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Planning my solar kiln build, have questions

Started by boonesyard, May 07, 2019, 06:25:46 PM

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boonesyard

I have a couple questions for those with the solar kiln expertise:

1- I'm located at 46 degrees north, but see where it is advised to add 10 degrees if you plan on using it in the winter. How much use (actual drying) can I really expect to get in the extreme cold we experience here if I build it at 55 degrees. Is it worth it, or should I just stick to the simpler 45 degree plan? 

2 - It seems there is a variation to the original VT plan (pineywoods plan?). The later being a sealed unit (no vents) with a metal collector under the poly panels and a dehumidifier. Any thoughts on which would be a better option here in the north if I'm trying to use it year round?
LT50 wide
Riehl Steel Edger
iDRY Standard kiln
BMS 250/BMT 250
JD 4520 w/FEL
Cat TH255 Telehandler
lots of support equipment and not enough time

"I ain't here for a long time, I'm here for a good time"

firefighter ontheside

I live at 38° and plan to build mine at 45°.  I'm doing it more for ease of building, but will benefit from the extra angle in the winter.  Can't hurt for you to get a little more sun shining on it in the winter.

I've read a bunch about dehumidifiers being destroyed by the corrosives coming out of the wood.  What kind of dehumidfier would you get?  How many will you have to buy?  If you air dry first, thatmay help the life of the dehumidifier.
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GeneWengert-WoodDoc

The extra 10 degrees will give you a bit more solar input after September 21 (maybe allow you a few extra days of good drying in the fall) and then some extra heat in early March.  However, unless you get above 50 F inside, you will not see much drying.  So, in your latitude, the extra wintertime input is not worth much in terms of drying.  Go with 45 degrees angle.

Many dehumidifiers require a minimum operational temperature, like 65 F or hotter.  In your location, you need to consider how many hours a day between September until April will you be able to get the kiln and its contents over 65 F.  That is, how many hours will the outside temperature be over 45 F, as a rough estimate.

It is well to also understand that if the kiln gets much hotter than outside, then the heat you are collecting is not being used to dry lumber, as if you used the heat for evaporating water, then the temperature would drop.

Another solar design to consider is building an insulated box... that is, a kiln...with internal fans.  Then build separate solar collectors that would provide heat in spring, summer and fall, but on colder days, you could supply heat from a wood furnace, propane, natural gas, etc. and maybe some solar on sunny days for a few hours.  Of course, this is expensive to have two energy systems, so many people find out that once you build the kiln, using the kiln 100% as a dehumidification chamber is the most practical and economical.  Compared to solar, this approach allows drying 365 days a year, especially in your climate.  A solar kiln in MN might get only four loads per year of air dried lumber coming into the kiln, while a DH kiln might get 26.  The energy cost for a dehumidifier is around $60 per 1000 BF for green lumber, but the cost drops with more air drying prior to going into the kiln.  Plus with drier lumber going into the kiln, you will get more loads per year.

 In fact, air drying prior to kiln drying speeds up solar drying too.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

boonesyard

Gene,

I appreciate your response. I wondered how much actual value I would get from a solar kiln at my location. I had first considered going with a DH kiln, but after seeing the number of members using solar kilns, thought I should check it out. This may steer me back in that direction.

Anything going in to the kiln will be air dried, but getting 20-30 loads a year vs 4-6 loads a year is a big deal. I currently have a concrete slab that would work well for the base of the DH kiln build, but it is not insulated. I would imagine insulation could be put down on top of the concrete, and then a wood kiln floor over that. Can anyone recommend a wood structure DH kiln thread here? I'm sure there are a number of them, I'll start looking.  :P
LT50 wide
Riehl Steel Edger
iDRY Standard kiln
BMS 250/BMT 250
JD 4520 w/FEL
Cat TH255 Telehandler
lots of support equipment and not enough time

"I ain't here for a long time, I'm here for a good time"

GeneWengert-WoodDoc

You can insulate the existing slab by draining any water away from the site and then put vertical insulation around the perimeter of the slab, running 30" or so deep and maybe 4" thick of rigid foam board.  Most builders in your area know of this approach.  The soil under the slab, being dry, is an excellent insulator too.  The only small issue is that the concrete will absorb heat (it is called a heat sink), which means you will get the same average temperature, but not the hot peaks or nighttime cooling.  So, also insulate the top of the slab with maybe 2" of foam within a wood frame and wood top to hold the lumber's weight.  This is good for both solar and DH.

Solar in your cold location is more for the hobbyist.  For a business, DH is the best option. Here is part of the reason.  A solar kiln building might have a cost of $2000 for 3600 BF annually.  Given a life of the kiln of 10 years, the kiln building cost is $55 per 1000 BF.  A DH kiln building, with 10 year life and maybe 15 years, with 20 loads (of 3000 bf per load) per year and a kiln cost (building and compressor) of $20,000, the kiln cost is $33 per 1000 bf.  of course, there is electric cost, maintenance cost, etc., but in many cases the DH is cheaper, as well as providing drying every day.  With a larger DH unit, the price goes down.

