11 ms·

Blue Frontier and its energy-efficient AC

196 points by elsewhen 3y ago

sp332 3y ago
Tech Ingredients on YouTube built a dessicant-based air conditioning system with enough info to DIY one. https://youtu.be/R_g4nT4a28U https://youtu.be/R_g4nT4a28U and a full-scale test https://youtu.be/7w4rg3UcsgI https://youtu.be/7w4rg3UcsgI
- baxuz 3y ago
  Was just about to post this one. Amazing series.
- KennyBlanken 3y ago
  I can summarize that thirty minute long video in a few sentences: 1)Indoor air is pumped into the bottom of a vertical pipe serving as a poor man's cooling tower, with calcium chloride solution sprayed down against the room air flowing upward and back into the space. The solution is very hygroscopic. 2)The diluted solution is pumped through a solar water heater, and then into the top of a second, similar cooling tower; the hot solution gives up moisture to outside air and increases in concentration. 3)The still-warm solution is then pumped through a radiator to chill it, and then further chilled by another radiator placed at the top of a third vertical water chiller which acts as a swamp cooler, spraying water down into a pipe circulating outside air. I imagine there might be room for further optimization, like leveraging some of the heat from some other steps to pre-warm solution, etc - similar to how steam boilers use 'economizers' and such.
  - willcipriano 3y ago
    A key point at the end of the 2nd video, the test room doesn't get very cool.
  - Ballas 3y ago
    Thank you. I have decided not to watch anymore of their videos after a number of inaccurate statements made as fact that was disproven with a single Google search. If they are not even going to fact check things they state as fact, then I cannot trust anything they state, and so my time is spent better elsewhere.
mech765 3y ago
How is the dessicant recharged after it absorbs the water?
- nicktelford 3y ago
  Stated in the article. It's dried using a heat pump.
  - SpaceNoodled 3y ago
    It's not quite clear where the water goes.
    - tekla 3y ago
      The same place the water goes now
    - hasbot 3y ago
      I have a desiccant based dehumidifier and the water just drips into a pan the same as any dehumidifier.
    - plus 3y ago
      Presumably into the (outside) air.
    - jjoonathan 3y ago
      The desiccant pumps water out of the hot humid daytime air and pumps it into the cool humid nighttime air.
gottorf 3y ago
> The startup's AC units suck moisture out of the air for more efficient cooling. As someone who lives in the Gulf Coast area, any amount of moisture sucked out of the air is welcome. Take it all! There's an infinite amount of humidity around here. :-)
- hn_throwaway_99 3y ago
  But the AC unit then adds all the moisture back in for evaporative cooling.
- jjoonathan 3y ago
  No, it doesn't dehumidify your house. That's where the efficiency comes from. Cooling and dehumidification usually come together, but this lets you have cooling without dehumidification which is more efficient. No comment on desirability.
  - macintux 3y ago
    Ooh, that's interesting. I hate AC because of the dehumidification.
    - rainbowzootsuit 3y ago
      I suggest that you raise the blower speed to raise the evaporator temperature away from the saturation/ dew point temperature of water and you will have your desired outcome.
  - analyte123 3y ago
    It does dehumidify the air, perhaps even configurably: https://bluefrontierac.com/wp-content/uploads/2023/10/BF_LD-DOAS.pdf https://bluefrontierac.com/wp-content/uploads/2023/10/BF_LD-...
- bob1029 3y ago
  > As someone who lives in the Gulf Coast area Same. I made a similar comment but deleted when I saw yours. I've got a half-ton central dehumidifier that has to run 24/7 basically all year. If I could just flow my HVAC over some desiccant instead... I am all ears on this one.
gloryless 3y ago
AC is a fairly nuanced problem, and I like to see evaporative cooling getting an update. Obviously there is a chemical component here but for a ton of climates evaporative cooling is the best choice.
api 3y ago
This seems like it would work really well in precisely the kind of hot sweltering areas at highest risk from climate extremes like India, Central America, etc.
- jjoonathan 3y ago
  The idea is to recharge the dessicant at night, do these places have high nighttime RH? If so, that smells like trouble.
scythe 3y ago
Surprisingly, I thought it would be this: https://www.pnnl.gov/news-media/efficient-dehumidifier-makes-air-conditioning-breeze https://www.pnnl.gov/news-media/efficient-dehumidifier-makes... Two new dehumidifiers from two different USG labs licensed to two different companies? And they told us that industrial policy couldn't do competition.
- rawgabbit 3y ago
  The airjoule dehumidifier appears very promising.
RC_ITR 3y ago
One thing that I think gets lost in the shuffle of air conditioning discourse: AC units are generally heat pumps and they generally have smaller temperature differentials to overcome (i.e. heating a house to room temperature while it is snowing is a much bigger job than cooling a house to room temperature on all but the hottest of days). This means, generally, AC is more energy efficient than direct heating like a furnace. The narrative about 'AC is going to destroy the world via emissions' is mostly because the already developed places have cooler climates than emerging places.
- lupyro 3y ago
  Living in Arizona, this is always a surprising fact to remember since the electric bill is highest in the summer. On one hand I understand heating has way bigger temperature differentials to overcome but heat is so easy to make. Most machines and technology create heat as a waste or byproduct so it always feels like purposely creating heat should be so easy.
