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The current experimentation work aims to enhance the hemispherical solar distiller’s yield by employing contiguous extended cylindrical iron bars as energy storage corrugated absorbers. After installing the contiguous extended cylindrical iron bars, the absorber surface is similar to the semi-circular corrugated surface; the extended cylindrical iron bars represent sensible storage materials. To get the optimal diameter of contiguous extended cylindrical iron bars that achieve the highest performance, three hemispherical distillers were designed, fabricated, and tested in the same El Oued, Algeria weather conditions, namely; first is a conventional hemispherical distiller (CHD), and the second and third are hemispherical distillers that include contiguous extended cylindrical iron bars (HD-CECIB) at different diameters of (8, 10, 12, and 14 mm). The experiments were conducted in two scenarios; in the first scenario, contiguous extended cylindrical iron bars with diameters of 8 and 10 mm were installed in the second and third distillers (HD-CECIB8 and HD-CECIB10), respectively. In the second-test scenario, contiguous extended cylindrical iron bars with diameters of 12 and 14 mm were installed in the second and third distillers (HD-CECIB12 and HD-CECIB14), respectively. The results show that 14 mm represents the optimal diameter of contiguous extended cylindrical iron bars that achieve the highest performance. The cumulative yield of a reference CHD reached 4.8 L/m2·d. In comparison, the utilization of contiguous extended cylindrical iron bars with 14 mm diameter (HD-CECIB14) improved the accumulative yield to 8.35 L/m2·d with an improvement of 74% when compared to CHD. Also, the daily thermal efficiency of HD-CECIB14 reaches 70.3%, with an improvement of 72.3% compared to CHD. Furthermore, the economic feasibility illustrated that using contiguous extended cylindrical iron bars of 14 mm diameter is a very effective choice because it reduces the distillate water costs produced by 41.2% compared to CHD.

Solar energy has recently become a viable option for desalinating seawater, primarily in arid regions. However, increasing the productivity of solar still by integrating experimental base and modelling methods is still subject to prediction errors; therefore, the main objective of this research is to postulate and test boosting algorithms for predicting the efficiency and productivity of the system. Five boosting regressors were deployed and evaluated: categorical boosting, adaptive boosting, extreme gradient boosting, gradient boosting machine, and gradient boosting machine (LightGBM). The proposed regressors are implemented based on the system’s actual recorded dataset (consisting of 720 observations). The dataset consists of input variables, which are the wind speed (V), cloud cover, humidity, ambient temperature (T), solar radiation (SR), (Tio), (Tw), (Tv), and (Tt). Also, the output variable is represented by the productivity of the system. The dataset was separated into training (70%) and testing (30%) sets. In order to decrease regressors errors, hyperparameter optimization was employed. GradientBoosting approach provided the best prediction, with 95% R2accuracy and 39.57 root mean square error (RMSE) error. The LightGBM technique achieved 94% R2accuracy and 40.07 RMSE error in the testing dataset. The results reveal that GradientBoosting outperforms the cascaded forward neural network in predicting system productivity (CFNN).

Hemispherical solar still with 8 mm thick wick materials at the bottom of its basin increases freshwater yield. Three 0.1 m2hemispherical solar devices were utilized for the experimental study. The system was experimentally tested in three ways for consecutive days. The first basin was a traditional one (THSS), the second basin was completely covered with a wick with 8 mm thickness (THSS-W), and the third basin was completely covered with the wick with a thickness of 8 mm and the glass cover cooling at a rate of 2 L/h (THSS-WC). The results showed that the wick utilization in the hemispherical basin gave high production compared to the traditional one. However, the glass surface cooling in addition to the wick utilization gave the best yield enhancement. The system with a traditional hemispherical basin provided a distillate of 3.25 L/m2, the system with a hemispherical basin covered with a wick provided a distillate of 4.55 L/m2, while the system with a hemispherical basin covered with a wick and the glass cover cooling produced a distillate of 5.5 L/m2. Accordingly, THSS-W and THSS-WC yields increased by 40% and 69.23%, respectively, when compared to THSS yield. The economic feasibility presented that the dual utilization of the wick and the glass cover cooling (THSS-WC) reduced the total cost of distillates produced from hemispherical solar distillers by 38.4% compared to THSS.

The present work highlights the importance of using the Fresnel lens technique to enhance the productivity of a conventional solar still (CSS). In this regard, the effect of using Fresnel lenses to improve the productivity of a CSS is investigated experimentally under the climate conditions of Basra city (30.5258°N latitude and 47.7738°E longitude), Iraq. The Fresnel lenses integrated conventional single-slop-basin type solar still (CSSFL) adjustable to be rotated manually at different angles was examined, compared to the CSS which showed a remarkable enhancement of producing output. The study concerned the variation of daily solar radiation and temperature effect on the distillate output and the efficiency of both the conventional and modified solar stills at 1 and 2 cm saline water depths during July and September of the year 2019. The experimental results showed better performance during July where it has been found that the productivity of the CSSFLimproved over the CSS by about 68.6% at 1 cm depth and about 59.3% at 2 cm depth. Moreover, the average daily thermal efficiency of the CSS and the CSSFLat 1 cm depth was 21% and 36%, respectively. Several conclusions and recommendations are presented for future work.

Desalination is now successfully practiced in many countries as drinking water supply has become a growing problem in most parts of the world. Algeria, like the Maghreb countries, has generally adopted two desalination processes (membrane processes and distillation processes which require a phase change, evaporation/condensation), the latter method is subject of our study. An experimental study was made on two similar stills with a single slope, size 1 m × 1 m, the first distiller D1 is used as a control and the second distiller D2 has a simple external mirror glued to its backlog. The same experience has been done in different climates with improvement results ranging from 9% to 21%. In our case, a complete study was concerning the improvement, the efficiency, the investment and finally the error analysis of the instrumentations that have not been done before. We obtained a very interesting improvement which varied between 42% and 45%, the efficiency is 35% and the recovery period of the sum invested is recovered in 23 d, which shows that this technique is more favorable under the climatic conditions of the West Southeast region of Algeria than elsewhere.

In recent decades, energy and water desalination using solar energy has played a vital role for the survival of human beings due to the cost and shortage of clean water; and gave considerable impetus to decrease greenhouse gas effects produced from burning fossil fuels. Thermal energy storage materials (TESMs) are used to store the energy through the daytime (sunshine time) and discharge this energy during nighttime (sunset time) and hence they have been used in water desalination systems to enhance its performance. TESM such as phase change materials (PCMs), myristic acid, sponge’s cubes, cotton, jute, cloth, porous materials and sponge sheet, quartzite and natural rock, coated and uncoated metallic wiry sponges, sand, gravels and aluminum filling are quite attractive in the solar desalination, especially in solar stills (SSs), to enhance thermal performance of SS by improving its thermal energy storage capability. We found from this review that the TESMs have a significant effect on enhancing the fresh water output from the SS especially when paraffin wax is used as PCM, which has large storage density with narrow range of temperature difference. In this review paper, various solar TESMs, especially PCM, tested by the researchers to improve the freshwater output as well as thermal performance of SSs, are analyzed and discussed in detail.