Indigenous solar desalination technologies for sustainable potable water supply

Water plays an important role in mankind’s day to day life activities and most of the regions of the globe are under severe water scarcity. In India, several regions are under severe water stress and deaths are reported every year due to unsafe water consumption. Desalination of sea water is an effective option to satisfy the fresh water demands. Desalination industry is widely expanding in India and its market value wound be around USD1.9 billion in 2019. The desalination is an energy intensive process and it requires at least a ton of oil to produce 20 tons of fresh water. For every one ton of fresh water produced nearly 25.0 kg of CO2 is emitted to the atmosphere. Solar energy can be used to power desalination technology there by cut off in carbon emission can be achieved. India receives nearly 3.5 to 6.0 kWh/m²-d of solar radiation which paves the way for setting up solar thermal or PV based desalination units. Solar stills have been widely used to meet the fresh water demands. Solar stills are a sustainable option for remote and rural locations were access to electricity and fresh water is minimal. Cascaded vertical double slope still and Active multi effect evacuated vertical solar still can produce fresh water of around 20 kg/d from saline water of 5.0 wt% salinity which is fairly sufficient for a family of 4 to 5 members. The units can mitigate at least 80 tons of CO2 emission during their life time of 20 yrs. Cost of distilled water is around 33.0 USD/kL for 12% interest rate and it can be reduced to 19.0 USD/kL for 5% interest rate. The production cost and environmental benefits of these solar desalination units are highly competitive and viable in rural areas.