Solar Kiln - Winter Drying

[Woodslabs]

Hi All.

First i would like to thank everyone who provided feedback on my kiln design.  The kiln looks and works great, see pics below.  I also included some pics of the kiln dried wood that just came out of the kiln.

My question is now.  Winter drying... I assume the fans will run a hour after sunrise to an hour after sunset?  I will block the vents with Styrofoam insulation to keep in as much heat as possible.  Anyone have any other tips?

I was thinking of running natural gas to it next year to heat it during the winter.  Has anyone done this with a solar kiln?

[beenthere]

Looks like, in the pic, that the solar collector is in the shade of a tree. Or is it just the photo shot?

[YellowHammer]

Anyone have any other tips?

My solar kiln would slow down tremendously in the winter, as expected, due to a lack of sun. I use a 40°F dehumidifier to make up the difference. 

[xlogger]

Woodslab, looks like our solar kilns are cousins ;D. I ask YH in a private message but probably should of ask here. My DH keeps the humidity lower in kiln but drops very little water, is it worth running? It seems when I run the DH it is around 10-15% lower humidity in kiln,
Update, the reason I found out on the lower humidity is I had the sensor too close to the heat of the DH which must of make the RH look like it was lower than it was. I also reset the DH and it dropping water fine now.

[Woodslabs]

It has some shade in the late afternoon due to tree cover.  It gets up to 52 C on a hot day.

When you run a Dehumidifier in the winter at night, wont the water freeze?  Does it ever drop to below 0?

[xlogger]

This is my first year with my solar kiln but I don't think the DH runs on low temps and I'm sure if it did it would freeze. So I like you would like to hear from someone who lives in colder climate area with home Dh in their kiln to response.

[GeneWengert-WoodDoc]

As a general guideline, wood dries very, very slowly when under 50 F (10 C).

Under 50 F, the air holds very little moisture...a cubic foot when foggy might hold about 1/14,000 pounds of water.  When vapor condenses on the cold coils, this condensation releases heat which warms the cold coils so they do not freeze.  But if there is little water being condense due to little moisture being in the air, the cold coils get colder and freeze more easily.  In other words, a DH works best in warm humid air.  What this means, even if a DH did not freeze, is that it cannot remove much water from cool or cold air, as the air has so little.

At 120 F the air can hold 100 times more water per cubic foot.

A solar kiln's collector, even if two layers, is a source of a lot of heat loss.  Adding heat to a solar kiln when the sun is not shining or it is cold is very inefficient unless the collector has an insulation blanket on it.  Of course, the walls and floor need to be insulated well too.  Even on a sunny day, if the temperature is around 50 F, the solar input for eight daytime hours is less than the heat losses, so it is better in cold weather to go non-solar, if you want the kiln to work.  So, in answer to your original question, cover to collector with a good insulation blanket if adding heat.  If heat is not added, winter solar drying is very slow.

This also brings to mind how a solar kiln works in the summertime when much beyond 45 degrees north.  Although the hours of sunlight are long, the sun angle on a steep, south-facing roof is very low for many hours.  That is, the sun rises in the NE, so the collector does not see much sun for quite a few hours.  Likewise in the evening when the sun sets in the NW.