Solar drying uses sun energy but is performed in a solar dryer designed and built for this purpose.
Solar food dryer is built to dry food using solar energy. Sunlight enters an enclosed chamber (sun collector) where it strikes a dark surface converting its energy to heat. The heat dries the food. Airflow is accomplished by a natural draft (warm air rises) which can be controlled by adjusting vents. The same principle is used for controlling draft in a traditional smokehouse.
The sun collector and the drying chamber can be combined in one unit or separated. When the collector is free standing, the heat it generates is directed intothe drying chamber. Solar dehydrators may have backup electric heating to provideheat when the sun is not around.
Solar drying is an improved “open air sun drying” method which offers significant benefits:
- Fast drying.
- Higher drying temperatures.
- Offers airflow and temperature control.
- Food is protected from elements.
The following drawing depicts one tray solar dryer.
The inside of the dryer is lined up with a black absorbing material or painted black. Cold air flows in at the bottom but the sun rays will heat up the drying chamber andthe air in it. Warm air rises up and leaves the chamber. This natural air flow depends on the difference in height (pressure) between fresh air intake and hot air exhaust. The bigger the difference the faster the air flow.
The following drawing is a step up design of the previous arrangement.
During the day the solar dryer works on sun energy. The warming chamber supplieswarm air to the drying chamber which is loaded with three removable trays. At night time there is no significant drying, besides, there is a danger of condensation build up as cold night air cannot hold moisture. This will happen in hot and humid areas like Louisiana or Florida. The optional heating element can be switched on and the drying will continue through the night. The heating element can be placed in the warming chamber instead.
There is a pipe stack through which escapes warm and moist air. The higher the pipe, the bigger the difference in pressure between fresh air inlet and warm air exhaust. This results in a stronger air flow. By making air intake and pipe outlet adjustable, the air flow and humidity can be controlled during drying. Thermometerand humidity sensor can be installed for more precise control.
Both devices, solar dryer and meat smokehouse employ similar design features:
- Fresh air intake
- Smoke (hot air) exhaust
- Air flow
- Insulated frame
- Heating element
Using meat smokehouse to dry tomatoes. When drying tomatoes heating element supplies warm air. During smoking meat, burning wood alone or with help of the heating element provides warm temperature and smoke. In both cases the temperature of the air is around 140° F (60° C.