So, how much dry lumber do you want to produce annually? Are there markets for this volume in your area?  You only make a profit when the lumber is sold.

Also, if you set your price so your profit is $50 per 1000 BF, you will make $180 in the solar kiln annually and the DH makes $3000 annually, or more if you air dry well beforehand.

Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

YellowHammer

A solar kiln is effective, but slow.  One memorably cloudy year, I put a load in the kiln about Thanksgiving and got it out a little before Easter.  Solar kilns only operate if there is an adequate supply of solar... :D  

A DH kiln will produce a kiln dried and sterilized 4/4 load from pre air dried wood every 7 to 9 days, year after year.  Production numbers are more based on the capacity of the DH unit building and your level of insulation and construction quality for the building.

Nyle can provide excellent and proven kiln construction plans for both stick built and container kilns.  I've built one of each, they both work well.  Insulation is critical, as lost heat translates into lost money.

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

boonesyard

We've decided to go the DH route. It has taken a year to to find our niche in the area, but our small business has certainly taken off. My wife and I are setting this up for a retirement business (we like to work). The market has taken us towards custom cutting on site, off site, and there is a market for local hardwood. The bottle neck in our area is definately the kiln. They are far-and-few between and backed up 3-5 months. We have our own lumber to dry, custom cut customers want their product dried and a larger custom shop has an overflow that's always looking for more drying room.

I have no experience with a kiln and I know there's a lot to learn, but with publications I've readbut and the help of this forum we're confindent we can make it work. Now it's a matter of size and construction type to get the ball rolling. We're also in the process of building a sawmill shed to get it out of the weather with some additional room for air drying lumber. Hey Tim, can you bite off any more?!  8) 
LT50 wide
Riehl Steel Edger
iDRY Standard kiln
BMS 250/BMT 250
JD 4520 w/FEL
Cat TH255 Telehandler
lots of support equipment and not enough time

"I ain't here for a long time, I'm here for a good time"

GeneWengert-WoodDoc

This seems like a very wise decision.  A few hints...

Make sure you think about where you will put the second and third kiln, if you find that expansion is necessary.  You do not want the first kiln in a bad position that would limit expansion.

Do not use cash for the kiln and components, and rolling stock, as you will need cash for stickers, inventory, etc.  Certainly pay the bank loan off as soon as reasonable.  But, drying has erratic cash flow...some months are awesome and some have little income, but expenses are monthly even when sales are slow.

Incorporate, with an LLC, your operation.  This protects your home, etc. if something bad happens.  If you offer trucking delivery, make this service a second corporation.  A good lawyer and also your county extension office can offer you assistance in getting it set up correctly.

Marketing your services and your dried lumber is a key.  Again, the extension office can help with a marketing and business plan.  Exude quality in everything you do...this will attract and keep customers.  Do not dry lumber thicknesses, grades and species that you cannot sell easily...a little thinking about markets beforehand is helpful.  At the same time, think about how you might be able to get any wood for your customers even though you do not dry it...for example, make an arrange with Yellow Hammer here that if one of your customers needs some sweet gum or quartersawn sycamore, you can get it for this customer because you know YH and have already worked out an arrangement.  

One thing you can offer is drying of smaller loads.  So, do not get a huge kiln only.  Plan on a smaller kiln so you are more versatile.  Two smaller kilns are better than one large one...or maybe one larger and one smaller.

It is helpful to be able to reach 150 F, so if possible consider the NYLE L300.  You can easily dry any species and thickness with any quality requirements.  NYLE does have plans available.

Make sure you charge enough for your services.  Consider charging by the day.  A starting point might be $20 per day per 1000 BF.  Smaller loads require more attention, so charge more. Charge for stacking.  Charge for storage.  Also, offer free air drying, which means the kiln time will be reduced, which helps you and the customer.  Keep in mind that an open shed with Shade-Dri curtains is very effective air drying.  Make sure that you and your customer have a clear understanding about drying defects...some defects are "caused by the wood quality" and not by your actions.  Document what drying conditions you use and make sure they are "by the book."  A lawsuit for drying degrade is expensive, even if you win.

You will need a place (small building with racks) to store and display your dried lumber.

Join the Great Lakes Kiln Drying Association group...two meetings a year with educational programs and tours.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

boonesyard

Thank-you very much for your insite. I know size for the first kiln is is something I need to decide. I'm thinking 2000-3000 bf for this first one to get the ball rolling. 

I'm very fortunate in that we have a municiple general contracting company which allows me the equipment, recources and connections to set this business up correctly. There is no quesiton though, that our greatest asset has been this forum and everyone's expereience and knowledge here in setting our small retirement business up. I'll take 20 years in 20 minutes every time.  :D  
LT50 wide
Riehl Steel Edger
iDRY Standard kiln
BMS 250/BMT 250
JD 4520 w/FEL
Cat TH255 Telehandler
lots of support equipment and not enough time

"I ain't here for a long time, I'm here for a good time"

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