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• Experimental investigation on copper basin and graphite nanofluid was performed. • The influence of weather and operational parameters was examined. • A new prediction method using a modified version of RVFL network was proposed. • Firefly Algorithm was applied to optimize parameters selection of the RVFL. This study introduces a modified random vector functional link (RVFL) as an alternative prediction method for the thermal performance of a developed pyramid solar still (DPSS), which consists of a copper basin integrated with graphite nanofluids. Experimental work is performed to investigate the performance enhancement of the DPSS. The real experimental data are recorded and utilized to build the proposed prediction models based on artificial neural network (ANN). Four ANN prediction models are presented, evaluated and compared to strength the prediction of the thermal performance of the DPSS. Different six statistical criteria are used to determine the optimal prediction model to be implemented in the prediction of the hourly freshwater (HF) and instantaneous energy efficiency (IEE) of the DPSS. From the experimental investigation, the use of proposed DPSS has total freshwater productivity of 5.26 L/m2. The performed comparative study shows that the proposed RVFL approach tunned by firefly algorithm (FA), called FA-RVFL, is of optimal performance to be the best model among the investigated prediction models. The proposed FA-RVFL model is characterized by a determination coefficient of 0.981 and 0.999 and regression values of 0.996 and 0.999, respectively for the total data sets of HF and IEE. The present study shows the efficiency of proposed DPSS to enhance the freshwater capacity. Besides, it proves that FA-RVFL can be used as an effective tool to predict the thermal performance of the solar stills compared to the other models with no need for further experiments, thus saving financial expenses, effort, and time. [ABSTRACT FROM AUTHOR]

Today, clean water availability is quite hard especially for people living in remote areas and coastal ones. Even for those who find underground water, they need to treat it before using. Solar still is a very useful method to be used in desalination and purifying water as it uses solar energy which is available around the globe with no cost and is eco-friendly. Many types of solar stills are invented to increase its daily productivity (stepped solar stills, inclined solar stills, pyramid solar still, wick, etc.). In this regard, this paper represents a mini-review of a new type of solar still named tubular solar still (TSS), its working method, thermal analysis, performance and method of enhancement. The remarkable improvement is attributed to the use of nanotechnology (ZnO nano-rod shape) by which the productivity and efficiency are increased by 30% and 38% respectively. Moreover, some futuristic developments on TSS are included in this review. [ABSTRACT FROM AUTHOR]

Solar-driven desalination methods, particularly solar stills (SS), and their improvements have been widely paid attention. Along with that, the current work aimed to evaluate the augmented evaporation/condensation performance of a modified double slope solar still (MDSSS) compared to conventional solar still (CSS). For evaporation enhancement, three alternative combinations were applied in the still basin, which consisted of nanoparticles/fluid (carbon black/water), heat localization (wick), and sensible storage (gravel) materials. In other meaning, three cases were experimented; namely: MDSSS-I with gravel immersed in carbon black (CB) nanofluid, MDSSS-II with gravel atop thermal insulation and covered with black wick, and MDSSS-III with dispersed CB nanoparticles on the top of the second case combination. These modifications were suggested to enlarge the wet area subjected to solar radiation, increase thermal conductivity, and localize the heat on the water surface. On the other hand, for condensation improvement, passive water-based glass cooling technique was integrated with all cases to degrade the glass cover temperature. Besides the experimental investigation, thermo-economic assessment analysis of the system was performed via estimating energy and exergy efficiencies, and production cost. The results proved the aimed enhancements for all cases and the best performance was achieved from the MDSSS-III. In this case, the yield, average energy efficiency, and average exergy efficiency were improved by 68, 50.6, and 146.3%, respectively, compared to CSS. In addition, MDSSS-III attained highest cost saving by 30.7% compared to CSS as the cost per liter of freshwater productivity was 0.0147 $/L, and 0.0212 $/L, respectively. Hence, integrating such locally-available materials with DSSS may open a new sight for further enhancement and increase the opportunities for establishing large-scale practical plants. • Modified double slope solar still (MDSSS) were experimented compared to conventional one (CSS). • Alternative combinations were proposed from three materials: gravel, wick, and carbon black nanoparticles. • The MDSSS-III achieved best performance with enhanced average energy efficiency 50%. • The MDSSS-III achieved highest saving in freshwater price by 30.7%. [ABSTRACT FROM AUTHOR]

In this study, efforts were made to enhance the performance of inclined wick solar still (IWSS) by integrating different basin metals and a novel wick-metal chips pad. Three different metal materials (aluminum, copper, and steel) were used as basin and their metal chips were sandwiched in a novel wick-metal pad. Experiments were carried out to figure out the influence of different basin metal materials and their metal chips filled in a wick pad on the thermal performance of IWSS. The enhanced solar still was compared with conventional inclined wick solar still (CIWSS). Results revealed that using aluminum and copper basins led to increase the productivity by 34.23% and 54.26%, respectively, compared with CIWSS. The use of metal chips sandwiched between two layers of wicks (wick-metal chips pad) caused an increase in the daily production by about 27.76%, 41.54, and 65.3% for steel, aluminum, and copper, respectively. This implies that the basin materials and the novel wick pads with metal chips, which acted as evaporation surface and heat storage medium, played a vital role in enhancing productivity. Also, the maximum thermal efficiency was 60.98% for the modified IWSS with copper basin and a novel wick-copper chips pad. While, the maximum thermal efficiency for the CIWSS with steel basin was 37%. To understand the temperature distribution through different layers of desalination surfaces, a numerical simulation was carried out under real weather conditions using the finite element software; COMSOL Multiphysics. Results showed that, there was a good agreement between experimental work and numerical investigation. Image 10485 • The proposed inclined wick solar still has thermal efficiency of 61%. • Different combinations of basin metals and novel wick-metal chips pads were studied. • Aluminum and copper basins lead to increase the productivity by 34% and 54%. • Experimental results have been successfully verified by numerical simulation. [ABSTRACT FROM AUTHOR]