The availability of fresh drinkable water and water security is becoming a global challenge for sustainable development. In this regard, solar stills, due to their ease in operation, installation, and utilization of direct sunlight (as thermal energy), promise a better and sustainable future technology for water security in urban and remote areas. The major issue is its low distillate productivity, which limits its widespread commercialization. In this study, the effect of silicon (Si) particles is examined to improve the absorber surface temperature of the solar still absorber plate, which is the major component for increased distillate yield. Various weight percentages of Si particles were introduced in paint and coated on the aluminum absorber surface. Extensive indoor (using a self-made halogen light-based solar simulator) and outdoor testing were conducted to optimize the concentration. The coatings with 15 wt % Si in the paint exhibited the highest increase in temperature, namely, 98.5 °C under indoor controlled conditions at 1000 W/m² irradiation, which is 65.81% higher than a bare aluminum plate and 37.09% higher compared to a black paint-coated aluminum plate. On the other hand, coatings with 10 wt % Si reached up to 73.2 °C under uncontrolled outdoor conditions compared to 68.8 °C for the black paint-coated aluminum plate. A further increase in concentration did not improve the surface temperature, which was due to an excessive increase in thermal conductivity and high convective heat losses.

The ever-increasing water stress and availability of fresh drinking water are becoming a major challenge in rural and urban communities. The current high-end and large-scale technologies are becoming way more expensive and not friendly to the environment. In this regard, solar still is becoming a prominent and promising future technology due to its environment-friendly nature, less maintenance and operational costs, and simple design. The technological challenge regarding solar still is its low distillate yield. In this study, an attempt has been made to investigate the effect of tin oxide (SnO₂) on the absorption surface of solar still towards improvement in sunlight absorption, which would lead to high distillate production rates. Various concentrations of SnO_2, i.e., 0.5wt, 1wt, 3wt, 5wt, 7wt, 10wt, 15wt, and 20wt, have been mixed in black and applied on the absorber plate to further optimize the suitable concentration. The experiments have been performed in both indoor (simulated) and outdoor conditions. An increase in surface temperature of absorber plate has been observed with increasing concentration of SnO₂ under both the indoor and outdoor conditions, which is due to high solar spectrum absorption properties of SnO₂ in the ultraviolet (UV) and near to far-infrared (IR) regions. The highest surface temperature of 101.61C has been observed for specimens containing 15wt SnO₂ in black paint under indoor conditions at 1000W/m² irradiation levels, which is 53.67 higher compared to bare aluminum plate and 16.91 higher compared to only black paint coated aluminum plate. On the other hand, the maximum temperature of 74.96C has been recorded for the identical specimens containing 15wt SnO₂ under uncontrolled outdoor conditions. The recorded temperature is 47.96 higher than the bare aluminum plate and 14.88 higher than the black paint-coated aluminum plate. The difference of maximum temperatures under indoor and outdoor conditions is due to uncontrolled outdoor conditions and convective losses.

The extensive and inefficient utilization of fossil fuels leads to high environmental concerns and energy security. Scientists are merely emphasizing on renewable energy sources and their appropriate utilization. In this regard, on-demand production (by dry cell alkaline water electrolysis) and utilization of brown’s/oxyhydrogen (oxyhydrogen) gas deemed feasible due to its less capital cost, simplicity, low maintenance, and high calorific value. Furthermore, oxyhydrogen is considered to be clean because it does not produce NOx, SOx and carbon during its combustion as compared to conventional fossil fuels. This review is focused on different applications which has a potential to use oxyhydrogen gas for their combustion process. Moreover, it was emphasized on effective utilization of oxyhydrogen gas as on-demand production by the application. As fuel with hydrogen contents is considered to be dangerous to handle, so in the final section of the article an attempt has been made to detail various safety parameters such as flash back arrest, combustion nozzle design and working temperature for production and utilization of oxyhydrogen. It is concluded from the study that oxyhydrogen gas has a future for replacing conventional fuels as primary and secondary source for combustion applications due to their sustainability, combustibility and environmental friendliness.