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.
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.
> 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. :-)
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.
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.
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.
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.
Two new dehumidifiers from two different USG labs licensed to two different companies? And they told us that industrial policy couldn't do competition.
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.
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.
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.
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.
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.
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.
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.
"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).
Heat batteries were tried in furnaces a couple of decades ago, but they used some sort of high heat capacity bricks and forced the house air through them. As GP asks, the matter of maintenance was forgotten.
Recently I heard someone is trying this again with water heaters. The working fluid has roughly four times the heat capacity of water, so your “water” heater is substantially a fluid heater with either no water tank or a very small one. Incoming water is heated with the fluid, and the fluid is heated on demand. Only the heat exchanger has maintenance concerns.
Driving the whole thing with a heat pump makes the math a little more fiddly, since peak pump efficiency and peak power prices overlap some of the same parts of the day. You’re calculating BTUs per dollar, not watt hours per dollar.
It’s already cheap to just use a larger water heater as the thermal battery.
Few households use more than 80 gallons of hot water per day which is still within the normal range of hot water heaters. Just add a timer so it doesn’t kick on until powers cheap and you’ll be good to go. At least assuming your cheap electricity window is long enough to fully heat the water.
This is one of the reasons people overestimate the need for grid energy storage. People time shift electricity to the night because it’s cheap. If it was cheaper 10AM-4PM then significant demand would shift to that window.
Sounds like we would need “smart” water heaters that can query energy prices. That most likely means they would be online sharing all kinds of data most of us probably don’t want shared and would have a small monthly fee. The water heater might even be very inexpensive because of this.
I know it wouldn’t have to be implemented this way, but of course that’s how it would go.
Not necessarily smart. Here (France), most water heaters can be controlled with an extra "pilot" wire, or closing a circuit. It has been common practice since maybe the 60s to have multiple mettering rates, and a dry contact (relay) on the electricity meter to switch on/off some loads (mostly electric water heaters, though some electric space heaters can be connected as well).
These days, rates can be more flexible thanks to "smart" meters (communicating via PLC). Just after the russian invasion of Ukraine, there were plans in place to open the dry contacts of customers outside of the scheduled hours in case the electricity grid needed to shed extra load. Thankfully this didn't end up being necessary.
What I'm saying is that you don't really require smart end devices. Put the incentives in place (deep discounts) and the rest will follow. You probably need at least one smart device to control the others if a timer is not enough, and I think the electricity meter is a good fit for that role.
so i put on my scientist hat and started to write a reply going through the mechanics of beating water's heat capacity, first pointing out that what you want for these types of systems is likely high volumetric heat capacity rather than gravimetric. then i went on to discuss the density of room temp ionic liquids (RTILs), only to find myself digging into their heat capacity numbers and man, you're right! I forgot how well water stores heat compared to other liquids. RTILs vol. heat capacity has trouble breaking 2 J/cm3-K![1]
To beat water's specific heat, you have to cheat and use a phase change material (special wax) that melts near the desired water temp, or a bit higher if you use a cold water mixing value.
Not necessarily. If you're trying to heat water to 120º you may not want the paraffin to phase change at all. Because then you have a problem transferring heat from liquid->solid->pipe->liquid.
Phase change seems to work better for trying to maintain an ambient temperature. The input side is always going to be cold, and at some times of year far colder than others.
>I really wish science journalism would pay more attention to stuff like this.
I think the journalist did answer your questions and the answer is "no one knows how viable this is in the real-world, not even this company":
Blue Frontier is still in the very early stages of proving its technology and breaking into the massive global AC industry. The company will need to show in field tests that its units work as well as it says they have in the lab—without requiring more space or maintenance than the AC units already on the market.
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.
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.
I dunno, from my experience of having small server room in company I work for with 2 AC units the devices will fail when they want to fail and aside from cleaning maintenance never found actual issue before it happened in both units.
Seemed like moving it to be done every 2 years would just save us money
Other than replacing the belts and filters there isn't much you can do. They should be a sealed system where there is nothing that can be done once it leaves the factory. Those belts are filters are important to maintain - they only stop a minority of failures though.
It's a closed loop system. The desiccant is regenerated occasionally, which can usually be arranged to happen at desirable times (cheaper/cleaner electricity depending on your priorities). The regeneration is done with a heat pump, so if it can be accomplished at a relatively low temperature the COP could be spectacular for seasonal use cases.
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 :-)
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.
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.
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?
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.
I wonder if you could just pump the liquid desiccant outside, do the drying outdoors, and then pump it back inside. Then you wouldn't need to worry about air handling for the moist air.
When retrofitting a house to replace traditional AC with this, it may not be easy to get air from where the AC is located (usually the middle of the house) to the outside. If you pump desiccant outside, maybe you can squeeze desiccant hoses in right next to your refrigerant lines.
Also, there's all that waste heat outside at the condenser anyway. It seems like you could use that heat to help dry the desiccant. I guess that creates a different tricky optimization problem: if you wait too long to start drying your desiccant at night, when you finally do, you risk making the house too cold because you are stealing its heat. Maybe you just pause desiccant drying until whenever AC is needed again.
There was a neat "trash tv" show that I saw a while back talking about A/C's and Vacuum cleaners being invented and the "necessities" behind them (complete with obviously fake/acted "scenes from the 1850's with corresponding gigantic moustaches"). They talked about the rationale of A/C being related to "consistency in humidification in a printing press environment" - https://www.theatlantic.com/business/archive/2017/09/tim-har...
Literally an "Air, Conditioner", with cooling being a byproduct. The line in the video was something like: "he recognized that you could simply dry out the air completely, and _then_ re-introduce the appropriate amount of humidity". To dry it out, you cool it down and "condense" the humidity.
