Using solar kilns to dry timber, using the heat of the sun, is quite feasible and
very attractive in certain countries. They require no conventional services (electricity,
gas etc.) and are useful to rapidly reduce the moisture content of freshly felled
timber and so avoid biodegradation. At their simplest, solar kilns can be a “glass-
Drying times for timber in solar kilns
Compared to Conventional heat and Vent “compartment” kilns, using solar kilns to dry timber is slow, but faster than air seasoning of timber stacked in the yard:
• Drying “green” moisture content to about 12% moisture content (expressed on a dry wood weight basis) is about 3 times as long as using a conventional kiln.
• Drying “green” moisture content to about 20% moisture content is about 2 times as fast as air seasoning.
In fact when using solar kiln to dry timber the usual process is to air season the timber first down to 60%. Before moving the timber into the solar kiln.
Attractions of using solar kilns to dry timber
• Using solar kilns to drt timber is particularly attractive in tropical regions
with high levels of solar radiation but where power sources are limited or non-
• Degradation of stock due to insect and fungal action can be a severe problem in some tropical regions if timber is allowed to remain at elevated moisture contents for extended periods of time. Solar drying can be used to avoid these degradations with their consequent financial losses.
• Although using solar kilns to dry timber might be slower than if conventional “heat
and vent” kilns are used this slower drying can in fact produce higher quality stock
by avoiding a number of drying defects which can occur if timber is dried too rapidly:
such problems are especially prevalent in many tropical timbers which are especially
vulnerable if dried too rapidly. Furthermore, at night, when a solar kiln cools and
the relative humidity consequently rises within the kiln undesirable stresses in
the timber are relieved -
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Reasons to Dry Timber: An Introduction to Timber Drying
Timber Drying -
Factors controlling the Drying of Wood
The Structures of Softwoods and Hardwoods and their effect on Wood Drying
An Introduction to the Air Seasoning of Timber
Layout of a Timber Drying Yard
Design of Stacks in the Timber Drying Yard
Types of Kiln Drying Equipment
Benefits of Kiln Dried Timber production compared to Air Seasoning Timber
Using a Dehumidifier to Dry Wood
High Temperature Timber Drying
Avoiding Case Hardening by Monitoring the Drying of Timber. Also Collapse & Staining of Timber