  - megaman821 3y ago
    Also, a person in Arizona is going to use much less energy than a person living in Minnesota. Not to mention the energy used in Arizona is going to come from lower carbon sources than in Minnesota. It just breaks people expectations that a big, complicated machine uses less energy than simply setting something on fire.
    - sumtechguy 3y ago
      they are more efficient long term. short term though it is 'it is cold in here turn up the heat' the time it takes a heat pump to make that happen is much longer than say a natural gas system. the NG system uses more energy though to do it in a shorter amount of time. but it happens perception wise faster.
  - RC_ITR 3y ago
    My reasoning is that everyone in the US had parents who knew you'd die if you didn't heat your house, but in most cases, AC is a comfort thing, so AC was treated as the luxury and heat as the normal.
scottLobster 3y ago
I'm curious as to how much maintenance the desiccant would require under realistic loads. Does it need to be flushed/replaced periodically? Is is corrosive to its enclosure? I really wish science journalism would pay more attention to stuff like this. I've been burned by all the Popular Science articles from 20 years ago about zero-emission coal plans with filtered exhaust and built-in carbon capture facilities. They all sound the same, and all leave out details necessary to determine viability. I'm convinced at this point that most science journalists have simply learned to not ask questions beyond a certain point. But hey I'm happy to be surprised if this actually works.
- specialist 3y ago
  That was my first question too. I found the following. Sadly, because journalisming is oh so hard, they omitted the actual innovations. TLDR: Novel liquid desiccant functions as a "humidity battery" (my phrase). A salt solution which captures and releases moisture. It's closed loop and doesn't need to be replenished. Claimed OpEx $/hWh (for just the dehumidifier) is ~ $20/hWh, vs > $600 for Li-ion and ~ $400 for ice thermal based systems. It's safer and more durable. Liquid Desiccants as Breakthrough Energy Storage [2021] https://www.youtube.com/watch?v=2SwMyGzXsuE https://www.youtube.com/watch?v=2SwMyGzXsuE Liquid Desiccants and Our Cooling Process - Blue Frontier, LLC [2021] https://www.youtube.com/watch?v=r8B4LQTQ94g https://www.youtube.com/watch?v=r8B4LQTQ94g https://bluefrontierac.com https://bluefrontierac.com "At Blue Frontier, our mission is to transform buildings into sustainable, comfortable, and interactive spaces. Our first step towards achieving this goal is the commercialization of a revolutionary air conditioning technology. Blue Frontier’s AC system combines dew-point-style sensible cooling with liquid desiccant dehumidification to reduce electricity use by up to 90% (non-fan). The desiccant is recharged and stored when electricity is the cleanest or lowest cost, and later used to deliver cooling when electricity is dirty or costly. These features enable our system to solve an array of today’s largest sustainability problems — from the Duck Curve to peak load management, from humidity control to integration of intermittent renewable resources." Note the "Duck Curve" bit. Their "humidity battery" (my phrase) allows them to do load shifting. In the actual AC unit(s). That's really bitchin'.
  - deleted 3y ago
Night_Thastus 3y ago
Oh, so it's a swamp cooler, but one that pre-dries the air passively? It could work, in some climates. But yeah, the cost and rate you need to replace the desiccant is the critical factor. In my experience, most commercial users don't want to screw with their AC systems more than once a year, and want it to "just work" without bothering with 'unnecessary' things like preventative maintenance. If it needs replacement on the order of once a month or more, then I doubt this will go anywhere.
- 4hg4ufxhy 3y ago
  Sounds perfect for AC subscription service.
  - Night_Thastus 3y ago
    When money is even slightly tight, AC maintenance feels like the first thing to go. It costs a fair amount of cash just to get people out there up on the roof. They'll only call in work when it suddenly is 85 in the dining room and they're wondering why.
    - hypercube33 3y ago
      save money in power that you trade for time (labor) and expendibles seems like a failure
      - Night_Thastus 3y ago
        Depends on how often the desiccant needs to be replaced and its cost. If it's once a year and costs as much as the filters do, and saves 20% power, then it's a no-brainer. If it's once a month and cost 1k each, saves 5% energy, then it's pointless. We don't know the numbers, so can't say for sure.
    - bluGill 3y ago
      Many businesses have learned that keeping up on maintenance is cheaper in the long run. If nothing else your insurance will check before paying out. You might adjust the temperature when things get tight - which saves a lot more money - but most keep it maintained.
csours 3y ago
It says they're adding water. You can currently improve cooling and efficiency by adding a misting system the external unit of a traditional air conditioner. I wonder how the efficiencies and costs compare.
foobarian 3y ago
It's not super clear from the article how this achieves such a drastic reduction in energy use. It seems that maybe they are not accounting for energy used to dry out the desiccant at night; in that case the 60% figure might make sense during the cooling cycle only. The opening blurb also makes no sense to me; as it is AC units already suck moisture out of the air. Ask anyone who had a clog in an AC drain line :-)
- ilyt 3y ago
  I'm guessing they made tiny part of whole system 60% more efficient and journalistic mispractice did the rest
