Energy and exergy performance evaluation of a drying coffee beans system using a photovoltaic–direct solar dryer at different drying temperature conditions

Abstract

This study investigates the impact of various drying temperatures on the performance evaluation of photovoltaic – direct solar dryers in the coffee bean drying process. The use of photovoltaic systems in solar drying provides opportunities for the future to support clean and eco-friendly renewable energy. Three drying temperature conditions were tested, namely 40°C, 45°C, and 50°C, with the optimum temperature obtained at 50°C. During the drying process, the weather appears to be very sunny and cloudless, resulting in an average solar intensity of 974.36 W/m². Utilising this solar dryer, it takes 12–16 hours for the coffee bean drying process to achieve a moisture content below 12.5% by the SNI 01-2907-2008 standard, starting from an initial moisture content of 45%. The drying and solar collector efficiencies ranged between 0% to 54% and 67.33% to 88.24%, respectively. Energy consumption is directly proportional to drying efficiency, depicted as the energy utilisation ratio (EUR), with the highest EUR being 22.96%. Meanwhile, the exergy flow (inlet, outlet, and loss) is directly proportional to the solar intensity, forming an open downward parabolic curve, with the average exergy efficiencies obtained at temperatures of 40°C, 45°C, and 50°C being 53.95%, 54.72%, and 56.88%, respectively.

KEYWORDS:

• Coffee beans
• direct solar dryer
• photovoltaic system
• energy analysis
• exergy analysis

Acknowledgment

The authors would like to thank the Department of Chemical Engineering at Diponegoro University for providing laboratory facilities for the implementation of this project. The authors would like to the Directorate of Research, Technology, and Community Service, Directorate General of Higher Education, Research, and Technology, Ministry of Education, Culture, Research, and Technology, and Diponegoro University for funding this research with contract number 449A-58/UN7.D2/PP/VI/2023.

Disclosure statement

No potential conflict of interest was reported by the author(s).

CRediT authorship contribution statement

Suherman Suherman: Conceptualisation, Methodology, Supervision, Investigation, Writing – review & editing, Validation, Funding acquisition. Hadiyanto Hadiyanto: Supervision, Investigation, Writing – review & editing, Validation. Muhammad Anas Asy-Syaqiq: Performed the experiments, Data curation, Software, Visualisation, Writing – original draft, Writing – review & editing. Ghina ‘Afifah Ghassani and Mia Ajundasari: Performed the experiments, Writing – review & editing. All authors read and approved the final manuscript.

Additional information

Funding

This work was supported by Kementerian Pendidikan, Kebudayaan, Riset, dan Teknologi [grant number 449A-58/UN7.D2/PP/VI/2023]; Universitas Diponegoro.