I am going to be building a permanent dry kiln (meaning it will be there for ten years plus).
What I am planning to build is a timbergreen design basically on steroids. It will b 24 feet by 36 feet giving three 12 foot chambers design to dry 10' wood. (4000 ft per chamber)
The top floor solar bank which has the 24x36 footprint (the bottom is 12 by 36 which gives a way to open the doors for ventilation but be able to lock them open.
Now here is my question, When using clear roof panels what is the trade off on price between using the poly and standard panels. They are going to have hot temps every day and how long will a standard clear panel last?
Although I can't answer your glazing question, I am interested in learning from your project and would like to see a floorplan to understand how your multi-floor kiln works. At a rate of 1 sq. ft of glazing per 10 bf of stock, a 12' wide chamber that holds 4000 board feet would require a collector surface at least 33' high. Is that what you have planned?
Being that the Collector is 36 feet long and 12 feet high I am a little shy but the 4000 feet doesn't take in the loss that the stacking beams and such so I will probably close to 3600 feet instead of the 4000 stated. It is funny on how 1" stacks take up room more than 1 ".
I appreciated the 1' rule though I was operating on opinion more than knowledge. My expertese has been in DH.
Here is a Sketch of the Kiln. Hopefully it translates.
Apparently it doesn't translate.
just_sawing,
The drawing does help explain your concept but a couple of quick calculations indicate that, at 100% efficiency, your glazing would be about 168 square feet per 4000 bf chamber, or about 42% of the rule-of-thumb recommendations. Obviously you aren't showing the fan system but going against the 'heat rises' principle would require substantial and continuous fan energy. Perhaps Dr. Wengert will chime in soon and give a more reliable and practiced opinion.
Only one chamber would be used at a time with the others used for air drying. This gives me a chance to load and unload the chambers while one is active. With the 12x36 foot frontage I would have 372 feet of solar.
I appreciate the input and what would I need as collector space for this. and if I reduced the footage to 2000 would if be more in line. The pressure fan will collect heat from the ceiling and the exhaust will deliver to the floor of the collector. I am thinking by having the doors solid I would be able to thermally isolate the room, I could gather more Solar by inclosing the doors with a transparent panels.
This design, which is an offshoot of the VT design, provides good heating. One key is to insulate the walls and floor of the collector with 6" minimum. Otherwise, due to the large wall area, heat losses will be quite large, so temperatures will be low, which means higher humidities, which means slower drying.
Note that the hump in the collector does not help (that is, it does not increase to solar shadow) and actually increases heat losses. It would be more efficient to use about a 40 degree roof line.
Note the the footprint we should use is the solar footprint- -the shadow that the sun casts at noon on a summer day, such as August 15. So, with your 24x36, your solar footprint is about 24 x 36 x 1.4 = 1200 sq ft. This means that you can dry 12,000 BF. However, you mention that you plan to use only one chamber (4000 BF) at a time for solar, so you have three times more energy than you need...at least on a sunny day much of the year. In the winter, with higher heat loss and less, solar input (lower angle and less daylight) you will still have surplus energy on a sunny day.
Here is a question...Why not build three kilns (just as you have described) and then also build a large air drying shed. It seems that with your present design, you have one kiln and two small sheds, plus an oversized collector.
Can you find someone that has built this design recently? If so, talk to them about how it works for them and what they might do differently.
The picture does come through ok...just click on the PDF file link at the bottom of the message.
I am guessing that your lumber stacks will be 12' long and 6' wide in two stacks. Be aware that this width does create a moisture difference from edge to middle of the pile. It also requires no less than 200 fpm velocity to avoid this, Especially without fan reversal. With gaps, you should be able to get about 130 BF per layer, so 4000 BF in two stacks would be 31 layers or about five feet high. Note that four wide stacks get very tippy.
One good hail storm can do a lot of damage to PVC panels. Polycarbonate panels are much stronger. Also beware that there are (at least) two brands of polycarbonate panels sold by the major home centers. One of them sells a panel that is 40% thinner but looks identical. And they sell it for the exact same price. (Don't buy the junk panels from HD.)
Lexan (R) polycarbonate is guaranteed ten years against hail and yellowing.
Really appreciate the input. One of the problems I have always had with drying is the labor of moving the stacks. Even with equipment the sticks get bumped and shifted on our uneven ground. I have decided to solve one problem by when the wood is stickard it is where it is air dried and kiln dried. This is also a labor issue.
My goal is to solve what sometimes caused problem of making the kiln down for up to a week at a time to get it unloaded and then loaded. This way I flip a switch make a call for the trucking firm.
With your input I am looking at reducing the collector to only above the chambers which would make it a 12 by 24 foot print with a 6 by 24 porch below it reflecting on the panels. I can reduce the back wall and increase the front coverage to close to a 14 foot collector face.
I did not draw in the center baffle wall but the center of the chamber where the down draft is will be a stud wall that allows you to stack against a 2X6 wall and gives you a solid stack and not wiggly. I have done this before and like it. This also give a place for the stacker sticks to be positioned on the rear side and not shift.
I have access to surplus squirrel cage fans that are 220 and airflow is not a problem. The fans are free but in time I will purchase the newer energy efficent energy star for cost savings.
I have attached the modified PDF to the bottom and thanks for the input.
Almost forgot to mention that I have freezer panels for the walls. They are 6 inches thick and are interlocking. I will insulate the ceiling and floor as much as possible.
I wrote a little review a while back on my glazing experience. Don't use plexi, it gets brittle quick. I have loved the double wall polycarb material. It offers insulation, its very impact resistant, easy to cut and install, rigid compared to lexan which flexes and looks wavy, and its fairly inexpensive. 4'x10' sheets are around $60 online for double wall, 8mm 10-year warrantee stuff. That's way cheaper than what I've seen for lexan.
If you increase the size of the collector a little bit, it will work when it is cooler outside, compared to a smaller collector.
My plan is to set the collector a little steep to get the winter sun better. Since I have a six foot porch in front will bounce light up to the collector in the summer.
I plan to set thermostates on all the chambers so when the chamber is 140 and above it will turn on the chambers air drying to assist the air drying. They will only add extra assist when there is extra heat and this will also keep too much heat.
By setting the Air assist on Air dry chambers it will blow through the green lumber through the stack but the doors are open so that air exits out and does not increase the RH.
I know it is a little different, but in the solar food dehydrator I built, I first used clear polly as the solar collector. It lasted one year, and then literally cracked and broke under its own weight due to becoming so brittle. I replaced it with darkly glazed safety glass, and while it was a little more expensive, it has really increased the efficiency of the dehydrator and should last for years.
I also considered replacing the original poly with Lexan, but I could only get it in clear. The safety glass was actually cheaper than the Lexan, should last just as long if not longer, and gave me the increased efficiency.
You can purchase clear films that are uv stabilized, so they will last longer.
Corrugated fiberglass is also an inexpensive, durable, fairly effective cover.
I haven't bought from them, but United States Plastics Corp thin wall sheet looks good . Rob