A Free Energy Desiccant based make-up
air drier and heat exchanger system
ENERGY Desiccant-Based Fresh Make-Up Air Drier and Heat Exchanger
System Shown Installed On An Attic Floor!
Fig 1 very carefully. It shows the typical "Don't Walk On
It, Or You Will Fall Through! (please, kindly, keep your feet
on the walkway) "type of attic floor with ceiling/floor joists
and pink fiberglass insulation between them.
light blue box contains a cylinder filled with six compartments
have intentionally selected a desiccant that is a safe chemical
that is hydroscopic (water loving) at low temperatures, but
hydrophilic (water hating) at higher temperatures.
light yellow box contains a heat-pipe fresh-air (make-up air)
idea is to bring in fresh make-up air to avoid "Sick House"
syndrome in our well insulated and otherwise "airtight" alternative
energy powered home.
Fig 1, There is an energy efficient compact florescent work
light and a quad electrical outlet box on the tan exterior
wall at the top left in this illustration.
into the quad box are two shrouded, and louvered duct fans
that blow air outward to remove air from the home.
1a. Version Showing The Individual Components By Callout Number.
fan connected to the red hose (1) exhausts
hot (160ºF or so in summer) attic air through the top
four desiccant cartridges (2) inside the
light blue box, thus using the attic's waste heat to dry the
desiccant. The other well-insulated red hose (3)
simply gathers up the very hot air high up at the attic roof's
apex and transfers it into the desiccant dryer inlet.
hot attic air thus removed, is then continually replaced by
fresh cooler air from the soffet vents under the eaves, thereby
cooling the attic space, and also reducing the temperature
difference across the attic floor and the cool space below.
via the green hose, (4) fresh, but too-humid
and too-warm air is sucked in from outdoors and passes through
the previously dried desiccant chambers (5) where
it becomes dried, (but still too warm) thus giving up its
large amount of latent-heat of vaporization to the desiccant,
as the desiccant chemically grabs the moisture from the incoming
via the middle green hose (6) , the now
dry, but still too-warm fresh air passes into the yellow box
and through heat pipe counter-flow heart exchanger inside
the yellow box's heat-pipe heat exchanger (7) ,
the cool but stale air about to be exhausted adsorbs the sensible
heat from the incoming dried fresh (make-up) air thus cooling
and conditioning the make-up air before it is mixed into the
cool space air via the final green hose (8)
that runs from the yellow heat exchanger box to the fresh
air register in the ceiling below.
other exhaust fan, via the brown hose (9) ,
sucks stale (and now warmed) air from the stale air exhaust
side (10) of the yellow box's heat exchanger
and directs it outside.
remaining brown hose (11) removes stale
but still cool air from the cool conditioned space, into the
inlet of the yellow box's heat exchanger by using the partial
vacuum created by the brown hose, (9) and
the exhaust fan at the heat exchanger box (10)
that there is no actual mixing of the incoming fresh air (7)
and the outgoing stale air in the yellow heat exchanger
box (10) . The two counter-flowing air streams
are kept completely isolated and separate. Only the heat is
the hot attic air (2) never mixes with the
fresh incoming air (5) in the blue desiccant
unit. The hot attic air is simply used to dry the desiccant
just before being instantly exhausted.
few minutes, an tiny ultra low power DC motor just rotates
the desiccant drum exactly 120 degrees of arc, thus moving
two new, previously dried, fresh desiccant canisters into
the incoming fresh make-up air stream.
two of the now wetted (from humidity previously removed from
the incoming fresh but humid air stream) desiccant canisters,
are moved into the hot dry attic air exhaust air stream to
begin anew, the desiccant's drying/reconditioning cycle.
using otherwise unused attic waste heat to a thermodynamic
advantage, we both reduce the attic temperature, and thus
also reduce the Air Conditioning heat load demand!
addition, we save energy in another important and "ghostlike"
and "phantom"! way
simultaneously, by chemically drying the air, remove very
large amounts of "hidden heat" ..the "latent heat of vaporization"(the
reason steam feels so hot on your hand!).
never having to run the electric heat pump compressor or Air
Conditioning compressor to remove this large latent heat of
vaporization, from the incoming make-up air (or the re-circulating
cooled air) enormous savings in Air Conditioning power consumption
pictorial illustration is meant primarily to be educational.