This seems like a neat continuation of the idea: Dry out the air before you cool it, and effectively time-shifting (and having separate systems) for the drying, the cooling, and the baking/restoration of desiccant.
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?
- 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...
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.
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)
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.)
> 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.
All/most window AC units I've seen have a mode labeled something like 'dry only', which I take to mean 'dehumidify only'.
In the humidity vs thermostat question the literature you are probably looking for is ASHRAE Standard 55.(1) The short answer is that you can feel comfortable at lower humidity and higher temperature.
I found a tool to let you play with the parameters.(2) For example the air speed from a fan causes some cooling sensation so the temperature can be higher for the same comfort.
The energy use to get there would need to be modeled by measure of the change in cooling degree days vs energy consumption and that is not universal answer across all scenarios because of climate, construction, and ventilation.
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.
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.
> 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.
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.
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.
97 comments
[ 1.5 ms ] story [ 148 ms ] thread1)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.
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. :-)
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.
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.
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.
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.
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.
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
Liquid Desiccants and Our Cooling Process - Blue Frontier, LLC [2021] https://www.youtube.com/watch?v=r8B4LQTQ94g
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'.
Thank you for finding this!
Recently I heard someone is trying this again with water heaters. The working fluid has roughly four times the heat capacity of water, so your “water” heater is substantially a fluid heater with either no water tank or a very small one. Incoming water is heated with the fluid, and the fluid is heated on demand. Only the heat exchanger has maintenance concerns.
Driving the whole thing with a heat pump makes the math a little more fiddly, since peak pump efficiency and peak power prices overlap some of the same parts of the day. You’re calculating BTUs per dollar, not watt hours per dollar.
Few households use more than 80 gallons of hot water per day which is still within the normal range of hot water heaters. Just add a timer so it doesn’t kick on until powers cheap and you’ll be good to go. At least assuming your cheap electricity window is long enough to fully heat the water.
This is one of the reasons people overestimate the need for grid energy storage. People time shift electricity to the night because it’s cheap. If it was cheaper 10AM-4PM then significant demand would shift to that window.
Sounds like we would need “smart” water heaters that can query energy prices. That most likely means they would be online sharing all kinds of data most of us probably don’t want shared and would have a small monthly fee. The water heater might even be very inexpensive because of this.
I know it wouldn’t have to be implemented this way, but of course that’s how it would go.
These days, rates can be more flexible thanks to "smart" meters (communicating via PLC). Just after the russian invasion of Ukraine, there were plans in place to open the dry contacts of customers outside of the scheduled hours in case the electricity grid needed to shed extra load. Thankfully this didn't end up being necessary.
What I'm saying is that you don't really require smart end devices. Put the incentives in place (deep discounts) and the rest will follow. You probably need at least one smart device to control the others if a timer is not enough, and I think the electricity meter is a good fit for that role.
I dont think much else even comes close
[1] Table 4, https://www.researchgate.net/publication/231542196_Heat_Capa...
Paraffin is 2.1 Kj/whatever
https://www.researchgate.net/publication/336006577_Comparing...
Phase change seems to work better for trying to maintain an ambient temperature. The input side is always going to be cold, and at some times of year far colder than others.
Tangent: Startup Andora Energy claims to have solved the maintenance problem with some novel carbon bricks.
Further: Their next gen product plans to use thermophotovoltaics, converting heat into electricity, directly. That'd be spiffy.
I think the journalist did answer your questions and the answer is "no one knows how viable this is in the real-world, not even this company":
Blue Frontier is still in the very early stages of proving its technology and breaking into the massive global AC industry. The company will need to show in field tests that its units work as well as it says they have in the lab—without requiring more space or maintenance than the AC units already on the market.
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.
They'll only call in work when it suddenly is 85 in the dining room and they're wondering why.
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.
You might adjust the temperature when things get tight - which saves a lot more money - but most keep it maintained.
Seemed like moving it to be done every 2 years would just save us money
Maintenance on this thing sounds like a nightmare. It's a heat pump and an evaporative cooler all in one.
I can see how it would work in theory, but I'm curious how it would hold up practically ~5-10 years into use.
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 :-)
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.
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.
When retrofitting a house to replace traditional AC with this, it may not be easy to get air from where the AC is located (usually the middle of the house) to the outside. If you pump desiccant outside, maybe you can squeeze desiccant hoses in right next to your refrigerant lines.
Also, there's all that waste heat outside at the condenser anyway. It seems like you could use that heat to help dry the desiccant. I guess that creates a different tricky optimization problem: if you wait too long to start drying your desiccant at night, when you finally do, you risk making the house too cold because you are stealing its heat. Maybe you just pause desiccant drying until whenever AC is needed again.
Literally an "Air, Conditioner", with cooling being a byproduct. The line in the video was something like: "he recognized that you could simply dry out the air completely, and _then_ re-introduce the appropriate amount of humidity". To dry it out, you cool it down and "condense" the humidity.
This seems like a neat continuation of the idea: Dry out the air before you cool it, and effectively time-shifting (and having separate systems) for the drying, the cooling, and the baking/restoration of desiccant.
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?
- 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...
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 [2] https://www1.eere.energy.gov/buildings/publications/pdfs/bui...
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)
All/most window AC units I've seen have a mode labeled something like 'dry only', which I take to mean 'dehumidify only'.
I found a tool to let you play with the parameters.(2) For example the air speed from a fan causes some cooling sensation so the temperature can be higher for the same comfort.
The energy use to get there would need to be modeled by measure of the change in cooling degree days vs energy consumption and that is not universal answer across all scenarios because of climate, construction, and ventilation.
(1)https://www.ashrae.org/technical-resources/bookstore/standar...
(2) https://comfort.cbe.berkeley.edu/
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.
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-c...