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This idea came to me on a visit to the tropical island of Saba over a decade ago. Saba is a tiny Caribbean island that sharply rises out of the ocean to a height of 3000 feet. One day we hiked up to the top on Mount Scenery. The environ up there was lush, green, and very humid. in fact ..clouds moving
across the Caribbean would crash into the mountain and for a few moments they cloaked us in a foggy bank<<sorry for the daydream let me get back to my point>> Saba despite being a tropical island Saba is basically a big rock and therefore has very little water. It's 900 residents must have water barged over once a week from nearby St. Martin (very expensive) My bright idea came to me during the hike . Why not extract all the water they need right from the air..?? I pondered that for a few moments and of course¨ first thought¨ logic told me that this endeavor would take are great deal of electricity (also a precious commodity on Saba) So where to get the watts.?? Bang ! It was so simple 1 gallon of water elevated 3,000 ft above sea level (with sea level ground in this case being a beach less than 50 feet horizontally & 3000ft Vert. down a steep slope) Eureka..... My 7 pounds (one gallon) of water was now to my enlightened mind.. suddenly 21,000 foot pounds of energy. Yes I know even @ 85 degrees and 90% relative humidity extraction of just one gallon from the air still takes a significant amount of energy BUT NOT ANYWHERE NEAR 21,000 foot pounds. Yes. water could be extracted from the air with freely generated electricity .......About 2 minutes later I realized how narrow-minded my thoughts really really were...... TO HECK WITH THE FREE WATER.the excess energy was the BIG CONCEPT !!. I believe you could go anywhere in the world that enjoys (grin) oppressively high relative humidity and build a tower with a simple condensation unit @ the top and a electric generator @ the bottom. The electric Gen working off of the pressure from a very high column of water. Now of course a 10 foot high tower would not work as the 70 foot pounds from 1 gallon of water elevated just 10 feet would not be enough to energy to power the extraction of said gallon..need more power? Just make the tower higher go up high enough to create enough pressure to cover the power needs then go on up 50% higher to claim you free energy.................................................**I have searched the net for years and years and never anywhere found mention of anything at all like this concept ??? Am I missing something or is this just maybe simple enough to actually work ?? (BTW over the 11 years I've been stewing on this I have never discussed this with anyone.tonight. I just decided heck 'ill throw it out there for public discourse.if some jerk steals the concept and makes a ton of $$ I will still know it was my idea. (Of course I'll subpoena all of you to testify when I sue the bastard )
Australia Solar Tower
http://cbc.ca/stori...21/aus_power_020821
Kindof like the reverse of this [ootleman, Oct 04 2004]
Energy producing water tower
http://www.solardat...data.net/arubot.htm
Similar [waynetta, Oct 04 2004]
Water Theater
http://dsc.discover...2&titleId=959746342
At least someone payed for a shiny animation! [create, Jun 07 2007]
Prototype wind turbine condenses 1,000 liters of water a day from desert air
http://www.geek.com...esert-air-20120418/
Marc Parent's WMS1000 wind turbine [swimswim, Apr 18 2012]
Mist Net Fog Harvesting
http://www.wateraid..._work/nepal/445.asp
One example of passive moisture collection. [neutrinos_shadow, Apr 19 2012]
eolewater.com
http://www.eolewate...products/range.html
The company behind [swimswim]'s link [spidermother, Apr 20 2012]
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Redwoods use this effect, but they're after the water, not the energy. |
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damn you. the name of the idea made me think of 'river of dreams' by billy joel, and now it won't leave my head. if there's one thing you don't need when you're working at 3am, it's billy f**king joel. |
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At first glance, I can't fault the principles, after all that's how conventiional hyropower works: Clouds condense into rain, which is collected and falls downhill, spinning a turine, providing water and electricity to the people below. |
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The fact that you're on a desert island which happens to have mountain peaks in the clouds, but no obvious precipitation or groundwater doesn't bode too well for your probability of success. |
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First you need to ensure stable climatic conditions, find some efficient method of precipitation, overcome system inefficiencies and losses, ensure sufficient economies of scale and make sure your plan isn't going to destroy the mountain's ecosystem. |
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i couldn't trust your link, [shz]. what if the song was replaced with 'my heart will go on'? aw, maaaan! now both songs are fighting each other. ok, distract yourself, distract yourself... ok, celebrity boxing - celine and billy face off in the ring. i can get on board that idea. |
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How much water would you need, and how quickly can you extract it? Conventional hydro-electric plants capture rainfall from thousands of square miles, and even the tiny generators that you can stick in your river will depend on rainfall from several square miles (at least) to form the river. |
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As a rough guess, multiply the amout of water in air (the absolute humidity) by the amount of air you can pass through your condensor. Then calculate the gravitational potential energy of this (if you can extract one litre per second and drop it a kilometer you will get 10 kW power with a perfectly efficient generator). At high temperatures, 1 kg of air (around 1 cubic metre) can hold 30 g of water. So for 10 kW (10 kg per second water) you would need at least 300 cubic metres of air per second (probably nearer 3000 due to losses from friction, evaporation, inefficiencies of the generator, etc). Not impossibly large, but challenging. If my sums are right. |
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A croissant for using foot-pounds rather than some crazy thing like kwh. BTW, you have more energy than you thought. I seem to remember that a gallon of water is 8.5 lbs, not 7…
<with calculator, humming something by Billy Joel…>
Very rough calculation: lets see, about 8,000 BTUs of condensation heat per gallon to be gotten rid of, estimate 800 BTUs of electrical energy required. Converting that to foot-pounds gives 622,000 foot-pounds. Oops. You may need to improve the efficiency by a factor of 27 or so for this to break even.
