Improving the performance of solar still using different heat localization materials

Solar desalination/purification (solar stills, humidification-dehumidification, solar disinfection) in high altitude during COVID19: Insights of gastrointestinal manifestations and systems' mechanism

From the starting of the pandemic different transmission routes of the pathogen was brought into the spotlight by researchers from different disciplines. This matter in high-altitudes was more boosted as the main parameters were not exactly realized. In this review we are about to highlight the possibility of consuming contaminated water generated form solar water desalination/disinfection systems in highlands. Three systems including solar still, solar disinfection (which experimented by the authors in 2019 in high altitude) and humidification-dehumidification were consider in this context. Ascribe to the risks of pathogens transmission in solar desalination/disinfection systems where the water resources are heavily polluted in every corner of the world, highlighting the risk of consuming water in high-altitude where there are many other parameters associated with spread of pathogen is of great importance. As it was reported, reliability of solar desalination and solar water disinfections systems against contaminated water by the novel coronavirus remained on the question because the virus can be transmitted by vapor in solar stills due to tiny particle size (60-140 nm) and would not be killed by solar disinfections due to low-temperature of operation <40 °C while for HDH contamination of both water and air by sars-cov-2 could be a concern. Although the SARS-CoV-2 is not a waterborne pathogen, its capability to replicate in stomach and infection of gastrointestinal glandular suggested the potential of transmission via fecal-oral. Eventually, it was concluded that using solar-based water treatment as drinking water in high altitude regions should be cautiously consider and recommendations and considerations are presented. Importantly, this critical review not only about the ongoing pandemic, but it aims is to highlight the importance of produced drinking water by systems for future epidemic/pandemic to prevent spread and entering a pathogen particularly in high-altitude regions via a new routes.

Productivity enhancement of solar still through heat transfer enhancement techniques in latent heat storage system: a review

Solar still is one of the sustainable and renewable technology which converts brackish or salty water into fresh water. The technology helps in CO₂ mitigation, global warming effect, and the use of solar desalination contributes towards decarbonization, mitigation of CO₂ and other adverse global warming effect, and it contributes to the sustainable development goals (SDG). However, due to the low production rate of the distillate, the performance of solar still gets affected. The phase change materials (PCMs) as latent heat storage systems can enhance the thermal performance of solar still (SS). Further, techniques like increasing the area of contact and thermal conductivity can be practiced to enhance the heat transfer in PCM-SS. The article reviewed the performance of various designs of solar still integrated with PCM. Furthermore, the effect of nanoparticles enhanced PCM-integrated solar still with different absorber designs and configurations was seen. Compared to conventional solar still (CSS), the heat transfer techniques in PCM's SS can significantly improve the overall distillate productivity of Tubular SS by 218%, followed by single basin single slope SS 149%, pyramidal 125%, hemispherical 94%, and stepped 68%, respectively. In addition, the night time productivity was increased by 235%. Also, it was observed that in comparison to tubular PCM-SS, the nanodisbanded tubular PCM-SS increases the productivity by 68%, whereas in stepped solar still by using external condenser arrangement the productivity was increased by 48%. In single basin single slope, the nanoparticle disbanded PCMSS increases the productivity from 11 to 33%.

Deep neural network prediction of modified stepped double-slope solar still with a cotton wick and cobalt oxide nanofluid

This research work intends to enhance the stepped double-slope solar still performance through an experimental assessment of combining linen wicks and cobalt oxide nanoparticles to the stepped double-slope solar still to improve the water evaporation and water production. The results illustrated that the cotton wicks and cobalt oxide (Co3O4) nanofluid with 1wt% increased the hourly freshwater output (HP) and instantaneous thermal efficiency (ITE). On the other hand, this study compares four machine learning methods to create a prediction model of tubular solar still performance. The methods developed and compared are support vector regressor (SVR), decision tree regressor, neural network, and deep neural network based on experimental data. This problem is a multi-output prediction problem which is HP and ITE. The prediction performance for the SVR was the lowest, with 70 (ml/m2 h) mean absolute error (MAE) for HP and 4.5% for ITE. Decision tree regressor has a better prediction for HP with 33 (ml/m2 h) MAE and almost the same MAE for ITE. Neural network has a better prediction for HP with 28 (ml/m2 h) MAE and a bit worse prediction for ITE with 5.7%. The best model used the deep neural network with 1.94 (ml/m2 h) MAE for HP and 0.67% MAE for ITE.