The black box illustration, conveys the principles of operation,
of such a desiccant air conditioning scheme, that works in
clarity purposes, it is not fully optimized in these drawings,
and therefore is not intended to be used, without further
refinements, as an actual construction plan.
the real world, we would package the yellow box and the blue
box together, in the same housing, together with a series
of cascaded particle and air pollution removal filters, and
a fresh Make-Up Air/Re-Circulated Air proportioning control
damper to create a single, fresh air ventilation system, to
use with our alternative energy homes.
let us take a peek inside the light blue desiccant box!
the light blue box is a slowly rotating :
what's inside the yellow box?
Pipe Heat Exchangers
pipe heat exchangers are sometimes used for air-to-air energy
recovery systems. These devices involve three fluids: the
two air streams between which heat is being transferred and
a third fluid sealed within the multitude of heat pipes making
up the unit.
a typical application exhaust air and fresh air are flowing
in opposite directions, i.e., in a counter-flow arrangement,
in adjacent ducts with the unit spanning the cross-section
of both ducts. In the winter (as seen above in the schematic)
heat transferred from the warm air being exhausted provides
the energy to evaporate the working fluid in the sealed heat
pipe. That vapor flows to the other end, where it condenses,
giving up the heat to the incoming fresh air. The condensed
liquid flows back to the warm end to complete the cycle. In
the summer the operation is reversed. The warm, but fresh,
air entering the building is pre-cooled by transferring heat
through the heat pipes to the cool, but stale, exhaust air
leaving. To compensate for the low heat transfer coefficients
with gases, the outside surfaces of the heat pipes are aggressively
a heat pipe anyway?
traditional heat pipe is a hollow cylinder filled with
a vaporizable liquid.
Heat is absorbed in the evaporating section.
Fluid boils to vapor phase.
. Heat is released from the upper part of cylinder
to the environment; vapor condenses to liquid phase
Liquid returns by gravity to the lower part
of cylinder (evaporating section).
have already shown you some FREE ENERGY tricks, that can be
used by you to get cool, and dehumidified air for free, by
simply recycling the otherwise wasted energy from a hot attic.
we will show how to modify a conventional compressor-based
air conditioning system to get more dehumidification without
increasing the operating cost or energy consumption of the
Dehumidification with Heat Pipes
Product Review - Environmental Building News June
Air conditioners cool air in two ways: they reduce air temperature
directly (removing sensible heat) and they remove
moisture from air, reducing its latent heat. In
some cases the relative balance between these two functions
is acceptable, but there are also many applications for which
additional dehumidification is needed.
traditional approach to these situations has been to overcool
the air (thereby extracting more moisture), and then to reheat
it to the desired temperature with gas or electricity. This
approach wastes energy twice: once for the additional cooling
and again for the reheating.
are several ways to increase the dehumidification capability
of an air conditioner (AC) that are not as wasteful.
of the best ways for many situations was adapted from NASA
technology by inventor Khanh Dinh. Dinh's heat pipes precool
the air before it reaches the evaporator coils (or chilled
water coils) of the AC unit, which increases the amount of
moisture that those coils extract. The heat pipes also reheat
the outgoing air, which leaves the system just slightly warmer
than it would have been had the heat pipes not been there
reheated air is also significantly drier than it otherwise
would have been. The amazing thing is that both the pre-cooling
and reheating are totally passive-requiring no added energy
or moving parts.
heat pipes work because they contain a refrigerant that evaporates
as the warm incoming air passes by the pipe, which removes
heat from that air. The refrigerant, now a gas, then rises
up along the pipe to the other side of the cooling coil. On
this side it encounters the chilled air, condenses into a
liquid, and runs back down to where it started. As the refrigerant
condenses, it returns the heat that it had extracted from
the air before the cooling coil (see schematic).
heat pipes are widely used in mechanical systems to reclaim
energy from exhaust air in preconditioning incoming fresh
air the amazing thing is that they can also be used to achieve
example, some of their heat pipes are configured in a loop
rather than a single pipe, so that the gas rising up the pipe
is not moving against the liquid running down.
engineering lingo, the sensible heat ratio (SHR)
is the amount of sensible cooling an AC unit provides as a
fraction of the total cooling. Thus, an AC unit with a typical
SHR of 0.75 removes 75% sensible heat and 25% latent heat
ratio may be appropriate in some cases, but there are many
situations, especially in the hot-and-humid Southeast, when
more latent heat removal is desirable.
