Energy and exergy efficiency analysis of solar still incorporated with copper plate and phosphate pellets as energy storage material

Experimental and numerical analysis of the thermal performance of pebble solar thermal collector

In this work, pebbles of higher specific heat than the conventional absorber materials like aluminium or copper are proposed as a absorber in the solar flat plate collector. The proposed collector are integrated into the building design and constructed with masonry. Tests were conducted by varying the operating parameters which influence its performance, like the flow rate of the heat-absorbing medium, and the tilt of the collector using both coated and uncoated pebbles. The maximum temperature difference that could be measured for a conventional absorber was approximately 8 °C for a flow rate of 0.6 L/min. While for a coated and uncoated absorber, it was 7 °C and 5.5 °C respectively. This difference decreased with an increase in flow rates from 0.6 L/min to 1.2 L/min. For all the flow rates, it was observed that the average difference in efficiency between the coated and the conventional absorber collector is 5.82 %, while the difference between the coated and uncoated absorber collector is 15.68 %. Thus, it is very much evident that by replacing the conventional absorber with the proposed coated pebble absorber, the overall loss in efficiency is just 5.82 %, but the advantages are enormous. Along with the experimental study, numerical analysis was also carried out with CFD modeling. The numerical results agreed well with experimental results with the least error. Therefore, CFD simulation can be further used to optimize the design of the collector.

Influence of high porous sponges for improving the interfacial evaporation from hemispherical solar distillers

The present study aims to improve the palatable water production from the hemispherical cover solar distiller (HSD). To augment the palatable water produced from the hemispherical cover, a black sponge was utilized as a porous medium using different thicknesses, which augments the interfacial evaporation through the capillary effect of the water through the sponge. The rate of condensation of the hemispherical cover depends on the higher interaction of air from the ambient through wind velocity as the exposure area of the hemispherical cover is relatively higher as compared to the other traditional distillers. The rate of evaporation from the distillers depends on the interfacial materials used in the distillation unit, and this is achieved by using a highly porous black sponge to attain a higher evaporation rate. The thickness of the black porous sponge was optimized (1 to 4 cm), which was the operating parameter for better interfacial evaporation through the sponge, and the same has been compared to the conventional HSD without a porous sponge medium. Results showed a significant improvement in the evaporation rate using a porous medium as the palatable water produced from the HSD was improved by 72.29% using 3 cm as sponge thickness inside compared to the conventional HSD without the porous medium. The cumulative palatable water produced from the HSD using 3 cm as sponge thickness was found as 7150 mL/m2, whereas the conventional HSD without sponge, it was found as 4150 mL/m2. Moreover, using a porous sponge layer as an interfacial evaporation medium, the exergy and energy efficiencies were improved by about 512.87 and 70.53%, respectively. Similarly, with the influence of a porous sponge as an interfacial evaporation medium, the distilled water cost decreased by 41.67% more than the conventional HSD.

The impact of the corrugated absorber shape on the performance of a hemispherical solar still for water desalination: an experimental study

Solar stills utilization has received great interest in arid isolated regions. In this study, experimental approaches have been investigated to prove the impact of the corrugated absorber shape on the hemispherical solar still performance. Four geometric corrugated shapes including present flat, triangular, semi-circular, square forms were tested for the corrugated absorber. Five hemispherical solar distillers have been fabricated and tested. The first distiller includes flat absorber (HSD-FA), the second distiller includes square corrugated absorber (HSDSA), the third distiller includes semi-circular corrugated absorber (HSD-SCA), the fourth distiller includes triangular corrugated absorber (HSDTA), and the fifth distiller is conventional (CHSD). The first and second distillers were compared with the CHSD on the first day. On the second day, the third and fourth distillers were compared with the CHSD as well. Experimental results obtained showed that, the total freshwater yield of the HSD-FA, HSDSA, HSDSCA and HSDTA were improved by 16.67, 27.08, 39.58 and 48.96%, respectively, compared over that of the CHSD. These results prove that the use of the triangular corrugated absorber shaped provides the highest thermal efficiency, and the optimum corrugated absorber shape is the triangular corrugated absorber shape.

