Ankur Gupta

This study experimentally analyzes the effect of hybrid CNT-ZnO nano-particle coating under similar controlled conditions for performance comparison of the photovoltaic thermal (PVT) dryer. The developed system was evaluated under three configurations: uncoated absorber (Case I), CNT-coated (Case II), and CNT-ZnO-coated (Case III). Significant improvements in thermal and drying characteristics with enhancement of 46.91% in thermal efficiency and 15.90% in drying efficiency was seen using advanced CNT-ZnO-coated system. The findings of SEM, XRD, FTIR, and TGA analysis show that hybrid CNT-ZnO-coated nanoparticles improve thermal stability and heat retention, resulting in easier drying and better energy use. This suggests that hybrid CNT-ZnO nano-particle coating is an effective approach for strengthening the effectiveness of the PVT dryer.

This study examines the heat and mass transfer coefficient, thermal effusivity, and other thermal properties of solar-dried cocoyam chips, as well as the drying kinetics. The research also assessed the economics of the solar dryer. For these reasons, a solar dryer with a partitioned collector was developed that creates a double airflow travel distance to delay the airflow inside the collector. The partitioning of the collector delays the airflow and helps to create more turbulence for the airflow with increased energy. The solar dryer was locally developed at the Michael Okpara University of Agriculture and tested during the humid crop harvesting period of September for the worst-case scenario. The obtained drying curves and kinetics for cocoyam drying are subjected to the vagaries of weather conditions. The drying rate showed declining sinusoidal characteristics and took about 25 h to attain equilibrium. Analysis of the airflow velocity showed gravitation between laminar and turbulent flow, ranging from 171.69 to 5152.77. Specific heat capacity, thermal conductivity, and effusivity declined with moisture content while the thermal diffusivity increased. However, the values of thermal effusivity ranged from 12.2 to 47.94 W·s^1/2·m⁻²·K⁻¹, which is within the range of values for insulators. The heat and mass transfer coefficient varied as a function of the airflow velocity. Fitting the drying curve into semi-empirical models showed that the two-term model was the best-fitted model for the experimental data from drying cocoyam. Using the solar dryer in Nigeria can save $188.63–$1886.13 in running costs with a payback period of 0.059–0.59 years (21.54–215.35 days) at a rate of 10–100% of usage.

In the present study, an innovative stand‐alone solar photovoltaic thermal (PVT) dryer has been designed and tested in hot‐humid weather conditions of North‐East India for drying green chili. The electrical output of the hybrid PVT solar dryer has been utilized to operate the blower for the dryer making the system self‐sustained. A comparative analysis of the drying phenomena under the open sun and in the PVT based dryer is performed. Mathematical modeling is also done to investigate the drying kinetics of green chili for both drying conditions. Results indicate that the moisture content of 0.030 (d.b.) in the solar dryer and 0.035 (d.b.) in the open sun has been reduced for a span of 21 and 37 hr, respectively. Hybrid PVT solar dryer has achieved an average thermal efficiency of 31.37% and an average specific moisture extraction rate of 0.228 kg/kWh. The overall energy consumption for drying green chili is calculated to be 4.90 kWh/kg. Also, the overall thermal efficiency of 64.16%, thermal efficiency of 30.15%, and average electrical efficiency of 12.92% are secured. The results demonstrate the improved performance of the present PVT dryer for green chili drying in comparison to some of the conventional direct/indirect solar dryers.Practical Applications: The present PVT solar dryer system can be utilized for drying the products using thermal energy produced by PVT air collector as well as generating electrical power in the decentralized off‐grid areas. Solar drying is not adequately popular in the North‐Eastern part of India due to the unavailability of solar drying systems for farmers. The agricultural products can be dried in the farming areas by installing this system. This PVT solar dryer provides a solution to the farmers for drying at zero energy cost and can be used as a source of income generation. This PVT solar drying system can be used to increase the storage life and reduce the spoilage and deterioration of agricultural commodities. Energy efficient solar drying process, high‐quality products, and faster drying rate compared to traditional drying method can be achieved with the help of using this system.