Our greenhouse-style solar dryer dome has a parabolic roof covered with polycarbonate sheets and a concrete floor. One unit of the dome is 7m wide x 10m long x 3m high, with a loading capacity 1,000kg of cherry drying on 19 units of two level raised beds. Six units of exhaust fans are powered by a 300-watt solar panel to ventilate the dryer.

 

This is a parabola dome, designed for commercial fruit and vegetable production. It is covered with 6mm thick polycarbonate sheets on a concrete floor.

 

The parabolic shape helps to reduce wind load and efficiently receive incident solar radiation. The polycarbonate sheets allow a greenhouse effect inside the dryer. The sheets also provide protection from the rain and insects and reduce convection and radiation heat losses to the environment.

 

Solar radiation passes through the polycarbonate roof, heating the air and produce inside, as well as the raised beds and concrete floor. Ambient air is drawn in through a small opening at the bottom of the front side of the dryer, heated by the floor and the produce exposed to solar radiation. The heated air absorbs any moisture. Drying is faster if the product is directly exposed to the solar radiation and heated air.

 

Most air is sucked out by six exhaust fans at the top of the rear side. The polycarbonate sheet also protects the crop from UV light, maintaining its original taste, colour, and smell. Temperatures in the dryer are higher than outside. We dried our coffee 2-3 days shorter than natural sun drying and the quality is good.

 

Each solar dome has 14 movable two level raised beds. The frame of each bed is constructed from metal hollow pipes with a surface area of (2.4 x 1.2m) and 7cm deep. The surface is a steel screen plate with small holes (maximum diameter of 6mm) and 1.5m between levels for easy access and air circulation.

 

Six air exhaust fans are at the upper back edge of each dome for dryer temperature control. At both sides of the entrance door, the inlet air hole (front air vent) is 3 x 0.3m and covered with an adjustable mosquito net. It can be fully, or half opened on two levels for proper air circulation.