Comparative Study of Hemispherical Solar Still Using Different Novel Basin Materials With and Without Internal Reector: Yield, Energy, Exergy, Water Quality and Cost Analysis

The present work deals with the experimental investigation of Hemispherical Solar Still (HSS) using different basin materials with and without Internal Reector (IR). Three solar stills such us HSS with Steel Basin (HSS-SB), HSS with Zinc Basin (HSS-ZB), HSS with Copper Basin (HSS-CB) was fabricated. Experiments was conducted with and without IR. It was found that, the productivity of the HSS-CB (4.99 kg/m 2 /day) was better than HSS-ZB (4.26 kg/m 2 /day) and both of them were better than HSS-SB (3.64 kg/m 2 /day). Also, It was found that the productivity of the HSS-CB&IR (5.67 kg/m 2 /day) was better than HSS-ZB&IR (5.04 kg/m 2 /day), and both of them were better than the HSS-SB&IR (4.28 kg/m 2 /day). The results revealed that use of IR improves the yield of HSS from 12 to 15.6%. Also thermal and exergy eciency of the HSS was improved by 14.4 to 20% and 21.1 to 25.4% using IR than the without IR. Furthermore, recovery period and water quality analysis has been carried out. The recovery period of HSS-SB, HSS-ZB, HSS-CB, HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR are 43, 38, 33, 36, 32 and 29 days, respectively.


Introduction
Water is the basis of the life on the earth planet, and it is very necessary for durability of the human life on it. One of the biggest challenges encountered the human civilization was who can offer a healthy and fresh water in a reasonable cost especially in the third world countries (Hussein 2015;Rostami et al. 2020). In fact, the natural sources of the fresh water are decrease gradually day by day due to many causes such as e uence of river water by the factories waste, huge population growth, and climate change (Hussein et al. 2016). It is useful to mention that the freshwater quantity was about (1%), while the other available water (about 97%) in the ocean is salty and cannot be used for animals, planets and the human demand. The remaining water sources (2%) can be found in the north and south Polar Regions as an iceberg (Benabderrahmane et al. 2020). For all these reasons, the SS can be used e ciently to covert the brackish water to a fresh water by using free solar energy. The device which was used to manage this process is called the SS and the principle of its work depends on the famous physical evaporation-condensation concept (Ghodbane et al. 2021). The comprehensive details about the characterization and types of the SS was reviewed by Kabeel and El-Agouz 2011, Chauhan et al. 2021, Alnaimat et al. 2021and Jobrane et al. 2021. The conventional single or double slope SS produced low productivity due to shadow effect occurs by the basin walls. This leads to reduce the solar radiation absorption and decreases its e ciency (Taheri and Zahedi 2020). To get a solution to the above-mentioned drawbacks of the SS and enhances the SS productivity, many researchers are suggested several unconventional designs like regenerative (Sakthivel et al. 2010), air bubbled (Pandey 1984), stepped (Omara et al. 2014), wick (Minasian, A. and Al-Karaghouli 1994), V-type ), thermoelectric (Rahbar and Esfahani 2012), masonic (Navale et al. 2016), tubular (Rahbar et al. 2015), pyramid (Al-Madhhachi and Smaisim 2021), trays , hybrid (Mandi et al. 2021) and hemispherical (Ismail 2009) SS. In the latter design of SS, the cover has a hemispherical shape in order to increase the amount of the solar energy collected by the SS by reducing the shadow of still walls.
In hemispherical design, both the e ciency and productivity are inversely proportional with the depth of water. In spite of the large number of published papers related with different designs of SS, the number of works related with the HSS are very limited up to date. Ismail [23] designed, fabricated and experimentally tested a transportable HSS under climate conditions of Dhahran city (KSA). The SS consisted from a hemispherical cover, distillate collector of a conical shape, mobile support structure, absorber plate, fresh water container and a circular basin. It was deduced that, the SS was able to convert around 50% of the saline water to a fresh water and its daily e ciency was about 33%. Also, he concluded that this e ciency was decreased with increasing the water depth. (Arunkumar et al. 2012) researched HSS under the weather conditions of Coimbatore (India). Two cases were considered, in the rst case, the water owing to cool the HSS cover. While, in another case this owing was not considered. They concluded that, the HSS e ciency was increased from 34 to 42% by adopting the cooling of its cover. The experimental study of the HSS with and without PCM was carried out by (Arunkumar et al. 2013). The SS was integrated with a concentrator, whereas the para n wax contained in a black painted copper balls were placed in the basin. The temperatures of PCM, air, water and inner and outer covers of the SS were measured. They found that the SS productivity was increased by about 26% by using PCM. (Raju et al. 2017) investigated HSS by coupling it with evacuated tubes, paraboloid concentrator and heat pipes under outdoor conditions of Bangalore city (India). The experimental investigation of the performance of a cylindrical SS with a hemispherical dome (CSSHD) was carried out in Najaf city (Iraq) by (Khadim et al. 2021). The cylinder height was varied as 5, 15 and 20 cm. It was found that, both the thermal e ciency and yield amount were increased with increasing the cylinder height until it reached respectively (23.3% and 7.25 L/m 2 .day) compared with (15 % and 4 L/m 2 .day) for single slope SS. Moreover, they suggested that (CSSHD) was more e cient in winter compared with summer.  reported the HSS with an iron-ns installed at its basin. The optimum number and length of these ns which are necessary to reduce the shadow effect were studied. They tested three different designs of the HSS under outdoors conditions of El-Oued city (Algeria). The rst one was a conventional type without ns, whereas the second and the third types included respectively ns group at (5 cm) and (7 cm) distance between each ns. The n length was varied as 3, 2 and 1 cm starting from the absorber plate of the basin, while its diameter was xed at 1.2 cm. It was found that, the yield of the SS was increased up to 56.73% when the third design was utilized and the n length was taken as 2 cm. The experimental investigation of the HSS by using respectively black metal trays of iron, zinc and copper in the bottom of their basins was performed by ) under the climate conditions of El-Oued city (Algeria). It was observed that, the improvement in the productivity was increased by about (53.125%) when the copper trays used compared with the same SS without it. Also, they concluded that using of copper trays increased respectively the yield and thermal e ciency of the SS to their highest value (7.35 kg/m 2 /day and 57.2%) compared with (4.8 kg/m 2 /day and 37.4%) without using any trays. ) examined experimentally the possibility of using aluminum foil sheet as an absorber cover to increase the yield of the greenhouse SS and compared it with a similar traditional SS which had an absorber of a black surface under the same outdoors conditions of El-Oued city (Algeria). They deduced that, the output of the modi ed still remain poor (1.004 kg/m 2 /day) and an extra modi cation need to be adopted. Based on the previous literature review, our deep experience in the solar energy and since there is a lack of the fresh water in most of the southeastern regions in Algeria such as El-Oued city (region of study) where a high population live there. Therefore, the major purpose of the present work is to investigate experimentally for the rst time the effect of the re ective aluminum foil sheets on the performance of the HSS with various basin materials.

