Abstract
This research introduces the development of an automated forced and natural solar dryer (AFNSD) equipped with a photovoltaic-powered IoT technology, temperature-responsive control system that seamlessly alternates between natural and forced convection to improve efficiency and minimize energy consumption. In contrast to traditional fixed systems, it avoids both over-drying and product spoilage. The affordable, solar-driven design makes it ideal for off-grid communities. By combining drying kinetics analysis with economic and environmental evaluations, the system aligns with and promotes sustainability objectives. The thermodynamic performance and sustainability indicators were also evaluated. The developed AFNSD was used for drying orange slices at different tray positions (lower, middle, and upper), and three slice thicknesses (4, 6, and 8 mm). the obtained results showed that thinner orange slices (4 mm) placed on the lower trays reached the equilibrium moisture content more quickly, with an average drying time of about 13 h. In contrast, thicker slices (8 mm) positioned on the upper trays required the longest drying time, averaging around 25 h to reach the equilibrium moisture content. The thermodynamic analysis showed that the maximum energy efficiency of the solar collector (SC) (\(\:{\eta\:}_{en,\:\:SC})\:\)was about 70.98%. And the maximum exergy efficiency of the SC (\(\:{\eta\:}_{ex,\:\:SC})\:\)and the drying chamber (DCh) (\(\:{\eta\:}_{ex,\:\:DCh}\)) were about 21.93% and 43.64%, respectively. additionally, the sustainable indicators of both SC and DCh of the developed AFNSD, showed that the improved potential (IP) was in the range of 2.03 to 12.61 W in the SC and from 0.03 to 1.85 W in the DCh. The average waste energy ratio (WER) was 0.9 for the SC and 0.7 for the DCh. And the sustainability index (SI) ranged from 1.02 to 1.28 in the SC and from 1.2 to 1.77 in the DCh.
Data availability
All data are presented within the article.
Abbreviations
- \(MC\) :
-
Moisture content.
- W :
-
Sample weight
- \({\dot {m}_a}\) :
-
Mass flow rate
- \({\dot {E}_a}\) :
-
Energy flow rate
- \({h_a}\) :
-
Enthalpy
- \({v_a}\) :
-
Air velocity
- \({z_a}\) :
-
Height
- g :
-
Gravity acceleration
- \(\dot {W}\) :
-
Work done
- \(\dot {Q}\) :
-
Heat transfer
- \({\dot {Q}_u}\) :
-
Useful energy
- \({\dot {Q}_{in}}\) :
-
Input energy
- \({\dot {Q}_{ls}}\) :
-
Energy loss
- \({I_s}\) :
-
Solar radiation intensity
- \({A_{SAC}}\) :
-
Surface area of the solar collector
- \({C_{pa}}\) :
-
Specific heat of air
- \({T_c}\) :
-
Air temperature
- \({\eta _{en}}\) :
-
Energy efficiency
- \({m_w}\) :
-
Quantity of removed water from date sample
- L :
-
Latent heat of vaporization of water
- \({t_d}\) :
-
Drying time
- \({\eta _{ex}}\) :
-
Exergy efficiency
- u :
-
Internal energy
- s :
-
Entropy
- \(\alpha\) :
-
Absorptivity of glass
- \(\mathop {Ex}\limits^{.}\) :
-
Exergy
- \(\tau\) :
-
Transmissivity of glass
- \({\mu _{ch}}\) :
-
Chemical energy
- \({T_0}\) :
-
Atmospheric temperature
- i :
-
Inlet
- o :
-
Outlet
- \({\text{SAC}}\) :
-
Solar air collector
- Dryer:
-
The solar dryer
- DR:
-
Drying room
- AFNSD:
-
Automated forced and natural solar dryer
- CFD:
-
Computational fluid dynamics
- SC:
-
Solar Collector
- DCh:
-
Drying chamber
- ETSC:
-
Evacuated tube solar collector
- SRI:
-
Solar radiation intensity
- IP:
-
Improvement potential
- WER:
-
Waste exergy ratio
- SI:
-
Sustainability Index
- SD:
-
Solar dryer
- MC:
-
Moisture content
- PV:
-
Photovoltaic
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Acknowledgements
The authors would like to acknowledge Deanship of Graduate Studies and Scientific Research, Taif University for funding this work. This research was funded by the Hungarian National Research, Development, and Innovation Office, grant number TKP2021-NVA-22. This work was also supported by the Flagship Research Groups Programme of the Hungarian University of Agriculture and Life Sciences.
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Open access funding provided by Hungarian University of Agriculture and Life Sciences. This research was funded by the Deanship of Graduate Studies and Scientific Research, Taif University.
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Conceptualization, A.E.E., methodology, A.E.E., software, A.E.E., validation, A.E.E., formal analysis, A.A.T.O., A.A.T., and A.E.E., investigation, A.E.E., M.S.A., and A.F.A., resources, A.E.E., M.S.A., A.A.T.O., A.A.T., and A.F.A., data curation, A.E.E., M.S.A., W.A.M.A., and A.F.A., Writing - original draft, A.E.E., writing—review and editing, A.E.E., A.S., O.S., W.A.M.A., and M.H.E., visualization, A.E.E., supervision, A.E.E., project administration, A.E.E., funding acquisition, A.S., O.S., and M.S.A., All authors have read and agreed to the published version of the manuscript.
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Elwakeel, A.E., Oraiath, A.A.T., Abdurraziq, W.A.M. et al. Energy, exergy, and environmental performance of a solar dryer for orange slices across tray levels and thicknesses. Sci Rep (2026). https://doi.org/10.1038/s41598-025-23535-5
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DOI: https://doi.org/10.1038/s41598-025-23535-5