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

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 CO(2) 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.