Though, come to think of it, maybe that estimate of 800 BTUs for cooling is way too high...hummm, especially since it's a fog, most of it is already condensed. |
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Pssst... guys... a gallon of water is 8 lbs (or 4 quarts, or 8 pints, or 128 ounces), not 7 or even 8.5 lbs.
As noted above, the energy required to extract water through chilling (not to mention the losses incurred through energy conversions) would far outweigh the energy potential of the falling water. [UB]'s suggestion about using sheets would be more doable, if you don't mind the aesthetics of the whole thing. Your first inspiration in this matter, which would net free potable water for the island population, is a fine idea in itself, and very doable. Why clutter up the whole island (a beautiful place worthy of preservation, by your description) trying to get a little bit of electricity? |
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I'll split the difference with you...8.3 lbs at that temp. 1 fluid oz. = 30 milliliters. It's a measure of volume, not of weight.
Or, to be more exact:
1 avoirdupois oz is 28.349 g.
1 troy oz is 31.103 g.
1 fluid oz is 29.573 g. (at some temp)
Also,
1 troy oz is 20 pennyweight, 480 grains.
1 apothecaries’ oz is 8 drams, 480 grains
1 fluid oz is 8 fluiddrams, 480 minims
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one u.s. gallon of water = 8.345 pounds
one u.k. gallon of water = 10.022 pounds |
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both at standard temperature and pressure, of course. |
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in order for this to work, you'd have to extract the water through condensation as unabbuba noted. the trick is to get the air temperature (at the condensing surface) below the dewpoint, which is the temperature at which the water vapour will condense. |
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according to a psychrometric chart, air at 85F (29C) and 90% rh contains approximately 25g water vapour per kg of air (approx. 1.25kg/m^3 at sea level). converting to imperial units gives a vapour density of 0.0026 lbs of water per gallon of air, which means you would have to collect 3209 gallons of air to collect 1 gallon of water. concur with kropotkin: it's a challenge, all right. |
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// air at 85F (29C) and 90% rh//
[swice] mentions a particular set of humidity and temperature conditions which don’t jive with being in the cloud on top of Mount Scenery, where I would think the humidity is 100%. As native Americans discovered, you just need to provide an appropriate hydrophilic surface to collect the water without any energy input at all.
Since there is always quite a bit of wind, processing a lot of air is no problem. And no need to extract potential energy. The whole thing can be passive. |
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mihali tells us that a U.S. gallon of water weighs 8.3 lbs. and a U.K. gallon of water weighs 10 lbs. So swice's devices would work better in the U.K. than the U.S.? |
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That's okay...I'm not jealous. |
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But I wonder if there wouldn't be some way to make a big killing on the arbitrage between the two. |
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They still have gallons in England?
The scam that I noticed last time I was in Europe, was that they sold gasoline in liters, but charged the same price for those little liters as Americans paid for fat US gallons. And nobody noticed! |
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I think this is a brilliant idea. |
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Condensing the moisture (in
clouds/fog/mist) may not be a
big issue as the clouds may be
in a supercooled state and any
seed will can trigger
precipitation. (like in making
artificial rain) |
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However I see one limitation :
the need to reach high
altitudes and saturated clouds. |
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I checked on some meteological
websites and found that rain
clouds, such as cumulonimbus
cloud, are formed at heights of
400m to 800m. |
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Very few buildings in the world
reach heights of 400m. The cost
should be exorbitant. Utilizing
moutains is good but may be
limited to certain areas. |
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Also towers/mountains have a
major limitation : they cannot
be adjusted to the most optimal
height where clouds will condense. |
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We need something more flexible
and cheap to build. Offhand I
can think of using Helium
balloons that forms a network
of condensation surfaces. The
heights of the balloons can be
adjusted easily too. And they
and be shifted to differents
sites as needed. (need to check
how high can Helium balloon go,
how long do they last, and much
do they cost). |
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So we can lay these "cloud
harvestors" over ocean area, on
islands without moutains etc
and harvest the water in the
clouds.