hn_throwaway_99 3y ago
So basically, as I understand it, the full process is as follows, starting with dry dessicant: 1. External air is blown over the dessicant, which pulls moisture out of the air. 2. That dry air is then blown over water, which rehumidifies the air and also cools it by evaporative cooling. This part here is essentially the same as a swamp cooler. 3. The air is then cooled further by what is essentially a normal air conditioner, but which doesn't have to work as hard because the water is already cooler from step #2. 4. The dessicant, though, needs to be dried out, so as the article explains it I think the desiccant is heated by a heat pump to dry it out. Please someone correct me if my understanding is wrong. It's an interesting design which basically combines a swamp cooler with a heat pump (after all, AC is just a heat pump that pumps heat out of the house). I'm skeptical of the 60% number though given the extra energy that needs to be applied to dry out the desiccant.
- malfist 3y ago
  I wonder if it's using the waste heat from the AC to dry the dessicant
- sushibowl 3y ago
  Could you use the heat pumped out of the house by the AC to dry the desiccant?
- 0xfae 3y ago
  You could use the waste heat from the heat pump (standard A/C) in step 3 to heat/dry the desiccant in step #1. That heat is, like you said, just dumped outside now. Why not make use of it?
  - ilyt 3y ago
    Similarly we could use air exhaust from home itself to heat up AC in the winter
- xenadu02 3y ago
  With regard to regenerating the desiccant: Presumably the same heat pump used for the normal A/C cycle would be used to handle this. Add some valves and controllable dampers which are potential failure points but not expensive. Instead of dampers you could have a separate exhaust fan but either way you need to extract the hot and very humid air from the regen cycle to avoid dumping it into the building. There's a tricky optimization problem for a system like this. In heat pump mode your ideal time of day is around solar noon when temps are hottest... with an inverter (fully variable) compressor and fan you can run both at lower power to generate just enough heat needed for regen. That can clash with your cooling load and electric rates though so it may make more sense to run at night when you need to run longer or higher power to generate enough heat. Most consumer A/C systems sold in the US don't even have inverter compressors yet so that is some added cost/complexity. Many have variable speed indoor and outdoor fans but not all. There may be some decent gains to be had just by adopting the latest "conventional" refrigeration tech.
owenversteeg 3y ago
TLDR: it uses a desiccant to dry the air before it passes through an evaporative cooler, thus pre-cooling the air. At night when power is cheap it uses a heat pump to dry the desiccant. You can get 4 hours use out of the desiccant. They also use alternative refrigerants "such as propane" but I do not see how that would improve efficiency, there are plenty of A/Cs using that today. I don't quite get how this reduces the energy consumption - I must be missing something here, or they've PR-ified it and it doesn't actually reduce total energy consumption, just reduces peak load. Adding water to salt and then removing it is at best an energy neutral process and in practice obviously involves losses and heat you cannot harvest (warm water vapor coming off of warm drying salt!) These A/C systems exist - search "desiccant enhanced evaporative cooling" - and have gotten more or less nowhere in the real world as far as I know. Am I missing something here or is there any actual total energy savings?
- owenversteeg 3y ago
  Ideas I've had so far: - dry out desiccant using sunlight or other heat ? - waste heat while the A/C is in operation helps dry the desiccant? - take advantage of some natural humidity difference to partially dry it? - take advantage of other sources of waste heat, which are semi-plentiful in environments where you use A/C, to dry it? That said, none of these happen at night, which is when the article says it's dried... also some would involve physically moving the desiccant around which magnifies complexity...
- infecto 3y ago
  I think they are the energy reduction is their novel closed loop desiccant system in a typical package unit.
analyte123 3y ago
Dehumidification is really under-explored. If you live in Florida or the Gulf Coast (or similar areas around the world), your home can be at risk of mold and humidity damage during shoulder seasons when the AC is not frequently running (not to mention thermal discomfort [1]). And, dehumidification is key to reducing indoor allergens in these climates, particularly dust mites and mold. What I couldn't figure out is if there are any circumstances where running a traditional condenser dehumidifier (whole-house, in the attic) would save you energy/money for the same thermal comfort range. A DoE simulation study I can't find says no, but some HVAC forum posters say that it can, and based on experience I'm inclined to think it could in some circumstances. The desiccant wheel dehumidifiers seem to get a lot more water out per kWh [2], making it a win as seen in this new integrated technology. However, running a floor dehumidifier dumps 800+ watts of waste heat into the space you're dehumidifying, making it impractical for thermal comfort with condensers and maybe even desiccants. I would pay good money for a window-unit dehumidifier that could be used either in apartments or without having to pay for installation and ductwork of a whole-house dehumidifier. [1] https://en.wikipedia.org/wiki/Thermal_comfort#PMV/PPD_method https://en.wikipedia.org/wiki/Thermal_comfort#PMV/PPD_method [2] https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/ns/eemtg082011_a6_laboratory_evaluation_erv.pdf https://www1.eere.energy.gov/buildings/publications/pdfs/bui...
