A renewable energy-driven thermoelectric-utilized solar still with external condenser loaded by silver/nanofluid for simultaneously water disinfection and desalination

A review of techniques for simultaneous enhancement of evaporation and condensation rates in solar stills

The solar stills can solve the problem of freshwater shortage for the people living in remote areas. Through this work, the performance of hybrid solar desalination arrangement was investigated. The system comprised of parabolic trough solar collector, automatic solar tracking system, separation room, modified solar still, two condensation units, feed water tank, and supplementary and measuring tools. The effect of using various water flow rates on the effectiveness of parabolic trough solar collector was tested. Also, the influences of integrating condenser to the modified solar still with and without phase change material were studied. The experimental results revealed that the best flow rate for parabolic trough solar collector was obtained as 10 L/h (100 L/day), where its effectivity was 61%. Under this condition, the obtained freshwater was around 61 L/day from a total saline water of 100 L/day. In addition, integrating a condenser to the modified solar still improved its productivity. So, the total yields of conventional and modified solar stills were 2500 and 5145mL/m2.day, respectively. Therefore, the distillate of modified solar still was improved by 105.8% as compared to that of the conventional solar still due to using the hot feed water and external condenser. Moreover, using phase change material enhanced the modified solar still yield. The total yield of conventional solar still and modified solar still with hot feed water, condenser, and phase change material was 2575 and 6150mL/m2.day, respectively. Consequently, the productivity of the modified solar still with hot feed water, condenser, and phase change material was improved by around 138.83% over that of the conventional solar still. Finally, the conventional solar still had an average efficiency of 31.5%. Also, when using the hot feed water and external condenser with the modified solar still, the thermal efficiency was reported as 49.7%. Also, the modified solar still with hot water, condenser, and phase change material had a thermal efficiency of 56.5%. Finally, the water costs of 1 L from the CSS and MSS are 0.063 $ and 0.050 $, respectively.

Five different solar stills (SSs) have been tested in this experimental study. Hemispherical SS, tubular SS, pyramid SS, double slope SS, and conventional SS are the five SS systems. The primary goal is to determine which SS will perform more effectively at the testing location. Initially, the SSs were evaluated with no changes and the outcomes were contrasted with those of the conventional SS. Secondly, exterior reflectors have been added to four SSs. Third, hemispherical SS and tubular SS with reflectors have been utilized with phase change material (PCM) combined with Ag-Nanoparticles. Lastly, tests using reflectors, fan, and external condensers have been conducted on the hemispherical SS and tubular SS. The findings showed that the increase in productivity for hemispherical SS, tubular SS, pyramid SS, and double slope SS without modifications are 107 %, 97 %, 66.5 %, and 30 % greater than that of conventional SS, respectively. Furthermore, the results depicted that employing reflectors improved the productivity rise for tubular SS, hemispherical SS, pyramid SS, and double slope SS to be higher than conventional SS's productivity by 168 %, 153 %, 113 %, and 85 %, respectively. Besides, the effect of employing PCM-Ag with hemispherical SS and tubular SS (with reflector) is increasing their productivity to be 202 % and 212 % higher than conventional SS's production, respectively. Also, the hemispherical SS and tubular SS with reflector, fan, and a condenser showed 217 % and 236 % higher productivity than conventional SS. The actual cost of producing water for the conventional SS, hemispherical SS, and tubular SS with reflectors and fan is 0.0244, 0.012, and 0.013 $/L, respectively.

As population density rises, the need for potable water grows. Solar distillation is the method of transforming briny water into drinkable water. We use solar desalination to desalinate untreated water. People commonly apply the desalination process to obtain pure water using solar stills. The primary classifications of solar stills are active and passive. This work aims to boost productivity by experimentally implementing the condensation and evaporation processes inside the still. To achieve this, we incorporate a magnetic field and an external condenser into the traditional distillation apparatus. The findings indicate that the outputs of the traditional solar still, the traditional solar still with a magnetic field and an external condenser (CSS-MACO), and the traditional solar still with a magnetic field (CSS-MAG) are 3.800, 5.210, and 5.800 L/m2/day, respectively. Therefore, the utilization of a magnetic field results in a 52.63% increase in productivity, while the combination of a magnetic field and an external condenser leads to a 37.10% improvement, compared to the typical solar still. From a cost analysis perspective, incorporating a magnetic field alongside a conventional solar still is the most cost-effective choice in terms of the total expense per liter of pure water. To be more specific, the cost is 0.016 USD, which is 30.43% lower than the CSS cost.

