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http://green.blogs.nytimes.com/2011/08/12/a-new-way-to-squeeze-humidity-out-of-the-air/

Squeezing Humidity Out of the Air


It’s not the heat, it’s the humidity, they say. And according to one company with a distinct take on air-conditioning challenges, buildings can cut cooling costs substantially by dealing with the humidity separately.

A central air-conditioning system made by Advantix Systems, formerly an Israeli company but now based in Miami, removes moisture from air and cools it with a mixture that is 60 percent water and 40 percent salt. Humid air is pumped past the salty mixture and water from the air tends to flow into the salt.

If the salt is chilled, the air will be cooled, too. A diagram explaining the system is here.

Finding a separate way to remove the humidity is important, said Hannah Choi Granade, president of the company’s American subsidiary, because conventional air-conditioners have only one way to squeeze the humidity out of the air that they cool: by chilling the air to a low enough temperature that it reaches the dew point and the water drains out.

If it gets cold enough, the humidity will condense on hard surfaces, like beads of water accumulating on the outside of a glass of iced tea.

But to do that, a conventional air-conditioner may have to chill the room air to 52 degrees or even lower. That can make the air too cold to use directly, so some systems have to reheat it before introducing it into the room being air-conditioned.

Yet if the air can be dried out directly, it need not be overcooled and then reheated, according to advocates of these “desiccant” systems.

Humidity can worsen in office buildings that install efficient lighting, window tinting to screen out the sun or computers that use less electricity. All those steps reduce the accumulation of heat so that the air-conditioning does not need to run as much.

But if the humid air does not pass through the air-conditioning equipment often enough, the temperature in the room will hit the desired level before the humidity is removed, and the air-conditioner will shut off. And when outdoor air on a muggy August afternoon is lowered to a temperate 72 degrees, the result is very high relative humidity, possibly followed by mold and mildew.

A system at Advantix’s Miami headquarters works well in removing humidity, Ms. Granade said. The cooling system would work in a dry place like Las Vegas, too, but would not yield energy savings, she added. In fact, Ms. Granade said, her product does not get an Energy Star rating because the government’s rating system does not take humidity into account.

Desiccant air-conditioning systems have been around for a while; usually they rely on a solid material that absorbs moisture and is mounted on a big wheel that rotates through the path of the air being treated. When the wheel passes out of that pathway, the solid material is heated to drive off the moisture so the solid is ready for another pass.

Advantix says its system is more reliable because the pores through which the solids absorb water can get clogged with contaminants but the salt can handle it, and its system consumes less energy.

The company started out building dessicant systems for ice rinks in Israel, where high humidity produced a fog over the ice. (Such systems originally ran on salt from the Dead Sea but now use commercial stocks of lithium chloride, a component of sea salt.)

Today Advantix builds systems in Israel and India and sells them to pharmaceutical factories, where humidity control is important, as well as to hotels and other customers. It has only about 70 systems in the United States but is now trying to market them to health clubs, which need high air turnover. The salt also absorbs molecules that cause odors.

One such club is CrossFit ATP in Dania Beach, Fla., near Fort Lauderdale, where the system was installed five months ago. “It’s awesome,” said Juan F. Bacca, the owner, in a telephone interview. “My main concern was the stagnant, stale, musty, sweaty boxing-gym smell that I had,” he said, especially in an upstairs room where dozens of people learn martial arts.

Mr. Bacca said that people exercising often liked the room warm, but when the conventional system held the temperature to 78 degrees, it did not remove enough moisture and the room was “sticky and muggy.” The new system solves that problem and saves him about 15 percent on his energy bills, he said.

In Miami, another customer is the Duty Free Americas warehouse, a 30,000-square-foot space with some merchandise that should not get warm, like fancy chocolates. “It works very well,” said Lorenzo Lorenzo, the warehouse manager.

The warehouse reaps large energy savings, he said, and the system purifies the air so well that “my employees in that department rarely catch a cold.” The system has been in place there for three years.

Advantix’s machines are installed on the usual spot at commercial buildings: rooftops. They are no odder-looking than conventional units. Inside, salt is chilled by an ordinary compressor, the same kind of compressor that is used in conventional air-conditioners, and it picks up moisture from the passing air. The salt gets wetter and wetter.

A second pot of salt is heated, using waste heat from the air-conditioner. As it gets warm it gives off water, getting drier and drier. When the two volumes of salt, hot and cold, are adjacent, water flows from the cold wet salt to the hot dry salt. Thus the system continuously ejects moisture.


Eric D. Schwerin
Rosemont Seneca Partners, LLC
1010 Wisconsin Ave., NW
Suite 705
Washington, DC 20007
(202) 333-1880
eschwerin@rosemontseneca.com
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