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Improving performance of tubular solar still by controlling the water depth and cover cooling
Abstract
Recently, tubular solar still (TSS) is considered as one of the preferable options for pure acquisition water, particularly, for small applications located in coastal and arid regions. Such areas are usually doesn't have a sufficient power source for water desalination or infrastructure to transport pure water. This paper presents an improvement in the daily rate of water production by offering TSS integrated with cover cooling. The system consists of a transparent solar tube to increase the amount of solar irradiance, which is combined with a black basin to enhance the absorption and improve the water evaporation. TSS was manufactured using lightweight materials, gaining strong and durable weight, from locally available materials. In this study, different basin water depth (0.5, 1, 2, and 3 cm) were investigated to obtain the best water depth. Furthermore, trying various water cover cooling flow rate (1, 2, 3, and 4 L/h) to get the optimal water-cooling flow rate. The experimental results show that the TSS with lower water depth gives the best performance, where the productivity was reached to 4.5 L/m2, while with the large water depth at 3 cm give a daily productively of 3 L/m2. Also, the best cooling water flow rate was obtained at 2 L/h. Under the best conditions corresponding to 0.5 cm water depth and 2 L/h cooling water flow rate, the maximum efficiency was achieved, which was about 54.9%. In comparison with TSS without cooling, the proposed TSS successfully improved the yield and efficiency of the TSS by about 31.4% and 32.6%, respectively. Moreover, the daily thermal exergy efficiency increased by about 9%. From an economic point of view, the cost per liter of clean water output was found to be 0.023 for TSS without and with cover cooling, respectively.
... On the other hand, Kabeel et al. 135 created a cylindrical solar distiller (CSD) with a black container and a clear solar tube to increase the absorption of solar energy and water evaporation. Experiments were undertaken to maximize performance by changing the water level of the basin by increments of 0.5, 1, 2, and 3 cm and assessing different water flow rates of (1 L/h, 2 L/h, 3 L/h, and 4 L/h). ...
... When compared to the standard design, the data demonstrated that the modified tubular configuration resulted in significant improvements in terms of both productivity and efficiency. The traditional tubular stills had an accumulated productivity that ranged External heater Chennai, India 59.52% To achieve a larger pure water production of 2.5 kg and 3.4 kg, respectively, the inclusion of an electrical heater resulted in a considerable increase in the average water temperature, which went from 49°C to 52°C Arunkumar et al. 134 Cooling the cover to improve productivity India 64% A conventional distiller system was compared to a convex tubular desalination system, demonstrating superior production efficiency and reduced water output rates Kabeel et al. 135 Figure 50. Also, A.E. Kabeel et al additional focus is on improving drinking water production 145 using nanostructured phase change materials (PCM) in a tubular solar still (TSS). ...
... The experimental set-up and model of (TSD).135 ...
Solving global water shortages has become an urgent challenge, hindering sustainable development. Therefore, comparing different solar still designs from application and economic perspectives is necessary. Solar distillation is considered a major innovation in the alternative energy sector for purifying brackish or brine water into clean water. Despite the extensive literature on improved solar stills, determining the most efficient designs for residential and industrial applications remains difficult. This review compares the productivity of spherical, hemispherical, and tubular solar still designs. The aim is to study the factors that influence the efficiency of each type and to analyze recent research and results obtained under different conditions. The results show that innovations in solar distillation design can take many forms to improve efficiency and productivity. For example, adding parabolic mirrors can increase productivity in spherical, hemispherical, and tubular stills by 35 to 70%. Likewise, innovative designs such as rotating spheres and changing bowl shapes significantly increased the productivity of spherical and hemispherical stills. Likewise, retrofitting a still with vacuum generation technology can significantly increase yields by 50 to 70%. In addition, using nanomaterials, especially nanophase change materials (NPCM), has increased the efficiency of the spherical and tubular stills by 116.5%, producing 7.62 kg/m2 per day. Therefore, the NPCM-equipped model was still the most efficient option among the three designs.
... Its operating principle is the same as that of single-slope and doubleslope solar stills. After the process of evaporation and condensation of water on the inner surface of the tubular cover, the condensed water flows down due to gravity and is collected (Kabeel et al. 2019). The geometry of the tubular solar still eliminates the shading effect of the side wall, does not require a Sun-tracking system, facilitates the removal of accumulated salts in the basin, and has a larger condensation area compared to the other types of solar stills (Younis et al. 2022). ...
... The pyramid solar still, with a basin of 0.75 m 2 , has been tested under Egyptian climatic conditions with a solar intensity of 730 W/m 2 (Sharshir et al. 2022). The tubular solar still, covering an area of 0.36 m 2 , was studied under Egyptian climatic conditions with an average solar intensity of 776 W/m 2 for the month of July (Kabeel et al. 2019). The cascade solar still, featuring a basin area of 0.45 m 2 , was studied in Iran, where the solar intensity was equals to 610 W/m 2 in May (Sarhaddi et al. 2017). ...
... As for the pyramid solar still, utilizing a corrugated plate as an absorption surface increases its efficiency by 52.54% compared to the single slope (Ghandourah et al. 2022). While the use of circular hollow copper fins with glass wool insulation can yield a maximum daily productivity equal to 5.33 l/m 2 /day (Asadabadi and Sheikholeslami 2022), for the tubular solar still, maintaining a minimum water depth in the basin with an optimal cooling water flow results in better performance, achieving a productivity of 4.5 l/m 2 / day (Kabeel et al. 2019). The utilization of a semi-circular corrugated absorbent plate instead of a flat plate results in a productivity of 4.3 l/m 2 /day (Ghassemi and Danesh 2013). ...
Water scarcity is increasing day by day due to population growth, economic development, and environmental pollution. Solar stills present a promising technical solution for purifying water. However, the problem lies in the appropriate choice of the solar still type for the desalination unit, aiming for high productivity and low cost. The objective of this work is to compare five geometrical types of passive solar stills to determine the most suitable and efficient one for freshwater production. First, five solar still geometries were selected based on a literature review. The comparison of these five technologies was conducted using the multi-criteria decision method (MCDM), specifically the TOPSIS method. To achieve this, six technical and economic sub-criteria were taken into account. The preference weights for these sub-criteria were calculated using entropy as the objective method. The results indicate that the cascade solar still ranks first among the other technologies, with a closeness coefficient CCi value of 0.74, followed by the pyramid solar still with a value of 0.56. These results were validated through sensitivity analysis, with a probability of 67% for the cascade solar still and 33% for the pyramid solar still. This analysis allowed us to select the cascade solar still as an efficient solution for freshwater production when compared to other types.
... 43 2. 15 Schematic of multi wick solar still [64]. ………………………...……... 34 2.16 Schematic of multi wick solar still [65]………………………..……….. 34 2.17 Schematic of experimental setup [69]………………………..…..…….. 36 2.18 Schematic of basin depth, water depth and WCD during experiments [73]. 38 2.19 Cross sectional view of a hemispherical solar still [74]………………... 38 2.20 Schematic diagram of the experimental setup [75]……………….…... 39 2.21 Schematic diagram of a regenerative still [76]. ...
... Kabeel et al. [69]. To maximize solar radiation absorption, the system consisted of a transparent tube integrated with a black basin. ...
... 17: Schematic of experimental setup[69]. ...
In this study, experimental tests were carried out in order to increase the performance of a single slope solar still combined with PCM material (paraffin wax) and a solar-powered electric heater. Two identical single‒slope solar stills were designed, fabricated and tested under the same climatic conditions during the summer, spring and autumn seasons 2021 in Al-Arish city, Egypt. The first one is a conventional type solar still (CVSS) and the other still is a conventional with PCM and electric heater (CVSSWPCM and electric heater). The electric heater was supplied with power directly by a PV system where fixed in the same place of the two solar stills. The electric heater was installed in the centre of the paraffin wax reservoir where located directly beneath the absorber plate of the modified still. Several parameters were measured during the experiment, including solar intensity, meteorological aspects, accumulative productivity from the two stills, and average basin water, glass, and paraffin wax temperatures. The performance of the modified solar still was evaluated at different operating temperatures and compared to the performance of the conventional one. There were four cases studied: without a heater (paraffin wax only) and with a heater operating from the beginning of experiment at 58 oC, 60 oC, and 65 oC. Also different water depths cases were studied for the two solar stills at 65 oC operating temperature conditions for the modified solar still. The resulting experimental outcomes revealed that the daily accumulated productivities of CVSSWPCM (paraffin wax only) are enhanced by 14%, 17%, and 16% at spring, summer and autumn respectively. The accumulated productivities of CVSSWPCM and heater are enhanced by 172.5%, 158.8% and 446% at control temperature of heater 58 °C at spring, summer and autumn respectively. The accumulated productivities of CVSSWPCM and electric heater are enhanced by 203.5%, 181.3% and 513% at control temperature of heater 60 °C at spring, summer and autumn respectively. The accumulated productivities of CVSSWPCM and electric heater are enhanced by 252.4%, 214.5% and 586% at control temperature of heater 65 °C at spring, summer and autumn respectively.
