Solar fruit/veggie dehydrator

[madlabs]

Hi All,

I'm going to make a solar dehydrator in the next few weeks to be ready to harvest this year's bounty from the garden. Looking around the web one finds quite a bit of info, but I was wondering if folks in this group might have some first hand information or designs to share. Or any good places to go and ask questions.

Thanks!

Jonathan

[GaryGary]

Hi Jonathan,

I've tried to assemble some good DIY first hand solar food dryer projects here:
http://www.builditsolar.com/Projects/Cooking/cooking.htm#Drying

If you want a way to get your feet wet without much cost, I saw one the other day built from cardboard -- pretty simple.

Gary

[Bruce S]

Took me a little while to sift through my Mother Earth News mags ( kept getting side tracked by an article or two ) .
Once I found what I was looking for I looked it up on their website.
Here's a link
http://www.motherearthnews.com/diy/recycleable-solar-dehydrator.aspx#axzz2XF6ukQ8e

This was one that I built just 'cause it looked so easy to do. This bugger gets toasty! Takes a long while here in the muggy midwest but it worked! I no longer have it I've gone onto a bigger unit I get get pics of ours , but its not one this easily replicated since it was made out of a double wide speed rack and black weed barrier  (5feet wide 5feet long 6feet tall) reaches well over drying temps by 11AM
 

[madlabs]

Thanks for the links guys. I think I have settled on the Appalachian style similar to the one linked in MEN. Here is a great pdf with good collector info:

http://appropriatetec.appstate.edu/sites/appropriatetec.appstate.edu/files/HPImprovingSolarFoodDryers.pdf

I'm planning on making the collector able to easily separate from the rack housing, for easier winter storage. I might even make it possible to change the angle of the collector, although I imagine I'll be mostly using it during late summer fall, with some strawberry drying in the spring.

What did y'all use for racks? I'm thinking of making mine from wood and stainless mesh, but the mesh price isn't cheap.

Thanks!

Jonathan

[DamonHD]

That's a very interesting PDF: thanks for the link.

Rgds

Damon

[Bruce S]

We went to places like goodwill and bought the cookie racks mostly SS or coated wire racks that can be used in the oven. Chefs call the size 1/2 sheet which means about 30 inches wide.
Others I've built using the black plastic replacement screen stretched tight over 1x2 plastic wood. NOT had any problems with loading them up even with tomatoes.
Best luck ! the hardest part after drying is NOT eating them!
Cheers 

[madlabs]

Bruce,

Do you also use solid sheets for really juicy things so that it doesn't drip?

Jonathan

[Bruce S]

Not directly no, we usually put a cookie sheet under the juicy ones.
We've found that putting them on solid sheets causes problems.
As the heat builds up the solid sheets get hot and either start to actually cook the tomatoes or cause the fruits to not dry correctly. Lost a whole sheet of bananas that way.
I'll get pictures up here of dried hot peppers and tomatoes if you'd like.
I can take pics of the unit too with the covering off. Squash, tomatoes and peppers are packed away and unit is due for a baking soda wash while the next round of stuff (Apples, cherry tomatoes) coming into season.
We grow indeterminate varieties when possible.
Cheers   

[madlabs]

Ahh, that makes sense. Glad I asked.

Another question. I was thinking of making the trays seat against opposite sides to make the airflow sorta "S" curve over the trays. Hope the ascii art below helps that make sense.

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I was thinking of this because it seems if the trays are fully loaded that airflow might be restricted.

Thanks!

Jonathan

[Bruce S]

We do stagger them left to right, since the sun rises on this from the right. I will also warn you about using black or dark colored pans  .
They get real hot real fast! I'm forgotten a time or two and keep earning why to wear gloves or use a towel. I use old black metal shelves to "assist" the bottom with getting heated up so I can try using a 12Vdc muffin fan for quicker drying, those bad boys get hot PDQ.

[Frank S]

 I'm not much on vegies or fruit but do like to dry herbs & other spices. While in Spain a couple years back I met a man who uses a similar unit like you guys have described to dry fish and pork.
 I used to make sun dried beef jerky on my balcony in Kuwait by using simple aluminum foil reflectors 

[Bruce S]

Hey Frank S;
Glad you chimed in here too both spots you you've been in or are now at are relevant to needing lots of sunshine.
I stayed away from pork! not because I don't like 'cause I do love a nice rib, but pork unlike beef is unforgiving. We do a lot of dried stuff but I know my limits .
However I have dried both Swia, Talapia and Crappie; All are white meat fish and all dry nicely.
 

