Performance evaluation of a multi-mode drying system with thermal energy storage for high-value agricultural products

Abstract

Sustainable solutions, such as solar dryers, are crucial to addressing the energy-intensive nature of drying agricultural products. These dryers can potentially revolutionise sustainable farming practices, significantly reducing environmental impact. Heat pumps are reliable and efficient, but their energy consumption is high, and solar system efficiency could be better and more consistent. This work optimises performance by integrating heat pumps and solar systems with thermal energy storage for temperate climatic conditions. This study aims to develop and evaluate a versatile dryer capable of operating in five distinct modes: solar with and without Thermal Energy Storage (TES), heat pump with and without TES, and a hybrid mode that integrates solar, heat pump, and TES. Field tests were conducted in the climatic conditions of Ramanagara district, Bangalore, Karnataka, focusing on high-value crops like cardamom, pepper, and cashews. To assess performance, 10 kg of cardamom was dried over eight hours across all five modes, with a detailed analysis of local weather conditions. The highest solar radiation recorded during testing was 847 W/m². Results revealed that incorporating TES enhanced the drying process by stabilising the chamber temperature, with TES-enabled modes showing an average increase of 4 °C compared to non-TES modes. The hybrid mode showed the greatest improvement, achieving 81 % moisture removal and reducing the weight of 10 kg of cardamom by 5.3 kg. Additionally, TES extended the dryer's operational time, resulting in more efficient dehydration of high-value crops while maintaining consistent temperatures. These findings highlight the transformative potential of hybrid drying systems in promoting sustainable agriculture. The enhanced energy efficiency offered by such systems supports broader adoption by improving energy use in agricultural processing.