• Energy Research

Solar dryers have proven to be one of the best environmentally friendly approaches for drying purpose of medicinal plants and agricultural crops. Use of solar radiations in drying purpose of plant parts has proven economically as well as environmentally responsible and sensible application. Plants are the treasure of nature with hidden medicinal properties to treat diseases. Plant material should be processed properly for extraction of medicinal molecules in terms drying to decrease the manufacturing loss and to increase the standard of product. Cognizances of ethnobotanical knowledge on plant wealth are extremely beneficial in utilization and exploration of natural resources. Conventionally, low drying temperatures between 30-40°C, with economically beneficial techniques are required to protect sensitive active ingredients. Therefore, the objective of reviewing research in medicinal plant drying is to find out optimum drying temperature and best solar dryer for drying purposes of plant parts in terms of quality and drying costs. Rendering to human requisites, solar appliances for drying purposes will be used as the best alternative to standard sun-drying technique. This review focused on effective drying is demand of present scenario for the application of heat trapped from solar radiations for drying purpose in order to maintain the quality and active ingredients of plants. Conventionally, low drying temperatures between 30-40°C, with economically beneficial techniques are required to protect sensitive active ingredients. Indirect type of solar dryers can easily fulfill all the terms for dying plant products in terms of standard and yield.

Abstract Exergy analysis is very helpful for reducing irreversibility and rising the efficiency of solar collectors. The major objective of the present study is to organize a review on exergy analysis of different parabolic solar collectors. The effects of various flows and geometrical parameters of parabolic thermal collectors on the exergy efficiency were presented and discussed. In addition, comparative study was carried out to select the best solar thermal system for maximum exergy efficiency with minimal thermal losses. This study indicated that the hybrid nanofluids enhanced the exergy efficiency significantly as compared to without hybrid nanofluids. Passive techniques comprising twisted tape inserts, fins and insertion of swirl devices in the stream for changing the stream patterns causes to interrupt the thermal boundary layer and accordingly high exergy efficiency. This review would also throw light on the scope for further research and recommendation for improvement in the existing solar thermal collectors. Finally, this work will be beneficial for the scholars working on exergy analyses of solar parabolic collectors.