general, the need for enhanced moisture removal depends on
factors such as the outdoor humidity, the amount of outdoor
air coming into the building, the amount of humidity generated
indoors, and the desired indoor humidity level.
method by which enhanced de-humidification can be achieved,
is by cleverly arranging some passive heat pipes, to straddle
th3 air conditioner's evaporators coil. No additional compressor
power is needed as this additional passive heat pipe based
de-humidifier is powered solely by the temperature differentials.
heat pipes may be described as having two sections: pre-cool
and reheat .
first section is located in the incoming air stream. When
warm air passes over the heat pipes, the refrigerant
vaporizes, carrying heat to the second section of heat pipes,
placed downstream. Because some heat has been removed
from the air before encountering the evaporator coil, the
incoming air-stream section is called the pre-cool
passing through the evaporator coil is assisted to a lower
temperature, resulting in greater condensate removal.
The "overcooled" air is then reheated to a comfortable
temperature by the reheat heat pipe section ,
using the heat
transferred from the pre-cool heat pipe.
Air heating and air conditioning are inherently energy inefficient.
with its large heat capacity is, by volume, 3550 times more
efficient in transporting heat than air is!
water heating and cooling transport, called "hydronics" should
be used as much as possible in alternative energy
"Forced Air Handler's" big problem, is the attempt to force
air to flow down a long tube using pressure from the
is inherently an extremely inefficient process.
a soda straw and try to blow air through it without puffing
your cheeks out!
little air flows because of turbulence creating a high back
try sucking on the same straw.
how the airflow increases and is smooth with little effort.
you suck air out nature abhors a vacuum and replacement air
air flow is now laminar, smooth and turbulence free!
design, "forced Air" heating is extremely wasteful of blower
power. In addition air is a terrible heat transport medium
for any real hest over a distance.
by using local zone units, many of which have a couple of
small 12 volt DC muffin fans that use suction to move more
over the heat exchanger, and thus take only a couple of watts.
proper small suction fan design, coupled with local zone heat
exchangers, and combined with the awesome heat
transport capacity of hydronics, we can heat and cool a local
zone without huge energy penalty incurred with ridiculous
"Forced Air" inefficient supply end blowers trying to push
turbulent air down long ducts.
all the I 2 R losses from 1-3 KW of blower motor heat end
up canceling out 1-3KW of cooling, there is a double
whammy, since now an additional 1-3 KW of cooling must be
re-supplied to meat the original cooling demand. Now the
blower losses increase slightly more. Forced Air Handlers"
are a needless, tail-chasing, energy wasting vicious-circle
They are a poor design, a holdover from the cheap energy heyday
of the 1940's and 1950's that presumed cheap energy, that
now really needs to be avoided!
the large and extremely energy inefficient "Forced air Handlers"
in common use, such a alternative energy home's
"Unforced Make-Up Air Handler" is
to be smaller and far more energy efficient.
is said to be an "Unforced" air handler because small fans
suck air and create a partial vacuum wherever air movement
Mother Nature "Abhors A Vacuum" She kindly and benevolently
rushes in to do almost all the air-moving work for free !
If outside air is hot and humid and the attic is vented. Wouldn't
the hot attic air be humid and not dry the
desiccant, and not be hot enough to drive the H2O from the desiccant?
a very good question!
the Mollier Diagram below.
that air that contains 100% humidity (fog point) at 23 degrees
centigrade (72°F) temperature becomes air with just 20%
relative Humidity by heating to just 122°F! Attics on
a summer Solar day often reach about 150°F-160°F.
if it is a sweltering, muggy 110°F outside with 90% relative
humidity, that hot attic air will become a very DRY 20-30%
when heated. This is why you can successfully use a attic
heat powered desiccant dryer to slash your air conditioning
The Mollier diagram is a very useful tool to solve HVAC-problems
graphically. It includes all humidity functions in one chart.
4a: Mollier diagram: curves of constant relative
humidity . The region below 100% (fog region) is not valid
4b: Curves of constant enthalpy are added to Fig.4a
. Also example 1 is included below.
To warm up air from 20 °C to 25 °C and humidify
the air from 40 %RH to 60 %RH 20.2 kJ/kg would be needed.