... 43 2. 15 Schematic of multi wick solar still [64]. ………………………...……... 34 2.16 Schematic of multi wick solar still [65]………………………..……….. 34 2.17 Schematic of experimental setup [69]………………………..…..…….. 36 2.18 Schematic of basin depth, water depth and WCD during experiments [73]. 38 2.19 Cross sectional view of a hemispherical solar still [74]………………... 38 2.20 Schematic diagram of the experimental setup [75]……………….…... 39 2.21 Schematic diagram of a regenerative still [76]. ...
... Kabeel et al. [69]. To maximize solar radiation absorption, the system consisted of a transparent tube integrated with a black basin. ...
... 17: Schematic of experimental setup[69]. ...
Improving The performance and productivity of a single slope solar still by a paraffin wax and solar electric heater
... 43 2. 15 Schematic of multi wick solar still [64]. ………………………...……... 34 2.16 Schematic of multi wick solar still [65]………………………..……….. 34 2.17 Schematic of experimental setup [69]………………………..…..…….. 36 2.18 Schematic of basin depth, water depth and WCD during experiments [73]. 38 2.19 Cross sectional view of a hemispherical solar still [74]………………... 38 2.20 Schematic diagram of the experimental setup [75]……………….…... 39 2.21 Schematic diagram of a regenerative still [76]. ...
... Kabeel et al. [69]. To maximize solar radiation absorption, the system consisted of a transparent tube integrated with a black basin. ...
... 17: Schematic of experimental setup[69]. ...
... The performance of TSS coupled with cooling cover was experimentally studied by Kabeel et al. 77 Effects of different depths of basin F I G U R E 3 1 (a) TSS with a parabolic concentrator (b) cooling flow mechanism. 76 F I G U R E 3 2 TSS with cover cooling. ...
... The difference in temperature between saline water and glass cover F I G U R E 3 3 Variation of water depth with basin water temperature and water flow rate with cold water temperature. 77 F I G U R E 3 5 Variation of exergy destruction with time. 80 F I G U R E 3 6 Efficiency and daily productivity of TSS with enhancement techniques. ...
Access to safe drinking water remains a global challenge, primarily due to the prevalence of water contamination in various regions. Numerous methods have been explored to address this issue and convert polluted water into potable sources. However, the cost associated with these methods often hinders their widespread adoption. Solar distillation, harnessed by abundant solar energy, emerges as a promising and sustainable solution. Although solar distillation technology has made significant advancements in recent years, the endeavor to boost its efficiency remains a substantial challenge. Typically, solar stills yield between 4 and 6 liters of fresh water per square meter of solar still per day under ideal circumstances. Notably, both single‐basin and double‐basin solar stills have been extensively researched to discover methods for enhancing their productivity. A notable innovation in this field, the tubular solar still (TSS), has gained recognition for its capacity to improve productivity. The present review article systematically examines the development of efficient and cost‐effective solar distillation systems on a global scale. It provides a comprehensive analysis of the literature pertaining to techniques employed to enhance TSS performance. The study categorizes these techniques, conducts in‐depth evaluations of both experimental and simulation studies, and offers a meticulous comparison of various strategies to optimize TSS functionality. Furthermore, the article identifies existing research gaps and puts forth prospective directions for advancing TSS efficiency.
... conducted experimental studies on spherical SS with parabolic reflectors at water masses of 1, 2, 3, 4 , and 5 L. It was published that increasing Wd enhances yield. Wd and water-cooling flow rates' effects on a tubular type SS were published by Kabeel et al. 2019a. The maintained Wds are 0.5, 1, 2, and 3 cm; water flow rates during cooling were 1, 2, 3, and 4 L/h. ...
... It was reported that the yield of pyramid SS increased as Wd decreased. In Egypt, Kabeel et al. (2019a) researched the performance of nano-black paintcoated pyramid SS at various Wds and found that minimum Wd has yielded more output. In India, Suneja and Tiwari (1999) published a paper that reported the Wd effect of an inverted absorber double basin SS. ...
This study analyzes the energy and exergy destruction of a solar still with black painted wick materials (SS with BPWM) at different salt water depths (Wd) of 1, 2, and 3 cm. The coefficients of heat transfer for evaporative, convective, and radiant heat transfer have been calculated for a basin, water, and glass. The thermal efficiency and exergy losses caused by basin material, basin water, and glass material were also determined. An SS with BPWM at Wd of 1, 2, and 3 cm has produced a maximum yield of 0.4, 0.55, and 0.38 kg per hour, respectively. An SS with BPWM at Wd of 1, 2, and 3 cm has produced a daily yield of 1.95, 2.34, and 1.81 kg, respectively. From the SS with BPWM at Wd of 1, 2, and 3 cm, respectively, daily yields of 1.95, 2.34, and 1.81 kg were obtained. The highest exergy loss of the glass material, basin material, and basin water for the SS with BPWM at 1 cm Wd was 728.7, 133.4, and 123.8 W/m², respectively. The SS with BPWM’s thermal and exergy efficiency are 41.1 and 3.1% at 1 cm Wd, 43.3 and 3.9% at 2 cm Wd, and 38.2 and 2.9% at 3 cm Wd, respectively. The results show that compared to the exergy loss of basin water in SS with BPWM at 1 and 3 cm Wd, the basin water exergy loss of SS with BPWM at 2 cm Wd is minimal.
... Numerous techniques have been applied to the traditional single-sloped solar still (TSS) to augment productivity by considering the impacts of these variables on the efficiency and productivity of the solar still [6,[27][28][29][30][31][32][33][34][35][36]. Several authors studied different solar still design concepts (single or double slope [7,37,38], spherical [12,13], tabular [39][40][41][42][43], and pyramid [44][45][46]). ...
... Their results showed that the maximum efficiency of modified tubular solar still was 61.4% with an optimal thickness of saline water of 2 cm. Kabeel et al. [40] studied the influence of saline water depth and water cooling effect on the performance of tubular solar still. Their results showed that the best performance can be achieved with the lowest depth of saline water and optimal mass flow rate of the water cooling over the transparent tubular solar still. ...
Solar energy desalination process is the most efficient and cost-effective method for producing fresh water from saline water by employing solar energy from the sun's free source of heat. In the current study, experimental and theoretical methods were used to investigate the performance of a novel design of conical solar still integrated with conical glass cover and conical basin area with continuous volume flow rate at different values of volume flow rate, 80, 60, and 40 mL/sec compared to traditional solar still. Experimental results showed that maximum productivity and efficiency can be achieved by utilizing the conical solar still at lower volume flow rate of saline water. Highest efficiency can be obtained by utilizing traditional single solar still (TSS), conical solar still with volume flow rate of 80 mL/sec (CSSF), conical solar still with volume flow rate of 60 mL/sec (CSSH), conical solar still with volume flow rate of 40 mL/sec (CSQ), and conical solar still with volume flow rate of 40 mL/sec with an array of the mirror (CSQM) on average is 28.2, 42.04, 53.78, 63.4, and 69.15 %, respectively. Freshwater productivity of CSQ was enhanced by employing the arrays of the mirror. Daily freshwater productivity of CSSF, CSSH, CSQ, and CSQM was enhanced on average by 221.5%, 160.4%, 157%, and 174.7%, respectively, over the freshwater productivity of TSS. Theoretical model is obtained utilizing Mathcad software and is validated by comparing it with experimental findings. The theoretical results obtained from the mathematical model are in good agreement with the experimental results.
Keywords: Conical solar still, Conical shape, Evaporation surface, Condensation surface, Freshwater productivity, Desalination process.
... The tubular solar still (TSS) coupled with [18] and without heat pipe is investigated to specify the effect of charging the odd receiver with heat from solar heat pipe or study the impact of receiver geometry on the absorbed energy from solar radiation. The effect of glass cover cooling was empirically investigated [19]. Water depths of 5, 10, 20, and 30 mm were tested to assess the stills' thermal and exergy efficiencies with and without cover cooling. ...
Solar energy is still commonly used to produce clean drinking water due to its simple construction, low maintenance, and ecofriendliness. This work aims to experimentally investigate the yield upgrade and the thermal performance of a novel concentrated single‐axis tracking trough tubular solar still (TSS). This tubular still is identified by three baffles that generate four interrupted sections in the U‐receiver, which is inserted with copper mesh and fitted in a hexagonal‐shaped glass cover. Two identical TSS models were side‐by‐side outdoor tested in Baghdad‐Iraq 33.3° N and 43.3° E from January to March 2024. The first is inserted with black copper mesh (Model I), and the other has no insertion (Model ll). The effect of the inserted copper mesh (60, 120, and 180 g) and the receivers' tilt angle (5°, 10°, and 15°) on the still performance are involved. The still thermal performance is analyzed per heat transfer coefficients, energy, and exergy efficiencies. The results revealed that the accumulated daily yield is enhanced for Model I by 78.9%–194.8% while the thermal efficiency is enhanced by 68.3%–206.4% when it is tilted at 15° with the insertion of 60–180 g copper mesh, respectively, compared with Model II. It is concluded that an effective improvement in the solar still yield is obtained by using copper mesh.
... This design ensures that the water is exposed to a significant amount of radiation being subjected to it from all directions. Kabeel et al. [24] explored (TSS) by changing the water volume contained within the basin and using cover cooling to increase the condensation rate. The findings indicated that an optimum depth of water of 0.5 cm and a 2 L/h cold water flow increased the amount of drinkable water generated by a cover cooling TSS, achieving the highest output of 5.85 kg/m 2 . ...