Effect of using nanofluids and providing vacuum on the yield of corrugated wick solar still

Passive solar still is the simplest design for distilling seawater by harnessing solar energy. Although it is undeniable that solar still is a promising device to provide an additional freshwater source for global increasing water demand, low thermal efficiency along with daily distillate yield are its major disadvantages. A conventional solar still can produced 2 to 5 L/m2day. Various studies have been carried out to improve passive solar stills in terms of daily productivity, thermal efficiency, and economic effectiveness. Most of the researches that relate to the daily output improvement of passive solar still concentrates on enhancing evaporation or/and condensation processes. While the condensation process is influenced by wind velocity and characteristics of the condensed surface, the evaporation process is mainly affected by the temperature of basin water. Different parameters affect the brackish water temperature such as solar radiation, design parameters (for example water depth, insulators, basin liner absorptivity, reflectors, sun tracking system, etc). The inclined angle of the top cover is suggested to equal the latitude of the experimental place. Moreover, the decrease of water depth was obtained as a good operational parameter, however, the shallow water depth is required additional feed water for ensuring no dry spot existence. Reflectors and sun-tracking systems help solar still absorb as much solar intensity as possible. The internal reflector can enhance daily yield and efficiency of stepped solar still up to 75% and 56% respectively, whereas, passive solar still with the support of a sun-tracking system improved daily yield up to 22%. Despite large efforts to investigate the impact of the different parameters on passive solar distillation, the effect of the basin liner (including appropriate shapes and type of material), needs to be analyzed for improvement in practical utilization. The present work has reviewed the investigation of the solar still performance with various types of basin liner. The review of solar stills has been conducted critically with rectangular basin, fins basin, corrugated basin, wick type, steps shape, and cylindrical shape basin with variety of top cover shapes. The findings from this work conclude that the basin liner with a cylindrical shape had better performance in comparison with other metal types and provides higher freshwater output. Stepped type, inclined, fin absorber, and corrugated shapes had the efficient performance. Further exploration revealed that copper is the best-used material for the productivity of passive solar still.

The impact of using nanofluid on the performance of solar stills: A comprehensive review

Solar still only finds its application in remote and low population density areas due to its low productivity. This paper aims at improving the freshwater output of single-slope solar still (SS) by coupling it with an evacuated tube collector (ETC). The performance of this ETC coupled still is further enhanced by using a heat exchanger (HE), an internal reflector (IR) and an external condenser. The experiments are carried out with various still modifications, namely, SS (HE+IR+condenser), SS (HE+IR), SS (HE+condenser), and SS (HE only). These modifications are done to expedite the rate of evaporation of basin water and the rate of condensation of the water vapors. The performance of these four arrangements is simultaneously compared with a conventional still on all testing days. Two solar stills of similar dimensions are fabricated to carry out the experiments. One still is applied with modifications while the other is kept conventional. The maximum productivity of 2259 ml and an efficiency of 33.4% is achieved for SS (HE+IR+condenser) as per the experimental results. The results indicated that using a HE and an IR in a solar still had a considerable impact on the still productivity but an external condenser had a little effect on the still performance. The results also indicated that the increase in overall efficiencies of all four modified designs is very small in comparison to conventional still. Abbreviation: ETC: Evacuated tube collector; SS: Solar still; PCM: Phase change material; CS: Conventional still; FPC: Flat plate collector; ASv: Annual salvage value; HTF: Heat transfer fluid; Sv: Salvage value; CPL: Cost per liter; MCannual: Annual maintenance cost; CRF: Capital recovery factor; Pa: Annual freshwater production; SFF: Sinking fund factor; A: First annual cost; TAC: Total annual cost; C: Capital cost; HE: Heat exchanger; t: Bank interest rate; IR: Internal reflector; n: Average life of still.