Comparative study of double-slope solar still, hemispherical solar still, and tubular solar still using Al2O3/water film cooling: a numerical study and CO2 mitigation analysis

Solar still, as one of the important devices for generating water using renewable energy, has been widely used in arid as well as coastal areas where access to fresh water is limited. This paper uses CFD simulation to compare double-slope solar still, hemispherical solar still, and tubular solar still using nanofluid film cooling. Al₂O₃-water nanofluids with a concentration of 0.1% are used due to facilitate sunlight penetration into the absorber plate inside the solar desalination. It is assumed the flow is steady, laminar, and air is an ideal and incompressible gas. The simple algorithm is considered to calculate the relationship between pressure and velocity and to separate the transfer and pressure interpolation terms from the appropriate upstream designs. Also, the economic, exergoeconomic, and CO₂ mitigation parameters of various solar stills were investigated. The study revealed that the water productivity of double-slope solar desalination using nanofluids film cooling is improved by about 4.8% compared with tubular solar desalination with nanofluid film cooling. Also, the lowest CPL of 0.0362 $/L was obtained in the double-slope solar desalination using nanofluid film cooling. The net CO₂ mitigation of 14.08 tons, 13.72 tons, and 13.44 tons was obtained for double-slope solar desalination, hemispherical solar desalination, and tubular solar desalination, respectively.

Exploring the photo-thermal conversion behavior and extinction coefficient of activated carbon nanofluids for direct absorption solar collector applications

This work aims to explore the optical and thermal conversion characteristics of activated carbon-solar glycol nanofluids with various volume fractions namely 0.2, 0.4, and 0.6%, respectively. Kigelia africana leaves were synthesized into porous activated carbon nanomaterials by using the high-temperature sintering process and the pyrolysis process in a muffle furnace. The experimental investigation was carried out with different nanofluid concentrations by using the solar simulator. Nanofluids were heated with the assistance of a solar simulator test system and the convection/conduction heat loss was decreased by using the glass as an insulating material around the test section. Prepared nanofluid with 0.6 vol% activated carbon augmented the thermal conductivity by 14.36% at 60°C. The maximum temperature difference of 10°C was attained at 0.6% volume concentrations of nanofluid as compared with base fluid (solar glycol). In addition, maximum receiver efficiency of 94.51% was attained at 0.6% volume fractions of activated carbon-based nanofluid compared with solar glycol thru a light radiation time of 600 s. Moreover, activated carbon-based nanofluid exhibited significantly higher absorption efficiency as the majority of the radiation was absorbed by the nanofluid. It is concluded that activated carbon-based nanofluids could be a suitable low-cost highly stable material for developing working fluid for direct absorbance solar collector-based applications.

Determination of the effect of water depth on the yield of a solar still using an automatic feedwater system

Herein, the water depth in a pyramidal solar still was kept constant using an automatic feedwater system through an auxiliary tank. Six water depths ranging from 5 to 50 mm were investigated. All variables were measured continuously but were logged automatically every hour. Increasing the water depth increased the water volume, thereby increasing the thermal capacity of the solar still. Therefore, increasing water depth increases the nocturnal yield but decreases the diurnal yield. Over the whole day, lower water depths resulted in higher accumulated yields. These accumulated yields increased by 37% by decreasing the water depth by 90% from 50 mm. The desalination system can work without human intervention, improving its sustainability. Moreover, the automatic feedwater system facilitates the end-user operation processes and succeeds in maintaining a constant optimal water depth in the solar still.

