Enhancement of solar pond stability performance using an external magnetic field

• Published in: Energy conversion and management 2021-09, Vol.243, p.114427, Article 114427
• Main Authors: Tian, D., Qu, Z.G., Zhang, J.F., Ren, Q.L.
• Format: Article
• Language: English
• Subjects: Active method; Computational fluid dynamics; Convection; Dimensional stability; Electrical conductivity; Electrical resistivity; Energy absorption; Fluid flow; Hartmann number; Heat; Heat storage; Illumination; Interface erosion; Magnetic control; Magnetic field; Magnetic fields; Mass transfer; Ponds; Solar energy; Solar magnetic field; Solar pond; Solar ponds (heat storage); Thickness; Two dimensional models
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2021.114427

•Active method by external magnetic field is proposed to improve solar pond stability.•Improvement of heat storage capacity and stability is analyzed quantitatively.•Magnetic field effectively represses interface erosion in solar pond.•Nondimensionalized magnetic field effect on solar pond performance is discussed. A solar pond is a simple and reliable system that collects and stores solar energy for applications with low-grade heat supply. The main obstacle to the long-term stable operation of a solar pond is interface erosion induced by double-diffusive convection. In this study, an active method of using an external magnetic field is proposed to repress the intense convection region and improve its corresponding operating stability. A two-dimensional transient model is developed and solved using the lattice Boltzmann method with multiple-relaxation-time collisions. The double-diffusive convection, variation of solar energy absorption to depth, and changes in solution electrical conductivity are considered in the model. The fluid flow, heat, and mass transfer characteristics were investigated under continuous high illumination with or without an external magnetic field. When magnetic control is exerted on a solar pond, the decrease in the nonconvective zone thickness caused by interface erosion changes from 14.75% to 0. The state of the solar pond is transformed from a thermally unstable state to a theoretically stable state after 35 h of continuous high illumination. Further, the external magnetic field can delay concentration homogenization and improve the heat storage performance of a lower convective zone. A Hartmann number above 56.67 is recommended to enhance the stability of the solar pond. This research sheds new light on methods to improve the long-term stability of solar ponds.