Comprehensive assessment of a greenhouse solar dryer for handmade paper drying: economic, environmental, drying kinetics and post-drying analysis

The present investigation evaluates the performance of a 5 m³ greenhouse solar dryer for drying eco-friendly handmade papers. A comprehensive year-round thermal assessment was conducted under three intermittent and one continuous fan operation modes across varying paper batch sizes (75–300). Handmade papers of different thicknesses (100, 200 and 250 Gram Per Square Metre) were successfully dried from 55–60% to 9–10% moisture content (wet basis) within just 3.25–8 h resulting in a significant improvement when compared to traditional open sun and shade drying methods. Throughout operation, the dryer-maintained temperatures between 45 and 60°C with efficiency ranging from 11.2% to 32.5%. From a sustainability perspective, the developed system demonstrated good results with an energy payback period of 2.4 years, a carbon dioxide mitigation of 19.03 tons, and an economic payback period of merely 0.6 years. Among the five mathematical models tested to predict drying kinetics, the Midilli–Kucuk model exhibited the most accurate fit to experimental data with a coefficient of determination R2 ranging from 0.9972 to 0.9975. Following the drying process, the dried papers underwent quality evaluation through both visual inspection and standardised burst testing.