This research paper describes the drying kinetics of ber (Zizyphus mauritiana) fruit and economic evaluation of hybrid photovoltaic/thermal (PV/T) solar dryer fabricated using locally available materials, e.g. galvanized iron sheet, glass, PV panel and fan. Ber fruits were dried to the safe level moisture content (20%) in a period of 240 h with the drying load of 18 kg. Four mathematical models were evaluated to predict the behaviour of ber (Zizyphus mauritiana) drying in a combined hybrid PV/T solar dryer. Experimental data of moisture ratio (MR) and temperature obtained from dryer were fitted to the four empirical drying models. The performance of the drying model was compared based on their statistical parameters: coefficient of determination (R²), root mean square error (RMSE) and reduced chi-square (χ²) between the observed and predicted MR. The logarithmic model was found to be the most suitable for describing the thin layer drying behaviour of ber (Zizyphus mauritiana). The effective moisture diffusivity was 3.34 × 10⁻⁷ m²/s and the efficiency of this dryer was found to be 16.7%. The developed hybrid PV/T drying system produces better quality products in shorter time by the efficient use of solar energy. The economic evaluation of the hybrid photovoltaic thermal (PV/T) solar dryer revealed that high value of IRR (54.5%) and low value of payback period (2.26 Years) make the dryer unit cost-efficient ensuring its economic viability.

Date palm (Phoenix dactylifera L.) fruits are widely grown in rural areas of arid Rajasthan of India. The grown date palm fruits are generally dried in forced convection mode. However, given the socio-economic status of farmers, dryer facility affordability has become crucial. Additionally, there is a critical need for a simple winnower, especially with its operation. To address the highlighted issues with the dryer and winnower and given a location already receiving abundant solar radiation, a solar photovoltaic (PV) winnower cum-dryer was designed and developed. The developed winnower cum-dryer was tested in actual conditions to realize the performance. First, the drying experiment for dehydrating date palm fruits and, second, the winnower experiment for separating grains from straw were carried out. The date palm fruits used for experimentation have a moisture content of 65% on a wet basis. During the drying trial, the dryer reduced this moisture content by 39% in 6 days. In contrast, in the open sun drying, it took 8 days. The drying chamber’s temperature gradient was reduced to 2–3 °C from 6–8 °C in the system provided with a preheater, resulting in uniform drying. The observed effective moisture diffusivity and the dryer’s efficiency are 4.34 × 10⁻⁹ m²·s⁻¹ and 16.1%, respectively. A high IRR of 57.4% and a shorter payback period of 2.10 years were found in the economic analysis, indicating that the dryer is cost-effective. The winnower operation results suggest that about 200–300 kg grains could be separated daily when used as a winnower without natural wind. Overall, the developed winnower cum-dryer produced better-quality dried date palms in a shorter time than open drying by efficiently using solar energy and separating the grains from straw to enhance the utility throughout the year.

The experimental analysis revealed that the system was found suitable to overcome the problems of corrosion, salt scaling and algae. The system was able to provide 2.65 litre of distilled water per day for about 320 days per annum. The economic evaluation of the distillation unit revealed that high value of IRR (62.88 per cent) and low value of payback period (1.9 Years) make the unit very cost efficient. The economic attributes of the system revealed its economic viability. The system is useful for getting distilled water which can be used in batteries, laboratories. It can also be used for drinking by mixing with saline water in places where water quality is saline