- MostlyStable 3y ago
  Had a new Heat pump HVAC system installed last year and had them put in a whole house dehumidifier at the same time, since my winter indoor humidity was frequently topping 70%. It keeps the indoor humidity between 40-50% which has noticeably improved the mild-to-moderate mold issues that I had previously and it doesn't seem to consume much power (I haven't been able to obviously note it in my power use graphs the way I can the regular HVAC)
  - sokoloff 3y ago
    I also installed a whole house dehumidifier (in New England). It gives a noticeable improvement in indoor air quality, but I can definitely see it on my electric usage. (I wish I could un-see it. It removes a little over 2L/kWh per the spec sheet, but that also means it's using about $2-3/day in a lot of the summer.)
deleted 3y ago
[deleted]
cogman10 3y ago
I'm having a hard time picturing where each of these phases are happening. Is the dry air cooled by evaporation cooling in circulation in the cooling area? Or is it being used to cool off the condenser coils? If the air is being rehumidified indoors, then wouldn't that cause condensation problems on the chilling coils? If it's happening outdoors then wouldn't there be issues (particularly in high humidity regions) extracting enough moister from the dry air before sending it forward? I have wondered if in particularly arid regions where swamp cooling is a thing, if it wouldn't make sense to use evaporation cooling in conjunction with a condenser coil to push the temps indoors down a lot further.
WhatIsDukkha 3y ago
I wonder at the bacterial issues of the hot/warm/cool cycle of the water in the desiccant ie Legionaires disease etc.
- teruakohatu 3y ago
  The desiccant is salt so that may help. Legionaires also likes a very specific temperature range, so raising it above a certain tempreture for a short period is enough to remove it.
timbit42 3y ago
How does this compare to an air-to-air heat pump?
- deleted 3y ago
  [deleted]
habibur 3y ago
Wondering how they plan to dry the salt mixture that's continuously getting wet while the AC runs.
- woah 3y ago
  I think it says they dry it at night
0xbadcafebee 3y ago
> First, a salty mixture known as a desiccant sucks moisture out of the air, reducing its humidity. Then, some of that now-dry air moves past a wet surface. Water evaporates back into the dry air Huh? They dried the air and then wetted it? Makes no sense, so I googled it: > The operation of a desiccant cooling system is based on the use of a rotary dehumidifier (desiccant wheel) in which air is dehumidified. The resulting dry air is somewhat cooled in a sensible heat exchanger (rotary regenerator), and then further cooled by an evaporative cooler. The resulting cool air is directed into a room. The system may be operated in a closed cycle or more commonly in an open cycle in ventilation or recirculation modes. A heat supply is needed to regenerate the desiccant. Low-grade heat at a temperature of about 60–95°C is sufficient for regeneration, so renewable energies such as solar and geothermal heat as well as waste heat from conventional fossil-fuel systems may be used. The system is simple and thermal coefficient of performance (COP) is usually satisfactory. https://www.sciencedirect.com/topics/engineering/desiccant-cooling-system https://www.sciencedirect.com/topics/engineering/desiccant-c...
pixiemaster 3y ago
Slashdot needs an „Advertorial“ moderation type.
spandextwins 3y ago
Isn’t that like the Tesla heat pump?
- deleted 3y ago
  [deleted]
crmd 3y ago
I live in New York City and for probably half of the A/C season, running this expensive 6 KW load to dehumidify versus cool. Very interested in any technology to reduce this expense.
- tootie 3y ago
  Same. It sounds like this tech could be tuned for cooling or dehumidifying.
purplezooey 3y ago
I hope it reaches mass production. The market for residential air conditioners is awful. Most units do not last 10 years without needing major repairs and have negligible efficiency gains over those made 20 or 25 years ago.
- deleted 3y ago
  [deleted]
SV_BubbleTime 3y ago
This is an ad.
kragen 3y ago
my calculations and very limited experimental notes on this from 02020 https://derctuo.github.io/notes/desiccant-climate-control.html https://derctuo.github.io/notes/desiccant-climate-control.ht... cover domestic heating, cooling, humidity control, and water harvesting applications, listing 33 alternative desiccants, with wholesale costs for 10 of them and thermodynamic data for fewer, plus some links about related research and the economics of load shifting see also https://dercuano.github.io/topics/cooling.html https://dercuano.github.io/topics/cooling.html with its list of notes like https://dercuano.github.io/notes/solar-air-conditioner.html https://dercuano.github.io/notes/solar-air-conditioner.html from 02016 which explores the thermodynamics of using wood rather than calcium chloride as the desiccant fwiw blue sky or whatever they call themselves never bother to say what desiccant they're using, so probably they aren't sure yet. they say it's a new desiccant, which is unlikely given that they also say it's a non-flammable, nontoxic salt, dissolved in water. non-flammable implies inorganic, and you aren't going to discover a new nontoxic inorganic salt in 02023; we already know all the elements that aren't ridiculously radioactive. https://www.technologyreview.com/2023/07/26/1076731/materials-air-conditioning/ https://www.technologyreview.com/2023/07/26/1076731/material...

