Impact of direct heat extraction on the thermal storage and stability of solar ponds

Abstract

Direct heat extraction from solar ponds, achieved by pumping hot brine directly without an internal heat exchanger, offers reduced cost but may disturb convective flow and compromise stability. This study employs a transient two-dimensional large-eddy simulation (LES) model to investigate turbulent double-diffusive flow during direct extraction. By resolving the interaction between pumping and convective flow in solar ponds, the model evaluates the effects of pumping velocity, injection and outlet positions, and pond width on both stability and heat extraction efficiency. The results show that heat extraction generally enhances thermal stability by lowering temperatures in the lower convective zone (LCZ). Due to strong mixing in the LCZ, stability and extraction efficiency remain largely insensitive to injection and outlet positions. Installing the injection and outlet on the same side and higher altitude reduces installation costs with minimal impact on stability and efficiency. Pond width strongly influences performance, as wider ponds increase outlet temperature and extraction rate, improving short-term efficiency but intensifying vertical mixing, which may reduce long-term thermal storage. Overall, direct heat extraction has a limited disturbance on the stability of solar ponds. These findings provide practical guidance for optimizing solar pond design to balance efficiency, stability, and cost.