Thermal modeling, characterization, and enviro-economic investigations on inclined felt sheet solar distiller for seawater desalination

Sustainable desalination can be achieved by adopting renewable energy-based low-cost and low-impact desalting techniques. In this investigation, capability of inclined felt sheet solar distiller in desalting seawater is assessed by evaluating its performance, distillate water quality, economics, and environmental impacts. The distiller with 1.18-m² aperture area produced around 4.60 L/day of distillate for a cumulative incident solar radiation intensity of about 20.52 MJ/m² day. Its pollutant removal efficiency is very much superior to other available solar stills reported in literatures. Thermal model developed for estimating distiller's performance is able to predict its productivity with reasonable accuracy (only 8.0% deviation from experimental values) and was used for estimating distiller's performance in various seashore locations in India with varying clear days (191 to 246). Yearly mean distillate production and thermal and exergy efficiencies of the proposed distiller range between 3.60 to 4.50 L/day, 36.45 to 42.39%, and 2.85 to 3.65%, respectively, in east seashore locations of India. Moreover, 18.46 tons of CO₂, 132.72 kg of SO₂, and 54.20 kg of NO emission can be mitigated by adopting the distiller for potable water production. Distillate production cost of inclined felt sheet solar distiller is in the range of 1.15 to 2.29 INR/L and highly depends on the interest rate at which the distiller is financed. Generation of reasonable quantity of high-quality potable water at low cost with huge environmental benefits makes proposed inclined felt sheet solar distiller a suitable option for quenching thirst in coastal and remote locations.

Effects of solar geometry and operation period on stability of solar desalination systems: a review

The sun is the primary source of life on the earth. The heating effect of the sun provides a more fruitful environment for mankind. In addition, solar energy in the form of thermal radiation has been utilized for solar thermal applications and space heating. With abundant solar radiation, the emergence of the solar desalination has been emerged as a viable solution for water purification by utilizing solar stills. However, solar-powered distillation is relatively a slow process due to the requirement of bulk heating. To suppress thermal conduction to bulk water, various photothermal materials were employed. However, there are many governing parameters which influence the productivity, including solar intensity, cloud, wind, ambient air temperature, humidity, solar absorption of blackened surface, depth of bulk water, feed water type, angle of condensation surface, water film thickness, underneath the condensing surface, and experiment period. Further, systematic and continuous experiments for extended periods are essential for determining the stability and durability of a solar desalination system. The main objective of this article is to review all the experimental studies conducted for two months at minimum up to 1-year duration. In addition, all the SDSs handled in this study further were examined by solar geometrical factors, including day length (DL) and position of the sun or zenith angle (θ_z). As a result, the sunshine hours, day length, and the solar zenith angle play an important role in the water evaporation rate. Lower solar zenith angle and longer day length (more sunshine hours) are desirable for higher water productivity.

A comparative study of hemispherical solar stills with various modifications to obtain modified and inexpensive still models

The present study aims to obtain the best modification of the hemispherical solar distillers that achieves the highest productivity with the lower inexpensive. To achieve this goal, this paper dealt with conducting a comparative study, operating performance analysis and an economic study of two different modifications, and comparing them with the reference distiller in order to obtain the best adjustments that achieve the highest productivity at the lowest cost. In the first modification, CuO nanoparticles with three different concentrations (0.1, 0.2, and 0.3%) were added to the basin water, to increase the intensity of absorbed solar energy, improve the thermal properties of basin fluid, and then increase the rate of vapor generation inside the distillation basin. In the second modification, water film glass cooling technology with three different flow rates (1.5, 2, and 2.5 L/h) was utilized to increase the water vapor condensation rate. In this experimental study, three hemispherical distillers were fabricated and tested under the same climate conditions at a 1-cm basin fluid depth, namely, conventional hemispherical solar still (CHSS), hemispherical solar still with glass cover cooling (HSS-C), and hemispherical solar still with CuO-water-based nanofluid (HSS-N). The experimental results presented that the average daily accumulative yield of CHSS is 3.85 L/m²/day, while the daily accumulative yield of HSS-N increases to 5.75, 6.40, and 6.80 L/m²/day with improvement 49.3, 66.2, and 76.6% at volume fraction 0.1, 0.2, and 0.3%, respectively. Also, the daily accumulative yield of HSS-C increases to 4.9, 5.35, and 5.7 L/m²/day with improvements of 27.3, 39, and 48% at water film flow rates of 1.5, 2, and 2.5 L/h, respectively. The cost of distilled water produced from CHSS is 0.0106 $/L, while the utilization of HSS-C (2.5 L/h) and HSS-N (0.3%) reduces the cost of distilled water to 0.0072 and 0.0066 $/L, respectively. Based on accumulative yield and economic analyzes, it is recommended that the modified HSS-N (0.3% volume fraction) be utilized to achieve the highest accumulative yield and the lowest price of the produced distilled water.

