We attempted to build a solar food dryer, using the sun energy to hygienically dry fruits in Cambodia. We have search through the internet and came across a design which we can try out.
We bought wood and cut the to shapes and assemble them together. Finally, we painted it and allow it to dry before using it.
Sun energy is collected through the transparent plastic and heats up a wire mesh inside. Air intake from the front sucked in and heated up by the wire mesh, the hot dry air rises because of convection in the dryer and flow into the drying chamber behind. The fruits prepared for drying are placed on trays to be dried in the chamber. On a hot day, the temperature in the chamber reaches about 50 degress Celcuis and humidity falls to below 30%. Drying takes about 3 days.
The temperature and humidity of the drying chamber was measured from night time till the next evening. It was noted that the humidity at night reaches above 80% while its temperature drop to below 30 degress Celcius. During the day, the temperature in the chamber increases to above 50 degrees Celcuis and the humidity falls close to 30%. Drying of the fruits takes place only during the day time.
The result was partially successful. Somehow we could not get complete drying of the fruits. Probably due to condensation of moisture at night. 
Hence for the next improvement to the design, we must introduce continuous drying process through the night which we will require some heating process.
In conjunction with the solar dryer, we design a vacuum sealing machine to store the dried fruits in a vacuum sealed plastic bag. The machine does not use electricity but working on the priciple of a reverse bicycle pump for sucking the air out of the plastic bag and using fire from a candle stick to seal the plastic bag.
