Open Access

ARTICLE

Development and Thermal Evaluation of a Cocoa Solar Roaster Using a Dual-Axis Parabolic Cylinder Collector (PCC)

E. V. Macias-Melo¹, P. R. Torres-Hernández², K. M. Aguilar-Castro¹, I. Hernández-Pérez¹, P. García-Alamilla³, C. E. Torres-Aguilar¹, M. I. Hernández-López⁴, S. Medina García⁴, J. Serrano-Arellano^4,*
1 División Académica de Ingeniería y Arquitectura (DAIA-UJAT), Universidad Juárez Autónoma de Tabasco, Cunduacán, CP 86690, Tabasco, México
2 Maestría en Ciencias en Ingeniería, División Académica de Ingeniería y Arquitectura (DAIA-UJAT), Universidad Juárez Autónoma de Tabasco, Cunduacán, CP 86690, Tabasco, México
3 Laboratorio de Ingeniería de Procesos, División Académica de Ciencias Agropecuarias (DACA), Universidad Juárez Autónoma de Tabasco (UJAT), Carretera Villahermosa-Teapa Km. 25, La Huasteca, Centro, Villahermosa, 86280, Tabasco, México
4 División de Estudios de Posgrado e Investigación, Tecnológico Nacional de México/IT de Pachuca, Carretera México-Pachuca Km. 87.5, Colonia Venta Prieta, Pachuca de Soto, CP 42080, Hidalgo, México
* Corresponding Author: J. Serrano-Arellano. Email:

Frontiers in Heat and Mass Transfer https://doi.org/10.32604/fhmt.2025.074900

Received 21 October 2025; Accepted 27 November 2025; Published online 04 January 2026

Abstract

This study presents the design, construction, and thermal evaluation of a solar-powered cocoa roaster based on a Parabolic Cylinder Collector (PCC) with dual-axis solar tracking. The system integrates three functional subsystems: the cylindrical-parabolic reflecting surface, the stainless-steel absorber tube, and a microcontroller-based tracking mechanism. The prototype enables continuous acquisition of key thermal variables (solar irradiance, ambient temperature, absorber surface temperature, and bean temperature), allowing a detailed characterization of heat transfer processes during roasting. Roasting experiments were conducted at controlled durations of 40, 55, and 70 min between 10:00 and 14:00 h. Maximum roasting temperatures of 125°C–137°C were reached under average irradiance levels of 685.7–930.5 W m⁻². The lowest final moisture content was 2.19%, within the recommended range for high-quality cocoa. Longer roasting durations promoted thermal energy accumulation within the absorber tube, enhancing convective and radiative heat transfer to the bean mass even under fluctuating irradiance. The experimental trends reveal a strong coupling between irradiance variability, absorber temperature, and internal air-beam heat transfer. Comparison with reference parabolic trough collector studies indicate that, although the process-level roasting efficiency (3.83%–7.45%) is lower than conventional collector-level thermal efficiencies, the operating temperatures and moisture-reduction rates align with the thermal requirements of food-processing systems rather than high-enthalpy solar applications. These results also demonstrate the potential of coupling PCC-based solar concentration with low-temperature convective–radiative roasting processes. Overall, the findings confirm the feasibility of implementing PCC-based roasting technologies in rural or off-grid regions, where solar-driven heat transfer offers a sustainable, low-cost alternative to fossil-fuel-based roasting systems, enabling a controlled thermophysical environment for cocoa transformation.

---

Keywords

Parabolic cylinder collector; roasting cocoa; solar roaster

---