C5 for what its worth when I took a course from a top expert in dehydrator, from small backyard ones to travelling around the world to help work on making huge ones for whole villages to use.. without a solar run fan to move that air around, he said that if we had to "just do" passive solar, we could expect upward loss's of 60 percent on the average year.. he had a chart on the number of days in area's of Canada and other countries on the days that would give good passive solar drying, and let me tell ya.. its not a lot of days at all in the grand system and it often comes at times in the summer when we are not having a overflow of things needed to be dried from the gardens and then when we do need to be able to a lot of drying, we have already passed the prime days..

FG

Farmgal, have you had any experience with the modified passive solar dehydrators that flow top-down? I've heard they're 30%-45% more efficient and don't typically require any forced air modifications.

Much better for our Canadian climates.

I'm about to make 4 or 5 different versions to begin testing with next spring. Possibly even this fall for apples, etc if the weather cooperates. But most of my time and money and resources will go into the 2 most promising versions.... it'd be nice to be able to settle on which those may be. lol

Denob [ "Split this topic from here on to Passive Solar Dehydrators..." ]

Well, That was a strange swicheroo. Oh well.

Ive had great success with small versions of this. Somehow, it hasn't scaled up. It should be a hot rod of dehydrators. It should be cooking...but its not and Im scratching my head trying to figure out why this hotrod is running like a banana is shoved up the tail pipe. Ive got 3 ,yes,3 boxes made from sliding door windows. The best ones only have one. Im wondering if its the glass. Does the sliding door window have some type of heat shield. Is the 2 layers of glass supressing sun penetration. Ild be getting better air movement by the wind alone.

Im too stubborn to jump to the electric fan at this point though I have a couple extra solar panels lying around if I need them. It would defeat the purpose. LOL. My dehydrator doesn't suck...but that's the problem. I need it to suck. Im about to cut more roof vents...but Im guessing its the windows. Any window installers in the House?

I basically have a supped up version of the first one in this YT clip but with three panels so it generates first thing in the morning till the sun goes down in the evening.
http://www.youtube.com/watch?v=oVTcnCuX2Qc
Ill have photos when its done...but first I must get ....the suck factor worked out.

C5... are you talking about a dual pane glazed unit? If so, and the seals are still good between the two pieces of glass, it's very likely that the inert gas, Argon, is still locked inside. Also, do you know if the glass is Low-E treated?

If so, yes to both or either, your heat transfer is substantially prohibited...

That's probably my problem. The windows are recycled so I don't know what's in them. Oh Joy. more work and money. hopefully I don't break them trying to cut them out again. Its not like I cant re use them for a green house. maybe Ill try a few poly sheets instead.
I hear what Farmgal is trying to say...but this is supposed to be passive. I have cheap solar panels doing nothing but a fan will eventually break down. The original was just a simple heat generator with a screen inside, put at an angle. It was actually too hot and "Cooked" a few tries. I had to partially cover it with a towel to get the heat down, during peak sunshine and kept a thermometer inside it . The original was meant as a disaster special that could be built in a few hours...to save things thawing in the freezer during an emergency. It dried meat well. Apples would slide off the screen though. My initial experiments were meant as a test to see if poor people that couldn't afford food stores (Already victims of 2008 and unemployment) could still build stores by dehydrating dumpster dived vegies or other cast off foods. It worked fantastic...but...it needed horizontal screens...and more of them because when food finally shows up, you have to do it all at once.

So part of the phallus going limp in this project has been the dismal heat generation. First I solve that. Then I can work on enhancing air movement. It sure looks cool on the approach to the house though. Nothing says,"I am a Free Man" like a solar dehydrator. Preparedness begins by accepting that refrigeration is a privilege and not a right. Once that is accepted, all else follows.

http://cog.ca/ottawa/wp-content/uploads/2012/10/2012_Session_G_Small_Scale_Home_Dehydration_Fruits_Vegetables.pdf

tracked down the basic seminar online from the event that I went to.. in person we went into a lot more detail on the homemade solar dryers

Farmgal, have you had any experience with the modified passive solar dehydrators that flow top-down? I've heard they're 30%-45% more efficient and don't typically require any forced air modifications.

Much better for our Canadian climates.

I'm about to make 4 or 5 different versions to begin testing with next spring. Possibly even this fall for apples, etc if the weather cooperates. But most of my time and money and resources will go into the 2 most promising versions.... it'd be nice to be able to settle on which those may be. lol

OddMott, nope, but ears and mind are wide open to the idea! please share as it comes together!

Looks like I'm going to have to go bigger, before I even get a chance to experiment with several styles. :-S

My Aunt & Uncle run a market farm, planting 20-30 acres of produce each year. They always have a TON of "seconds" that don't look as good as grocery store waxed & shined crap that customers tend to shy away from. They're looking at dehydrating as a way of producing value-added goods and eliminating the waste.

So i have to figure something out that can handle their demand.

I basically have a supped up version of the first one in this YT clip but with three panels so it generates first thing in the morning till the sun goes down in the evening.
http://www.youtube.com/watch?v=oVTcnCuX2Qc
Ill have photos when its done...but first I must get ....the suck factor worked out.

The last dryer on this video is the one I built The secret to getting it right is the three regions
Air intake to top of dryer (wider is better)
Dryer , warm air from top
Damp air out flow from bottom ( wider is better)
The other realllly important thing is it has to be air tight to keep max air flow