Heat Reclamation

TUESDAY, NOVEMBER 18, 2008

Heat Reclamation
You may be saying to yourself, “I wonder what kind of whack-o schemes and projects that wing-nut has been up to lately?” Well, I’m glad you asked.

For one thing I (and some hardy friends!) have been trying to see far into the season we can go without turning on the central heat in our homes. This is based on several motivations, including an interest in human physiology, and the fact that the price of heating oil was over $4/gallon when I thought up the idea. But that’s all for a different post. Anyway, I’m aiming now for December 1st, and so far, doing quite well– right now it is 32F (0C) outside, 51F (11C) inside, and I’m typing quite comfortably. We’re allowed to use space heaters, judiciously, but for the most part I haven’t needed to. I have noticed that my house is forming icicles sooner than my neighbors’. Good sign!

So, as part of my overall strategy to reduce oil use, I decided to fashion my kitchen into a winter-bunker. It’s a large kitchen, and already has the sofa, DVD player, etc. in it– not to mention all the food– so I really could just spend the winter in this one room. I made a insulated curtain for one kitchen doorway from a thick quilt, and have bought an old salvage door which I am working on installing in the other doorway. When done, I’ll be able to seal off the bunker from the rest of the house, and, I hope, just stay warm with a space heater. Cool, no?

In the process of all this I got to thinking about the clothes dryer, which is right under the kitchen and vents outdoors right next to the window. In past winters I’ve enjoyed watching the dragon-breath of steam wafting up past the window, and admired the snow-free zone which was kept cleared around the vent all winter. The other day I looked at the dryer to see how much energy, exactly, it uses in doing its thing. Guess what? 5,600 WATTS! Yeah… that’s a lot! Also I got to thinking about the huge VOLUME of air the dryer sucks out of the cellar, which is being replaced by frigid outdoor-temp air rushing in through all the gaps in our cellar windows, etc. Terrible!

I’m considering some type of clothes line for the summer (though my yard is awfully small and shady), but in the winter line-drying isn’t a good option at the Palace. So, for this season, I started to think of ways to reclaim the heat from the dryer, rather than dumping it outside. First idea: just undo the vent hose from the exit hole, and redirect the warm air back into the cellar. E-Z, and stops the air-sucking-out problem, but it seems no good to be humidifying the very air you’re trying to use to dry things. Plus, what good, really, does warm air in the basement do?

So I thought next about instead running the hose up to the kitchen, where the warmth would be useful, and even the humidity might be desirable (in the winter). But as I pictured the amount of humidity involved, and envisioned the dank, dripping windows, etc., as well as the pleasant-only-in-small-quantities aroma of dryer exhaust air, I decided against this as well.

Third incarnation, I thought about sourcing a surplus old iron radiator (Smallish State is littered with such), putting it in the kitchen, running the dryer house in one end of it, another hose out the other, and thence to the outdoors. Thus some of the heat would get transferred from the dryer air to the radiator, warming the kitchen, but the moisture would still get blown outside (some water might condense inside the radiator, but that’s okay.) However, I still pictured half or more of the heat escaping outdoors, which bothered me. And the problem of cold-air-suck remains, because you’re blowing the exhaust outside.

So, for Theoretical Version 4.0, I mentally added a condensing coil of copper tubing to the hose after it leaves the house. Then, another hose at the bottom of the coil returns back inside, downhill all the way, before turning up at the end. A small hole at the low point of the “U” is made, with a bucket below. Water in the humid air leaving the house condenses running through the cold coil, runs down the exit hose, falls into the bucket. The air, now cooler and drier (but still warmer than ambient outside temperature) is returned to the cellar. Voila! Maybe. Suggestions?

POSTED BY TURBOGLACIER AT 5:59 PM
11 COMMENTS:

Johanna said…
Interesting…

Though I challenge your assertion that you need a dryer in the winter. I don’t own one here in this Canadian climate, the vast majority of Europeans have never owned one, and we have no difficulty at all drying everything on racks. It might take a bit longer right now, with the heat off, but once it’s on things dry overnight (better for the clothes, too).

