Abstract
Background: We referred to nearly 40 years of development and application progress of solar dryer in China literature, especially its application in the field of Chinese herbal medicine drying. Objective: We explored the development direction of China’s development and application of solar dryers, especially focusing on its development and application in traditional Chinese medicine drying. Method: Five types of solar dryers including the greenhouse type solar dryer, the collector type solar dryer, the collector-greenhouse type hybrid solar dryer, the integrated solar dryer and the focusing type solar dryer accounted for the development and application of solar dryers up to 95% in China. The first three types of solar dryers are low temperature dryer (less than or equal to 70°C), while the latter two kinds of solar dryers are high temperature dryer (more than 70°C). In this paper, we respectively introduced and compared the structure, working principle, applications, advantages and disadvantages, and the research status of these five dryer. Results: The integrated solar dryer and the focusing type solar dryer belong to the high temperature dryer types are the future direction of development. Among them, the integrated solar dryer is relatively simple structure and has more promotion prospects. These two kinds of key drying device used in the dryer is the development direction of high efficient vacuum tube. On the other hand, because of their low cost, simple structure and the dry material requirements etc., the three types of low temperature dryers at low temperature for drying materials are also indispensable in the practical application. In contrast, the collector-greenhouse type hybrid solar dryer has more advantages, is the development direction of low temperature drying category. Conclusion: The collector tube which is the key element of the dryer was the core technology of solar dryer. Our country develops more successful of the all-glass vacuum solar thermal collectors and heat pipe-glass vacuum tube. Efficient vacuum tube collector technology is the future developed direction and is equally important to improve the quality of traditional Chinese medicine and dried.
Highlights
Solar energy as a green energy is a clean, cheap and renewable energy
China is located in the northern hemisphere in the eastern part of Eurasia, with abundant solar energy resources
According to the material receiving solar energy, the solar energy drying device can be divided into two categories: direct and indirect heating, otherwise known as radiant and convection
Summary
Solar energy as a green energy is a clean, cheap and renewable energy. With the gradual warming of global climate and global not renewable energy decreased year by year, it is expected the solar energy will play an even more important role in social production and life in 21st Century. In the field of traditional Chinese medicine production, using the oven or steam dryer instead of the traditional drying process to dry traditional Chinese medicinal materials and certain forms such as pills which could meet the production concentration and large processing capacity requirements. Solar installation drying certain traditional Chinese medicinal materials, Chinese medicine decoction piece and Chinese patent medicine could keep the original components and color, flavor, good appearance quality, and quality assurance. Speaking, the research on application of solar drying has started later and the research is relative lag, especially in the application of traditional Chinese medicine is the study of the drying less. Many varieties can be used the solar drying device, such as traditional Chinese medicinal materials, Chinese medicine decoction piece, Chinese patent medicine, arts and crafts pottery, preserved fruit, vegetables, meat, fish, grains and wood, etc. We will proceed to a brief presentation on the status of their application and research in Chinese medicine, and discuss its future development prospects
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