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Abstract The present work aimed to explore the optimized conditions of hydrothermal co-liquefaction (co-HTL) of the green seaweed “Enteromorpha clathrata (EN)” and the lignocellulosic agricultural waste “rice husk (RH)”. Separate hydrothermal liquefaction (HTL) of EN and RH showed bio-oil yields of 26.0% and 45.6%, respectively. However, co-HTL under optimized conditions showed significant increase in the bio-oil yield by 71.7% over that of EN, and insignificant difference with that of RH. Nevertheless, the conversion ratio of co-HTL showed 10.6% significant increase over that of RH. GC-MS results showed that main compounds of EN and RH bio-oil lump into the C15–C20 and C5–C12 regions, mainly representing carbon range of diesel and gasoline, respectively. Short-chain (C5–C12) and long-chain (C14–C20) compounds in the bio-oil obtained by co-HTL represented 72% and 28%, respectively. In addition, the ratio of aromatic compounds in the bio-oil of RH was reduced by 9.3% as a result of co-HTL. In conclusion, results suggested 50% ethanol as a co-solvent, 300 °C and 45 min as optimum conditions for co-HTL of EN:RH (1:1 w/w). The present study demonstrated an efficient route for co-HTL of 3rd generation feedstocks with 2nd generation feedstocks which will have a significant impact on large-scale applications.

Abstract The present work aimed to explore the optimized conditions of hydrothermal co-liquefaction (co-HTL) of the green seaweed “Enteromorpha clathrata (EN)” and the lignocellulosic agricultural waste “rice husk (RH)”. Separate hydrothermal liquefaction (HTL) of EN and RH showed bio-oil yields of 26.0% and 45.6%, respectively. However, co-HTL under optimized conditions showed significant increase in the bio-oil yield by 71.7% over that of EN, and insignificant difference with that of RH. Nevertheless, the conversion ratio of co-HTL showed 10.6% significant increase over that of RH. GC-MS results showed that main compounds of EN and RH bio-oil lump into the C15–C20 and C5–C12 regions, mainly representing carbon range of diesel and gasoline, respectively. Short-chain (C5–C12) and long-chain (C14–C20) compounds in the bio-oil obtained by co-HTL represented 72% and 28%, respectively. In addition, the ratio of aromatic compounds in the bio-oil of RH was reduced by 9.3% as a result of co-HTL. In conclusion, results suggested 50% ethanol as a co-solvent, 300 °C and 45 min as optimum conditions for co-HTL of EN:RH (1:1 w/w). The present study demonstrated an efficient route for co-HTL of 3rd generation feedstocks with 2nd generation feedstocks which will have a significant impact on large-scale applications.

AbstractThe countries of North Africa suffer from a serious problem that affects a large number of people. The trouble is the provisioning of drinking water. Several techniques are used but solar distillation; which seems to be an appropriate, economical, and easy solution. Conventional solar distiller is used in the Saharan areas but the yield of this device is low, that's why there are several studies that are focused on improving this distiller. The technique of double glazing gives an increase in the efficiency of a solar collector; hence, the idea of using the same technique in a conventional solar distiller. Two covers of glasses separated by 1 cm, isolated from the four sides was put on a distiller of dimensions 0.5 × 0.5 m. The results show that this technique minimizes the distiller's yield by 56.52% when compared with the conventional solar distiller.

AbstractThe countries of North Africa suffer from a serious problem that affects a large number of people. The trouble is the provisioning of drinking water. Several techniques are used but solar distillation; which seems to be an appropriate, economical, and easy solution. Conventional solar distiller is used in the Saharan areas but the yield of this device is low, that's why there are several studies that are focused on improving this distiller. The technique of double glazing gives an increase in the efficiency of a solar collector; hence, the idea of using the same technique in a conventional solar distiller. Two covers of glasses separated by 1 cm, isolated from the four sides was put on a distiller of dimensions 0.5 × 0.5 m. The results show that this technique minimizes the distiller's yield by 56.52% when compared with the conventional solar distiller.

Abstract Single-effect solar still is a simple solar device used for converting the available brackish or waste water into potable water. This device has many advantages like, easily fabricated from locally available materials and cheap maintenance with low skilled labor. A lot of works were undertaken to improve the productivity of the still. Throughout the review on solar still performance, the results indicated that, the basin water depth is considered the main parameter that affects the still performance. Also the review showed that; the solar still cover with inclination equal to latitude angle receives sun rays close to normal sun rays throughout the year. The still productivity also increases with decreasing the cover thickness and increasing its thermal conductivity. The still basin material plays an important role in improving the productivity of the still, rubber basin was considered the best used material in improving the absorption, the storage and the evaporation effects. The previous studies also showed that, the daily production of still was greatly enhanced by using sponge cubes, fins and stepped. The coupling of a solar collector, hot water tank, external reflector, internal condenser and greenhouse with a still increased the productivity. Finally; from the previous efforts it was clear that; using the sun tracking is more effective than the fixed system in enhancing the still productivity; also the PCM is more effective for lower masses of basin water on winter season.

