Solar Drying

After the 1970s, the first batch of solar drying device was built up in the world. Until the end of the 1980s, 7 sets of solar drying device with the area of more than 500m² have been constructed in overseas, among which 4 sets in the US, 2 sets in India and 1 set in Argentina. The grape solar drying device, which was put into operation in California of the US in 1978, is the biggest solar dryer in the world, with which the concentrator area reaches 1951 m², and possesses a 396 m² rock heat storage bed and can dry 6 to 7 tons of grape in each day. Moreover, there are also some small scale solar dryer, for example a small-sized banana commercial dryer in Brazil which the concentrator area is 3.5 m², drying box volume is 1m³, and 500 dried bananas can be sold after two days.

After the 1970s, solar dryers were developed rapidly in China, especially in the countryside, where solar drying experiment has been conducted on many agricultural products. During the period from 1976 to 1986, about 60 sets of solar drying box have been constructed with the total concentrating area of 5000 m², which promptly couldn¡¯t be utilized due to the lack of theoretical instruction, the irrational design on the dryer and its bad utilization effect.

After being tackled in the seventh five-year project, the research on solar drying technologies and application level have been raised up dramatically, in particular in the built solar drying demonstration device functioned as demonstration and promotion. Right now, the built solar drying device is in a concentrating area of 15000 m². But since drying materials have diversity, the drying process is different and drying for agricultural products has characteristic of season variety, solar dryer lies in the difficulty to be industrialized and commercialized.