Experimental setup and description
The present manuscript aims the experimental investigation of the re ective aluminum foil sheets effect on the performance of HSS with various basin materials. This was achieved by comparing the use of a re ective aluminum foil sheets by placing them on the inner surfaces of the HSS with various basin materials (Steel, Zinc and Copper). To realize this idea, two different experiments were carried out in the present work. In the rst day, experiments was conducted on HSS-SB, HSS-ZB and HSS-CB without IR, as shown in Figure 1. In the second experiment three modi ed HSS were used and their walls were covered by the aluminum foil sheets. In the second day, experiments was conducted on HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR, as shown in Figure 2. The HSS was designed, fabricated and experimentally tested. The HSS consists of a transparent hemispherical cover of 40 cm in diameter, distillate collector and a circular basin 38 cm in diameter and 4 cm in height. The depth of basin saline waste water for each HSS was taken constant at 1 cm. These experiments were conducted in El Oued city (latitude of 33.3676°N and a longitude of 6.8516°E) under Algerian weather conditions. Aluminum foil sheet has a shiny side and a matte side. The re ectivity of bright aluminum foil is 88%. The thickness of aluminum foil sheet is about 0.2 mm. Figure 3 shows the photographic view of experimental test rig.

Measurements
The range, uncertainty, and errors values for the experimental data's are presented in Table 1.   HSS-CB&IR is 7.5% and 14.5% higher as compared to the everyday average EHTC of the HSS-SB&IR and every day average EHTC value of the HSS-CB&IR is 6.5% higher than the everyday mean EHTC value of the HSS-ZB&IR. In HSS-CB&IR, copper material and IR improves the Ts.w and so it has greater hourly and everyday EHTC than the HSS-ZB&IR and HSS-SB&IR. From gure 6, it is found that yield production from the HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR are increasing in the before noon and decreases in afternoon. The highest yield of 0.82, 0.91 and 0.97 kg was produced from the HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR, respectively. The everyday yield production from the HSS-SB&IR is 4.28 kg, from the HSS-ZB&IR is 5.04 kg and from the HSS-CB&IR is 5.67 kg on 15-8-2020. While using the copper basin and IR in the HSS, yield was augmented by about 32.49% and 17.9% related to the HSS-SB&IR, HSS-ZB&IR, respectively.
In the HSS-CB and HSS-CB&IR, due to copper properties and IR it stores the more heat energy in the basin and water. Also it decreases the heat losses from the HSS basin to the air so yield production from the HSS-CB is greater than the HSS-SB and HSS-ZB and yield production form the HSS-CB&IR is greater than the HSS-SB&IR and HSS-ZB&IR.   -8-2020. The EE of the HSS-CB is 56.87% and 21.88% higher than EE of the HSS-SB and HSS-ZB and EE of the HSS-CB is 16.4% higher than the HSS-ZB. The EE of the stills is maximum for the HSS-CB because EE directly related to yield and available solar intensity. For the period of noon hours, the difference between Ts.w and Tg is greater so at the time of noon hour EE is higher than the evening.