... These include the double slope receiver [58], pyramid [59], spherical [60], tubular [61,62], stepped [63], and hemispherical solar stills [7], among others. Additional fins [7,52], internal and external reflectors [64], absorber plates [65], porous materials [66,67], wick materials [68], solar tracking [69,70], slope angles [71], cover cooling [72], and other features might all help achieve even greater increases. Some unaddressed research gaps are identified by an examination of prior studies and research from the literature review. ...
A sustainable and cost-effective technique for desalinating water with solar energy to alleviate the freshwater scarcity is the solar still. In this study, four different cases including the case-I: conventional solar still (CSS), case-II: CSS with fins and sand, case-III: CSS with fins, hybrid enhanced nano PCM, sand and sponges, case-IV: CSS with fins, hybrid enhanced nano PCM, crushed stone and sponges have been comprehensively investigated in terms of thermal, productivity, exergy, economic, environmental and sustainability point of view. The assessments were executed at the Rajshahi (latitude: 24°22′N, longitude: 88°36′E), Bangladesh. Later, the performance case-III was investigated by using river (Padma) water and discolored water, respectively. Average thermal efficiency on daily basis of case-III is about 32.44% and 6.47% higher than case-II and case-IV due to the improved heat storing configuration. In addition, cases-II, III, and IV all had exergy efficiency improvements of 18.89%, 74.75%, and 53.54%, correspondingly in comparison to case-I. For cases I, II, III, and IV, the payback periods are 185, 159, 126, and 135 days, accordingly. In cases-I, II, III, and IV, modified SS results in cost-per-litre reductions of 73.5%, 77.29%, 81.89%, and 80.63%, correspondingly, as compared to market prices. Cases-I, II, III, and IV's energy production factors are 0.137, 0.099, 0.138, and 0.195 yr-1, respectively. The research also supports the claim that adding fins, sponges, black sand, and hybrid enhanced nano-PCM to CSS results in a higher sustainability index.
... There is a fall in productivity from 1 rpm to 0.5 rpm when using a hollow cylinder in conjunction with a flat plate solar water collector, but the increase in productivity ranges from 146 to 260% at different revolutions per minute (rpm) from 0.5 to 10 rpm [8]. Wind speed, temperature, and sun radiation availability are some of the factors that can affect how effectively solar distillation works [9][10][11][12][13][14][15]. ...
This study includes an experimental investigation of a conventional and improved solar still, both dual-tilt. The enhanced solar energy is coupled to a rotating hollow metal cylinder. The purpose of this study is to enhance the productivity of solar energy in the production of distilled water and reduce the production cost. The hollow cylinder enhanced the surface area needed for water to evaporate, while the thin layer of basin water in contact with the cylinder surfaces reduced the thickness of the layer of water to be heated. Adding an aluminium mesh layer to the surface of the rotating hollow cylinder caused the temperature of the basin water to rise, increasing the distilled water throughput from the still. This study included calculating the economic feasibility of the traditional and improved solar stills, as the cost of the traditional still is about 87 dinars to produce one litre, while the improved still costs 65 dinars to produce one litre.
... Kabir et al. [31] investigated how the addition of cap cooling to tubular solar still (TSS) for increased the rate of water production per day. The device consists of a dark bath and transparent solar tubes that work together to accelerate water evaporation and increase solar radiation. ...
Numerous human activities and a rapidly growing world population are increasing the demand for freshwater. Fresh water production relies heavily on the use of conventional fuels and is associated with environmental pollution, leading to the need to look for other alternatives such as clean energy (solar energy). There are many villages and rural areas in the world without access to clean water. Many desalination systems have been developed to address this shortcoming. This study describes strategies for increasing clean water solar energy productivity that are currently in commercial and experimental development stages. Solar stills are the most prudent method for delivering new water since they just sudden spike in demand for the energy of the sun, which is promptly accessible in nature. The focus is on technologies that can be used independently, especially those that can be integrated into solar thermal systems. The results show that the solar thermal distillation yield is inversely proportional to the basin water depth and is directly related to the wind speed in the absorbing region, the temperature of the glass covers and the incident solar radiation. Add to the technology used inside and outside the system to improve productivity.
... Allowing the brackish water to absorb the solar radiation directly is one of the most effective methods to enhance the performance of the solar still [38]. For instance, using dark color liquids and particles mixed with a fluid to be desalinated is examined by [39]. ...
This study showcases a solar still desalination system that utilizes solar energy to produce freshwater from brackish water. The study examines the impact of incorporating recycled waste as porous media on the traditional solar still's productivity and efficiency. Specifically, spongy materials and crushed rubber granules from discarded tires create a porous bed within the solar still. The study investigates the effects of various types, sizes, thicknesses, and colors of porous materials. The results of the experiments are compared to those of conventional solar still without any porous media. The findings indicate that incorporating a sponge can increase productivity by up to 190% while using crushed rubber can increase productivity by up to 225%.
... The cylindrical enclosure of the TSS's unique design precludes the need for any thermal insulation, which would have increased the amount of heat that builds up inside the TSS [2]. An experimental comparison of TSS and double slope SS reveals that , with maximum efficiencies of 41% and 3 5% for the tubular and triangular solar stills,respectively , the tubularsolarstill produced 20% more potable water than the triangular solar still [8]. ...
The solar distillation process efficiently addresses freshwater scarcity by using renewable energy sources. Our research focuses on enhancing convex tubular solar distillation by integrating wick material with Phase Change Material (PCM) enriched by nanoparticles. We rigorously examined seven cases, including Case 7 (TSS with Jute Wick, 3cm PCM incorporated with Al2O3 nanoparticles), which demonstrated the highest efficiency at 50.39%. Uncoated jute material outperformed its black-coated counterpart, with a 4.61% efficiency increase and an 11.34% advantage over black cotton. PCM, particularly with a 1 cm depth, improved efficiency by 15.97%, while increasing PCM depth led to consistent efficiency gains, reaching 47.9% with a 3 cm depth. The incorporation of nanoparticles enhanced TSS effectiveness by 5.15%.
... A 20% increase in daily solar radiation boosted the daily production by 8.8%, but an increase in water depth lowered it. Kabeel et al.77 combined cover cooling with a tubular solar still to investigate its influence on the still's efficiency.The experiment was done in Cairo, Egypt. At a low water level of 0.5 cm, the still without a cooling cover yielded the most (4.5 L/m 2 ).When the cover cooling integrated still had a 2 L/h cooling flow rate and 5 mm water height, the maximum yield (5.85 L/m 2 ) was generated. ...
Solar stills can be an easy and environmentally viable solution in today's world, where a lack of fresh water sources is a major challenge. Solar stills, on the other hand, aren't economically viable due to their poor efficiency. It has been the subject of several studies to improve its efficiency and output. The goal of this review article is to understand and summarize recent studies conducted to improve the efficiency and commercial viability of solar stills. It focuses on using experimental and numerical techniques to manipulate different parameters that affect freshwater production in stills in order to arrive at a suitable condition where the efficiency and productivity of the solar still are maximized. Effects of modifications such as addition of baffles, fans, fins, phase change material (PCM), etc., and its consequent influence on freshwater production rate are presented in this article. Fins, for example, improved the efficiency of solar still by about 40% and productivity by about 16%. PCMs too increased the productivity rate by around 50%–90% depending on the type of PCM used. Baffles were found to be more effective when they were mounted closer to the front wall of the solar still. The findings and conclusions of all the studies are summarized. This review article aims to provide an overview of solar stills and the various modifications that may be done to improve their overall efficiency.
... For instance, Kabeel et al. [87] controlled the basin water depth inside the tubular distiller with cooling its cover to improve the performance. The system is shown in Fig. 12. ...
... Test the performance of solar stills can be achieved by varying the water depth (Kabeel, Sathyamurthy, et al., 2019). Several studies of solar stills with variations in water depth, including testing pyramid solar stills with a water depth of 1 cm, produce the highest productivity and Efficiency , tested the tubular Solar still with the lowest depth (0.5 cm) and the cover glass coolant flow rate of 2 Liters/hour to obtain the highest productivity and Efficiency (Kabeel, Sharshir, Abdelaziz, Halim, & Swidan, 2019). The lower the water depth, the productivity will increase accordingly (Alwan, Shcheklein, & Ali, 2021). ...
Passive Solar is still suitable for Indonesia's islands and coastal areas. Various attempts have been made to increase the performance of passive solar stills, including using porous materials, fins absorber models, and making water in the form of a thin layer. This study aims to increase the distillate output and Efficiency of Solar still. This study's method compares stone fin solar stills absorbers using water depth variations of 1 cm, 2 cm, and 3 cm with conventional solar stills at a water depth of 1 cm. The study resulted in the distillate output of stone fin solar still absorber of 3.35 (liter/m2.day) higher than the conventional solar stills 2.44 (liter/m2.day) at a depth of 1 cm. The highest Efficiency of solar stills using the stone fin solar still absorbers is 58.45% higher than conventional solar stills, 43.60% at a depth of 1 cm. Solar stills with lower water depths resulted in higher distillate output and Efficiency. Solar stills using stone fin absorbent plates produce higher productivity and Efficiency than conventional ones
... The first step involved examining two setups: one with a half-cylinder basin and the other with a cuboid basin. In all experiments, the depth of saltwater in the basin was fixed at 0.01 m, considering that water productivity decreases by increasing the depth of water [42]. Fig. 2 shows a photograph of the benchmark case. ...