Hemispherical solar distiller with truncated circular cone-shaped reflector mirrors (TCC-RM): optimum inclination of reflector mirrors

The present study aims to achieve the highest cumulative yield of the hemispherical distillers, by designing and constructing new reflector mirrors, which are truncated circular cone-shaped reflector mirrors (TCC-RM). To obtain the optimum inclination of TCC-RM that achieves the highest hemispherical distiller's performance, eight inclination angles (10°, 15°, 20°, 25°, 30°, 35°, 40°, and 45° with vertical) were experimentally studied. To achieve this, a series of experimental tests were carried out on the three hemispherical solar distillers: the first represents the reference distiller (traditional hemispherical solar distiller (THSD)) and the other two devices are the hemispherical solar distiller with truncated circular cone-shaped reflector mirrors (HSD-TCCRM) with different inclination angles. The experimental results indicate that utilizing TCC-RM with a 25° inclination angle achieves the maximum cumulative yield of 8.35 L/m² with an improvement of 42.74% compared to THSD. While the utilization of TCC-RM with the inclination angles of 30°, 35°, 20°, 40°, and 15° achieves the cumulative yield of 7.9, 7.3, 7.05, 6.67, and 6.6 L/m² compared with 5.85 L/m² for THSD. On the contrary, adjusting the inclination angle of TCC-RM at 10° and 45° affects negatively the cumulative yield of the HSD with TCC-RM in comparison with THSD. Based on the data of cumulative yield, daily efficiency, and the economic analysis it is recommended to utilize TCC-RM with a 25° inclination angle to achieve the highest performance and minimum distillate cost of hemispherical solar distillers.

Enhancing the performance of conventional solar still using sensible heat energy storage materials

The lack of drinkable, safe water is one problem that governments around the world are dealing with. There are many methods for desalinating saltwater, such as solar distillers, which can be used in remote places without access to traditional energy sources to produce distilled water. In this manuscript, two solar stills [conventional solar still (CSS) and CSS with high thermal conductivity material (HTCM)] were researched at the "School of Mechanical Engineering, B.S. Abdur Rahman Crescent Institute of Science and Technology, Vandalur, Chennai, India," under the same climatic condition. The HTCM (silicon carbide) works as a sensible heat energy storage material, which was placed at the basin of the CSS. The silicon carbide used in the present research is used to enhance the freshwater production during lower solar intensity period and furthermore after evening time. It has been found that the maximum fresh water production from the CSS is 1.5 kg/m² and the CSS with HTCM is 2.9 kg/m². The daily yield production from the CSS with HTCM is 93.7% higher compared to the CSS. The study also has shown that the maximum daily thermal efficiency of the CSS is 13.43% and the CSS with HTCM is 26.09%. The CSS with HTCM produced 94.3% higher thermal efficiency as compared to the CSS.

Energy, exergy, and economic analysis of solar still using coal cylinder fins: an experimental study

The phenomenon of drinking water scarcity has turned into the foremost issue that the world's populace is facing today. The Algerian desert regions, including the El Oued region (southeastern Algeria), also suffer from drinking water shortages, despite the presence of huge quantities of underground salty water. Solar distillation is among the easy and cheap solutions to solve this problem because this method relies on renewable energy (solar energy) as a key factor in providing drinking water from saltwater. As solar energy is intermittent energy, energy storage is required for augmenting the yield. Coal cylinders are low cost and locally available materials that can be used as fins and energy storage materials. In this research, two solar stills such as conventional solar still with a black absorber (CSS-BA) and CSS with a black absorber and coal cylinders (CSS-BA&CC) were fabricated and tested. The CSS-BA&CC produced a potable water yield of about 4.16 kg per day while the CSS-BA could only produce 2.88 kg, which is 44.44% lower when compared to the CSS-BA&CC. The thermal efficiency was noted to be 22.04 % and the exergy efficiency is 1.07 % in the CSS-BA. Similarly, the thermal efficiency is 32.46% and exergy efficiency is 1.90% for the CSS-BA&CC. The experimental results proved that the potable water yield of the CSS-BA was enhanced by coal cylinders (sensible heat energy storage material -SHESM) which is a locally available low-cost material.

