influxmoment wrote:
| 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
| jonnycomputer wrote:
| What possible advantage would that give?
| udev wrote:
| I am rusty on my thermodynamics, but could this cycle be reversed
| for heat-pumps?
|
| 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.
| m3kw9 wrote:
| Once I see my local HVAC specialist start selling one with
| rebates, then I know this is legit and scalable
| Simon_O_Rourke wrote:
| I can understand that, I spent a holiday in Scotland one year
| where it hardly went above 80, but felt like Salt Lake City in a
| heatwave.
| rr808 wrote:
| When looking at dishwashers Bosch were selling some that had
| Zeolite cyrstals that magically seemed to create heat out of
| moisture absorption, which seems to good to be true. I guess this
| is similar crystal? https://www.bosch-home.com/us/experience-
| bosch/crystaldry https://en.wikipedia.org/wiki/Zeolite
| mdorazio wrote:
| 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).
|
| [1] https://www.eia.gov/tools/faqs/faq.php?id=1174&t=1
| jeofken wrote:
| 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).
| bufferoverflow wrote:
| The peak efficiency is at around 38mph
|
| https://cdn.shopify.com/s/files/1/0196/5170/files/model_s100.
| ..
| dzhiurgis wrote:
| 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.
| consp wrote:
| 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.
| SoftTalker wrote:
| 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.
| jonnycomputer wrote:
| I'd be interested in seeing data on that too.
| jonnycomputer wrote:
| 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.
|
| [1] https://www.eia.gov/todayinenergy/detail.php?id=36692
|
| [2]
| https://jrenewables.springeropen.com/articles/10.1186/s40807...
| dpierce9 wrote:
| 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.
|
| [1] https://www.eia.gov/todayinenergy/detail.php?id=42915
| jonnycomputer wrote:
| 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.
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