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Old 11-08-13, 04:37 PM   #21
peacmar
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Well that's the basic idea, first order of business will be to design an air handler that will move the damp air around and second is to find the parts to do so. I think it will be a batch load system at first until I can work out some sort of idea of the capabilities of such a system. Quarts per hour or whatever it happens to be. I can easily tap into the boiler lines at any point in the basement to put the regeneration unit wherever works best. Now, I have all winter to scheme this up and put it into motion. Unfortunately I won't be able to truly test it out till spring arrives. Thinking about it now, I already have created an air exchange loop for my clothes drier and could use a damper system to circulate outside air into the drier and moist air outside. I wonder if convection currents would suffice or if I would need to force air. I guess that depends on the amount of moisture absorbed and the humidity of the outside air. Many things to prepare and test before I can call it a working system. Then, eventually, when I am able to construct a solar heater for my mass storage tank, I will hopefully be able to run the system without burning wood. As the future plan is to use solar as a primary heat source and wood fired heat as backup.

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Old 11-12-13, 01:58 PM   #22
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I wonder how the U of MD group kept the calcium chloride liquid? Keep it heated above it's melting point?
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Old 11-12-13, 08:32 PM   #23
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Boz,

Please google the term: Hygroscopy

Nature is awesome!
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Old 11-13-13, 12:45 AM   #24
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I found another decent website:

Scavenging-Air Regen

Follow the links scattered on the page for all the info.

A retail, residential, affordable dessicant wheel dehumidifier:

http://www.sunpentown.com/sddede.html

Last edited by jeff5may; 11-13-13 at 12:59 AM.. Reason: more info
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Old 11-13-13, 08:56 AM   #25
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Quote:
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Boz,
Please google the term: Hygroscopy. Nature is awesome!
Which lead me to this: "Calcium chloride is so hygroscopic that it eventually dissolves in the water it absorbs: this property is called deliquescence."

OK, more thinking to do. And I need to find the patent and read it again.
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Old 11-13-13, 09:10 AM   #26
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Hi just joined the forum, I found this thread whilst looking up solar air heating for my outside office/workshop/equipment store. The store is cold and damp and I was investigating making and using a beer can solar air heater to provide warm ducted air to the building. These are really cheap to make and when done properly actually look quite good.

However, I also want to dry the air entering the building to stop damp in the equipment stored in there. Hence researching solar dehumidifiers.

The beer can/soda can air heater (check it out on instructables) provides a free solar powered warm air flow, I was wondering if this could be fed through a silica gel bed to dry out the air entering the building?

Additionally whether a second air flow from the beer can air heater could be used to regenerate another silica gel bed. The silica gel beds could be periodically swapped over to regenerate one whilst the other is drying the inlet air.

Having read this thread I thought of possibly using a dessicant wheel such as the one posted by Daox so that the swapping over the dessicant could be automated/motorised.

Could a dessicant wheel be made to turn under gravity? The wetter side would be heavier and therefore, if the unit was angled correctly turn the wheel under its own weight, with the lighter drier side gradually moving up as it dried.

Ross
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Old 11-13-13, 01:03 PM   #27
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Quote:
Originally Posted by Ross D View Post
Could a dessicant wheel be made to turn under gravity? The wetter side would be heavier and therefore, if the unit was angled correctly turn the wheel under its own weight, with the lighter drier side gradually moving up as it dried.
This would be very easy to test. You wouldn't even need a whole wheel, just a simple balance, and silica gel. Try it out and let us know what you have learned.

* * *

But back to the de-humidify question, I haven't been following this thread, but...

Whenever you heat air, the amount of moisture it contains remains the same, but at the same time, the relative humidity (AKA: "RH") gets smaller. This is because warm air can hold more moisture than cold air.

So, no matter what the relative humidity of the outside air is, when you heat it, the new RH will be lower, and thus capable of holding more moisture.

On sunny days, if you continuously brought in cold air from the outside, heated it, circulated it around your space, and then dumped it outside, you would de-humidify your space. If you got some cheapo PV panel (I think there actually is such a thing now) and used it to power your beer can heater fan, your system would only run on sunny days.

Personally, I doubt that the gel approach will be very useful useful... but I'm open to being show to be wrong.

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Old 11-13-13, 02:17 PM   #28
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AC,

I have been pondering this idea and following this thread for awhile. Both solid (silica gel cartridge) and liquid (brine solution) systems have been used in commercial applications since the energy crisis of the 70's happened. Apparently, either method is much more efficient than ammonia systems at transferring latent energy loads. Many supermarkets and factories use their inherent waste heat stream as a source of "free" energy to regenerate the dessicant.

Only lately has the residential segment caught on to this process. The big eye-opener to residential architects and energy experts was the University of MD 2007 solar decathlon "leaf" house, cited earlier in the thread. They won the silver medal. Since then, the university has (you guessed it) built another "watershed" house for the competition and won Gold with it in 2011. It is truly a mad science project that works exceptionally well.

http://2011.solarteam.org/design

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Old 11-13-13, 05:53 PM   #29
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The idea of dehumidifying the air before it is circulated through the building is to reduce the moisture content of the air.

If outside air is used as the building cools at night, it will eventually reach the dew point of the air and the building will become damp, condensing on the cooler surfaces and equipment stored in there.

By recirculating the internal air during the day, dehumidifying it and heating it, the overall moisture content within the building will reduce. Which will reduce any condensation overnight, it should also contribute to overall higher temperatures within the building.

Ross
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Old 11-13-13, 06:09 PM   #30
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Quote:
Originally Posted by jeff5may View Post
...Both solid (silica gel cartridge) and liquid (brine solution) systems have been used in commercial applications since the energy crisis of the 70's happened...
OK, so we're talking about driveway salt dissolved in water, right?

Do we have a how-to yet?

Hmmm...

I just took a 50 lb bag to the dump, too.

So what is the critical % and how do you measure it?

Looks like the CO2 sensor project I did could be used, but you'd excise the CO2 part, and keep the humidity/temperature sensor, and use that as your input to modulate your PWM stream which could control your pump... Or use the set-point approach... on & off as required.

But getting rid of the water in the brine would be the real task.

-AC

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