Performance enhancement of a single basin single slope solar still using agitation effect and external condenser

Combined influence of fin, phase change material, wick, and external condenser on the thermal performance of a double slope solar still

This paper presents five different designs of single slope solar water stills. These still designs would probably be useful in small homes wishing to purify water for their daily drinking needs. Models of the stills ranging between 1 m2 and 1.5 m2 glazing area are manufactured and tested in real outdoor conditions. Two of the stills are double glazed and have external condensers, with one of them using forced steam extraction. A third still is mounted on a sun tracking pillar. The remaining two are simple collapsible and portable units but of different slopes. A method of evaluating the designs is illustrated. It relies on a focus on the purpose of a solar still and what scarce resources are required to get outputs from it. Thus, the stills are evaluated based on function, quality, productivity and cost. It is found that the tracking unit out performs the others on function and quality criteria but it is outcompeted on efficiencies and cost criteria. Condensate drip-back was found to be an issue that necessitates use of slopes that do not necessarily yield maximum energy incidence on the stills. It was also found that double glazing and external condensation did not help improve performance on any of the criteria. It is concluded and recommended that an ideal single slope solar water purifier operating in weather similar to Cape Town’s summer season, would need to have a thin single glazing, sloped towards 45°, portable and sun tracking.

Solar radiation plays an important role in the desalination process due to its abundance in areas with potable water shortage and also occupies an important position in renewable energies due to simplicity of application. Still distiller is viewed by researchers as suitable source of potable water because of low cost of fabrication, easy operation and zero emission technology. Studies by researchers is geared towards exploring new models to enhance the efficiency of solar stills and increase the production rates. The main aspiration of this work is to experiment the effect of incorporating a passive condenser into a modified conventional solar still to enhance daily productivity rate. It has been found that modified passive still distiller coupled with external condenser gives about 11.85% higher production rate as compared to the modified conventional still distiller. Daily and accumulated distillate yield for the still distillers have been studied and analyzed. As a result of the findings, the researchers recommend the sawdust padding around still distillers can maximize productivity leading to efficient water distillation in regions where that require still distiller usage. This recommendation has desired result of enhancing access to potable water in areas with water scarcity and do contribute to sustainable and cost-effective water purification method.

The present study aims to find the technical feasibility of recently evolved nanomaterial, i.e. carbon nanotubes (CNT), enhanced with paraffin as a novel energy storage material for desalination application. As a primary investigation, the thermo-mechanical properties like density, melting point, thermal conductivity, etc., of CNT enhanced paraffin were first analysed and then integrated with solar desalination application. Three solar desalination stills: (i) conventional solar still, (ii) solar still loaded with fossil paraffin and (iii) solar still loaded with CNT-doped paraffin were fabricated and experimented at Chennai, India (Lat. 13° 08′ N, Long. 80° 27′ E). From the investigation, it is inferred that there is a significant increase (of about 26%) observed in the thermal conductivity of CNT-doped paraffin as compared to fossil paraffin. The cumulative yield of the conventional still, solar still with paraffin and solar still with CNT enhanced paraffin was found to be 2.5 kg/m2, 3.4 kg/m2 and 5.8 kg/m2, respectively. There was 41.4% and 26.4% enhancement, respectively, observed in the daily yield of the solar still with CNT-doped paraffin as compared to conventional still and the still with virgin paraffin. The productivity efficiency was 46.45% for the still with CNT blended paraffin contributing to 24% and 19.6% increase in the efficiency as compared to the other two stills considered for experimentation in this study. Thus, it is concluded that CNT enhanced paraffin is identified as a better potential energy storage material as compared to conventional paraffin in solar desalination application.

A solar still is a low-cost device for the generation of freshwater. However, the yield of conventional solar still is meagre; thus, the researchers have used various active and passive methods to augment the freshwater production from a solar still. This article reports the various developments in solar stills using TEMs. TEMs are used for heating, cooling or simultaneous heating and cooling purposes or even generating electricity in solar still. Researchers have used the TEMs in solar still with evacuated tubes, parabolic collectors, heat storage materials, heat sinks, heat pipe and finned tanks. The maximum freshwater yield on TECs is eight times more than the yield with the glass. It is observed that with the use of TEGs to produce electricity and using this electricity to produce forced convection, the daily yield is increased by 14%. Abbreviations: HDH: humidification and dehumidification; PCM: phase change material; PTSS: portable thermoelectric solar still; PV: photovoltaic; SS: solar still; TEC: thermoelectric cooler; TEG: thermoelectric generator; TEM: thermoelectric module Highlights A solar still is a low-cost device for the generation of freshwater. The present study reviews the use of TEMs in solar still for the last two decades. The use of TEMs in solar still enhances its productivity. Solar still using TEMs are also equipped with other devices like evacuated tubes, parabolic collectors, heat storage materials, heat sinks, heat pipe and finned tank. The portable solar still using TEMs are also discussed, but their yield is low.

Investigation of the performance of a double-glazing solar distiller with external condensation and nano-phase change material