An experimental investigation of a water desalination unit using different microparticle-coated absorber plate: yield, thermal, economic, and environmental assessments

This study aims to augment the performance of a solar desalination unit. To experimental examine this idea, a modified solar still with three different microparticles doped in black paint-coated absorber were designed, fabricated, and tested in Jaipur, India. Three different microparticles such as copper, aluminum, and tin with particle size of 50-80 μm with weight concentration of 10% were doped in black paint and then coated on the absorber of solar still. The coated absorber of solar still were compared with the conventional solar still without any microparticle coating to obtain the effect of different coating materials on the water productivity, thermal performance, economic, and environment-economics analysis of solar still. The result showed that under the water depth of 1 cm, coating of copper, aluminum, and tin on absorber augmented the full-day water yield by 33.13, 22.18, and 11.53%, compared to conventional solar still without any coating. In addition, full-day energy and exergy efficiency of solar still with copper-coated absorber exhibited maximum values compared to all other solar stills, owing to the higher thermal conductivity and excellent solar-thermal conversion behaviors of copper. The cost of water per liter estimated through economic analysis was found to be US $ 0.0074 for conventional solar still, which was significantly reduced to US $ 0.0066 in the case of solar still with copper-coated absorber along with the payback time of 2.7 months. The environment-economic assessment estimated that solar still with copper-coated absorber plate has reduced the 13.19 tons of CO2 emission. It is concluded that augmented heat transfer rate from water basin to inner glass surface through utilization of microparticle coating would pave a pathway to develop energy-efficient low-cost solar-based desalination system.

Experimental investigation on the performance improvement of tubular solar still using floating black sponge layer

The experimental study in this manuscript aims to enhance the performance of tubular solar distillers. The tubular distillers are characterized by having a large surface area for receiving and condensing compared to a single-slope distiller, and accordingly, the use of floating sponge layers is a good and very effective choice in increasing the rate of evaporation and thus improving the cumulative yield of the tubular distillers. In order to obtain the optimum specifications of the sponge layers that achieve the highest performance of the tubular distillers, four tubular distillers were designed and constructed; the first is a reference distiller without sponge and the other three tubular distillers contain the sponge layers with different specifications. The experimentations were conducted in two stages: in the first stage, three different thicknesses of the sponge layer (20, 30, and 40 mm) were studied. In the second stage, three different densities of the sponge layer (16, 20, and 30 kg/m³) were studied. All test cases were compared with reference distiller under the same climatic conditions of Egypt. The results show that the utilization of a floating sponge improves the tubular distiller performance. The peak improvement in the accumulative yield of tubular distillers was achieved in case of utilizing a sponge layer with a 30-mm thickness and 16-kg/m³ density. The reference distiller gives maximum accumulative yield of 3.72 L/m² day while the floating sponge layer utilization improves the accumulative yield to 5.92 L/m² day with 59.2% improvement. Also, the utilization of floating sponge layer reduced the cost of distillate yield by 36.3% compared to reference distiller.

