Here is a quick guide for you
Two methods of drying logs
1. Forced Air drier
An insulated container or building with air heat exchangers at one end an some open vents at the other. A boiler heats water, which is converted to hot air via the heat exchangers and blown through the container or building to dry the logs.
The effectiveness of this and the time it will take to dry logs will depend on how the logs are stored ( metal mesh stillages are best to ensure airflow), the temperature of the air and the amount of air passing through the kiln. The hotter the temperature the better so long as there is a reasonable airflow. All things being equal , in the summer when the outside air temperature is 20 degrees your drier will be able to achieve 20 degree higher temperatures inside the drier. The difference in drying time between 40 degrees and 60 degrees is huge.
2. A Traditional Kiln
An insulated building or container with radiators in and powered vents that open once the air reaches a certain relative humidity level. At this point fans blow the wet air out and switch off, close the vents and the air heats up again with the process being repeated until the logs are dry. This is generally a more efficient method of drying logs - set up is tricker though.
A Constant Heat and Insulate, Insulate , Insulate
I cannot stress the importance of this enough. It takes a large amount of energy to heat the logs up to the point where the moisture begins to escape into the air. If you are only running your kiln 12 hours a day you are repeatedly having to do this and drying times reflect this. Keeping the temperature constant in the kiln rapidly increases drying time. Insulation is key, it costs next to nothing to insulate your container or building and makes a massive difference to the effectiveness of your kiln
Boiler Choice
Essentially two principle biomass choices that can power wither type of drying method.
a) Woodchip
Expensive to install, hardly any hassle to fuel, provides a constant heat 24 hours a day.so that temperature is min
b) Batch fed (Logs)
Cheap to install, requires regular refueling, about 30% less effecient, a nightmare to fuel over night to keep the temperature in the kiln constant. Best to turn the heat exchnagers right down to minimum so that temperature is maintained with as little draw on the boiler as possible.
RHI
Unless you are going to install a boiler of greater than 200kwh then forget any sort of real payback on your investment, even then returns are not what they were
Drying Times
These vary massively on the setup ( boiler type, boiler sizee, type of kiln, size of kiln, how the logs are stored, outside air temperature). My 10ft insulated forced air dryer, with 100kwh of heat exchangers on full blast ( wood chip boiler) will dry 10m3 from green to 20% in just two days in the height of summer with a temperature of 68 degrees in the container. In the winter when its freezing outside in may take twice this long. Initially I get the temperature up as high as possible and have the fans on a low speed, the speed of the fans is then increased as the logs dry through the cycle.
Hope this helps