Abstract:
This experimental study aims to improve the performance of a tubular solar still using enhanced thermal management methods. Paraffin wax with a melting point of 44 °C is used as a phase change material (PCM). Three main methods of improving solar still desalination performance were analyzed including pure PCM, nano-enhanced PCM with Co3O4, and the combination of nano-enhanced PCM with aluminum shavings, and compared to a conventional tubular solar still. In order to improve the thermal performance of the portable desalination design, copper tubes containing industrial metal waste, as the porous media, and baffles coated with micro Al2O3-black paint were utilized in the solar still basin. The addition of 0.3 % Co3O4 nanoparticles along with aluminum shavings led to improve the thermal properties of paraffin wax by reducing >50 min in the melting time. Based on the obtained results, the enhancement in cumulative productivity reached 5.69 %, 15.30 %, and 24.56 % for these three scenarios compared to the conventional solar still with a cuboid basin, respectively. Also, the average efficiency improved from 41 % to about 46.7 %, 51.2 %, and 64.3 %, respectively. Furthermore, the measured total dissolved solids (TDS) of the distilled water in all scenarios was within an acceptable range.
Highlights:
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A tublar solar still was designed and experimentally prepared for water desalination.
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Phase change material, enhanced with nano-Co3O4 and Al shavings, was investigated.
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Cumulative productivity enhanced by 24.56 %, compared to a conventional solar still.
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Average efficiency reached 64.3 % for the solar still with nano-enhanced PCM and Al.
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Applying enhanced PCM and porous media led to a melting time reduction of >50 min.
... -Cooling the cover by water: the flow of drops of water continuously [68] or intermittently [69] on the surface of the cover increased the resulting system efficiency by 8% [70], 20% [71], and 54% [72]. In addition, system productivity increased by 41.30-56.50%, ...
Freshwater scarcity is a problem that is becoming more and more of a concern over the world, and as a result, the search for solutions has become a race against time. One of the most crucial solutions for this issue is seawater desalination. The simplest and easiest type of desalination technology is seawater desalination using a solar still system. This present study reviews the past/current status of vacuum solar still systems to pave the way for researchers to improve this technology. This paper aims to describe the design specifications and highlight the merits and demerits of various vacuum techniques used in solar stills systems upon which research has been done in the recent past. Also, a discussion on future ideas is given with some recommendations in the field of vacuum solar stills improvement to economically produce sustainable potable water. The current study concludes that lowering the operating pressure of solar still systems improves system productivity and efficiency by roughly 100% and 70%, respectively. According to the research, forced vacuums account for 52% of all vacuums, while natural vacuums account for 48%. Forced vacuum is an ideal method since it combines creating vacuum conditions and evacuating the non-condensable gases, which is not possible in a natural vacuum. The system productivity and efficiency of the forced vacuum conditions are higher by 80% and 25% than that of the natural vacuum conditions. The cost of freshwater produced per liter in natural vacuum conditions is less than that of forced vacuum conditions.
... Several researchers have focused their attention on improving SSs performance by using different modifications [3,4]. Many modifications have been suggested and investigated to enhance the performance of SSs such as tubular SSs [5,6], double slope SS [7,8], pyramid SS with nanoparticles [9], pyramid SS integrated with evacuated tubes [10], pyramid still coated with TiO2 nano black paint [11], inserting internal or external reflectors, cooling the glass cover [12], using activated carbon [13], inserting internal or external condensers [14], the use of wick materials [15], using silica nanocomposites which are fumed in black paint [16], as a porous absorber, using nanomaterials [17,18], atomizer with ultrasonic waves [19], the use of hydrogel materials [20], the use of airing multifunctional textile [21], SS integrated with nanoparticles [17,22,23], the use of phase change materials or gravels [24], evaporation of thin films [23,25], energy storage [26], wick [27], organic colloids [28], humidification-dehumidification solar still [29,30], sponges [31], double-slope SS with rubber scrapers [32], and so on. The freshwater production in the SS systems is shown to be inversely proportional to the saline water depth. ...
Artificial intelligence has been involved into different research fields. One of the interesting fields is the mechanical engineering field. This research work intends to introduce an alternate prediction approach that can predict the Hemispherical Solar Still (HSS) performance effectively without using an empirical method. The thermal performance of the HSS is predicted using five prediction models including Decision Tree (DT), Random Forest (RF), Gradient Boost (GB), Support Vector Machine (SVM), and K-Nearest Neighbor (KNN), which are performed, assessed, and compared. The proposed prediction models are built using real experimental data that has been recorded. The effective prediction model to be employed in the prediction of the hourly productivity and the instantaneous efficiency of the HSS is determined using five statistical error values. The comprehensive comparative analysis that was carried out demonstrates that, as compared to other models, the Decision Tree model may be used to estimate the thermal performance of solar stills without the need for additional experiments, saving money, effort, and time as its R2 and EVS values were near to one and the other statistical values (MSE, NAE, and Median Absolut Error) were very small. According to the results of the experiment, the HSS has an average hourly productivity of 0.478 L/m2 with the daily water production of 0.477, 0.465, 0.476, 0.477 L/m2 day for the proposed DT, SVM, RF, KNN and GB models, respectively. In addition, an average instantaneous efficiency of 45.199% with daily efficiency 45.188, 46.374, 46.375. 44.794 and 45.2 % for DT, SVM, RF, KNN and GB, respectively. Therefore, the proposed models appear a superior performance prior to performance estimation of HSS and can be considered as an efficient solution for this issue.
... Many studies on evaporation have been conducted. Some study that has been explored include the effect of pressure and material on evaporation, the impact of the angle of the glass roof and the mirror at the base of the basin on evaporation; the effect of sunlight on evaporation; the effect of water level on evaporation; the effect of temperature on evaporation; and the use of mist sprayed from a nozzle to evaporate water [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. However, no previous study has explored the effect of wind speed on the evaporation of sea water in desalination chamber. ...
Water is very important to human life, and its use is increasing as the population grows. However, sources of fresh water on the earth's surface are limited, as seawater covers most of the earth. Therefore, seawater desalination is a potential solution to water shortages. Desalination is the process of removing salt from seawater to produce fresh water. Desalination is particularly useful approach in Indonesia because two-thirds of this nation’s territory is ocean. Desalination involves two stages: evaporation and condensation. Wind speed affects the rate of evaporation. Thus, this study explores the effect of wind speed on the rate of evaporation. Wind speed was regulated using a fan, and wind speeds of 0 m/s, 0.6 m/s, 2.6 m/s, and 5 m/s were tested; the water temperature was kept constant at 60 ℃. The data were analyzed statistically to determine the effect of wind speed on the evaporation of seawater. The highest rate of evaporation occurred at a wind speed of 5 m/s and the lowest at a wind speed of 0 m/s. The highest amount of condensation occurred at a wind speed of 0.6 m/s and the lowest at a wind speed of 5 m/s.
... With insulated material, the temperatures were approximately 3.72 kg/m 2 , 3.40 kg/m 2 , 2.70 kg/m 2 , and 2.08 kg/m 2 for the same water depths. In Kabeel et al. (2019), the effect of different water depths (0.5 cm, 1 cm, 2 cm, and 3 cm) on the performance of a tubular solar still (TSS) was investigated. The study founded that the productivity of still reached about 4.5 L/m 2 at a water depth of 0.5 cm, while at 3 cm, the daily productivity was 3 L/m 2 . ...
This experimental study aimed to investigate the impact of water depth, inlet water temperature, and fins on the productivity of a pyramid solar still in producing distilled water. The experiment was conducted in three parts, where the first part explored the variation in water depth from 1 cm to 5 cm, the second part evaluated the effect of increasing inlet water temperature from 30°C to 50°C, and the third part added fins at the bottom of the still at a specific inlet water depth. Results showed that basin depth had a significant impact on the still’s production, with a maximum variation of 40.6% observed when the water level was changed from 1 cm to 5 cm. The daily freshwater production from the pyramid solar still ranged from 3.41 kg/m2 for a water depth of 1 cm to 2.02 kg/m2 for a depth of 5 cm. Adding fins at the bottom of the pyramid solar still led to a 7.5% increase in productivity, while adjusting the inlet water temperature from 30°C to 40°C and 50°C resulted in a 15.3% and 21.2% increase, respectively. These findings highlighted the essential factors that can influence the productivity of pyramid solar stills and can be valuable in designing and operating efficient water desalination and purification technologies.
... To promote the distillation yield and energetic effectiveness of solar stills, many scholars have investigated and focused on utilizing different configurations of glazier covers within solar stills. The glazier cover has an intrinsic significance in the distillation process since it has three purposes: employing as a condensation surface, involving humid air, and heat transport dispersion from the solar distiller housing into the surrounding by radiation and convection [10,11]. Different designs of top glass coverage have been utilized within solar distillers, including single slope [12,13], double slope [14], pyramidal [15], stepped [16], tubular [17], spherical [18], conical [19], half-barrel [20], hemispherical [21], and ….etc. ...