The effect of magnetic field on the performance improvement of a conventional solar still: a numerical study

Due to growing demand for potable water, the improvement of fresh water production systems such as conventional solar stills is a crucial issue. Conventional solar stills are one of the simplest methods of the production of fresh water from saline water; however, they are fairly low-performance devices. Since oxygen is a paramagnetic gas, the humid airflow in a conventional solar still can be controlled by an externally imposed magnetic field. Therefore, this paper presents the effect of magnetic field on the performance improvement of a conventional solar still as a novel technique. The governing equations of the problem are discretized by the finite volume method. The impacts of the applied magnetic field arising from a multilayer solenoid on the streamlines patterns, temperature and mass fraction contours, the production rate of water ([Formula: see text]), and the average heat transfer rate (Nu) are presented at five specified times (cases). The influences of important factors such as intensity (0≤NI≤100000) and location of the magnetic field (X_c=0.15, 0.49, and 0.83) on the heat and mass transfer rates are explored. It is found that the production rate of water and heat transfer rate are increasing functions of magnetic field intensity. For the applied magnetic field with NI = 10⁵and X_c = 0.83 m, water productivity and convective heat transfer rate can be increased by about 43%, 38%, 41%, 40%, and 48% for cases 1, 2, 3, 4, and 5, respectively.

Performance improvement of modified tubular solar still by employing vertical and inclined pin fins and external condenser: an experimental study

The current experimental work aims to improve an accumulative yield of tubular solar distillers. This was achieved by utilizing the pin fins and external condenser coupled with the tubular solar distiller. The tubular distillers are characterized by having a large receiving and condensing surface area compared to a traditional single-slope distiller; therefore, the utilization of pin fins is very effective to increase the evaporation rate, as well as the external condenser was utilized to increase the condensation rate. In order to achieve this vision, the experimental study mainly included two axes: namely, in the first axis, the effect of utilizing the pin fins on the cumulative yield of tubular solar distillers was studied, as well as obtaining the optimal orientation of the pin fins to reduce the shadow effect generated inside the basin. In the second axis, the effect of utilizing an external condenser and the inclined pin fins on an accumulative yield of the tubular solar distiller was studied. To investigate this idea, in the first study axis, three tubular distillers were constructed and tested at the same conditions, namely conventional tubular solar still (CTSS), modified tubular solar still with vertical pin fins (MTSS-VPF), and modified tubular solar still with inclined pin fins (MTSS-IPF). In the second study axis, two tubular distillers were constructed and tested at the same conditions, namely CTSS and modified tubular solar still with inclined pin fins and condenser (MTSS-IPF+Condenser). The results presented that the enhancement in accumulative yield reached 18% and 27.6% for utilizing the vertical and inclined pin fins, respectively, as compared to CTSS. These results show that the utilization of inclined pin fins represents a good option to improve the accumulative yield of tubular distillers. Also, the accumulative yield and the daily efficiency achieved by utilization of the external condenser and the inclined pin fins (MHSS-IPF+Condenser) reached to 5.94 L/m²/day and 54.9% with an improvement of 70.2% and 71.6%, respectively, as compared to CTSS.

Enhancement of the performance of hemispherical distiller via phosphate pellets as energy storage medium

