Aux heater for Solar Kiln

[Peakebrook]

I have a solar kiln with DC fans powered solar panels. 

I am looking to increase the temperature (150 degree range) to set the sap in pine.  Due to the location of the kiln, I do not have access to electricity.

Does anyone know of a heating unit that could be used to add supplemental heat?  Most home-use heating units turn off when the temperature rises above 90F.

[pineywoods]

Peakebrook, you can get that kind of temp with solar alone. Go to my gallery, look in albumn1. There's drawings there for my solar kiln. It hits 160 deg easily. Take notice of the black-painted roofing tin mounted on the bottom side of the rafters.  That's the key for getting high temps. There's a thread on here somewhere describing the whole setup, but I can't find it, else I would give you a link.

[WoodMiller]

Sorry for the late post, but I just saw this thread....
Pineywoods - do you have any figures for how long you are able to maintain the 160 degree temp in your solar kiln?  As I understand it, the collector causes relatively rapid heat loss once the sun angle is lowered.  Just wondering if you are able to maintain an 8 to 12 hour 'cook' time....

WoodMiller

[pineywoods]

Sorry for the late post, but I just saw this thread....
Pineywoods - do you have any figures for how long you are able to maintain the 160 degree temp in your solar kiln?  As I understand it, the collector causes relatively rapid heat loss once the sun angle is lowered.  Just wondering if you are able to maintain an 8 to 12 hour 'cook' time....

WoodMiller

No hard figures exist. Too many variables. How much lumber of what species will influence heat retention. A big stack of red oak will retain a lot of heat. How well the box is insulated.. Keep in mind the collector itself is not exposed to outside air. It's covered with a clear glazing, with an air gap between. Also if the de-humidifier and fan are running, they will add about 500 watts of heat to the interior air. As for maintaining 160 degrees for 8 hours, I doubt it, but my experience is that 2 or 3 heatings of 4 hours will do the same thing. A solar kiln is CHEAP, build one and experiment. Just don't make the mistake of trying to follow the drying schedules published for conventional kilns. Solar is a whole different ballgame.