solar clothes dryer

seeker · May 2009

New guy! This place is incredible!
I have many projects/ideas on my table, good to share both output and input... we all benefit.

1st is solar-powered clothes dryer. Washline works but clothes end up stiff and take long to dry. Also, windblown contaminants are a problem, living on dirt road, guy next door cutting his grass, etc. (almost forgot the birds...)

Solution might be to take a regular clothes dryer, eliminate the heating element (where the greatest energy is consumed), retain the 110v ac part to run fan and rotate drum (minimal energy) and use power of the sun to heat the drying air.

Heating the air is the core of the project.
One possible method: I have on-hand, huge heat sinks (from old ups unit) formed into a barrel-shape with air passage thru the middle. It's approximately 5" diam and 12" long, lots surface area inside due to fins. Heat up the assy with a frenal lens and blow the heated air into the dryer.

1st problem is, how to effectively transfer the suns heat to the heat sink assy.
(I can't just heat one spot with a blinding, 1/4 " point of light. Need to heat the whole outer surface of the heat sink.)

2nd problem is, how much air and at what temp can I get out of the heat sink assy.
(there's a sliding curve relating the temp vs air flow. The slower the air flows, the hotter it gets, but how slow is 'too-slow'?)

3rd problem is (maybe it's really the first problem), how much air and at what temp do I need to approximate original drying system.

So, we have a project, folks.... Any ideas?????

seeker

mike95490 · May 2009

Re: solar clothes dryer

Somebody, had rigged a hot air plenum system to his dryer, and the intake air was fed from the house attic. Cooled the attic, and dried the clothes

BB. · May 2009

Re: solar clothes dryer

Usually simpler is better (at least to start). A black metal plate in a wooden/plastic insulated box with an old sliding glass door on top is a good start (using as much "cheap recycled material" as practical). Probably a filter for the inlet air to the box (reduce contamination of your solar collector).

On problem is that driers tend to be hard on clothing--if it takes 4x longer to tumble dry your clothes--you might just be wearing them out that much faster.

Building "drying shed" with glass front and lots of ventilation to get the clothes dry, then tumbling the last bit might be a good compromise.

To a degree, these kinds of projects lend themselves well to shade-tree engineering. Build a collector and run a fan on it--graph the volume vs temperature results. Extrapolate to what you will need for a drier.

If, for example, the average electric drier is 6kWatts. And you build a 70% efficient collector, you want to dry your load in 90 minutes (same as electric drier) and full sun during the day is around 800-1,000 watts per sq. meter:

6,000 watts * 1.5 hours * 1/800 watt*hours per m^2 * 1/0.70 = 16 sq. meters

16 sq. meter = 172 sq feet = 13 foot x 13 foot "collector panel"

So--it gives you a rough idea of what you would need to power an solar heated drier. If you accept 3+ hours of drying time--then 1/2 the area would be needed. Of course, you are left with only running the drier during the daylight (through clothes in the morning, use a timer to turn the drier on at noon, etc.).

Obviously, if you have a heat source (say a hot attic like Mike suggested)--you can kill two birds with one stone.

-Bill

ehorn · May 2009

Re: solar clothes dryer

As usual, a very useful post B.B

Not knowing the O.P washing machine unit - a Spin Dryer may reduce the energy (and/or time) requirements of the drying process as well.

n3qik · May 2009

Re: solar clothes dryer

mike90045 wrote: »

Somebody, had rigged a hot air plenum system to his dryer, and the intake air was fed from the house attic. Cooled the attic, and dried the clothes

Any links??

Guess I just got my next GREEN project this summer.

BB. · May 2009

Re: solar clothes dryer

As always (as Ehorn suggests--and welcome the the forum!)--look for the simple answers first (like an extractor) before proceeding to the more jerry-rigged / Rube-Goldberg contraptions.

Here is an older drier thread that discusses the fuel options and using an extractor to get extra water out.

-Bill

jacobs · May 2009

Re: solar clothes dryer

Florida is defiantly much more humid and presents more problems than here in the west but here a clothesline works great. We've been using clotheslines for the last 45 years except when temps drop below 40 degrees. Bedding dried outside are so nice and fresh. Driers just don't cut it.

seeker · May 2009

Re: solar clothes dryer

thank you.
You can always count on good ol' american engin-oooity to get the ball rolling.