196 points by elsewhen 3y ago

Tech Ingredients on YouTube built a dessicant-based air conditioning system with enough info to DIY one. https://youtu.be/R_g4nT4a28U https://youtu.be/R_g4nT4a28U and a full-scale test https://youtu.be/7w4rg3UcsgI https://youtu.be/7w4rg3UcsgI

baxuz 3y ago
Was just about to post this one. Amazing series.
KennyBlanken 3y ago
I can summarize that thirty minute long video in a few sentences: 1)Indoor air is pumped into the bottom of a vertical pipe serving as a poor man's cooling tower, with calcium chloride solution sprayed down against the room air flowing upward and back into the space. The solution is very hygroscopic. 2)The diluted solution is pumped through a solar water heater, and then into the top of a second, similar cooling tower; the hot solution gives up moisture to outside air and increases in concentration. 3)The still-warm solution is then pumped through a radiator to chill it, and then further chilled by another radiator placed at the top of a third vertical water chiller which acts as a swamp cooler, spraying water down into a pipe circulating outside air. I imagine there might be room for further optimization, like leveraging some of the heat from some other steps to pre-warm solution, etc - similar to how steam boilers use 'economizers' and such.
- willcipriano 3y ago
  A key point at the end of the 2nd video, the test room doesn't get very cool.
- Ballas 3y ago
  Thank you. I have decided not to watch anymore of their videos after a number of inaccurate statements made as fact that was disproven with a single Google search. If they are not even going to fact check things they state as fact, then I cannot trust anything they state, and so my time is spent better elsewhere.

mech765 3y ago

How is the dessicant recharged after it absorbs the water?

nicktelford 3y ago
Stated in the article. It's dried using a heat pump.
- SpaceNoodled 3y ago
  It's not quite clear where the water goes.
  - tekla 3y ago
    The same place the water goes now
  - hasbot 3y ago
    I have a desiccant based dehumidifier and the water just drips into a pan the same as any dehumidifier.
  - plus 3y ago
    Presumably into the (outside) air.
  - jjoonathan 3y ago
    The desiccant pumps water out of the hot humid daytime air and pumps it into the cool humid nighttime air.

gottorf 3y ago

> The startup's AC units suck moisture out of the air for more efficient cooling. As someone who lives in the Gulf Coast area, any amount of moisture sucked out of the air is welcome. Take it all! There's an infinite amount of humidity around here. :-)

hn_throwaway_99 3y ago
But the AC unit then adds all the moisture back in for evaporative cooling.
jjoonathan 3y ago
No, it doesn't dehumidify your house. That's where the efficiency comes from. Cooling and dehumidification usually come together, but this lets you have cooling without dehumidification which is more efficient. No comment on desirability.
- macintux 3y ago
  Ooh, that's interesting. I hate AC because of the dehumidification.
  - rainbowzootsuit 3y ago
    I suggest that you raise the blower speed to raise the evaporator temperature away from the saturation/ dew point temperature of water and you will have your desired outcome.
- analyte123 3y ago
  It does dehumidify the air, perhaps even configurably: https://bluefrontierac.com/wp-content/uploads/2023/10/BF_LD-DOAS.pdf https://bluefrontierac.com/wp-content/uploads/2023/10/BF_LD-...
bob1029 3y ago
> As someone who lives in the Gulf Coast area Same. I made a similar comment but deleted when I saw yours. I've got a half-ton central dehumidifier that has to run 24/7 basically all year. If I could just flow my HVAC over some desiccant instead... I am all ears on this one.

gloryless 3y ago

AC is a fairly nuanced problem, and I like to see evaporative cooling getting an update. Obviously there is a chemical component here but for a ton of climates evaporative cooling is the best choice.

api 3y ago

This seems like it would work really well in precisely the kind of hot sweltering areas at highest risk from climate extremes like India, Central America, etc.

jjoonathan 3y ago
The idea is to recharge the dessicant at night, do these places have high nighttime RH? If so, that smells like trouble.

scythe 3y ago

Surprisingly, I thought it would be this: https://www.pnnl.gov/news-media/efficient-dehumidifier-makes-air-conditioning-breeze https://www.pnnl.gov/news-media/efficient-dehumidifier-makes... Two new dehumidifiers from two different USG labs licensed to two different companies? And they told us that industrial policy couldn't do competition.

rawgabbit 3y ago
The airjoule dehumidifier appears very promising.