Time-wise variant of Thermal e ciency (TE) and Exergy e ciency (EE
Time-wise variant of TE and EE of the HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR are shown in Figure 10. The TE of the HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR are rises in morning and reached peak value at 14:00 and then it decreases till 19:00. The TE of the HSS-SB&IR starts with 5.71% at 07:00, had a raising trend and got 63.75% at 14:00 and then it had a reducing trend till 19:00 (28.66%). Also TE of the HSS-ZB&IR starts at 9.02% at 07:00, had a rising trend and reached 69.3% at 14:00 and then it had a reducing trend till 19:00 (29.96). Similarly the TE of the HSS-CB&IR starts at 11.53% at 07:00, had a raising trend and reached 72.16% at 14:00 and then it had a reducing trend till 19:00. The daily TE of the HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR are 31.45, 36.62 and 41.12% on 15-8-2020. The TE of the HSS-CB&IR is 30.76 and 12.29% higher than TE of the HSS-SB&IR and HSS-ZB&IR. Similarly, the TE of the HSS-ZB&IR is 16.45% higher than the TE of the HSS-SB&IR. The use of copper basin and IR in the HSS enhances the water temperature, EHTC, yield and hence it had greater TE than the TE of the HSS-ZB&IR and HSS-SB&IR. The EE of the HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR are raises in morning and reached peak value at 14:00 and then it decreases till 19:00. The EE of the HSS-SB&IR starts at 0.05% at 07:00, had a raising trend and got 4.28% at 14:00 and then it had a reducing trend till 19:00 (0.6%). Also EE of the HSS-ZB&IR starts with 0.08% at 07:00, had a raising trend and got 4.83% at 14:00 and then it had a reducing trend till 19:00 (0.72%

Assessment Of Current Study With Available Related Works
In Table 2 shows the comparison of our results with published similar works. From the Table 2, it can be noticed that the productivity of "V" type SS with mirror [31] is minimum with a value equal to 11.92%. However, for the double SS with re ector, it is maximum with a value equal to 93.39% [32]. The present study produced maximum yield of 4.28, 5.04 and 5.67 kg/m 2 using HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR, respectively.  Table 3 depicts the properties of saline and distilled water. It is observed that P H value of saline water is 8.12 and distilled water is 7.12 which is within the consumable levels. After distillation, salt content (2.86 g/l) presents in the saline water was completely removed so that electrical conductivity of the distilled water was drastically decreased from 5300 to 28 µS/cm and TDS of the distilled water was drastically decreased from 7042 to 22 mg/l.

Economic Evaluation
In Table 5, the recovery period of HSS-SB, HSS-ZB, HSS-CB, HSS-SB&IR, HSS-ZB&IR and HSS-CB&IR is summarized. The payback period of HSS-SB is 43 days, HSS-ZB is 38 days and HSS-CB is 33 days. The amount invested is returned in the case of the HSS-SB&IR is 37 days, HSS-ZB&IR is 32 days and HSS-CB&IR is 29 days.

Conclusions
This work highlights the positive effect of an IR on the performance of HSS with various basin materials.
This simple technique includes a re ective aluminum foil sheets on the inner walls of the HSS with various basin materials (steel, zinc and copper). The conclusions are as follows: Using the re ective aluminum foil sheets and high thermal conductivity metal basins (copper) enhances the e ciency of HSS. Aluminum foil sheets increase the re ection of the solar radiation inside the basin, and the trays increase the absorption of solar radiation resulting increases in temperature of the brine water.
The distilled water production from the HSS-SB, HSS-ZB and HSS-CB are 3.64, 4.26 and 4.99 kg/m 2 .
The distilled water production from the HSS-SB&IR during the day is equal to 4.28 kg/m 2 . However, it is equal to 5.04 kg/m 2 from the HSS-ZB&IR and it is equal to 5.67 kg/m 2 from the HSS-CB&IR.
The daily accumulation of HSS was improved by 17.03 and 37.08% by using the zinc and copper basin as compared to the HSS-SB.