Charging of an Air–Rock Bed Thermal Energy Storage under Natural and Forced Convection

Ashenafi Kebedom Abrha (), Mebrahtu Kidanu Teklehaymanot, Mulu Bayray Kahsay and Ole Jørgen Nydal
Additional contact information
Ashenafi Kebedom Abrha: School of Mechanical and Industrial Engineering, EiT-M, Mekelle University, Mekelle 231, Ethiopia
Mebrahtu Kidanu Teklehaymanot: School of Mechanical and Industrial Engineering, EiT-M, Mekelle University, Mekelle 231, Ethiopia
Mulu Bayray Kahsay: School of Mechanical and Industrial Engineering, EiT-M, Mekelle University, Mekelle 231, Ethiopia
Ole Jørgen Nydal: Department of Energy and Process Engineering, NTNU Norwegian University of Science and Technology, N-7491 Trondheim, Norway

Energies, 2024, vol. 17, issue 19, 1-19

Abstract: An air-rock bed thermal storage system was designed for small-scale powered generation and analyzed with computational fluid dynamics (CFD) using ANSYS-Fluent simulation. An experimental system was constructed to compare and validate the simulation model results. The storage unit is a cylindrical steel container with granite rock pebbles as a storage medium. The CFD simulation used a porous flow model. Transient-state simulations were performed on a 2D axisymmetric model using a pressure-based solver. During charging, heat input that keeps the bottom temperature at 550 °C was applied to raise the storage temperature. Performance analysis was conducted under various porosities, considering natural and forced convection. The natural convection analysis showed insignificant convection contribution after 10 h of charging, as observed in both average air velocity and the temperature profile plots. The temperature distribution profiles at various positions for both convection modes showed good agreement between the simulation and experimental results. Additionally, both cases exhibited similar temperature growth trends, further validating the models. Forced convection reduced the charging time from 60 h to 5 h to store 70 MJ of energy at a porosity of 0.4, compared to natural convection, which stored only 50 MJ in the same time. This extended charging period was attributed to poor natural convective heat transfer, indicating that relying solely on natural convection for thermal energy storage under the given conditions is not practical. Using a small fan to enhance heat transfer, forced convection is a more practical method for charging the system, making it suitable for power generation applications.

Keywords: air–rock bed; thermal storage; CFD simulation; natural convection; forced convection; porous flow model (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
References: View references in EconPapers View complete reference list from CitEc
Citations:

Downloads: (external link)
https://www.mdpi.com/1996-1073/17/19/4952/pdf (application/pdf)
https://www.mdpi.com/1996-1073/17/19/4952/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:17:y:2024:i:19:p:4952-:d:1491644

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().