A Sustainable Smart Dryer for Aromatic Herbs

Abstract

Nowadays, there is a growing consumer interest in medicinal and aromatic herbs. The microbiological quality of nutraceutical and aromatic plants has become a pivotal factor for buyers. Italian producers adhere to specific hygiene regulations to diminish the bacterial load of these plants, focusing primarily on operations between harvest and packaging, such as the crucial drying process. This drying process occurs at temperatures ranging from 20 to 50 °C, facilitated by devices equipped with a heat pump. It involves applying very dry air (with 5% humidity) to dehumidified products and heating them to the desired temperature. This rapid drying method preserves the colour, aroma, and chemical composition of the food, ensuring the production of high-quality products. This study aims to optimize the drying process using a dryer plant located in Grotte (Italy), powered by a photovoltaic Renewable Energy Source (RES) for nutraceutical and aromatic species produced in Sicily, namely rosemary and sage. Energy is generated by photovoltaic panels mounted on the roof and in one facades of the dryer structure, facilitating on-site energy exchange and self-consumption. The annual potential production of the photovoltaic generator is 8383 kWh, and the dryer was tested for four drying cycles using the energy generated by the solar source. This drying cycle lasts for 24.5 h, just more than one day. Sensors-acquired data were transmitted via Wi-Fi to a ThingSpeak account, enabling real-time monitoring of the drying process. The obtained information included variations in product moisture content and drying rates. The WSN-based system played a crucial role in decision support during the drying process, allowing precise monitoring of biomass moisture loss and drying rates for rosemary and sage. Interestingly, different biomass densities did not significantly impact the drying process for sage.