[madlabs]

Got most of the wood I'll need today, some full dimension cypress 1X8. Probably won't get to it until next week, I've gotta collect a few more materials. I plan on starting with the collector.

I'm gonna do beef jerky for sure and maybe some turkey for my sis who doesn't like beef. Although I'm thinking that when she has some awesome beef jerky she'll like it. I'm thinking some curry jerky.... Mmmm.

Jonathan

[Frank S]

Hey Bruce S; One thing you have to remember with pork is a fresh Kill has to be chilled down as soon as it is blooded then you smoke it in a smoke tent for 4 days. My Great Grandmother used to have my dad build her a smoke tepee every winter. it was 3 men lying down head to toe in diameter and half again taller than that.  Then  weaved a thatch cover several layers thick with green ceder branches  OK he didn't have buckskins to cover it with so he used the canvas from an old Marine tent. the inside was full of drying racks and a stone hearth.
 Now remember I was only 5 or 6 years old the last time I saw this so memories are not 100% but I do know the hogs were killed only if there was ice on the cistern.

[madlabs]

Frank, my grandad had a smaller but similar set-up. He had a canvas teepee too and put a BBQ type thing in the center. Like you, I was too young to really learn what he was doing but it sure was good.

Jonathan

[Frank S]

Madlabs; My great grandmother on my dad's side was half Comanche My Great great grandmother on my mother's side was half Cherokee One of her sisters was taken as the wife to the chief of the Crow nation over half of the folks with the last name of Crow around Lawton and Walters Oklahoma are my cousins. The Native American way of cooking runs in my blood but sadly for too many years while growing up and while in the military and after I was more of an Apple than a pomegranate so much of the cuisine was not passed to me.

[madlabs]

No native American in my blood. Gramps was a classic farmer type with a dose of redneck. He liked the simple life, though and being self-sufficient. No idea where he picked up the teepee smoker but I do remember the stuff being really good. He also made what he called "apple jack" where he took some hard cider he had made and left a container of it in a snowbank. When it froze he poured off the liquor into a jug. Sometimes when we were shoveling snow he would give me a little nip. He had to do this 'cuz my Grandma was dead set against alcohol, although I bet she knew. :-0

Jonathan

[Bruce S]

IF you have a good place to find digital Thermometers grab a couple (WE use 3) they will come in handy to find out if you have hot or cold spots. Both can be dealt with by using little muffin fans and a small solar panel/battery.

[madlabs]

Bruce, I have a digital humidity/temp sensor that I am going to make a little display for. I also have a couple of stainless dial type thermometers that I plan on incorporating too. I want to be able to see what is going on in there.

Jonathan

[Bruce S]

Good plan.
We went the same route to make sure all was going correctly. My wife is a pastry chef ,so ya know we already had the thermometers 
I've built others that did not go well. Luckily we were testing them on chile peppers and okra.

[madlabs]

Bruce,

After getting distracted by the hot tub last week I am getting back to the solar dryer. Now that I am making an actual plan, I have a few questions.

What is the sq/feet of your collector?

What vertical spacing do you use between racks?

How much gap for airflow on the side of each rack?

What size racks?

So far I think I have decided on a 2 'X 6' X 8" collector with acrylic for glazing. I think I am going to make a metal frame so that I can remove the collector and drying box to put inside for the winter. I'm going to set the angle for my area's spring/fall setting.

Jonathan

[GaryGary]

Hi Jonathan,

You might also consider using SunTuf corrugated polycarbonate glazing -- most Home Depots sell it for about $1.25 a sf.

The polycarbonate will hold up to much higher temperatures (270F), and will take a lot of abuse, and the corrugations make it a bit stiffer.

But, I think the plex would also be OK for this kind of collector as long as you don't let it stagnate (no airflow).

Gary

[madlabs]

You are quite right about the plexi, bad idea, heavier and more expensive too. Right after I posted that I think I decided to go for this Sunlite HP glazing:

http://www.solar-components.com/sun.htm

Lighter, cheaper. Kinda thin though. The thing about currogated is it's harder to get air-tight, but I'll take a look at that too. I also decided to make the collector 3'X5', a little more area and puts the drying cabinet closer to the ground.

Thanks!