In this experimental work, the performance of hemispherical distiller has been enhanced via phosphate pellets. To investigate the best approach to the phosphate pellet utilization in a basin of hemispherical distiller to achieve the highest performance, the present study was carried out in two stages. In the first stage, 250 g of phosphate pellets was arranged in a layer of 5 mm thickness placed at the bottom of the basin. In the second stage, the phosphate pellets were distributed in a homogeneous manner in basin salt water with two concentrations 1% (10 g/L) and 2% (20 g/L) without aggregation on the basin. To achieve this idea, in the first test stage, two distillers were compared, the first is the conventional hemispherical distiller which represents the reference distiller (CHSS) and the second is the modified hemispherical distiller with a phosphate layer (MHSS-PL). In the second test stage, three distillers were compared, the first is the CHSS which represents the reference distiller, the second is the modified hemispherical distiller which contained 1% phosphate (MHSS-1), and the third is the modified hemispherical distiller which contained 2% phosphates (MHSS-2). The experimental results show that the cumulative yield was 4.6, 6.32, 6.15, and 6.85 L/m2·day for CHSS, MHSS-PL, MHSS-1, and MHSS-2, respectively. The results showed that the utilization of the phosphate pellets as a storage medium enhanced the performance of the hemispherical distiller. The enhancement in the distiller productivity was 37.4, 33.7, and 47.9% for MHSS-PL, MHSS-1, and MHSS-2, respectively, compared to conventional hemispherical solar still (CHSS). The peak enhancement in the productivity was achieved in the case of modified hemispherical solar still with 2% (20 g/L) phosphate pellets (MHSS-2).

Performance amelioration of single basin solar still integrated with V- type concentrator: Energy, exergy, and economic analysis

Solar desalination is one of the most sustainable solutions to produce freshwater from brackish water. The present research work aims to experimentally investigate the effect of a V-shape concentrator integrated with solar still (SS). The V-shape concentrator integrated with the conventional solar still (CSS) is used to supply the saline water at elevated temperature to the basin of SS, which augments the freshwater yield compared to CSS. The experimental investigation was performed at different brackish water depths of 0.01, 0.02, and 0.03 m, respectively. The SS system was evaluated based on water yield, energy, exergy, concentrator efficiency, and economic analysis. The freshwater yield of the solar still integrated with V-shape concentrator (SSVC) was found to be 5.47, 5.10, and 4.89 L/m².day, whereas the yield of the CSS was 3.73, 3.27, and 2.91 L/m² .day at the water depths of 0.01, 0.02, and 0.03 m, respectively. The daily energy and exergy efficiency of CSS were 38.5, 33.5, and 29.4% and 1.9, 1.5, and 0.97 % in the case of 0.01, 0.02, and 0.03m water depth , respectively. However, the integration of concentrator significantly augmented the energy efficiency to 57.4, 51.7, and 44.9% and exergy efficiency to 3.8, 3.3, and 2.8% for the respective water depths . Life cycle studies demonstrated that the freshwater cost per liter for CSS and SSVC were 0.0102 $ and 0.0117 $ respectively, at a water depth of 0.01 m. It was concluded that the addition of V-shape concentrator and minimum water depth is useful to augment the energy efficiency, exergy efficiency, and yield of the SS in the very economical way.

Enhancing the double-slope solar still performance using simple solar collector and floatable black wicks

This research aims to investigate the effect of integrating a simple solar collector, floatable black wicks, and orientation as modified double-slope solar still (MDSSS), and to compare its performance with conventional double-slope solar still (CDSSS). Costs of the developed desalination system were estimated, and its performance was compared with the previous literatures. A black hose was coiled and used as simple solar collector for preheating the saline water that is fed to the solar still. The floatable black wicks were used to increase the evaporation surface area and cause a localization of absorbed insolation at the evaporation surface of saline water. The longitudinal axis of solar still was oriented to north-south and east-west, the and productivity from each side was quantified. The northern side of MDSSS has more yield than the southern side by 33.98% for the east-west orientation and preheating. For the east-west orientation, preheating, and floatable black wicks, the total yield of MDSSS exceeded the CDSSS by 45.65%. And at the same conditions, the daily average efficiency of southern and northern sides of MDSSS was 25.33 and 37.25%, while for CDSSS, it was 13.87 and 30.73%, respectively. Estimated costs revealed that cost per liter water was about 0.062 and 0.059 $ for CDSSS and MDSSS, respectively. Solar still can provide a reasonable amount of water for irrigation based on daily production by installing the MDSSS in furrow, but keeping the longitudinal axis to east-west can secure more amount of water. The used modifications improved the solar still productivity and efficiency. Graphical abstract.