Of course these cloud
harvestors can also be used
harvest static electricity, or
used as weather balloons etc
at the same time. |
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I believe many countries near
huge water bodies are very
suitable to deploy this
technology. |
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Clean water and enegy. I think
there's big money in your idea
too, while conserving the
environment. |
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Your idea will work quite well as originally sated from a purley thermodynamic model, but will yield very little water or energy without capturing an extemely large quantity of air. The winds would have to be blowing at 10kmh through an opening of 12 square meters to supply enough water for a typical household ing the United States. (I wont bore you with the calculations.) |
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The trick is to assume that a small fraction of the water can be extracted from the air with a minimal energy input. Avoid the steep part of the curved lines on the psychrometric chart. |
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The wheels in the sky keep on turning. anyways what happens when the wind blows into this sail. won't the energy you catch be more than the water energy. thus ripping the sails/ balloons. |
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sutheric - how does that compare to the average Saban (sp?) household who have to ship water in specially? |
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somebody who has more recently taken multivarible
calculas than i is gonning to have to do a little work on
this. You need to know the ranges of humidity,
temperature, and wind speed for the mountian top.
Work out the relationship to get a vector field. that
should tell you your conditions on the mountian top and
how much water there is availble. |
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Frank Herbert had the People of Dune doing someing
similar with "Wind Traps" basicly a tunnel down through
the mountian to cool the air and condense out the
water. I think a wind trap on this island would be a lot
more successful. |
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Essentially dig a cave on top that goes down oh a hundred
feet or so and slows and cools the wind the water should
condese out in the trap at the bottom then have a
chimney to draw the cooler air back out. |
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Run a pipe line in to drain the trap and see what
happens. |
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Once you get a feel for the dynamics of the set up you'd
be able to add more tunnels to increase capacity. |
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Plus a hydro plant at the bottom of the pipline would give
the power form the 2000+ foot head. |
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somebody needs to go back to the island and see if their
is any intrest. |
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doubt you make much money but you'd probally make a
lot of friends. |
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Assuming you had fairly strong winds, you could condense the water with an airfoil to drop the air pressure. In addition, if you filled the airfoil with a chemical that had the right temerature of phase change, you'd be able to use the natural temperature difference between night and day to increase the efficiency of the system. The water should condense onto the cold upper surface ofthe airfoil. |
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<as an aside, I saw a cool article on water generation using cool water from a deep sea supply, in hot dry climates, very cool I'll keep looking for a link> |
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I saw something similar on TV and they were thinking of building it in Israel. Basically, you cool a column of aid using a water mist at the top of the column/tower, the falling air (Cool air falls hot air rises etc) powers turbines at the base of the column. The water can be pumped up to the top of the tower using the electricity generated and providing the tower is tall enough an energy surplus results. The one they were thinking of building was 1km high. |
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It wouldn't need to be a vertical tower, it could just be a steep pipe running down the side of a mountaion with a turbine at the end. A thermal solar panel could also be employed to exaggerate temperature differences on the condensor surface. |
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Foot pounds? What kinda of science is that? METRIC, baby, that's where it's at. When the last few holdouts (The US being the dominant one) scrap their ridiculous system in favor of a good one, the world will be a better place. |
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OK, metric.
Let's assume that the air is saturated. You'll remove the moisture from the air via condensation. |
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The heat of vaporization of water is 40.7 KJ/mol