The replies are all well received and considered. The idea of using attic air rang my bell, since my attic runs 125-140 degrees in the summer, but there's one major drawback... how much itchin' can I stand before I go crazy? I'm afraid all the fiberglas insulation dust living up there would be force-injected into the clothes. Filtering? possibly, but wouldn't want to chance it, now that I think about it. Better I just add more insulation up there and try to improve the air flow to cool things down.

Next idea makes the best sense so far... get as much of the water out of the clothes BEFORE trying to dry them. My old washer has a spinner, but clothes still come out heavy all the way to the washline. Maybe I hook up couple old dryer drums to the front axle of my wrecked toyota and spin away? Don't laff... farmers used to cut logs that way!

Actually, all these alternatives to the 'solar clothes dryer' work great IF the main idea is ONLY to dry clothes. Unfortunately, I got slightly off track here... I live in Florida. Hot Florida. Very hot Florida. Did I say It's hot here?

It is just such a shame to have all this energy all around me and not do something with it!

The clothes dryer was an attempt at doing this, especially attractive because of how much energy it takes to provide the heat! Heavy-duty spinning the stuff makes much sense, so I will get right on it. Not sure where I'll go after that, to get them all the way dry. I do like the idea of weighing the clothes before and after the wash cycle to see how much water is left in them. Data is always dear.

But now what do I do with all these (free) rays falling all over my back yard? (Maybe find a way to heat some air with them and run it into my clothes dryer?)

Hope to be back with another 'hair-brained' idea.

Thanks for the help, folks, and keep thinkin'. ...keeps the altz-imers at bay.

seeker

ehorn · May 2009

Re: solar clothes dryer

seeker wrote: »

...But now what do I do with all these (free) rays falling all over my back yard? (Maybe find a way to heat some air with them and run it into my clothes dryer?)...

seeker

In addition to being energy hogs, conventional clothes dryers increase whole house heating and air conditioning bills by drawing a large volume of conditioned air out of the building through the dryer vent, which must then be replaced by unconditioned outside air that is sucked in through unplanned small air infiltration leaks around the house adding to energy costs.

A conventional clothes dryer might be relocated outside of the conditioned inner living quarters of a home, with a planned path for air blown out of the dryer vent to be replaced.
In the summer, a clothes dryer outside of the conditioned airspace does not increase expensive air conditioning bills. In the winter (for those who live in colder climates), a large family that does a lot of laundry could consider installing a simple air-to-air heat exchanger to recover some of the expensive heat from the clothes dryer, and use it to warm air in the conditioned interior living space.

Now if your floor plan supports a small, south facing area, you could consider creating a "drying closet" - similar to BB's suggestion, where a solar heating panel might look something like this.

Then, in conjunction with a water extractor, the nearly-dry high-RPM-spun clothes could be hung in a passive-solar-heated closet (with a tiled floor) where warm, dry moving air would quickly finish the drying process, in potentially less total time and less labor than an expensive conventional clothes dryer consumes today, without damaging delicate clothes. The drying closet would take the space normally occupied by a clothes dryer. This technique would have minimal/near-zero-energy consumption.

Best wishes

seeker · May 2009

Re: solar clothes dryer

Thanks, Ehorn! Wonderful ideas. I already isolated my current laundry room from my air-conditioned spaces, and added a small exhaust fan to vent the hot, moist air directly to the outside. I'll leave the w&d in place for 'rainy days', or, to keep the xyl happy. But I'm hoping to create a new lr according to some of the ideas given here.

The spinning-wheel and the can-pipe heaters look like candidates for a beginnning.
thanks again!
seeker

Dave Angelini · May 2009

Re: solar clothes dryer

Bugs, dust, stiff results, and pollen made us try moving the clothing into the garage. Dry time is longer but who is counting. Might not work in Florida but up here in the Sierra it is great. Hang a line with a quick disconnect and that is about it.

BB. · May 2009

Re: solar clothes dryer

I line dry in my garage too--Only problem is during winter--the additional humidity causes us a mold problem. We also line dry in the winter--but only during the day with windows/doors open--then toss in the drier to finish off (much less energy required).

