This is my home made solar dryer, it’s been successfully drying foodstuffs, from spring through till mid autumn, for the last five years. I live in Cataluña, NE Spain with sunny warm dry weather for much of the year.
After reading that the visible rays of light can denature nutrients in food quite rapidly, I researched and found details of how to make a solar dryer and protect the food from the suns rays at the same time.
There is a detailed drawing of the construction within the photos. It works by capturing the heat of the sun on a dark metal surface and then radiating the heat to the space underneath, providing sufficient warmth to dry the food. The food is placed on mesh trays, racks or solid platters, depending on their size and consistency, which are then slid in under the heated metal plate.
Corrugated metal sheet supports the trays, allowing the warm air to circulate freely around both sides of the food allowing it to dry quickly. The corrugated sheet also absorbs and radiates the heat back upwards, warming the lower surfaces of the drying foods.
To increase air flow, there are wide openings on two sides and whole structure is slightly angled so that the warm moist air can rise and escape from the upper open side, drawing cooler dry air in from below, thus creating a constant circulation of air.
This structure functions similarly to an oven grill (UK) broiler (USA) with minimal extra space for the trays of food to be slid in and out. [I will make this gap slightly see on the next version]. The access is protected from flying insects with a mosquito net that is attached at one side and weighted so that it stays in place.
To reduce the cooling effects of the breeze, a glass cover is placed over the metal heat capturing plate, concentrating the heat and allowing more to be absorbed.
The structure was designed to fit onto the top of an old wheelbarrow allowing it to be moved more easily.
After several disasters with ant invasions I now place the wheel and feet of the wheelbarrow in shallow trays of water to eliminate this problem.
I successfully dry almost all types of food grown on my plot and from the local area.
Herbs are strung up and hung from the beams in my house to dry in the shade, they are not likely to rot or oxidise and benefit from a cooler steady temperature to dry, whilst retaining a maximum of essential and volatile oils that would otherwise be lost through the higher temperatures of the dryer.
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