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Reverse Osmosis Dehumidifyer

liquid desiccant + reverse osmosis = dehumidifier
  [vote for,

I have searched the web, and not found anything *quite* like what I'm thinking of. The idea is relatively simple.

Start with a reservior of low-water liquid desiccant (such as a calcium chloride / water mix).

Pass it, and room air, through the conditioning unit, where air and desiccant first mix, then seperate. Boring units would use a sprayer or bubbler, then a gas/liquid seperator. More interesting units would look like a decorative fountain (water feature type fountain, not drinking fountain).

Send the now wet desiccant through a small reverse osmosis device. Since it is small, we don't need a fancy pressure exchanger to recover pressure from the dewatered desiccant... instead, a simple positive displacement hydraulic motor would suffice. The unit's hydraulic motor and electric motor together provide the power to turn the positive displacement pump which forces wet dessicent into the reverse osmosis device.

The dewatered dessicant is then sent back to the conditioning unit.

The pure water extracted by the reverse osmosis device can be used for drinking, or can simply be discarded.

Besides (probably) using less energy than a refrigeration based dehumidifyer, and not warming up the air (as would occur in a liquid desiccant system which didn't use reverse osmosis), there's another big advantage.

If you have a large enough reserviour of desiccant, you can de-water it at night, using cheap(er) off-peak electricity, and then use that dry desiccant over the course of the day for dehumidification.

goldbb, May 10 2009

Solar home with liq. desiccant dehumidifyer http://www.scienced...10/071021185051.htm
Their idea, however, uses heat and evaporation to renew the desiccant; that means that the system needs to be plumbed to the exterior of the home [goldbb, May 11 2009]


       does calcium chloride suspended in water still work as a desiccant for air?
loonquawl, May 11 2009

       If it's concentrated enough, it can. The trick is to keep it as concentrated as possible, so that it can absorb water from the air, without concentrating it so much that some of the calcium chloride precipitates out.
goldbb, May 11 2009

       The more concentrated the salt solution the more energy will be required of the reverse osmosis device to extract water from it. Consider sea water desalination: some water is extracted but not maximal water - as the brine concentrates the water return for energy expenditure increases, and so the effluent is a concentrated brine. "Concentrated as possible" is probably not ideal. The true optimal concentration could probably be determined with some fancy math.
bungston, May 11 2009

       so if you have a supersaturated CaCl solution on one side of the permeable membrane what do you have on the other side?
WcW, May 11 2009

       Clean pure water, under less pressure.
bungston, May 11 2009

       you may need to do some research there...
WcW, May 11 2009

       can you link to a site with more background info on this please?
supershnitzel, May 12 2009

       I'm curious to know how much less power this would use in comparison to an AC unit.   

       The power difference essentially is the compressor since you still will have to pump air around the house.   

       You have a nice practical idea though.   

tommyato, May 12 2009

       I think you both need to do some math, I don't think that there is ever going to be a single stage permeable membrane stiff enough to survive that level of pressure. LOTS OF PRESSURE!!!!
WcW, May 12 2009

       Ahh, but you haven't voted against the idea yet, so maybe you still think it might be possible :).   

       Since you make a point about the pressure limit a "single stage" membrane is likely to have, how about a two stage reverse osmosis device? Water is forced from the high concentration dessicant through a first stage membrane, to an intermediate region, then through a second stage membrane, out of which comes pure water.   

       Not that I'm really endorsing that idea -- two stages adds enough complication as to make the idea unpleasantly costly, and thus impractical -- but at this point I'm curious about whether it's possible.
goldbb, May 13 2009


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