Thermal performance, cost effectiveness and environmental analysis of a heat pump assisted regenerative solar still using slack wax as heat storage material

Abstract

In this research, the thermal analysis of a heat pump assisted regenerative solar still (HPARSS) using slack wax heat storage material was assessed and compared the results with conventional solar still (CSS) under the same climatic conditions. In HPARSS, the thermal energy obtained during the condensation was regenerated using compression heat pump and used to pre-heat the inlet saline water before it reached the solar still basin. The outcomes showed that the HPARSS has the maximum cumulative productivity of about 16.5 kg/m2 in 12 h observations which is 85.1% higher than CSS. The obtained energy and exergy efficiency of HPARSS were 67.4% and 81.9% higher than CSS, respectively. The maximum Coefficient of Performance (COP) of HPARSS was about 2.81. The diffused heat rate was estimated using entropy analysis and the results revealed that the maximum entropy attained in HPARSS and CSS were approximately 14.2 J/kg.K and 6.1 J/kg.K, respectively. The exergy destruction observed in HPARSS basin, saline water and glass cover were significantly reduced by 8.4%, 10.5% and 20.7%, respectively than CSS. The payback period (PBP) and CO2 emissions of HPARSS were estimated by 2.8 months and 91.2 tons, respectively. The outcomes showed that the HPARSS can be significantly reduce the potable water demand.