http://www.solarteam.org/page.php?id=641Are there some sound DIY applications for this in residential?
liquid desiccant waterfall
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Until the mid twentieth century, a house cooling system meant ... a
fan, and before that, a window. The key difference between a simple fan
and an air conditioner is dehumidification -- an important distinction,
because, as the saying goes, "it's not the heat, it's the humidity"
that makes Washington, D.C., area residents uncomfortable in the summer.
The problem with air conditioners is that they are energy hogs. A
conventional air conditioner uses a pump to compress and expand a
refrigerant, supercooling the air and causing the water vapor in the
air (the humidity) to condense (become liquid). It dumps the collected
water outside. This takes a lot of energy and generally it can only be
done with electricity. Electricity is generally a lot more expensive
to create than heat, for example, making conventional AC cost more too.
The LEAFHouse team is exploring a technology relatively new to
single-family home design called a Desiccant System. This concept has
been proven sound on larger buildings. The basic idea is to use a
material called a desiccant (in our case a type of salt called calcium
chloride) to absorb water directly from the air without all the
complicated machinery and energy requirements of conventional AC. As
the desiccant absorbs water, it becomes diluted and its ability to dry
the air declines. The desiccant needs to be regenerated. This can be
done by simply heating up the desiccant and letting the water evaporate
to the outside air. Thus, the desiccant is concentrated and ready to
return to its job of drying the indoor air. LEAFHouse uses heat from
the Solar Hot Water collectors to regenerate the desiccant. Remember
that heat is a lot easier and cheaper to make than electricity, so this
is a BIG improvement over conventional AC for dehumidification.
Most commercial systems use a solid desiccant. LEAFHouse has taken
the innovation of desiccant systems a step further by using a LIQUID
desiccant. We believe this will make the system safer, easier to
maintain, and cheaper too.
True to our philosophy of integrating technical and aesthetic goals, we
have chosen not to hide the Liquid Desiccant Waterfall (LDW) system,
but to make it a beautiful and functional indoor 'water feature'.
Likewise, the regenerator is a prominent techno-sculptural element that
will greet visitors on the Mall as they approach the front door to the
house.
In
summary, the dramatic Liquid Desiccant Waterfall removes humidity with
very little energy, greatly reducing the job of the air-conditioner
(used only for cooling). Calcium chloride, a highly absorptive salt, is
mixed into the waterfall, where it captures moisture out of the air.
Heat from the solar hot water collectors is used to regenerate the
desiccant.
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Ever consider a waterfall in the living room? I thought not. But
there are very good reasons to consider one. If you live in a hot and
muggy climate and want to build a new house that is naturally
comfortable and energy efficient, this is one simple and carbon
neutral way to do it.
Normally, flowing water does not take moisture out of the air. But
add just one ingredient to your indoor waterfall and, presto; cool dry
air is made from hot and muggy air.
The ingredient?
The secret ingredient is calcium chloride added to the water. Calcium
chloride, a salt, is a desiccant, just like table salt and the grain of
rice that you put in the shaker to keep it flowing freely. It is
hygroscopic, meaning it attracts water molecules from the air by
absorption or adsorption.
This liquid desiccant system is a wet flowing feature that can suck
the moisture out of your indoor air using almost no energy. The water
wall idea was first used by University of Maryland students to turn a
functional mechanism into an aesthetic feature in their LEAF House in the DOE Solar Decathlon.
To recycle the desiccant, the water is evaporated, re-concentrating the
salts to pull more moisture from the air in its next cycle. To keep
energy costs low, they used solar hot water heaters for the evaporation
cycle. Then once the desiccant is concentrated again, it is ready to do
more work pulling water out of the air.
These systems have been used in the commercial and manufacturing
sector for many years. Complex piping in commercial buildings (running
on carbon heavy fossil fuels) also use desiccant systems to remove mold
growth and other consequences of moist air.
Desiccant use in commercial A/C systems is not a lovely thing. A
waterfall is. And it is a very planet friendly low carbon cooling
system.