1 Kg of water is 55.6 moles.
Energy required to condense 1 kg of water (1 liter):
= 40.7 KJ/Mol * 55.6 mol = 2261 KJ |
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Gravitational potential energy available from 1 kg of water at 1000 meter height:
=(1 kg)*(1000 m)*(9.8 m/s^2)
=9800 kg*m^2/s^2 = 9800 J
=9.8 KJ |
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Now, that's not to say that it takes that much energy to transfer that much energy out of the water. heat pumps can transfer heat at greater than 100% efficiency (for example, they may be able to move heat at a rate of 100 watts, while only consuming 30 watts), but they're still not quite efficient enough to make this work. |
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You may be able to make use of an alternate heat sink, which would reduce the amount of energy required. You may also be able to take advantage of lower temperatures at night via bulk coolant storage (think industrial-style AC installations with glycol slush coolant). |
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The energy balance at first glance seems daunting, but without more investigation, I can't give this a solid bone. so [ ] from me, for now. |
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Just forget about the mountain. Saba is the perfect location for a small OTEC plant. Half a mile off the coast the ocean is about 1000 feet deep (the island is a volcanic mountain). |
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OTEC will provide ample energy and way too much fresh water, basically for nothing other than the cost of the system. Once it starts, it powers itself using the temperature differential of deep water and surface water. |
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If the point is only to harvest fresh water, then an even easier system is to just pipe in some cold ocean water from down deep, run it through a condensation plant (just a little higher than the town) then pipe it back out. As much fresh water as is needed can be produced this way. |
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Hey I just had this idea as well, and found you had already posted it. My version does not utilize mountains, just 1000m metal towers with angled fins all the way up to trap moisture, dew and rain, which is fed into the hollow column to produce a constant fall of water. No condenser required, the cold metal should be enough to condense the water. |
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This idea and one anno is all [swice] ever did. Interesting that it's surfaced now. |
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It does not have to lower the temperature as much as you guys think. In the right weather, it shouldn't take too much energy at all.(+) |
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The metal is an improvement as it
would serve better than a mountain to
conduct heat into the underlying rock. |
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I bet one could retrofit radiotowers to
accomplish this. These are already
positioned at elevation and so the tank
they will would be easily used by
downhill locales. |
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I think, at least in the situation of the Island of Saba,
the problem is better served by understanding why
the condition of high humidity and clouds can
produce a lack of water for inhabitants. |
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The island lacks basaltic volcanic material on the side
needed to capture rain and precipitation, instead
being rich in pumice and other porous material. Solid
basaltic flows are prevalent on the rain shadow- an
unfortunate mismatch. |
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Build a catchment on the appropriate side and water
could be collected. The isolated nature of the island
makes this a hard decision when the benefits are
weighed with the costs relative shipping in fresh
water from the plentiful sources nearby. |
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But I understand the concept is being played with
instead of the particular situation. Theory trumps
expediency, it seems. |
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If it works in a desert <link>, it would work on a tropical island. |
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[spidermother] (oops: [swimswim]) isn't that
<link>ed turbine working
by a different principle? Mountains make rain by
lifting air to higher altitudes, where pressure is
lower: the air expands adiabatically, cooling, so
water condenses. The turbine first compresses
air diabatically *then* allows it to expand
adiabatically* Although both are wind powered, of
course. |
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*At least that seems to be how it works: the
explanation in the link makes no sense, and the
manufacturer's website isn't as clear as it might
be. |
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Don't blame me; it was [swimswim]. But while I'm here, //after all that's how conventiional hyropower works: Clouds condense into rain, which is collected and falls downhill, spinning a turine// is not right. The metabolic energy of the leeches, and the heat of the soup, both need to be taken into account. |
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People are always mistaking me for [spidermother], until my faulty logic gives me away. |
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You're right [MP], they seem to use different principles. In the desert version //Air is drawn in through vents in the nose of the turbine and a generator heats it producing steam. That steam is then fed through a cooling compressor to form moisture that gets condensed into water.// ...and the water isn't subsequently used for hydro-power (though it could be, for a little bit of power). |
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As [pluterday] alluded to, in extremely humid areas, no energy is required to extract the moisture from the air. Various plants and insects collect water straight from the air; see link for Mist Nets. |
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I'm sure I'm not the only one thinking this but (re: the link) why heat the air producing steam then cooling it to get the steam to condense ? Why not skip right to the condensation bit. |
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////Air is drawn in through vents in the nose of
the
turbine and a generator heats it producing steam.
That steam is then fed through a cooling
compressor
to form moisture that gets condensed into
water.//// |
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Is there an interpretation of that that
makes sense? I assumed it was just garbled, and
that the way it really worked was //The turbine
first
compresses air diabatically then allows it to
expand
adiabatically// cooling it enough to condense
water. |
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I don't know. That quote just hurts my brain. Maybe //cooling compressor// refers to conventional phase-change refrigeration. Who knows. |
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(Later) Yep, following the links to the manufacturer's 'technical brochure', it's clear that it uses a heat pump to cool the air to below the dew point, and collects the condensate. The cooled, dry air is, of course, passed over the hot side of the heat pump. It's nothing but a conventional dehumidifier writ large. |
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And I was about to suggest genetic engineering... |
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I was figuring it was a small start up company that
had someone's nephew do the english brochure
translation. |
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Anyone here speak French well enough to go the
company website and see what it's supposed to say? |
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(Link provided to their English language website) |
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