Three main types of solar dehydrators exist: natural-convection dryers (which do not require electricity or mechanical energy for operation), forced-convection dryers (which commonly use an electric fan to maintain a constant airflow), and solar-assisted dryers (which uses an auxiliary heating source as its primary dryer).<ref>Hui, Y.H., Clary, C., Farid, M.M., et. al. Food Drying Science and Technology. Lancaster, Penn.: [DEStech Publishing], 2008</ref> Because of the energy-intensive nature of solar-assisted dryers, we limited our literature review to two types:
Two main types of natural-convection dryers exist: the simplest, a box dryer, is essentially just that: a large box with one face angled to catch the maximum amount of sun. The box serves as both the solar collector and the drying chamber, with air intake holes drilled low on the box and exhaust holes drilled high to allow moisture-laden, warm air to escape. The box dryer's simplicity allows it to be easily reproduced, and the single-chamber design keeps the heat where it's needed, reducing heat loss via convection. However, the single-box design dramatically reduces the dehydrator's working capacity, and the solar angle cannot be adjusted to maximize seasonal sunlight.
The other type, called a tower dryer, relies on an attached solar collector to heat air, which then rises, is directed into a tall drying chamber, then is released from ventilation holes at the top of the tower. The tower dryer's design is more complicated than that of the box dryer, requiring fabrication of a secure, flexible duct to move air from the solar box to the dehydration chamber. This allows for increased heat loss; however, the increased shelf space in the dehydrator tower and the ability to change the angle of the solar collector make it a more adaptable design for certain climates.
Forced-convection dryers require external power to operate. Household power (120V AC in the United States) is commonly used to power fans, which provide a mechanical assist to pull in and expel air, facilitating a faster drying speed. Forced convection dryers are commonly tunnel-shaped, or constructed to maximize surface area and air contact with the material to be dehydrated, but any dehydrator can be turned into a forced-convection dryer with the addition of an electric fan.
===Components of solar dehydrators===
There are a multitude of designs, shapes, and plans for solar dehydrators. However, all of them share a few similar components: a heat chamber, a method of keeping it off the ground, and a removable tray that contains the food.<ref>Fodor, E. The Solar Food Dryer: How to Make and Use Your Own Low-Cost, High-Performance, Sun-Powered Food Dehydrator. Gabriola Island, Canada: [New Society Publishers], 2005.</ref>