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This study explores the feasibility of solar desalination using black powder coated crushed granite stone, evaluating their energetic, exergetic, and economic aspects, wherein the stone bed preheats water for the solar still. In addition, the system integrates with a district heating network to meet desalination needs during off-solar or high-demand hours in which water from the powder-stone grid’s outlet flows through a heat exchanger, powered by district heating’s return flow. Desalination pipe absorbs heat and cools district heating line. The outcomes illustrated that cumulative distilled water for a water depth of 1 cm was 13.1% and 28.2% higher than cumulative distilled water for water depths of 2 cm and 3 cm, respectively. The energy efficiency was improved by 9.5% and 15.7% and the exergy efficiency was enhanced to 13.6% and 27.2% at 1 cm water depth compared to 2 and 3 cm water depths. The integration of the system with the district heating network could lead to a great improvement in the productivity; summer’s low district heating demand allows surplus heat to boost water production and lower outlet water temperature, benefiting both desalination and cooling process. The cumulative productivity will not be sensitive to the water depth anymore, increasing up to 105%, 135%, and 182% for 1, 2, and 3 cm water depths, respectively. This integration has a fascinating effect on the reduction in temperature of the district heating return flow (about 3°C), improving the cooling potential of the flow. [ABSTRACT FROM AUTHOR]

The explosion of the population is alarming as the demand increases exponentially for resources. The freshwater resources are being exploited, and innovative and economical methods are analyzed experimentally to extract freshwater from various sources. Desalination performed using solar energy is an economical method to obtain fresh water from seawater and brackish water, which are available prolifically in nature. Since the phenomenon of desalination demands solar irradiation, which is an intermittent source of energy, distillation is not feasible in some places where the solar intensity is low. In the solar desalination, the saturation temperature of the saline water is very less at low saturation pressure thereby requiring large latent heat of evaporation. Hence, vacuum pressure could be the most appropriate choice to extract drinkable water in territories where the intensity of solar irradiation is poor. In order to this, the utilization of evacuated tube collectors and vacuum technology in the solar desalination unit has been considered for discussion as it is the most sought-after subject of interest in the current scenario. Methods for implementing the vacuum technology are also introduced with plenty of experimentations. Vacuum technology implemented in the evaporator of desalination system has been supplemented with nano-fluids and phase change materials to accelerate the evaporation process, increase efficiency, and obtain a greater productivity. In this review, the performance of the solar desalination unit under the vacuum effect were discussed in detail. Furthermore, in economic analysis, the cost effectiveness and cost per liter of distillate (CPL) were discussed to estimate the payback period. Finally, this review also suggests the vision to identify the future scope for additional implementations. [ABSTRACT FROM AUTHOR]

Solar still, as one of the important devices for generating water using renewable energy, has been widely used in arid as well as coastal areas where access to fresh water is limited. This paper uses CFD simulation to compare double-slope solar still, hemispherical solar still, and tubular solar still using nanofluid film cooling. Al2O3-water nanofluids with a concentration of 0.1% are used due to facilitate sunlight penetration into the absorber plate inside the solar desalination. It is assumed the flow is steady, laminar, and air is an ideal and incompressible gas. The simple algorithm is considered to calculate the relationship between pressure and velocity and to separate the transfer and pressure interpolation terms from the appropriate upstream designs. Also, the economic, exergoeconomic, and CO2 mitigation parameters of various solar stills were investigated. The study revealed that the water productivity of double-slope solar desalination using nanofluids film cooling is improved by about 4.8% compared with tubular solar desalination with nanofluid film cooling. Also, the lowest CPL of 0.0362 $/L was obtained in the double-slope solar desalination using nanofluid film cooling. The net CO2 mitigation of 14.08 tons, 13.72 tons, and 13.44 tons was obtained for double-slope solar desalination, hemispherical solar desalination, and tubular solar desalination, respectively. [ABSTRACT FROM AUTHOR]