Modeling the performance of a solar pond under Tripoli's climatic conditions, with an advanced physical model.

Abstract

Solar ponds offer an effective solution for long-term solar energy harvesting and thermal storage, particularly in arid and semi-arid regions. This paper presents a numerical simulation framework for a solar pond with a salinity gradient, subjected to controlled thermal energy extraction rates of 10, 20, and 30 W/m² from the lower convection zone. The study aims to evaluate the operational feasibility of sustainable heat removal while maintaining the thermal gradient, salinity stability, and overall hydrodynamic integrity of the pond.

In addition to this conventional thermal extraction, an advanced physical model is presented as a visualization, not incorporated into the current numerical simulation process. This model, intended to serve as a basis for future studies, integrates the solar pond with a dedicated flash evaporator chamber for low-pressure steam generation. The thermal energy extracted from the lower convection zone is transferred to the evaporator chamber, where saline or brackish water undergoes controlled flash evaporation to produce steam suitable for thermal applications or for generating electricity and desalinated water at low temperatures. The concentrated brine produced from the evaporation process is managed to minimize freshwater loss and control salt concentration gradients.

A key innovation of the proposed system is a semi-closed salt management cycle, where salt depleted from the non-thermal zone (NCZ) due to diffusion and operational disturbances is continuously replenished through salt recovery and recycling from the evaporator unit. This approach significantly reduces external salt demand while maintaining the critical salinity gradient necessary for long-term pond stability. The numerical model incorporates interrelated constraints for heat transfer, mass diffusion, and buoyancy-driven flow, providing a scalable platform for detailed calculations and future optimization studies.

Simulation results demonstrate the feasibility of maintaining heat extraction of up to 30 W/m² without destabilizing the NCZ, provided that adaptive salt recycling strategies and controlled salt withdrawal are implemented. The proposed configuration provides a consistent and scalable physical basis for modeling the integration of solar ponds with evaporative steam production, offering a promising pathway toward sustainable, low-cost thermal energy systems with improved resource efficiency.