Hemispherical Solar Distiller Performance Utilizing Hybrid Storage Media, Paraffin Wax with Nanoparticles: An Experimental Study

The traditional method of obtaining fresh water for drinking is by burning fossil fuels, emitting greenhouse gases into the atmosphere. However, renewable energy is gaining more traction since it is available free of cost for producing fresh water. In this study, Al₂O₃ nanoparticles were distributed in a phase change material (paraffin wax) that had been fixed at a hemispherical distiller water basin. Three scenarios with three hemispherical distillers were examined. A conventional hemispherical distiller (CHD), a conventional hemispherical distiller with paraffin wax as a phase change material (CHD-PCM), and a conventional hemispherical distiller with PCM partially filled with Al₂O₃ nanoparticles (CHD-N-PCM) were tested under the same climatic conditions. The experimental results showed that CHD gave a daily yield of 4.85 L/m²/day, while CHD-PCM increased the yield to up to 6.2 L/m²/day with a 27.84% daily yield enhancement. The addition of Al₂O₃ nanoparticles to paraffin wax CHD-N-PCM improved hemispherical distillate yield up to 8.3 L/m²/day with a 71.13% increase over CHD yield.

Comparative study on the performance of solar still equipped with local clay as an energy storage material

The paucity of freshwater is very dangerous in the coming years. Many coastal countries suffer from a scarcity of freshwater. Solar desalination is the cheapest way to produce freshwater from any type of non-drinkable water (brackish water and seawater). In this work, single-slope single-basin solar still for seawater desalination was examined under Upper Egyptian weather conditions of Qena City (latitude 26.16°, longitude 32.71°). The main goal of the work is to compare the performance of conventional solar still, solar still supported with PCM, and solar still supported with local clay material to augment the solar still yield during both daytime and nighttime periods of operation. The results demonstrated that the total production of desalinated water from the simple conventional solar still, the solar still with PCM, and the solar still with local clay reached about 3885, 4704, and 5388.6 ml/m2, respectively. Moreover, compared to the conventional solar still, the yield was increased by about 21% when using the PCM, and about 38.7% when using the local clay material. Furthermore, it can be observed that the daytime productivity in the case of solar still supported with local clay was higher than that for the solar still supported with PCM, while the nighttime productivity was higher in the case of solar still supported with PCM compared with solar still supported with local clay. Moreover, the average daily efficiency of conventional solar still, solar still with PCM, and solar still with local clay reached about 34, 41.2, and 47%, respectively. Therefore, it is recommended to use the solar still with local clay for seawater desalination in such arid and hot climate of Qena City.

Performance improvements of hemispherical solar still using internal aluminum foil sheet as reflector: energy and exergy analysis

Various scientists are looking for effective and easy solutions for the augmentation of yield from the hemispherical solar still (HSS). In this study, aluminum foil sheet was used to reflect the intensity, hence augmenting the evaporation rate and daily yield. Experimentations were conducted on two SS: the first SS is HSS; the second SS is HSS with reflective aluminum foil sheet walls (HSS-RAFW). The highest distilled water production from the HSS and HSS-RAFW is 3.36 and 4.1 kg/m², respectively. Compared to the HSS, the yield of distilled water was augmented by 22.21% when using the HSS-RAFW. The daily energy and exergy efficiencies (EnE and ExE) of the HSS are 26.27 and 1.04%, respectively, and the daily EnE and ExE of the HSS-RAFW are 32.75 and 1.71%, respectively.

Assessment of the Thermo-Hydraulic Efficiency of an Indoor-Designed Jet Impingement Solar Thermal Collector Roughened with Single Discrete Arc-Shaped Ribs

This study illustrates the impact of single discrete arc-shaped ribs (SDASR)-type artificial roughness on the performance of a jet impingement solar thermal collector (JISTC). The impact of parametric variations of SDASR on the Nusselt number (Nusdr), friction factor (fsdr), and thermohydraulic performance (ηsdr) is examined. The spacer length (Ssdr) of the SDASR was changed from 0 mm to 300 mm in stages of 100 mm during the experiment. The fixed parameters of the SDASR were a relative discrete distance Dd/Lv of 0.67, relative discrete width gw/Hr of 0.87, relative rib height Hr/H of 0.047, relative rib pitch Pr/H of 1.7, angle of an arc αsdr of 60°, jet diameter ratio Dj/Dhy of 0.065, streamwise pitch ratio X/Dhy of 1.72, and spanwise pitch ratio  Y/Dhy of 0.82. The Reynolds number Re was altered from 3000 to 19,000. The Nusdr and fsdr  of a JISTC with a roughened absorber plate was found to be enhanced by 5.25 and 5.98 times as compared to an STC without artificial roughness. The optimal findings of Nusdr, fsdr, and ηsdr were achieved at Ssdr = 0 mm. The maximum value of the ηsdr obtained at Ssdr = 0 mm was 2.9.