Drying is known to be a difficult, resource consuming and expensive process.
The difficulty is created by the large variety of products that can be dried in different ways (continuous, batches, or intermittent modes), in manual or automatic processes, using different methods, etc. Chosing the proper drying method for each situation is very difficult, sometimes considered an art.
The devices employed in drying are also very varied, from a simple tarp on which products are just placed under the sun, to fluid bed driers in automatic and computer-assisted dying systems in factories. Often the driers are bulky and require a large space for installation.
With the exception of heat pump drying (which requires mechanical or electric power), all the other drying processes require a source of heat for removing the water from the product. The cost of energy is the largest expense with the drying process; for this reason, solar driers are an attractive option for processes where exists a significant area for installation of the solar collectors.