If you are wedded to the idea of having a clothes dryer, I wonder if you could retrofit a heat exchanger like on condensation dryers. I wonder about the insulation loss of running extra pipes outside and in, through either double glazed windows or a window and a storm window. In my climate, the copper coil would ice up fairly quickly.

I’m also confused about your house building icicles sooner, since, given similar sun exposure and the same ambient temperature, icicles will be more common on buildings with greater heat loss. Maybe the cold miser needs an energy audit?

11/19/08 7:09 AM
charlsiekate said…
How is your tropical roommate adjusting to the no heat thing? The low here in Georgia was 24 last night, which I’m sure is laughable to you New England folks, but we definitely enjoyed the heater. And a warm puppy at the foot of the bed.

Of course, I imagine our house is designed more for the summer heat than the winter cold, and I’m sure my house doesn’t have a heater that uses oil.

11/19/08 9:25 AM
Turboglacier said…
J: I may go with “drying racks” at some point. But space is limited here, and with multiple people doing laundry– well, I don’t know. In general these “European ideas” of which you speak are notorious for leading countries into socialism, prolonged life-expectancy, and other evils.

Heat exchangers– yes, looked into, but they are expensive to buy (like, $500) and not easy to build. And have to have a second fan, so need electricity, blah blah. I don’t think there would be much insulation loss– I’ve already got a hole through the basement wall for the existing exhaust hose, so I’d just use that (the hoses would really go through a window– that was just artistic license, and so I could draw clouds.)

Icicles: In mid-winter, I’d agree with your assessment– icicles form from buildings melting the snow on their roofs, which water then refreezes dripping off the eves. But we’ve had no snow yet, and the temps have barely been dipping below freezing. The icicle in the photo formed from the dregs of a rainstorm dripping off the window sill as the temp dipped down just to freezing over night. I believe my neighbors’ walls did not form any icicles because their excessively-heated walls kept their exterior temperature above freezing, preventing any ice from forming.

CKate: Luckily for Tropical Housemate, he moved on several weeks ago (he was only temporary). He would NOT enjoy what’s going on here now (this morning, e.g.: 28F outside, 50F inside.) In stroke of fantastic luck, I’ve found a new (more permanent) housemate who grew up in Caribou, Maine– frequently in contention with Bismarck, ND for the coldest spot in the Lower 48. So she will, I hope, feel right at home here. Also, she’s bringing two more cats, so we will have all that extra warmth!

11/19/08 10:21 AM
Turboglacier said…
Excuse: above should say “(the hoses would really NOT go through a window…)”

11/19/08 10:23 AM
The MSILF said…
I also don’t have a dryer as this apartment doesn’t have the hookup, and use the racks, which fold up completely…and it’s cold here in winter, not like your cold, but still…inside it’s cold. Now I’d really never go back. It seems so unnecessary. And I think here, where it’s also dry, a lot of people just redirect the dryer vent right back into the room in winter.

11/19/08 12:26 PM
Claire Colvin said…
I realize the schematic is just an artist’s rendering and not to scale, but I’m wondering about the length of hose/ pipe involved here. Any way to test if the exhaust output of the dryer moves at a sufficient velocity to force the air all the way through the lengthened system?

11/19/08 1:58 PM
Turboglacier said…
“Test” it? Of course there’s a way to “test” it: build it, and see if it works! How else?

11/19/08 3:03 PM
Rossie said…
Forgive me if this is answered farther down in the post – I stopped reading with the first sentence of the second paragraph as I am absolutely dumbfounded. You live in New England and are trying not to use heat? in the WINTER?? and other people have joined you in this effort???

Words fail

11/21/08 10:19 PM
Turboglacier said…
Rossie:

Oh yes– just so.

And some of the others who have joined are actually north of New England. J., are you still in? Sort of?

[Right now: 22F outside, 42 in my bedroom, and 53 here in the kitchen bunker with one space heater on. I’m wearing normal clothes, a hat, and down vest. Have been for comfortable for hours.]

