Are you wanting to dry timber from green or already air dried? If drying small quantities of timber to a low moisture content (7 - 8% for use in a centrally heated house) is your priority rather than drying it quickly from freshly cut/green planks, then you can do this without a kiln. Planks can be air dried outdoors down to a moisture content of between 15% to 18% and the rule of thumb is a year per inch thickness. I run a dehumidifier in my small workshop and simply put a small stack of air dried timber in the corner which then slowly dries to the required moisture content. It takes a while to dry in this way, for instance I often leave two inch planks for about 6 months. But there is the advantage that the workshop is also kept dry so that machinery and tools don't rust and dried timber stored in the workshop stays dry and ready for instant use. I adjust the dehumidifier settings so that the air is not too dry to start with, to reduce the risk of causing splits/degrade, then steadily reduce the humidity settings over a period of weeks/months, monitoring the air humidity with a cheap hygrometer and the moisture content in the timber with a pin meter. There is a table available showing the relationship between the equilibrium moisture content in the timber against relative humidity in the air. I aim for a final relative humidity in the workshop of about 40%. Even the smallest dehumidifiers are more than big enough for a small workshop. I've been using this method for about 10 years and have been drying more timber than I can manage to use, albeit that I only make a few things a year in my spare time. I've seen the same idea done but with the stack covered with a plastic sheet which also covers the dehumidifier so this may work faster.
Andrew
andrewbriggsfurniture.co.uk