Industrial Solar Dryers
In our continuing series on practical uses of solar energy, we now take a look at industrial solar dryers. They are a practical application being used here and now.
Industrial Solar Dryers
People have been harvesting the power of the sun to dry food for thousands of years. The traditional method has been to lay the food out in long rows and let the sun and wind do its work (with some assistance by fires for some products). This does yield dried food for the inclement weather months and allows cooks to utilize flavors that are out of season. However, traditional methods are also labor intensive and result in much lost food, due to spoilage, winds, and animals. Solar powered dryers are the modern solution to these problems.
Drying preserves the food by removing the moisture without cooking the material. Depending on the food product, drying will remove all but 5 to 25% of the water content. Successful food drying requires some standard conditions. You must have enough heat to allow the moisture to be removed without actually cooking the food. You must also have an adequate supply of dry air and air circulation which will help absorb and remove the moisture. When drying food, you want to remove moisture as while at the same time keeping the positive aspects of the food, such as the taste and color. You want to make sure that the temperature is adequate so that microorganisms do not begin to grow. Hardened, inedible food may occur if the temperature is too high. Natural environments do not always provide ideal conditions nor can they be manipulated into being ideal. Solar food dryers create model conditions and are free to operate once installed.
Industrial solar food dryers come in two types. With direct solar dryers, both solar collection and drying takes place inside a single, enclosed and insulated unit. A glass or plastic cover is used to collect radiation. These are typically ventilated which allows the air to pass through more effectively. The materials to be dried are placed on trays that are put directly into the unit. Indirect solar dryers are more efficient. They have a separate drying unit, allowing for more control over the process. The indirect dryer is used in larger scale industrial applications.
India is considered the leader in utilizing the solar powered industrial food dryer to generate income and jobs. There are active programs that teach women financial self-reliance by creating drying co-ops. Nepal and Tibet are also increasingly using this technology to benefit their poor farmers.
Solar drying has long been a tool of survival for farmers. Industrial solar powered dryers are taking this to a new level. These are considered an important component of the success of developing countries.