RC_ITR 3y ago

One thing that I think gets lost in the shuffle of air conditioning discourse: AC units are generally heat pumps and they generally have smaller temperature differentials to overcome (i.e. heating a house to room temperature while it is snowing is a much bigger job than cooling a house to room temperature on all but the hottest of days). This means, generally, AC is more energy efficient than direct heating like a furnace. The narrative about 'AC is going to destroy the world via emissions' is mostly because the already developed places have cooler climates than emerging places.

lupyro 3y ago
Living in Arizona, this is always a surprising fact to remember since the electric bill is highest in the summer. On one hand I understand heating has way bigger temperature differentials to overcome but heat is so easy to make. Most machines and technology create heat as a waste or byproduct so it always feels like purposely creating heat should be so easy.
- megaman821 3y ago
  Also, a person in Arizona is going to use much less energy than a person living in Minnesota. Not to mention the energy used in Arizona is going to come from lower carbon sources than in Minnesota. It just breaks people expectations that a big, complicated machine uses less energy than simply setting something on fire.
  - sumtechguy 3y ago
    they are more efficient long term. short term though it is 'it is cold in here turn up the heat' the time it takes a heat pump to make that happen is much longer than say a natural gas system. the NG system uses more energy though to do it in a shorter amount of time. but it happens perception wise faster.
- RC_ITR 3y ago
  My reasoning is that everyone in the US had parents who knew you'd die if you didn't heat your house, but in most cases, AC is a comfort thing, so AC was treated as the luxury and heat as the normal.

scottLobster 3y ago

I'm curious as to how much maintenance the desiccant would require under realistic loads. Does it need to be flushed/replaced periodically? Is is corrosive to its enclosure? I really wish science journalism would pay more attention to stuff like this. I've been burned by all the Popular Science articles from 20 years ago about zero-emission coal plans with filtered exhaust and built-in carbon capture facilities. They all sound the same, and all leave out details necessary to determine viability. I'm convinced at this point that most science journalists have simply learned to not ask questions beyond a certain point. But hey I'm happy to be surprised if this actually works.

specialist 3y ago
That was my first question too. I found the following. Sadly, because journalisming is oh so hard, they omitted the actual innovations. TLDR: Novel liquid desiccant functions as a "humidity battery" (my phrase). A salt solution which captures and releases moisture. It's closed loop and doesn't need to be replenished. Claimed OpEx $/hWh (for just the dehumidifier) is ~ $20/hWh, vs > $600 for Li-ion and ~ $400 for ice thermal based systems. It's safer and more durable. Liquid Desiccants as Breakthrough Energy Storage [2021] https://www.youtube.com/watch?v=2SwMyGzXsuE https://www.youtube.com/watch?v=2SwMyGzXsuE Liquid Desiccants and Our Cooling Process - Blue Frontier, LLC [2021] https://www.youtube.com/watch?v=r8B4LQTQ94g https://www.youtube.com/watch?v=r8B4LQTQ94g https://bluefrontierac.com https://bluefrontierac.com "At Blue Frontier, our mission is to transform buildings into sustainable, comfortable, and interactive spaces. Our first step towards achieving this goal is the commercialization of a revolutionary air conditioning technology. Blue Frontier’s AC system combines dew-point-style sensible cooling with liquid desiccant dehumidification to reduce electricity use by up to 90% (non-fan). The desiccant is recharged and stored when electricity is the cleanest or lowest cost, and later used to deliver cooling when electricity is dirty or costly. These features enable our system to solve an array of today’s largest sustainability problems — from the Duck Curve to peak load management, from humidity control to integration of intermittent renewable resources." Note the "Duck Curve" bit. Their "humidity battery" (my phrase) allows them to do load shifting. In the actual AC unit(s). That's really bitchin'.
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Night_Thastus 3y ago

Oh, so it's a swamp cooler, but one that pre-dries the air passively? It could work, in some climates. But yeah, the cost and rate you need to replace the desiccant is the critical factor. In my experience, most commercial users don't want to screw with their AC systems more than once a year, and want it to "just work" without bothering with 'unnecessary' things like preventative maintenance. If it needs replacement on the order of once a month or more, then I doubt this will go anywhere.

4hg4ufxhy 3y ago
Sounds perfect for AC subscription service.
- Night_Thastus 3y ago
  When money is even slightly tight, AC maintenance feels like the first thing to go. It costs a fair amount of cash just to get people out there up on the roof. They'll only call in work when it suddenly is 85 in the dining room and they're wondering why.
  - hypercube33 3y ago
    save money in power that you trade for time (labor) and expendibles seems like a failure
    - Night_Thastus 3y ago
      Depends on how often the desiccant needs to be replaced and its cost. If it's once a year and costs as much as the filters do, and saves 20% power, then it's a no-brainer. If it's once a month and cost 1k each, saves 5% energy, then it's pointless. We don't know the numbers, so can't say for sure.
  - bluGill 3y ago
    Many businesses have learned that keeping up on maintenance is cheaper in the long run. If nothing else your insurance will check before paying out. You might adjust the temperature when things get tight - which saves a lot more money - but most keep it maintained.

csours 3y ago

It says they're adding water. You can currently improve cooling and efficiency by adding a misting system the external unit of a traditional air conditioner. I wonder how the efficiencies and costs compare.

