Blue Frontier and its energy-efficient AC
technologyreview.com
technologyreview.com
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
"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.
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.
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.
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.
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.
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...
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 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...
see also https://dercuano.github.io/topics/cooling.html with its list of notes like 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/material...
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...
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 :-)
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.