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Worldwide, drinking water shortages are a major concern. In many parts of the world, fresh water sources are deteriorated and polluted by human activities and population growth. Using fossil fuels to distill water for human consumption requires a large amount of energy. It was suggested that solar energy could be used to distill polluted or salty water without harming the environment. The sun is a free and abundant energy source, especially in swampy and remote regions. However, the design and operation of solar stills limit their efficiency and productivity. Solar freshwater production systems are discussed in this review in terms of the latest developments in production and distillation efficiency. Based on various performance criteria, the study analyzes direct solar desalination processes. Detailed discussions of recent modifications and innovations are also included and highlighted in this paper. It is the goal of all the studies reviewed to achieve maximum productivity and efficiency, low capital costs, and ease of installation. Among the developments reviewed are phase change materials (PCMs), nanoparticles, and solar reflectors with high efficiency. In addition to features of solar stills, current modifications have been evaluated in terms of location, water temperature, solar radiation intensity, production level, inclination angle, productivity, and efficiency. Solar still performance parameters were also studied in relation to modifying the absorption area and using reflectors and condensers. Several improvements were made which resulted in high productivity rates. The distiller’s productivity increases from 10% to 180% when a phase change material is added. When a nanomaterial is added to paraffin in the still, productivity increases by 25% to 320%. Furthermore, Wicks increase the still’s yield by 20%-300%, depending on design. A few recommendations are made regarding future work in solar desalination based on this review at the end of the study. [ABSTRACT FROM AUTHOR]

To improve the performances of diesel engines and to reduce the pollutants they emit, aluminum oxide nanoparticles in varying quantities (50, 100, 150 ppm) have been added to conventional diesel fuel. The results of such experimental tests have revealed that the addition of nano-Al2O3 particles to the diesel fuel reduces its consumption by 0.488%, 1.02%, and 1.377%, respectively and increases the brake thermal efficiency by 1.4%, 2.6%, and 3.8%, respectively. The concentrations of undesired gases decrease accordingly by 1.5%, 1.7%, and 2.8% for HC and by 5.88%, 11.7%, and 17.6%, respectively, for CO. For the same percentages of nanoparticles, NOx increases by 2.65, 4.36, and 5.37, while the TSP (Total Suspended Particulate) decreases by 22%, 34.66%, and 49.7%, respectively. In the same conditions, sulfur dioxide pollutants increase by 4.57%, 8.8% and 12.89%, and H2S levels by 4.7%, 7.81% and 8.9%, respectively. [ABSTRACT FROM AUTHOR]