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Review

Exergy‑Based Performance Evaluation of Solar Dryers: A Critical Review of Adopted Approaches

Gustavo Aragão Correia ORCID ,  Keyse Santos Andrade ORCID ,  Marcos Fábio Farias Souza ORCID ,  Manoel Marcelo do Prado ORCID
    Received: 12 March 2026; Revised: 8 May 2026; Accepted: 20 May 2026; Published: 14 July 2026

    Abstract

    Drying is a key unit operation in industrial processes, yet it is inherently energy-intensive, particularly when conventional technologies are employed. Solar dryers have emerged as sustainable alternatives due to their reduced dependence on fossil fuels and lower environmental impact. However, improving their performance requires a rigorous thermodynamic assessment, for which exergy analysis provides a more comprehensive framework by accounting for both energy quality and process irreversibilities. Despite its potential, the application of exergy analysis to solar drying systems remains inconsistent in the literature, with significant variations in definitions, assumptions, and formulations adopted. This lack of standardization compromises the reliability and comparability of reported performance indicators. In this study, the formulations commonly used in the exergy analysis of solar dryers are systematically reviewed and critically evaluated. The results indicate that the widespread use of outlet air exergy in the calculation of exergy efficiency may not adequately represent the useful energy associated with the drying process. A more physically consistent approach is obtained by considering useful energy in terms of sensible and latent heat transfer, as well as by incorporating formulations derived from radiation theory that account for material absorptance and transmittance. Furthermore, practical recommendations are proposed to improve the accuracy of exergy-based evaluations, including continuous monitoring of product temperature and mass, and modeling the drying agent as a mixture of dry air and water vapor. These findings contribute to the development of a more consistent framework for the thermodynamic assessment and comparison of solar drying systems.

    Keywords

    References

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