Comparison of air drying, conventional kiln and solar drying

Broadly, there are two methods by which wood can be dried:  natural drying or air drying, and artificial drying.

Wood drying kiln provides a means of overcoming the limitations imposed by erratic weather conditions. In kiln drying as in air drying, unsaturated air is used as the drying medium. Almost all commercial woods of the world are dried in industrial kilns. A comparison of air drying, conventional kiln and solar drying is given below:

A、Wood can be dried to any desired low moisture content by conventional or solar kiln drying, but in air drying, moisture contents of less than 18% are difficult to attain for most locations.

B、The drying times are considerably less in conventional kiln drying than in solar kiln drying, followed by air drying.

1、This means that if capital outlay is involved, this capital is just sitting there for a longer time when air drying is used. On the other hand, installing an industrial kiln, to say nothing of maintenance and operation, is expensive.
2、In addition, wood that is being air dried takes up space, which could also cost money.

C、In air drying, there is little control over the drying elements, so drying degrade cannot be controlled.

D、The temperatures employed in kiln drying typically kill all the fungi and insects in the wood if a maximum dry-bulb temperature of above 60 °C is used for the drying schedule. This is not guaranteed in air drying.

E、If air drying is done improperly (exposed to the sun), the rate of drying may be overly rapid in the dry summer months, causing cracking and splitting, and too slow during the cold winter months.