An innovative designed convex basin is utilized instead of the flat absorber basin to maximize the exposure and vaporization surface areas. Moreover, a jute cloth layer is used over the convex basin as a wicking material for promoting the vaporization rates inside the modified distiller. Additionally, the influences of using phase change material (PCM) thermal storage on the distiller performance was studied on the distiller thermo-economic performance are investigated. Three hemispherical distillers are designed and tested, namely, modified hemi-spheric distiller with a wick convex absorber basin (MHD-WCAB), modified distiller with a wick convex absorber basin and PCM (MHD-WCAB + PCM), and reference hemispheric distiller (RHD). The performance of three proposed hemispherical stills is performed based on economic, energetic, and exergetic points. The daily distilled product reached 7.95 and 6.90 kg/m 2 /day for the MHD-WCAB + PCM and MHD-WCAB, respectively, 4.25 kg/ m 2 /day for RHD, achieving 87.06% and 62.35% improvement relative to the RHD. Furthermore, the daily energy efficiency of MHD-WCAB + PCM and MHD-WCAB is evaluated as 46.90% and 34.04%, respectively, representing an improvement rate of 85.67% and 61.74% compared to RHD. The daily exergy efficiency of MHD-WCAB + PCM and MHD-WCAB reached 3.88% and 3.39%, respectively, yielding an augmentation rate of 128.24%, and 99.41% over RHD.
... Other results are found based on experimental theoretical work [22][23][24][25][26]. It has been the goal of several earlier studies to increase the efficiency of solar stills, either by enhancing the construction of solar stills [27][28][29][30][31][32][33][34][35][36][37][38][39] or by integrating materials for heat storage [40][41][42][43][44][45][46]. ...
This study compares and contrasts the desalination efficiency of tubular solar still using cylindrical and rectangular troughs when operating under a vacuum. For this, a two-dimensional code was created using the Comsol Multiphysics. The mass and heat transfer, inside the tubular solar still with the two different types of troughs, was simulated parametrically. The effect of the radius of the cylindrical trough, the square rib of the rectangular trough and the vertical elevation of the trough on heat and mass transfer were investigated at the same volume of seawater introduced initially. The numerical results revealed that the efficiency of the water productivity using cylindrical trough is significantly better than with rectangular trough when it is placed in the middle of the tubular shell. The opposite case of the 2 types of troughs is established when the trough advances towards the upper side of the glass cover where the condensation occurs.
In this study, the main aim is to determine the most effective spacing for 1.6 cm-diameter black glass balls, utilized as a cost-efficient energy storage solution to enhance the performance of a conical solar distillation system. Three identical conical stills were utilized over a two-day experimental period to evaluate various setups. The first distiller, denoted as the conventional conical solar distiller (CCSD), operated without black glass balls on the initial day and served as the reference for comparison on the second day. The second and third distillers, labeled CSD-BGB3 and CSD-BGB4, featured black glass balls spaced 3 cm and 4 cm apart, respectively, while another set of experiments on the subsequent day involved CSD-BGB5 and CSD-BGB6, with black glass balls spaced 5 cm and 6 cm apart. The brine depth in the basins remained constant at 1.6 cm throughout the experiments. The study revealed that CSD-BGB3 achieved the highest yield from the distillation process, reaching 8250 g/m2, while the maximum yields for CSD-BGB4, CSD-BGB5, CSD-BGB6, and CCSD were 7600, 7100, 6600, and 5750 g/m2, respectively. The optimal spacing of 3 cm between the black glass balls led to a significant improvement in accumulated yield and daily efficiency by 43.48% and 42.59%, respectively, compared to conical solar stills without black glass balls. The findings suggest that a conical solar distiller equipped with 1.6 cm-diameter black glass balls spaced 3 cm apart offers the most efficient and cost-effective energy storage solution among the configurations examined.
Advantage of tubular solar thermal desalination system is its higher condensing surface area compared to other systems. Moreover, it can be fabricated even with low cost polyethylene sheets. In this chapter, the role of various surface coatings, energy storage materials, nano-particles, concentrators, condensing cover shape, condensing cover material, and operating pressure on performance of tubular solar desalination system has been explained in detail. Moreover, step by step detailed thermodynamic modeling along with salient features has been presented.
An experimental study of a conical solar distiller's usage of inexpensive energy storage material to increase distillation yield. Stainless-steel balls are utilized in experiments because they increase the surface area of the water and are excellent energy storage devices. The goal of this research is to determine the optimal distance between the stainless-steel balls (with a fixed diameter of 1.4 cm) as a low-cost energy storage material to improve the productivity of conical solar stills. As a result, three identical conical distillates were produced. Experiments are carried out over the course of two days. On the first day, the first distiller is free of stainless-steel balls, the second distiller has a distance of 3 cm between the stainless-steel balls, and in the third distiller there are stainless-steel balls at a distance of 4 cm. The second day, the first distilled is still witness. The second and third distillers have stainless-steel balls placed at the bottom of the basin at distances of 5 and 6 cm, respectively. The depth of the brine in the basins is 1.4 cm. The distillation productivity with storage of stainless-steel balls (a diameter of 1.4 cm) with a distance of 3 cm between the stainless-steel balls achieves a maximum yield of 9500 g/m2 compared to the distillation yields with storage of stainless-steel balls with a distance of 4, 5, and 6 cm between the stainless-steel balls, which amounted to 8800, 8200, 7400, and 5750 g/m2, respectively. The optimal distance between the stainless-steel balls was found to be 3 cm, with an improvement rate of 65.22 %. Finally, conical solar energy with stainless-steel balls as a low-cost energy storage material with diameters of 1.4 cm, and a distance of 3 cm between the stainless-steel balls is still optimal.
Present water resources are insufficient to fulfil future demand. Without eating or drinking, humans can go days, weeks, or months, but not longer than a week. Businesses and households are increasingly using water. Drinkable water is produced by filtering brackish, sewage, and saltwater in various countries. Some countries prioritise drinking water production. This article examines heat exchange solutions scientists have used to increase solar still water output. Numerous authors have created and examined basic and advanced solar stills. These authors examined what happens when the container, collector, and water's chemical and physical properties change. One technique to increase solar distillation yield is with a cylindrical collector. The system's surface area will rise. Our research examines the different ways solar stills have been made more efficient.
Purified drinking water is the basic need of human beings. Purification of water assisted by freely available solar energy can be the best alternative compared with other water purification techniques available in the market today which consume nonrenewable energy. Distillation, which is the most ancient method, is being used for water purification. The device in which solar thermal energy converts brackish water into pure drinkable form is known as a solar still. Present article reports an extensive study of numerous designs of solar stills. The article also includes a review of effect of each parameter that influences the water productivity that is, pure water. Considerations of thermodynamics, heat transfer, and mass transfer are also explained in brief. The reviews of various kinds of analysis namely, theoretical, experimental, computational, cost, and water quality have been reported. K E Y W O R D S drinking water, saline wastewater, solar energy, solar still, water quality 1 | INTRODUCTION Water is life and clean water is a crucial necessity for all living creatures. Humans require water for various day-today activities, including domestic and industrial. The earth contains almost 71% water out of which only 1% is potable. 1 The remaining water is not useful for humans for drinking as it contains various impurities. Impure water may lead to various health hazards. Hence, there is a significant need to purify the water to fulfill human needs. 1.1 | Techniques used for water purification Purification of water can be done by several technologies available in the market today. 2 A change in phase (thermal process) is one of the techniques in which the seawater is heated and condensate is collected as pure water for drinking. Examples of this technique are: multi-stage flash (MSF) and multi-effect distillation (MED). These systems require pumping arrangement and there arise scaling issues. A semi-permeable membrane can be used for the separation of solvents present in the water by allowing brackish water to pass through it. A Reverse Osmosis (RO) technique and Electro Dialysis (ED) technique uses a semi-permeable membrane. 3 Frequent replacement of a membrane is required in both these methods. Water purification using the change in phase process and using a semi-permeable membrane requires a prime mover. Equipment with these techniques is costly and non-affordable to many people. Water purification method must be cost-effective. Solar Energy is available at no cost and in a very large quantity that can be used directly or indirectly for water purification. 4 The direct technique includes solar still and indirect techniques include solar humidification-dehumidifica-tion, MSF, MED, membrane distillation, RO, and ED. Out of all these solar-assisted water purification techniques, the solar still is the best technique as far as cost and water productivity per unit overall dimensions are considered. The solar still works on the hydrological cycle. The brackish water is heated inside a basin of suitable size using solar energy. The basin is covered with transparent material from the top. The transparent cover allows solar radiation to enter the basin. The brackish water inside the basin gets evaporated and saturated vapor is formed. The vapor flows upward and gets deposited at the inner side of transparent condensing cover. The inner side of the condensing cover has comparably a lesser temperature than the upper side of brackish water. This temperature difference leads to the condensation of saturated vapor at
This study seeks to enlarge the yield and thermal performance and reduce the cost of the conventional pyramid distiller. Three modified pyramid distiller systems have been proposed, and their effects on the thermo-economic performance have been investigated. The first proposed system uses v-corrugated aluminum basin, black cotton fabric (wick material), and paraffin wax as PCM. In contrast, the second one uses the same parts as the first one, but the carbon black nanofluid is used instead of base water. The last modification was like the second one, but with the addition of CB nanoparticles to the paraffin wax to increase its absorptivity and heat transfer rate. Thermal analysis has been conducted to evaluate their thermal performance from the perspective of exergy and energy efficiency compared to the conventional system. Moreover, an economic investigation has been undertaken to evaluate yield's cost per one liter in each case. According to the results, it was found that the three established systems performed well from a thermo-economic point of view when compared to the conventional one. Compared to the conventional system, it is found that the third system yield has been enhanced by 76.9%, while its thermal efficiency has been increased by 101.5%, and the exergy efficiency has been improved by 109.7%. Finally, the save in the total yield's cost per liter is 29.7% when using the last system compared to the conventional one.
