Spherically encapsulated phase change material-assisted indirect solar drying enhances tomato nutritional quality, exergy efficiency, sustainability, and economic feasibility

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An indirect solar dryer for tomato drying was used under two operating conditions: Case 1, without phase change material (PCM) in the drying chamber (DC), and Case 2, with spherically encapsulated PCM incorporated into the DC. Drying kinetics, nutritional quality, morphology of the dried tomatoes, exergy performance, exergy-based sustainability indicators, and economic performance were evaluated under the two operating conditions. As a result, Case 2 achieves higher moisture removal and drying rates, lower moisture ratio and water activity, and better preservation of tomato cell-wall microstructure compared to Case 1. The energy and exergy efficiency of the collector remains nearly unchanged between the two Cases, because the same absorber plate is used under similar environmental conditions. The PCM integration leads to a slight increase in DC energy efficiency, and exergy efficiency increase to 53.91% in Case 2, a 9.33% improvement for Case 1. The exergy-based sustainability assessment reveals that Case 2 outperforms in terms of environmental and thermodynamic performance. The economic analysis shows that Case 2 has a higher annual output of 176.38 kg, and the economic payback period is calculated as 0.33 years (Case 1) and 0.5 years (Case 2). Conclusively, the Case 2 drying condition provides better-dried product and ensures long-term economic benefits.