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Solar still is a water desalination method that works by the principle of evaporation and condensation, which has been adopted earlier as a simple and low energy consumption method. However, it suffers from low reliability and poor performance. Hence, the current study provides a developed solar still combined with a heat pump and an evacuated tube water heater to augment the thermal processes. The heat pump was attached to advance the condensation process. Besides, the heater was combined with the system to afford a storage medium and boost the evaporation process. Firstly, a parametric analysis was performed in order to select a suitable water recirculation rate and operating temperature. The productivity increased linearly with the temperature by a rate of about 0.035 L/h/m2for a 1 ℃ temperature rise until below 68 ℃; then, the relation becomes exponential where the productivity increased by 0.16 L/h/m2after a 1.5 ℃ temperature rise. Daily, the modified design exhibited productivity, energetic efficiency, and exergetic efficiency of 13.38 L/m2, 44.12 %, and 4.17 %, respectively. Furthermore, including cover cooling boosted these findings to 14.22 L/m2, 47.79 %, and 4.69 %, which were higher than that of a basic distiller by 291.73, 16.05, and 30.28 %, respectively. From the cost perspective, the minimum distilled water price was obtained at a 20-year lifetime span and a 5 % interest rate of 0.0121 $/L.

The integration of thermoelectric generators (TEGs) into industrial processes and multi-generation systems presents a promising solution for recovering low-grade waste heat. This study explores the use of such waste heat in producing green hydrogen, utilizing TEGs as an alternative medium for energy recovery. The hydrogen production methods examined include proton exchange membrane (PEM) electrolyzers and alkaline electrolyzers. The heat sources are categorized into geothermal sources, solar energy sources, and general waste heat sources. By incorporating TEGs into hybrid systems, the overall system efficiency and rated power output, as well as green hydrogen production, are significantly enhanced. For instance, a system combining an organic Rankine cycle powered by a geothermal source with a TEG and a PEM electrolyzer can generate 98.37 kg/day of H2and produce 6781 kW of power, achieving an exergy efficiency of 55.39 %. Additionally, TEGs are employed in hydrogen storage and liquefaction to improve the efficiency of the compression and liquefaction processes by reutilizing waste heat. To provide a comprehensive overview, a bibliometric study using the VOSviewer tool is conducted to highlight the trends in hydrogen production via TEGs, analyzing authors' keywords and index keywords. Moreover, this study presents innovative methods and insights into the efficient recovery and utilization of waste heat for green hydrogen production, emphasizing the potential of TEGs in advancing sustainable energy solutions.

•Design of 100% renewable microgrid is optimized for a real agriculture load.•A parametric analysis is employed to uncover uncertainties in 7 key design parameters.•PV/WT/BAT/CONV microgrid is the winning design with the best economic performance.•Discount rate, project lifetime, and capital costs significantly affect the microgrid costs.•A tiny and tolerable supply shortage can cause considerable financial benefits.

•The evaporation–condensation processes of solar still were augmented.•Both active and passive designs of condensers were studied.•Nanofluid and ultrasonic foggers were integrated to boost vapor generation.•The productivity and efficiency of solar still were enhanced by 59.1 and 65.5%, respectively.•Feasible freshwater production was obtained with good water quality.

The increasing of the world population without increasing the natural resources caused water shortage in many regions around the world. Herein is a review of a new freshwater resource depending on harvesting the moisture of the atmospheric air. There are two main methods for extracting water from the ambient air: including composite materials method and cooling the air to the dew point. In the first method, the composite materials absorb the atmospheric air’s moisture and regenerate it into drinking water under certain conditions. Researchers have worked on changing the composite material type, and its additives and parameters to improve the productivity of water with acceptable cost. The second method requires just cooling of the atmospheric air until its moisture gets condensed. Power sources based on renewable energy have been developed to drive various techniques, such as vapor-compression cycles, absorption cycles, and Peltier effect-based devices. Beside reviewing different methodologies, this paper focused on the factors that affect the process of extracting water from the air. The formulas for computing the efficiency and water productivity were also mentioned. On the other hand, the research trend of the current topic was analyzed by conducting a comprehensive bibliometric analysis using VOSviewer software based on the Scopus database in the period (1988 – 2021).

•The performance of modified tubular solar still was investigated.•Multi additives were applied: atomizers, hang wick, nanoparticles, and cover cooling.•The freshwater productivity was maximumly augmented by 82.5%.•The thermal performance improvement reached 68.14% (energy) and 119.1% (exergy).•The freshwater price was reduced by 39.14% using all additives.

•Modified single slope solar still (MSS) has been investigated experimentally.•Coal, cotton fabrics, and carbon black nanoparticles are tested with the SS.•Energy and exergy efficiencies, along with 4E analysis are considered.•MSS-C shows the best performance when compared with all the studied cases.•The cost reduced by 25%, and the carbon emission mitigation increased by 127%.

•Novel nano-CuO@Co3O4-enhanced paraffin was developed, and compared to pure and mono nano-based paraffin.•Comprehensive characterization was conducted: SEM, TEM, EDX, XRD, FT-IR, and DSC analyses.•Thermal performance was evaluated under direct/indirect solar exposure.•Good nanoparticles distribution and thermal performance enhancement were successfully obtained.

•New desiccant mechanism using silica gel was tested on tubular solar still.•Experimental and predictive study was conducted to investigate performance of TSS.•Four longitudinal fins are fixed inside TSS to increase the surface area.•Distillate was enhanced by166% by using silica gel, fins, and gravels.•Efficiency was increased by 35% by using silica gel, fins, and gravels.