11/21/08 11:52 PM
Anonymous said…
something to consider:

the fine particles in dryer exhaust air(lint) can be potentially explosive if the suspended level of them in the air gets high enough.

you might want to exhaust the air into the top of a bucket filled with water (or get a commercial product similar to http://www.indoorlinttrapfilter.com)

Also heat exchangers can be created simply from easy to get materials.

1)figure out how many sq.in.(cm) you need(= to the cross section of your dryer exhaust)

2)divide the number into a number of 1/8th-1/4 in.(2-5mm)slots.

3)double the number of slots from #2 and figure out how many dividers you need(to separate the slots from each other)

4)accumulate(drink) enough pop/beer (as long as it comes in Al cans) to provide the raw material for your dividers.

5) remove the top and bottom of the cans and cut your material into the correct size (4-6″ squares depends on application and raw material).

6) using cardboard(or something similar) as a spacer create a slot that is open on 2 opposite sides(closed on the other 2). I have found that the Al tape you can get for duct work is perfect.

7) keep adding dividers to your creation alternating which side is open. when your done you want to have made something like (O#O#O#O#O#O) on one pair of sides and (#O#O#O#O#O#) on the other.

you should pre-filter the dryer air to keep the HE from filling w/ lint. you will also need to deal with the condensation. if your exhaust is still too warm add another exchanger or a small fan to pull room air through the other sides.

YMMV- good luck.

12/10/08 12:07 PM
Turboglacier said…
Thanks for the tip on explosive dryer dust, Anon. I found that putting a fine kitchen strainer or a scrap of nylon mesh over the exhaust does a good job of filtering the vast majority of it.

While the http://www.indoorlinttrapfilter.com device is clever, I can’t approve of it for heat-reclamation purposes. Running the dryer exhaust over a pool of water adds even more moisture to the house, causing (ultimately) further cooling. “After a few dryer loads”, the website says, “you simply pull the drawer out and refill back up with water.” But you pay energetically, one way or another, for all that additional water you evaporated…

12/10/08 12:55 PM

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One Response to “Heat Reclamation”

  1. Carl Says:

    Some thoughts from down-under (Auckland, New Zealand). Just stumbled across your blog as I’m looking for heating solutions coming into our totally mild by comparison (!) winter here…

    What would happen if you ran the dryer outside on the porch (do you have one?) and directed the warm humid air outlet back into an appropriate room of the house? Challenges:
    1. Would the dryer still function outside in very low temperatures? If a problem, this could be solved by building it’s own little “kennel”. (Hey, if you have a dog already, build him a bigger kennel and put the dryer at the back; I’m sure it’d love the heater when it’s going!!)
    2. Outside power? You don’t really want to run an extension lead out a window in winter! Just more draughts. So there’s cost in getting an outside plus wired properly.

    Our problem here is not dryness in winter but humidity (you won’t catch me venting a dryer into my house; in fact our whole laundry is located away from our house in a garden shed! Hence the kennel idea).

    My goal this winter is not to emulate your project (!) but rather to as efficiently as possible warm up and maintain our two bedrooms’ temperatures up from 50 to 65 degrees and maintain it overnight, especially in our young kids’ room. To do that we are running 2 x 250W dehumidifiers constantly to bring the humidity in each room down from 75% to hold it around 50%. This alone is naturally raising the temperature in each room a few degrees (dehumidifiers blow out air at a slightly higher temperature than it goes in) and therefore will hopefully reduce the amount of time our other more power hungry heaters are in operation, as they won’t have raise the temp as much and it’s easier to raise drier.

    I have been unable to find any commercial heat company here in NZ promoting effective pure dehumidification as a strategy to reduce winter heating cost in Damp. There are lots of “Positive pressure Ventilation” and “Heat Retention/Recovery” kits available. But all they do is suck in cold damp air from outside or your roof cavity and blow it across your windows to remove condensation, which gives you the impression that you have a drier house, but actually all they do is keep the damp air moving so it can’t settle anywhere (that’s my opinion anyway).

    I’m not sure if your Northern hemisphere logic could come up with any better solutions to my strategy but I thought I’d mention it in case you got bored with the science of “cold and dry” 🙂

    Keep up the good work. Great Blog

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