-Bill

Brock · May 2009

Re: solar clothes dryer

One cheap quick & dirty way to warm up air is to use that black NON-perforated black corrugated drain tile, 3 or 4 inch in diameter. Just lay 100+ feet out in the sun and put a fan at one end and you have an instant heater

If you can keep it off the ground in cooler weather you will retain more of the heat. For some reason though my wife won’t let me leave 250 feet of 4 inch tubing laid out in our back yard connected to the fresh air intake for the house in winter

n3qik · May 2009

Re: solar clothes dryer

For filtering I am looking at using an old panty hose for a filter.

System2 · August 2009

Re: solar clothes dryer

You can always use a hybrid system of clothes line (solar) until they are just about dry and then put them in the dryer for the last 5 minutes to get rid of the wrinkles.

RCinFLA · August 2009

Re: solar clothes dryer

I really like the hot air plenum system idea. Only concern is picking up some of the fiberglass insulation particles from the attic. Really bad for drying jockey shorts.

Kamala · August 2009

Re: solar clothes dryer

Boxers, no problem! Well, not so much anyway.
Or just go without. :cool:

System2 · September 2009

Re: solar clothes dryer

How much heat can you get using the black PVC tubing?

- Joe

mike95490 · September 2009

Re: solar clothes dryer

JoefromPhilly wrote: »

How much heat can you get using the black PVC tubing?

- Joe

Not much, the plastic has a low heat transfer rate, so while it's hot outside, it's cold inside, and takes a long time to transfer.

Black oxide copper is good, but pricey.

tallgirl · September 2009

Re: solar clothes dryer

Brock wrote: »

One cheap quick & dirty way to warm up air is to use that black NON-perforated black corrugated drain tile, 3 or 4 inch in diameter. Just lay 100+ feet out in the sun and put a fan at one end and you have an instant heater If you can keep it off the ground in cooler weather you will retain more of the heat. For some reason though my wife won’t let me leave 250 feet of 4 inch tubing laid out in our back yard connected to the fresh air intake for the house in winter

Let me guess -- she agrees with Ed Bagley's wife if y'all ever watch his show on "Planet Green"?

How about a closed loop system -- some 4x8 solar thermal panels with an air-cool heat exchanger? You could use a heater core from an old car for the exchanger.

System2 · November 2009

Re: solar clothes dryer

Another way to solve the problem is to use a centrifuge which will extract the vast majority of the water in only about 2-3 minutes at a fraction of the cost of a regular clothes dryer.

your link has been eliminated as it was a rule violation, niel

System2 · April 2010

Re: solar clothes dryer

Lots of great ideas - I especially like using the heat from the attic. To get around the problem of insulation bits in the air, why not put some type of puncture-resistant air bladder in the attic space? Air could come into the bladder from outside when dryer is not in use and from inside when the dryer is running.

So:

The air in the bladder would (in theory) be heated by the surrounding air in the attic. This would serve intake air to the dryer as it's fan pulls the air in.

The air used will already have been filtered by the house's air system. I would suggest putting the intake for the bladder in the ceiling over a door or window so that the bladder gets the warmest available air from within the house.

But:
The bladder would need to be sufficiently big enough to be able to heat the air from the intake to an acceptable temperature for as long as the dryer needs to run.

This is a rough sketch, of course. Anyone else have thoughts on how this might work?

BB. · April 2010

Re: solar clothes dryer

An air bladder is probably not going to work...

A typical (US) clothes drier exhausts around 200 cubic feet per minute. And runs for 1 hour (depending on clothes, temperature, humidity, etc.).

200 CFM * 60 min = 12,000 CFM
12,000 CFM / 8 foot ceiling = 1,500 sq.ft.

That would require a bladder of a good sized 2-3 bedroom home to supply that amount of air. I doubt that most people have attic areas of that volume available.

And given that the hot air from the attic would not be as not as hot as that from the heating system (around 150-190F)--then you would need more volume of air than my first estimate to dry the clothes.

-Bill

Cariboocoot · April 2010

Re: solar clothes dryer

BB. wrote: »

An air bladder is probably not going to work...

A typical (US) clothes drier exhausts around 200 cubic feet per minute. And runs for 1 hour (depending on clothes, temperature, humidity, etc.).
200 CFM * 60 min = 12,000 CFM

12,000 CFM / 8 foot ceiling = 1,500 sq.ft.

That would require a bladder of a good sized 2-3 bedroom home to supply that amount of air. I doubt that most people have attic areas of that volume available.

And given that the hot air from the attic would not be as not as that from the heating system (around 150-190F)--then you would need more volume of air than my first estimate to dry the clothes.