This paper presents a numerical and experimental investigation to study the effect of the
condenser area on the Natural Circulation Loop (NCL) solar still features under typical
summer and winter conditions. A computer code has been developed to predict the
transient thermal behaviour of the still. This computer code is used to predict the effect of
condenser area and wind velocity, on the still daily yield in summer and winter conditions.
The results revealed that the still daily productivity increases with the increase of the
condenser area until a critical value beyond which its effect becomes insignificant. In addition, it was found that the wind effect is more effective for small condenser area. The simulation shows that the maximum daily output of NCL solar still, under summer and winter conditions, can reach 4.73 kg/m2 and 2.71 kg/m2, respectively.
This study investigated the effect of an internal reflector (IR) on the productivity of a single-slope solar still (during the summer and winter) experimentally and theoretically. A mathematical model was presented which took into account the effect of all walls (north, south, west and east) of the still on the amount of received solar radiation to brine, and the model was validated with the experimental data. The model can calculate the yield of the still with and without IR on various walls. The results show that the simultaneous use of IR on front and side walls enhances the still's efficiency by 18%. However, installation of an IR on the back wall can increase the annual efficiency by 22%. The installation of IRs on all walls in comparison to a still without IR can increase the distillate production at winter, summer and the entire year by 65%, 22% and 34%, respectively. Furthermore, the effect of cloud factor on the installation of IRs on all walls was examined, and the results indicate that the increasing the cloud factor decreases the influence of IRs significantly.
Exergy analysis is a powerful indicative tool for thermal systems performance evaluation. Now a day, there has been an increasing interest in using exergy as a prospective tool for analysis. In this paper, an attempt is made to perform energy and exergy analysis of single slope passive solar still of size of 1 × 0.5 m with the glass thickness 5 mm and slope 13o. To examine the effects of water depth for same total daily solar intensity on energy and exergy efficiency, experiments were carried out at Chennai (13°5′2″N, 80°16′12″E), Tamil Nadu, India. The exergy destruction of different components of solar still for various water depths was also determined. The study found that the highest exergy destruction is takes place in basin liner as compared with the other components for all the water depths.
In this paper, a new radiation model for a single-slope solar still has been developed which for the first time takes into account the effect of all walls of the still on the amount of incident solar radiation on the water surface and each wall. In this model, the walls are projected on the cover to calculate the amount of beam radiation received by any components inside the still. This is in contrary to the previous models in which stills' walls were projected on a horizontal surface and their shadows on the water surface and the walls were either neglected or not computed properly. The predictions of the proposed model are compared with the experimental data obtained in the present work and data from the literature. It was found that there is a good agreement between the theoretical results and the experimental data. Moreover, time variations of the incident beam radiation on different parts of a single-slope solar still are investigated. The results show that the effect of the back and side walls is not inconsiderable and they should be taken into consideration to improve the accuracy of the thermal radiation analysis of single-slope solar stills' performance.
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.
Wettability is one of the most important factors which significantly influences solar still efficiency. Moreover, it determines the condensation mode, i.e., filmwise or dropwise condensation. In the present study, materials with different wettability were applied as the condensing surface to evaluate the effect of wettability on the distillate production of a single slope solar still. To compare the effects of dropwise and filmwise condensation on the condensate yield, the wettability of the condensing surface was changed by applying a nano-silicon solution according to a dip coating technique. All the experiments were conducted at three surface inclination angles. The results revealed that the nano-coating changed the condensation mechanism from filmwise to dropwise for all the materials. Also, it was concluded that dropwise condensation leads to increased condensate production at higher surface inclination angles. For example, condensate production of a glass surface was increased by 23% after nano-coating at a surface inclination angle of 50°. In addition, the amount of dripping was estimated before and after the coating process by using additional collectors. To illustrate, the amount of dipping from uncoated aluminium surface was 106 ml which increased to 198 ml after the coating process at a surface inclination angle of 30°.
In this study, absorber plate of a novel pyramidal basin type solar still is coated with TiO2 nano particles doped in black paint on the basin to analyze the performance under varied depth of water. Water depth is varied from 1 cm till 3.5 cm on a basin area of 0.25 m2 which is almost equal to the area of glass cover. Instead of using other sensible storing materials inside the basin which probably increase the weight, a novel solar still with the absorber plate coated with TiO2 nano particle mixed with black paint to improve the performance. Experimental results revealed that the use of TiO2 nano particle in black paint improved the water temperature by 1.5oC than that of absorber without nano particle. Similarly, the yield improved during the sunshine hours rather than the off shine hours. With increased depth of water in the basin, the water temperature is minimum which simultaneously resulted in lower yield on absorber without coating whereas the yield from the still improved by 12% at maximum water depth using coated absorber plate. The accumulated yield from the solar still absorber plate with and without coating was found to be 6.6 and 6.2 kg/m2 respectively at 1 cm water depth. TiO2 nano black paint coated pyramid solar still improves the distilled yield by 6.1% as compared to the conventional basin type pyramid solar still. Similarly, the values of instantaneous efficiency based on operational and climatic parameters using linear and non-linear were determined. From the cost breakdown analysis, it is found that present system is feasible as compared to the conventional pyramid solar still without coating.
This experimental and theoretical study presents the performance of copper oxide (Cu2O) nanofluid in a
single slope solar still fitted with an external thermoelectric condensing channel. Four thermoelectric
cooling modules (TEC) are installed around the walls of the external channel in order to make a cool
place in the vapor flow, and also the Cu2Oewater nanofluid with different volume concentrations is
employed. The temperatures of glass cover, basin water, absorber plate as well as distillated water
productivity, and daily energy and exergy efficiencies of the modified solar still are presented during July
in Razi university of Kermanshah (Iran). Moreover, the cost of distilled water for different cases is
calculated. The results disclose that the productivity, energy and exergy efficiencies of solar still equipped
with the external thermoelectric condensing channel enhance by about 38.5%, 38.9% and 31.2%,
respectively. In this case, by adding 0.08% volume fraction of the Cu2O nanoparticles in basin water, the
productivity, energy and exergy efficiencies are enhanced about 82.4%, 81.5% and 92.6%, respectively. The
cost analysis designates that in optimum mode, the cost of distillated water per liter is 0.021 $/L/m2 for
this modified solar still.
Active solar stills are well known for their higher amount of distillate production than conventional stills. In this paper, a tubular solar collector assisted solar still was suggested for desalting saline water. Its exergy performance, enviro–economic and economic analysis has been carried out. The obtained findings were compared to a simple solar still of similar dimensions. Results revealed that the annual yield of the traditional and modified solar stills was estimated to be ∼405.04 and ∼549.77 kg/m². The hourly exergy efficiency and global exergy efficiency of the passive system attained ∼7 and ∼30% and similarly for the active system ∼11 and ∼41%, respectively. The economic analysis shows that distilled water cost is minimum when the interest rate and the lifespan are 5% and 30 yrs, respectively, for the simple solar still (i.e. ∼0.018 /L in case of improved still. Further, the payback period of the passive and active solar distillers was estimated to be around 7.7 yrs and 21 yrs, respectively, based on the lowest interest rate (5%) and selling price of distilled water of 0.04 /annum on the basis of exergy for the active solar unit. It can be concluded that high distilled water production and less space occupancy are making the enhanced solar unit competitive and feasible.
The present study is devoted to developing a thermal model of modified multi–wick basin type double slope solar still (MMWBDSSS). Analytical expressions of temperatures of water, wick, walls, and glass covers, distillate yield and instantaneous efficiency have been derived. The experimental validation of thermal model has been carried out and a fair agreement has been detected between theoretical results and experimental observations. On the basis of annual energy and exergy, the energy matrices, namely, the energy payback time (EPBT); life cycle conversion efficiency (LCCE); energy production factor (EPF), enviroeconomic and exergoeconomic analysis has also been evaluated for the solar still with jute and black cotton wicks under the climatic conditions of Allahabad, Uttar Pradesh (U.P.), India. The CO2 emission mitigated per annum has been found to be 7.82 and 8.69 tons on energy basis; and 0.155 and 0.198 tons on exergy basis with jute and black cotton wicks at 1 cm water depth, respectively. The exergoeconomic parameter has been found to be 0.0623 kWh/Rs. and 0.0791 kWh/Rs. for the solar still with jute and black cotton wicks at 1 cm water depth, respectively for 4% interest rate and 50 years life span of the system.
