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Old 05-23-14, 11:38 AM   #1
Daox
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Default New Air Conditioner Conquers All Climates, Saves Up To 90% Energy



This is a very cool (no pun intended) article. I'm sure a bunch of us have thought up something similar, but its great to see actual research being done on it. They're combining swap coolers with liquid descendant dehumidifying for a super efficient cooling system. If you have a minute its well worth a read. I'd like to hear some feedback.

The idea of the Coolerado cooler alone is very interesting (and something I've been wanting to try). However, the humidity is really the main issue for me. Combining this with a liquid descendant is quite intriguing! They even mention using solar heat with the descendant dehumidifier.

New Air Conditioner Conquers All Climates, Saves Up To 90% Energy

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The U.S. Department of Energy's National Renewable Energy Laboratory has invented a new air conditioning process with the potential of using 50 percent to 90 percent less energy than today's top-of-the-line units. It uses membranes, evaporative cooling and liquid desiccants in a way that has never been done before in the centuries-old science of removing heat from the air.

"We'd been working with membranes, evaporative coolers and desiccants. We saw an opportunity to combine them into a single device for a product with unique capabilities."


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Last edited by Daox; 05-23-14 at 12:00 PM..
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Old 05-23-14, 05:07 PM   #2
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What? A coolerado (1/2 swamp cooler, 1/2 HRV) and a desiccant waterfall (seasoned veteran eco award winner) combined into one unit? Awesome!

The only thing that I find devious is that NREL holds a patent on the technology, and seeks vendors to license and manufacture the concept. Not the fastest or best way to bring products to market.
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Old 05-23-14, 10:20 PM   #3
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I wonder if you can reverse valve it to make heat - My climate calls for heat 75% of the time. I think we need AC hacker to reverse flow that puppy THEN patent it , No make that CO PATENT it with me
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Old 05-24-14, 05:17 AM   #4
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The nrel paper that describes the system is here:

http://search.nrel.gov/cs.html?url=h...nrel&n=4&la=en

The main process employed in the idea is absorption chilling, much like the ammonia water process. The big difference is that the liquid desiccant loop as well as the evaporative loop are open loops. This makes both loops many orders of magnitude more efficient than phase change or closed-loop absorption refrigeration methods. Water is the primary refrigerant in the system. Since all of the water doesn't need to be continuously compressed/heated, expanded/cooled, and recirculated, it takes a lot less energy to do the job.

In this application, the desiccant is used to pre-dry the outdoor source air, making the evaporative cooler downstream more efficient. The outdoor air stream is split in two: some of the air gets humidified and cooled as source water is evaporated into it; some of the air just gets cooled by membrane contact with the air being humidified. The dry air goes indoors, the humid air gets exhausted. The lower humidity incoming desiccated air forces a lower dew point and wet bulb temperature on the evaporative cooling process. Both coolerado and nrel call the evap-half-cooler a heat-mass-exchanger.

In the "leaf" and "watershed" solar decathlon houses, the desiccant stream is indoors, and the cooling effect comes from the water being plucked from the indoor air. The regenerator outdoors is solar powered. The design team found that the desiccant waterfall works so well, it can over-dry the air. They employ misters indoors to assist in cooling and to maintain comfortable humidity levels.

However, there is still a need for a regenerating device. Without a heat source, there is no way to remove the water from the liquid desiccant solution. With calcium chloride used as desiccant, the solution must be raised to 120 degF or so to effectively force evaporation. Luckily, this can be accomplished without a whole lot of supplied heat. Solar is a shoe-in for this purpose.

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Old 05-24-14, 03:25 PM   #5
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This dehumidifier/cooler topic has been discussed here before.

http://ecorenovator.org/forum/solar-...umidifier.html

Until this thread started, I didn't even know the coolerado existed. Now that I know, the wheels are turning. No wonder NREL patented this application: it would be dead easy to build the heat-mass-dehumid-exchanger.

In the NREL paper, it says that a 3 ton DVAP core measures approximately 18 x 20 x 20 inches in overall size. Each layer is 1/4 inch thick, so that would make it around 70 layers thick. During normal operation, it takes 400 cfm per ton of cooling.

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Old 05-25-14, 08:44 AM   #6
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The regenerating equipment is also very modest. Using a boiler, it requires 30kbtu of source heater and 1 cubic foot of exchanger volume. The hx requires only 50 cfm of airflow to carry away the scavenged moisture.

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Old 05-25-14, 11:37 AM   #7
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So this could be made for personal use , Just not commercial use or for resale if I understand that right.
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Old 05-25-14, 05:00 PM   #8
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NREL might have patented it to prevent the technology from being single-sourced.

No matter who owns the patent you can build one for "testing and evaluation." Thus, hacking your own is OK.
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Old 05-26-14, 12:03 AM   #9
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The only thing I can't figure out is what to use for a semi-permeable membrane. This is the layer that separates the liquid desiccant from the fresh air stream. It has to allow the water vapor from the incoming air to diffuse into the desiccant, but not let any desiccant leak into the incoming air. Any ideas on a suitable material would be appreciated.

The rest of the unit looks much like the HRV's that some members have constructed already. Pretty much coroplas and felt. The latest NREL generation design incorporates some extruded aluminum pieces for better heat transfer, and thus smaller size, but I can live with a larger heat exchanger to avoid exotic and expensive custom materials. Maybe some windshield reflector board will suffice.

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Old 05-26-14, 09:50 AM   #10
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That shouldn't be necessary if the air flow is kept low. I think the reason for including it is to allow it to run at an air flow comparable to conventional HVAC and thus be a drop in replacement.

Looking through the documentation, it looks like they use the desiccant solution to absorb moisture and then use "reverse desalination" to regenerate it. Reverse distillation is a great choice when there's a lot of "free" heat like solar thermal or heat coming off an engine or other device, but when there isn't, what about reverse osmosis?

Desalination - Wikipedia, the free encyclopedia

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