foobarian 3y ago

It's not super clear from the article how this achieves such a drastic reduction in energy use. It seems that maybe they are not accounting for energy used to dry out the desiccant at night; in that case the 60% figure might make sense during the cooling cycle only. The opening blurb also makes no sense to me; as it is AC units already suck moisture out of the air. Ask anyone who had a clog in an AC drain line :-)

ilyt 3y ago
I'm guessing they made tiny part of whole system 60% more efficient and journalistic mispractice did the rest

hn_throwaway_99 3y ago

So basically, as I understand it, the full process is as follows, starting with dry dessicant: 1. External air is blown over the dessicant, which pulls moisture out of the air. 2. That dry air is then blown over water, which rehumidifies the air and also cools it by evaporative cooling. This part here is essentially the same as a swamp cooler. 3. The air is then cooled further by what is essentially a normal air conditioner, but which doesn't have to work as hard because the water is already cooler from step #2. 4. The dessicant, though, needs to be dried out, so as the article explains it I think the desiccant is heated by a heat pump to dry it out. Please someone correct me if my understanding is wrong. It's an interesting design which basically combines a swamp cooler with a heat pump (after all, AC is just a heat pump that pumps heat out of the house). I'm skeptical of the 60% number though given the extra energy that needs to be applied to dry out the desiccant.

malfist 3y ago
I wonder if it's using the waste heat from the AC to dry the dessicant
sushibowl 3y ago
Could you use the heat pumped out of the house by the AC to dry the desiccant?
0xfae 3y ago
You could use the waste heat from the heat pump (standard A/C) in step 3 to heat/dry the desiccant in step #1. That heat is, like you said, just dumped outside now. Why not make use of it?
- ilyt 3y ago
  Similarly we could use air exhaust from home itself to heat up AC in the winter
xenadu02 3y ago
With regard to regenerating the desiccant: Presumably the same heat pump used for the normal A/C cycle would be used to handle this. Add some valves and controllable dampers which are potential failure points but not expensive. Instead of dampers you could have a separate exhaust fan but either way you need to extract the hot and very humid air from the regen cycle to avoid dumping it into the building. There's a tricky optimization problem for a system like this. In heat pump mode your ideal time of day is around solar noon when temps are hottest... with an inverter (fully variable) compressor and fan you can run both at lower power to generate just enough heat needed for regen. That can clash with your cooling load and electric rates though so it may make more sense to run at night when you need to run longer or higher power to generate enough heat. Most consumer A/C systems sold in the US don't even have inverter compressors yet so that is some added cost/complexity. Many have variable speed indoor and outdoor fans but not all. There may be some decent gains to be had just by adopting the latest "conventional" refrigeration tech.

owenversteeg 3y ago

TLDR: it uses a desiccant to dry the air before it passes through an evaporative cooler, thus pre-cooling the air. At night when power is cheap it uses a heat pump to dry the desiccant. You can get 4 hours use out of the desiccant. They also use alternative refrigerants "such as propane" but I do not see how that would improve efficiency, there are plenty of A/Cs using that today. I don't quite get how this reduces the energy consumption - I must be missing something here, or they've PR-ified it and it doesn't actually reduce total energy consumption, just reduces peak load. Adding water to salt and then removing it is at best an energy neutral process and in practice obviously involves losses and heat you cannot harvest (warm water vapor coming off of warm drying salt!) These A/C systems exist - search "desiccant enhanced evaporative cooling" - and have gotten more or less nowhere in the real world as far as I know. Am I missing something here or is there any actual total energy savings?

owenversteeg 3y ago
Ideas I've had so far: - dry out desiccant using sunlight or other heat ? - waste heat while the A/C is in operation helps dry the desiccant? - take advantage of some natural humidity difference to partially dry it? - take advantage of other sources of waste heat, which are semi-plentiful in environments where you use A/C, to dry it? That said, none of these happen at night, which is when the article says it's dried... also some would involve physically moving the desiccant around which magnifies complexity...
infecto 3y ago
I think they are the energy reduction is their novel closed loop desiccant system in a typical package unit.

analyte123 3y ago

Dehumidification is really under-explored. If you live in Florida or the Gulf Coast (or similar areas around the world), your home can be at risk of mold and humidity damage during shoulder seasons when the AC is not frequently running (not to mention thermal discomfort [1]). And, dehumidification is key to reducing indoor allergens in these climates, particularly dust mites and mold. What I couldn't figure out is if there are any circumstances where running a traditional condenser dehumidifier (whole-house, in the attic) would save you energy/money for the same thermal comfort range. A DoE simulation study I can't find says no, but some HVAC forum posters say that it can, and based on experience I'm inclined to think it could in some circumstances. The desiccant wheel dehumidifiers seem to get a lot more water out per kWh [2], making it a win as seen in this new integrated technology. However, running a floor dehumidifier dumps 800+ watts of waste heat into the space you're dehumidifying, making it impractical for thermal comfort with condensers and maybe even desiccants. I would pay good money for a window-unit dehumidifier that could be used either in apartments or without having to pay for installation and ductwork of a whole-house dehumidifier. [1] https://en.wikipedia.org/wiki/Thermal_comfort#PMV/PPD_method https://en.wikipedia.org/wiki/Thermal_comfort#PMV/PPD_method [2] https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/ns/eemtg082011_a6_laboratory_evaluation_erv.pdf https://www1.eere.energy.gov/buildings/publications/pdfs/bui...