In the present paper, the hybrid storage materials have been used to improve the solar still productivity. The hybrid storage materials represent a mixture of paraffin wax and graphite nanoparticles, the objective of using the present hybrid storage materials improve the thermal properties of storage materials as well as improve the still productivity. The conventional still and the solar still with a hybrid storage material was constructed and tested to investigate the improvement in a distillate production. Also, the effects of graphite nanoparticles mass concentrations in hybrid storage materials on the performance of solar still have been investigated. The experimental results showed that the accumulated distillate production of a solar still with hybrid storage materials is more than that of conventional basin still. The accumulated distillate production of solar still with hybrid storage materials reached to 7.123, 7.475, 7.937, 8.249, and 8.52 l/m² day for 0.0%, 5%, 10%, 15%, and 20% graphite nanoparticles mass concentrations, respectively. While the distillate production reached to 4.38 l/m² day for the conventional still. The percentage improvement in a water production was recorded 62.62%, 70.66%, 81.21%, 88.33%, and 94.52% for 0.0%, 5%, 10%, 15%, and 20% graphite nanoparticles mass concentrations, respectively, as compared to the conventional still. Also, the daily efficiency of solar still with hybrid storage materials was about 51.41%, 54.94%, 59.2%, 62.38%, and 65.13% for 0.0%, 5%, 10%, 15%, and 20% graphite nanoparticles mass concentrations, respectively, but for the conventional still the daily efficiency was about 32.257%.
The solar still is one of the best choices for obtaining fresh water, in small scale demands which covering
the demand for remote arid regions which do not have enough power source to distill water or infrastructure to deliver fresh water. In this study, experimental investigation of tubular solar still (TSS) is
presented. Two different models were constructed with different water basin absorber shapes; flat plate
(TSS-FP) and semi circular corrugated surface (TSS-SC). Those two models were tested at same climatic
conditions of 6 October City, Giza, Egypt (Latitude of 29.9381� N, Longitude of 30.9140� E). The TSS
thermal, exergic and economic performance and productivity for the two models were studied and
discussed. The TSS water production rate by using semi circular corrugated surface was about 4.3 L/m2
with enhancement by 26.47% rather than using a flat absorber with augmentation in thermal and exergy
efficiencies about 25.9% and 23.7% respectively. The water cost of the TSS-SC was 0.0067 US$/L with
reduction about 20.77% less than TSS-FP
A theoretical and experimental study was carried out on performance of a Tubular Solar Still (TSS) under vacuum operation condition, based on which a modified model was proposed. Theoretical analysis shows that a vacuum operation pressure augments the concentration differential of humid vapour around the trough and that around the condensation surface, intensifying the diffusion and natural convection of vapour in the cavity. It is further indicated that as the operation pressure approximates the saturation pressure of the saline water, buoyancy force due to mass transfer would surpass that from thermal diffusion, and dominate vapour transportation process in the still. The proposed model for predicting the freshwater yield adopted the diffusion rule of binary mixture in the calculation of the mass transfer coefficient. It has a deviation of −3% −11% against the current experimental results and was further verified by an independent dataset. Upon that the performance of current TSS under vacuum running condition was evaluated with the help of the model. In view of the efficiency in energy utilization, the evaluation results show that the energy utilization efficiency of the system has an increase over 80% compared with that under normal operating pressure condition.
In this study, two types of solar stills, triangular and tubular one, have been experimentally tested under a real weather condition. Following the same procedure, the experiments were carried out over seven typical winter days and the effects of solar radiation and ambient temperature on water productivity and total efficiency of the stills has been experimentally investigated. Furthuremore, to understand the detail structures of the air flow inside the enclosures, the fluid flow has been numerically simulated using computational fluid dynamics. Having the details of the fluid flow, the values of local entropy generation in the chamber have been obtained. The results indicated that the tubular still showed a better performance by 20% compared to the triangular one. The results of numerical simulation showed that the greater strength of the recirculating zones and the lower entropy generation are the main reasons to have a better water production in the tubular still. Furthermore, the cost of water production by the triangular solar still was found to be lower due to its lower manufacturing cost compare to that of tubular one. Based on the experimental results, two new correlations have been proposed to predict the water productivity in these systems.
This paper investigates the effects of nanoparticle-enhanced phase change material (NPCM) on solar still operation and performance. Technical and economic aspects were considered, to show an advance on earlier works using virgin phase-change materials (PCM). Three types of nanoparticle (TiO2, CuO and GO) were impregnated individually at 0.3 weight% in paraffin to form NPCM-1, NPCM-2 and NPCM-3 respectively. Experiments were conducted with four solar stills (SS) each of 0.5 m² area using respectively paraffin (SSPCM), paraffin-TiO2 (SSNPCM-1), paraffin-CuO (SSNPCM-2) and paraffin-GO (SSNPCM-3). There was observed an increase in thermal conductivity and a reduction in melting and solidification temperatures, with NPCM compared to PCM. The effects of NPCM on water temperature, storage temperature, hourly and annual productivity were determined. SSPCM, SSNPCM-1, SSNPCM-2 and SSNPCM-3 yielded 3.92, 4.94, 5.28 and 3.66 l/m²/day respectively, corresponding to 26 and 35% increases in productivity of SSNPCM-1 and 2 respectively over SSPCM. Economic analysis showed cost per liter (CPL) of water of 0.035, 0.028, 0.13 for SSPCM, SSNPCM-1, 2 and 3 respectively. Considering the advantages in productivity and CPL, SSNPCM-2 can be recommended as the best solar still compared to SSPCM, SSNPCM-1 and 3, providing clean water at less than half the cost of bottled water in India.
This paper presents an experimental investigation of a single-effect vertical tubular solar brackish water desalination device, with an aim to determine the mass transfer coefficient and its enhancement. The device consists of two closely spaced concentric pipes. The outside of the inner pipe is covered with a wicking material and wetted with hot brackish water. The water vapor evaporated from the wicking material condenses on the inside of the outer pipe. The measured productivity and temperatures at various points are given for different wicking materials thickness, water flow rates and chamber pressure under the condition of given heating power. Mass transfer coefficients are calculated from the experimental results and then applied in the prediction of water productivity. The maximum discrepancy between the calculation yield and measurement yield is relatively small compared with previous study. In addition, it was found that the yield of the solar still is 23.9% higher when the chamber pressure is lower by 25 kPa due to the enhanced mass transfer. Similar, doubling the ambient air velocity can increase the water yield by about 17.0%.
The current study discusses a new design regarding embedded simple distiller to a solar collector cylindrical shape. Investigating the performance improvement is based on solving transit thermal energy balance equations which can predict temperatures in different locations of the still. Introducing the pre–heater system was also modeled using a third ordinary differential equation for water as a working fluid. In order to validate the obtained findings, Dunkle's model was employed and outputs compared to previous works. Results demonstrated that the collector contributes appreciably in augmenting the basin water temperature higher than a simple still case and both couples of distillate amounts and instantaneous efficiencies were respectively (∼2.77 kg/m², ∼4 kg/m²) which an augmentation rate of yield of ∼ 44.40% and (∼40%, ∼80%) for the passive and active targets. The total cost of the collector materials was estimated to be about 63 US Dollars which represents a cheap price. Moreover, a critical issue was examined around heat losses of the proposed solar heater. At this stage, used empirical correlations available in literature enabling UL prediction (overall heat loss coefficient) of the former and flat–plate collector method has been performed. It was reached that the TSC can perform against a FPC with lower heat loss. Other parameters such as painted receiver, absorbtivity–emissivity effects and environmental circumstances have all influenced the TSC performance were also analyzed.
Solar steam generation is a promising water treatment technique which can harvest solar energy for water purification. In our work, for the first time, we designed a jellyfish-like solar steam generator that consists of the porous carbon black/graphene oxide (CB/GO) composite layer (body), aligned GO pillars (tentacles) and expanded polystyrene (EPS) matrix. The jellyfish-like evaporator was fabricated using the vertical three-dimensional (3D) printing technique, which can fast, automatically and precisely manufacture sophisticated components. The vertical GO pillars were directly 3D printed on and thus attached to the porous CB/GO composite layer. The porous CB/GO composite layer possesses a high broadband light absorption (99.0%) within a wavelength range from 250 to 2500 nm. The linear water transport inside the GO pillars can greatly decrease the contact area between the evaporation layer and bulk water, effectively suppressing the heat dissipation. The assembled evaporator displays an impressive energy conversion efficiency of 87.5% under one-sun illumination (1 kW cm⁻²) and superior water desalination performance. The ion concentrations (Na⁺, K⁺, Mg²⁺ and Ca²⁺ ions) of the seawater (Dead Sea and Chesapeake Bay) after purification are far below the ion concentration limit set by the World Health Organization (WHO) for drinking water. The jellyfish-like evaporator provides an effective water purification solution to alleviate the problem of water scarcity.