-Bill

Lower temperature = longer time. You don't really need to blast clothes with very hot air to dry them if you can be patient!

You could put many, many feet of duct work through the attic to act as a heat exchanger. But attics are hot in the Summer, not Winter, so where is the advantage over a clothesline?

russ · April 2010

Re: solar clothes dryer

When in the end he figures out how many kW it is saving İ expect the whole topic gets dropped.

My dryer uses about 2 kW and we run it once a week - İ am not going to put much effort into lowering that.

System2 · April 2011

Re: solar clothes dryer

We have a specific challenge. It is along the line of the scene in the movie Apollo 13 when the engineers pour a box of items available to the astronauts to repair an air filter and the engineers have minutes to make it work. I am with Days for Girls International and we provide washable feminine hygiene kits to women in impoverished nations. However, one issue that comes up is the need for a quick, private and compact practical drying option. All this would have to be accomplished with things that one could easily find in impoverished communities. A #10 can? A shoe box? An umbrella lined with foil? There is little space in slums, and taboos make hanging items just anywhere impossible. Hanging items inside a dank room won't work. Some areas are humid. We have been brainstorming but we could really use some genius to innovate some possibilities for women all over the world. Hoping you have some ideas! You can learn more about us at Thank you!

the links were edited out as solicitation links are not allowed no matter how righteous the cause. niel

russ · April 2011

Re: solar clothes dryer

@ Celeste - Have you ever been to the slums you are talking about?

I have, to a number of them - they are usually located so you have to go in the vicinity for business purposes.

Is this personal thingy dryer really very high up the slum dweller's priority list?

Russ

solarvic · April 2011

Re: solar clothes dryer

I was thinking sort of the same as tall girl before I read her post. Outside wood furnaces operate about the same as her idea. The furnace heats the water and circulates thru a heat exchanger you install in the furnace and the furnace blower blows the heat thru your registers. Since you are in florida you probably wouldn,t want an outside wood furnace but us people up north could use this. If you can think of a good way to heat the water you could get a woodstove heat exchanger. Tall girl had a good idea on how to heat the water. If you live where there is gas just get a gas dryer as they don,t use much electric. I figure my gas dryer uses about 150 to 180 watts to dry a load of clothes but I do have an LG energy star frontloader that spins out most of the water. :Dsolarvic:D

mike95490 · April 2011

Re: solar clothes dryer

CelesteofThrive wrote: »

We have a specific challenge. It is along the line of the scene in the movie Apollo 13 when the engineers pour a box of items available to the astronauts to repair an air filter and the engineers have minutes to make it work. I am with Days for Girls International and we provide washable feminine hygiene kits to women in impoverished nations. However, one issue that comes up is the need for a quick, private and compact practical drying option. All this would have to be accomplished with things that one could easily find in impoverished communities. .....

Solar drying oven (get a picture of a solar oven in your mind, but
we want to move air through it)

Cardboard box
glass or plastic side
paint inside dark color
outlet air slots
inlet air slots

sunshine makes it hot, air rises and circulates out, fresh air in.

Also, look up in "Build it" sites for Solar Air Heater - same idea, needs a clear cover on one side, air in, hot air out.

Peter_V · April 2011

Re: solar clothes dryer

CelesteofThrive wrote: »

We have a specific challenge. I am with Days for Girls International and we provide washable feminine hygiene kits to women in impoverished nations. However, one issue that comes up is the need for a quick, private and compact practical drying option. All this would have to be accomplished with things that one could easily find in impoverished communities.

Try googling "Solar Food Dehydrator" and see if any of the ideas are workable with the items on hand. Anything designed to rapidly dry fruit etc, should work even better on clothes.

Perhaps something like this:

Note: the "Drying box" does not have to be open to viewing so this would allow the desired privacy of the contents.
You could even put the solar collector (angled part) outside a wall with the drying box on the inside.

russ · April 2011

Re: solar clothes dryer

Right guys - I don't think you have ever seen the slums she is talking about.

This is one of the country club type of things where everyone has a couple glasses of good wine - says some wonderful things and goes home congratulating themselves.

There is normally sewage running in the walkways
There is very little sunlight gets gown to ground level
The building code is using any old stick or piece of plastic you can lay your hands on
Anything left laying out of sight will magically relocate itself to another shelter

Russ

solar clothes dryer

Comments

Categories