MostlyStable 3y ago
Had a new Heat pump HVAC system installed last year and had them put in a whole house dehumidifier at the same time, since my winter indoor humidity was frequently topping 70%. It keeps the indoor humidity between 40-50% which has noticeably improved the mild-to-moderate mold issues that I had previously and it doesn't seem to consume much power (I haven't been able to obviously note it in my power use graphs the way I can the regular HVAC)
- sokoloff 3y ago
  I also installed a whole house dehumidifier (in New England). It gives a noticeable improvement in indoor air quality, but I can definitely see it on my electric usage. (I wish I could un-see it. It removes a little over 2L/kWh per the spec sheet, but that also means it's using about $2-3/day in a lot of the summer.)

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cogman10 3y ago

I'm having a hard time picturing where each of these phases are happening. Is the dry air cooled by evaporation cooling in circulation in the cooling area? Or is it being used to cool off the condenser coils? If the air is being rehumidified indoors, then wouldn't that cause condensation problems on the chilling coils? If it's happening outdoors then wouldn't there be issues (particularly in high humidity regions) extracting enough moister from the dry air before sending it forward? I have wondered if in particularly arid regions where swamp cooling is a thing, if it wouldn't make sense to use evaporation cooling in conjunction with a condenser coil to push the temps indoors down a lot further.

WhatIsDukkha 3y ago

I wonder at the bacterial issues of the hot/warm/cool cycle of the water in the desiccant ie Legionaires disease etc.

teruakohatu 3y ago
The desiccant is salt so that may help. Legionaires also likes a very specific temperature range, so raising it above a certain tempreture for a short period is enough to remove it.

timbit42 3y ago

How does this compare to an air-to-air heat pump?

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habibur 3y ago

Wondering how they plan to dry the salt mixture that's continuously getting wet while the AC runs.

woah 3y ago
I think it says they dry it at night

0xbadcafebee 3y ago

> First, a salty mixture known as a desiccant sucks moisture out of the air, reducing its humidity. Then, some of that now-dry air moves past a wet surface. Water evaporates back into the dry air Huh? They dried the air and then wetted it? Makes no sense, so I googled it: > The operation of a desiccant cooling system is based on the use of a rotary dehumidifier (desiccant wheel) in which air is dehumidified. The resulting dry air is somewhat cooled in a sensible heat exchanger (rotary regenerator), and then further cooled by an evaporative cooler. The resulting cool air is directed into a room. The system may be operated in a closed cycle or more commonly in an open cycle in ventilation or recirculation modes. A heat supply is needed to regenerate the desiccant. Low-grade heat at a temperature of about 60–95°C is sufficient for regeneration, so renewable energies such as solar and geothermal heat as well as waste heat from conventional fossil-fuel systems may be used. The system is simple and thermal coefficient of performance (COP) is usually satisfactory. https://www.sciencedirect.com/topics/engineering/desiccant-cooling-system https://www.sciencedirect.com/topics/engineering/desiccant-c...

pixiemaster 3y ago

Slashdot needs an „Advertorial“ moderation type.

spandextwins 3y ago

Isn’t that like the Tesla heat pump?

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crmd 3y ago

I live in New York City and for probably half of the A/C season, running this expensive 6 KW load to dehumidify versus cool. Very interested in any technology to reduce this expense.

tootie 3y ago
Same. It sounds like this tech could be tuned for cooling or dehumidifying.

purplezooey 3y ago

I hope it reaches mass production. The market for residential air conditioners is awful. Most units do not last 10 years without needing major repairs and have negligible efficiency gains over those made 20 or 25 years ago.

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SV_BubbleTime 3y ago

This is an ad.

kragen 3y ago

my calculations and very limited experimental notes on this from 02020 https://derctuo.github.io/notes/desiccant-climate-control.html https://derctuo.github.io/notes/desiccant-climate-control.ht... cover domestic heating, cooling, humidity control, and water harvesting applications, listing 33 alternative desiccants, with wholesale costs for 10 of them and thermodynamic data for fewer, plus some links about related research and the economics of load shifting see also https://dercuano.github.io/topics/cooling.html https://dercuano.github.io/topics/cooling.html with its list of notes like https://dercuano.github.io/notes/solar-air-conditioner.html https://dercuano.github.io/notes/solar-air-conditioner.html from 02016 which explores the thermodynamics of using wood rather than calcium chloride as the desiccant fwiw blue sky or whatever they call themselves never bother to say what desiccant they're using, so probably they aren't sure yet. they say it's a new desiccant, which is unlikely given that they also say it's a non-flammable, nontoxic salt, dissolved in water. non-flammable implies inorganic, and you aren't going to discover a new nontoxic inorganic salt in 02023; we already know all the elements that aren't ridiculously radioactive. https://www.technologyreview.com/2023/07/26/1076731/materials-air-conditioning/ https://www.technologyreview.com/2023/07/26/1076731/material...