Jonathan

[Bruce S]

Bruce,
What is the sq/feet of your collector?

What vertical spacing do you use between racks?

How much gap for airflow on the side of each rack?

What size racks?

So far I think I have decided on a 2 'X 6' X 8" collector with acrylic for glazing. I think I am going to make a metal frame so that I can remove the collector and drying box to put inside for the winter. I'm going to set the angle for my area's spring/fall setting.

Jonathan

ML;
Mine is certainly not your typical setup.
Here are the dems.
H=72 inches W=48 inches D=24 inches. with a rack spacing of 5 inches bottom to bottom. It is ALL metal , even the wheels are metal. The covering I  use is the weed barrier sold at SAM's and big box Home improvement stores. I'm careful in ti I choose to have the barrier side out for when it rains, thus lowering the possibility of getting wet inside during summer popup storms.
Inside width is 22inches on both sides of the rack with a ledge that is 23/4 wide on each side allowing us to use the resale shops finds on older cookie cooling racks.
With an over cast day like today I've had a constant temp of ~101F I also have the plastic replacement window screening there to keep pests like gnats and fruit flies out.
We do not load it up like now like we have in the past and we alternate the drying racks so the air flow is better. It's been rather cool in St. Louis these past weeks only reaching low 80s so drying is more than usual.
Hope this helps.
Best of Luck!

[Frank S]

Bruce S brought up 1 interesting point. Every solar dehydrator that I have seen was a haven for insects and pests.
 most folks don't think about these at the time they construct them the odors will attract just about every air breathing critter on the planet . Think you could construct one that you could pull a vacuum on and there would still be some life form that would find a way inside, or fly around or hide under it so placement is very important.
 I know folks in Spain and Eastern Europe who have them built into the side of their homes they cn load and unload right from their kitchen but they have a tight sealing door to help keep out the uninvited

[madlabs]

Serendipity has weighed in!

As I was drinking morning coffee and pondering things like welding up a frame for the dehydrator and so on, I noticed the angle formed between the top of my picnic table and the bench and thought it looked a lot like the 35 degrees I was looking for. Break out some tools and so it is! Exactly! And the distance from the table to the ground is 5', exactly what I wanted!

So, I'm going to use the table for the base and make a collector and cabinet that can be easily seperated for storage. Sure, it might be in the way sometimes but is an 8' table, so plenty of room. Much easier to build with no frame requirements.

Bug protection for sure. Mine will live inside when not in use, but still need bug protection to the max. I am also going to line much of the inside with metal for easy cleaning.

I think I have a plan in mind and most of the materials to start with. So later this week after my 48 hour shift it will be time to get building.

Thanks for all the help!

Jonathan

[Bruce S]

As promised, here are some pics of my solar drying rack.
Once the tomatoes are dried, I'll be able to better get pics (If wanted )of the inside.
I do have herbs (oregano, basil, Kale, dill & cilantro) waiting in the wings I could take picks of those once hung and just before closing up for the day.
With a cool front moving into St. Louis and dropping temps from mid 90s to mid 70s but very sunny I took a picture of the probe I stole from the wifey .
[ Specified attachment is not available ]
This is the rack after cutting away to roll of weed barrier , but not yet trimmed out.
[ Specified attachment is not available ]
Nearly finished, I left enough cloth to roll for weights
[ Specified attachment is not available ]
My Apple test at end of 95F outside temp day, with inside hitting a sustained 103F

The probe inside. Outside 75F at 10:00 AM CST inside shows 95F
Sorry for the large pics! I'm testing a new image program and it's not playing nice!

Hope this helps
Bruce S

Just edited the pics and messed up the nice arrangement  , but at least they're not so large .

[Bruce S]

Here's the results of my tomato test along with a few other items.

This is why I normally put some type of weight on them. They are ready for the vacuum bags. I usually put in a little bit of white rice just in case.

In the mid-west humidity can be a problem  . So I have this as an inexpensive backup to fancy one.
[ Specified attachment is not available ]
I use old Apple tree branches for hanging herbs to dry.

[madlabs]

Bruce,

thanks for the pics! looks yummy too. I got a good start in on the collector for mine. Took some pics but I am away on my 48 hour shift so I'll post ;em when I get home. It's coming out pretty well, but I think I am going to make a frame instead of using my picnic table. This bugger is going to be bigger and heavier than I thought. Sigh. Bunch of cutting, welding, fitting and painting in  my future,

Jonathan