Thermal analysis of a compression heat pump-assisted solar still for Caspian regions of Kazakhstan

Water scarcity is a major issue in cities situated at the Caspian regions of Kazakhstan. To overcome this issue, two compression heat pump-assisted solar thermal desalination configurations are proposed in this research. A numerical model using the TRNSYS simulation package was developed to predict the energy performance of the proposed systems and was validated with experimental results available in the open literature. The influence of ambient parameters and water depth in the basin of a solar still and insulation thickness was analyzed. The performance of proposed configurations is compared with conventional solar still. The errors noticed at 2 and 10 cm depths are 23.6% and 12.1%, respectively. The simulation results confirmed that the heat pump-assisted regenerative solar still configuration has a 91.1%, 73.0%, 61.6% and 82.6% improved productivity during winter, spring, summer and autumn climates, respectively. The results confirmed that significant improvement in freshwater production was observed with heat regeneration compared to the configuration without heat regeneration. The maximum freshwater production with heat regeneration reached 18.0 kg m⁻² day⁻¹ in summer and 9.0 kg m⁻² day⁻¹ in winter. The optimal water depth in the basin is observed to be in the range between 0.5 and 2.0 cm, while the insulation thickness is between 5.0 and 7.0 cm. The results confirmed that the proposed configuration satisfies the water requirements in Kazakhstan.