Drying and Testing of Mint (Mentha piperita) by a Hybrid Photovoltaic-Thermal (PVT)-Based Greenhouse Dryer

Abstract

Mint has been used as a medicinal and aromatic plant since ancient times. Its leaves are used for flavoring, spicing, and mint oil, which is used to treat several diseases. In order to preserve this seasonal plant for consumers during the year, it undergoes various technological treatments, such as drying. The economy of medicinal plant production is burdened considerably by the energy costs of drying. To substitute high-cost fossil energy, a hybrid photovoltaic-thermal (PVT) ultraviolet (UV)-stabilized polyethylene greenhouse dryer was developed to lower the initial costs. The drying process from an initial moisture content of 80% wb to a final moisture content of 11% wb takes 21 h. Testing was done for different samples of dried mint powder and comparison was made to fresh samples. The results show that nutritional and calorific values are retained along with a major degree of its original color, which, coupled with a significant reduction in moisture content, resulted in longer shelf life of the dried product. Further, the results show that the efficiency of the dryer and net CO₂ mitigation over the lifetime was 34.2% and 140.97 tons, respectively. The carbon credit earned ranges from a minimum of $704.85 per ton of C to a maximum of $2,819.40 per ton of C.

Keywords:

• Carbon credit
• Carbon mitigation
• Greenhouse dryer
• Mint powder
• Photovoltaic-thermal

ACKNOWLEDGMENTS

The authors are grateful to the Ministry of Food Processing (MFPI) New Delhi, India, for providing financial help to carry out the above experiments. Our sincere thanks to colleagues and staff members of IIT, Delhi, for their active cooperation during the experimental work.

Notes

Tested samples are as follows. Dried samples: green leaf powder GH (1-GLP), stem powder GH (2-GSP), leaf and stem powder GH (3-GLSP), leaf powder (open)(4-OLP), and stem powder (open)(5-OSP). Fresh samples: fresh leaves (1-FL), fresh stem (2-FS), and fresh whole plant (3-FP).

Tested samples are as follows. Dried samples: green leaf powder GH (1-GLP), stem powder GH (2-GSP), leaf and stem powder GH (3-GLSP), leaf powder (open)(4-OLP), and stem powder (open)(5-OSP). Fresh samples: fresh leaves (1-FL), fresh stem (2-FS), and fresh whole plant (3-FP).