This paper presents an outlook to enhance the productivity of a basin type double slope multi–wick solar still by introducing the wicks. The experimental data for different months are presented, and analyzed the effect of climatic and operational parameters on the performance of modified basin type double slope multi–wick solar still (MBDSMWSS). The study has been conducted at Motilal Nehru National Institute of Technology Allahabad (MNNIT Allahabad), Uttar Pradesh (U.P.), India. A significant increase in the heat input, yield, and overall thermal efficiency have been obtained. In the instantaneous efficiency equation, the yield output and the heat input to the solar still is modified as input from both the glass covers and transparent walls are considered for the modified solar still. The result shows that, the maximum yield is obtained as 9012 ml/day (4.50 l/m² day) for black cotton wick in comparison to 7040 ml/day (3.52 l/m² day) for the jute wick at 2 cm water depth in MBDSMWSS. Also, for same basin condition, the overall thermal efficiency of MBDSMWSS with the jute and black cotton wicks are 20.94% and 23.03%, respectively.
This work presents a modified solar still with pin fins absorber and external condenser. An experimental comparative study is carried out between the modified solar still with pin fins absorber and condenser, still with pin fins absorber and conventional still. This experimental study is conducted to evaluate the thermal behavior (evolutions of absorber and glass temperatures) and the water production performance of the modified solar still with pin fins absorber and condenser compared to other designs. All experiments are carried out under the meteorological conditions of the region of Gafsa-Tunisia during the days 01/26/2016, 01/27/2016 and 01/29/2016. Experimental results are presented, quantified and discussed to show the utility of the proposed modified solar still.
The productivity of a solar still is influenced by the temperature difference between condensing and evaporating areas. Previous researches determined that increasing the difference between water–glass temperatures enhances the daily productivity of solar stills. To maintain this temperature difference high, fans, condensers, storing materials, reflectors, and the glass cover cooling were utilized. Continuous supply of air or water film over the glass cover leads to diminish the temperature of glass. Also, the cooling water film performs the important role of continuous self-cleaning of the glass cover. The presence of filth and dirt on the glass cover greatly diminishes the efficiency of still. Continuous cleaning of the glass cover keeps high levels of efficacy. In this regard, this paper aims to review the various methods of glass cover cooling used to enhance the performance of the solar stills. The cooling of glass covers is found to achieve a reduction in glass cover temperature in the range of 6–20 °C with an improvement in stills efficiency and productivity up to 15.5% and 20% maximum, respectively. It was concluded that for the tubular solar still with cooling air flow of glass cover, the daily productivity improved by approximately 32.8%, and improved by approximately 59% with cooling water flow more than the still without cooling.
This study describes the performance of three different experiments under the climatic conditions of Hail city (27.5°N, 41.7°E) in Saudi Arabia by using a tubular solar still (TSS) with a rectangular trough filled with a black cloth and saturated by raw water in the first experiment; a TSS with a half cylindrical trough without clothing in the second experiment, while in the third experiment TSS of the second experiment was integrated with a parabolic concentrator-solar tracking system (PCST-TSS). Results show a high potential of using PCST-TSS compared to conventional TSS. The obtained yields were 0.28, 0.214 and 1.66 L/day for 0.059 m² TSS area (4.71, 3.6 and 3.53 L/m²day) for the three experiments with daily efficiencies of 36.5%, 30.5% and 28.5% respectively. The PCST-TSS yield was increased by 676% with 45.5% cost reduction per liter (CPL). This promising technique is suitable for house roofs and small communities located in remote areas.
Over recent decades, the global demand for freshwater is increasing rapidly; however, the supply of freshwater
is limited. Solar still (SS) is a valuable solar device that is used for converting the brackish and saline water into purified water. Several investigations depicted in literature have been performed, either experimentally or theoretically, on SS to assess its performance under different climatic and operational conditions. Apart from experimental studies, theoretical analysis is beneficial for evaluating the effectiveness of virtually designed SS.
The theoretical analysis and simulation modeling of SSs can provide clear understanding on the mechanics, which may give directions on the design setup in experiments. In this review different theoretical approaches which have been used to assess the thermal performance of SS and exergy analysis of such devices are discussed.
The reviewed studies indicate that the productivity of the SS depends on different external and internal operating parameters. In addition, the distillate quantity varies according to the design features and the related technical advancements of the SS. Our findings indicate that there are still few more parameters and design aspects to be considered while designing new SS. The objective of this paper is to highlight design methods so as to allow the researchers to optimize the SS for further development. Recommendations for further research have been also proposed.
The performance of a cylindrical parabolic concentrator with focal pipe - coupled with a developed solar
still with (oil heat exchanger, Phase Change Material (PCM)) have been experimentally investigated to
improve the freshwater productivity. The cylindrical parabolic concentrator with focal pipe and oil heat
exchanger (serpentine loop) represent the external heat source to increase the temperatures of the basin
water and PCM. The PCM used as a heat storage medium. The influences of high heat exchanger oil tem-
perature on the performance of the developed solar still are experimental investigated. A comparison
between a developed solar still and the convenstional solar still is carried out to evaluate the enhance-
ment in the freshwater productivity under the same ambient conditions. The experimental results indi-
cated that, the freshwater productivity approximately reached 10.77 L/m
2
day for the developed solar
still, while its value is recorded 4.48 L/m
2
day for conventional solar still. The freshwater productivity
of the developed solar still is 140.4% higher than that of the conventional solar still in average. Also,
the daily efficiency approximately reached 25.73% for the developed solar still, while its value is recorded
46% for conventional solar still. The percentage decrease in the daily efficiency for the developed solar
still about 44% compared to the convenstional solar still in average. In the present experimental work
the estimated cost of one liter of freshwater productivity reaches approximately 0.1359 LE (0.0174 ) for developed solar still and conventional solar still, respectively. This results
is obtained during the period from June to August 2015 under the Egyptian conditions
Plastics have been the preferred choice of material for the commercial production of the solar stills. However, most of the currently available solar stills are either too big or too small for satisfying drinking water needs of a single family. Furthermore, methods for increasing the production of water from a solar still are often difficult and costly to integrate in a solar still. Here, we show the effect of adding a plastic channels as passive condenser on an inflatable solar still. The still has a basin area of 1.8 m2. The tests were performed in lab conditions at different water temperatures. The production of water achieved from the still at a water temperature of 73 ° C was 0.75 l/h. Furthermore, the production of water increased to more than 0.95 l/h with use of air flow over the the passive condenser to mimic wind or with use of wet tissue on the passive condenser to mimic evaporation cooling.
The performance of a modified wick still is investigated theoretically. The still is fed by the rejected warm water from Humidification-Dehumidification (HDH) unit. The performance is investigated also for using the glass film cooling. In addition, the effect of feed water flowing over the wick is considered. The still output yield would be predicted through this study for both day and night times. Results show that during the daytime, the wick still productivity decreases with increasing the flow rate and increases with film cooling. While, during the night time, the productivity increases for both with and without cooling film. The yield of wick still when using the glass film cooling is more than that without film cooling by about 5.3%, 30% for day and night times respectively. Therefore, the productivity of the wick still with and without film cooling is higher than that of conventional basin by 278.4% and 210.2% respectively.
Water is vital to life and supplying of potable water can hardly be overstressed in recent years. The conventional desalination processes require significant amount of energy to convert brackish water into potable water for human consumption and industry. With an extensive research on various desalination systems over the last few decades, solar desalination is one of the most promising methodologies to provide high quality water to the human community by using sustainable source. The demand for a small scale self-contingent desalination device is the need of the hour. Solar still is an innovative device that utilizes solar energy to produce distilled water from brackish water. Numerous experimental research works have been reported in the literature to analyze the performance of various types of solar stills under local climatic conditions. Thermal models have also been presented based on energy balances and the theoretical results have been validated through experimental data by many researchers. Thermal models have a great advantage of predicting the performance of virtually designed solar stills without spending much cost and time. Accordingly, the usage of most recent theoretical attempts and proposed ideas tackling this point is limited. An attempt has been made in this article to provide a comprehensive review on thermal models developed for various types of solar stills and modifications done to improve their performance over the years. Our findings indicate that few more parameters and design aspects to be considered while designing new solar still. The efficacy of this study is that it provides energy researchers’ insights into solar still design for clean water production and, thus, it promotes commercialization of this product in rural development. Finally, some general course of action are given for the selection of solar still with flexible, consistent and robust design. Suggestions for further research are also incorporated.
Abstract
This paper presents a new hybrid desalination approach comprising of evacuated solar water heater, jut geotextile and solar still. An evacuated solar water heater is integrated with the desalination stills to evaluate the continuity production of distillate. Two identical portable solar wick and one basin solar stills were designed to evaluate the systems performance. Jut linen woven fabrics were stitched to the plane wick (lengthwise and crosswise) and integrated with solar still. The jut fabrics were used to reduce the rate of water flow to the appropriate rate. The following variables are studied: Single and double layers wick; plane wick, lengthwise and crosswise linen; feeding hot water during night and two base slope angles of wick still (20 and 30°). Theoretical analysis is verified through experiments. Water productivity is increased by 114% over conventional still for double layer square wick (DLSW) solar still at 30° base slope angle. The daily average efficiency of DLSW was 71.5%. During experimentation, the distillate water productivity increased by 215% when hot brackish water was fed during night time.
Keywords
Solar stillDesalinationEvacuated solar water heaterWick