Abstract Single-effect solar still is a simple solar device used for converting the available brackish or waste water into potable water. This device has many advantages like, easily fabricated from locally available materials and cheap maintenance with low skilled labor. A lot of works were undertaken to improve the productivity of the still. Throughout the review on solar still performance, the results indicated that, the basin water depth is considered the main parameter that affects the still performance. Also the review showed that; the solar still cover with inclination equal to latitude angle receives sun rays close to normal sun rays throughout the year. The still productivity also increases with decreasing the cover thickness and increasing its thermal conductivity. The still basin material plays an important role in improving the productivity of the still, rubber basin was considered the best used material in improving the absorption, the storage and the evaporation effects. The previous studies also showed that, the daily production of still was greatly enhanced by using sponge cubes, fins and stepped. The coupling of a solar collector, hot water tank, external reflector, internal condenser and greenhouse with a still increased the productivity. Finally; from the previous efforts it was clear that; using the sun tracking is more effective than the fixed system in enhancing the still productivity; also the PCM is more effective for lower masses of basin water on winter season.

Abstract A new concept of active vibratory solar still is presented in this study. A flexible packed stretched media installed in the bottom of the basin to increase the efficiency of the still is applied. The flexible packed media is formed from stretched helical coiled copper wires, which are considered as a good media for heat absorbing and transferring and as a simple thermal storage system. Also, a vibrator (resonator) is installed in the middle of the system structure. The target of using the vibrator is to generate forced vibration to excite the flexible packed media to break the boundary layer and surface tension of the saline water and improve convective heat transfer, and also to excite the condensed polycarbonate glass cover to assist the condensed droplets to slide down before it becomes bigger and possibly falls down in the basin, thus increasing the water vaporization and condensation. Experimental and theoretical analysis including system dynamic modeling coupled with the exciting vibrator is presented and the condition of maximum excitation of the absorbing added media is determined. The performance is compared with the conventional solar stills (CSS). The governing equations including the flexible packed media, the harmonic vibratory excitation, and the energy storage are presented. The vibratory excitation effect is accounted by two new parameters the ‘vibratory performance gain and the ‘vibratory power effect’. The productivity due to added backed helical wires is found to be 3.4 l/m 2 day, with an efficiency of about 35%, and the productivity with vibration is increased to be 5.8 l/m 2 day and the average daily efficiency is about 60%. The nocturnal production ranges from 38% to 57%.

Abstract A new concept of active vibratory solar still is presented in this study. A flexible packed stretched media installed in the bottom of the basin to increase the efficiency of the still is applied. The flexible packed media is formed from stretched helical coiled copper wires, which are considered as a good media for heat absorbing and transferring and as a simple thermal storage system. Also, a vibrator (resonator) is installed in the middle of the system structure. The target of using the vibrator is to generate forced vibration to excite the flexible packed media to break the boundary layer and surface tension of the saline water and improve convective heat transfer, and also to excite the condensed polycarbonate glass cover to assist the condensed droplets to slide down before it becomes bigger and possibly falls down in the basin, thus increasing the water vaporization and condensation. Experimental and theoretical analysis including system dynamic modeling coupled with the exciting vibrator is presented and the condition of maximum excitation of the absorbing added media is determined. The performance is compared with the conventional solar stills (CSS). The governing equations including the flexible packed media, the harmonic vibratory excitation, and the energy storage are presented. The vibratory excitation effect is accounted by two new parameters the ‘vibratory performance gain and the ‘vibratory power effect’. The productivity due to added backed helical wires is found to be 3.4 l/m 2 day, with an efficiency of about 35%, and the productivity with vibration is increased to be 5.8 l/m 2 day and the average daily efficiency is about 60%. The nocturnal production ranges from 38% to 57%.

Abstract The high cost of the solar tracking systems is the major obstacle facing the growth of the solar harvesting technology. Therefore, reducing the solar tracking cost is necessary for developing this important energy sector. This study developed a simple and low-cost solar tracking system for parabolic concentrator (PCST) assisting tubular solar still (TSS). A single-axis solar tracking mechanism is developed based on two small light-dependent resistors (LDRs) shielded by a blank sheet which keeps the two cells shielded from sunlight. When the sunlight moves, one of the two LDRs will gain some light activating a switch to turn on the driving motor moving the system in the opposite direction till the LDR shielded again. By this simple mechanism, the two LDRs are shielded from sunlight all the time and consequently, the solar collector is always facing the sunlight. A simple parametric study is also conducted for an efficient PCST-TSS device with higher freshwater productivity. The performance of the most promising five design categories is compared. Results showed that the lowest cost tracking system was 34.6% lower than the highest one. Moreover, the lowest CPL was $0.0074/L which is 43.1% lower than the highest CPL category. Moreover, a comparison with other studies showed high potential for the present significant reduction in the cost which ranges between 43.1% and 87% compared with the recent related studies. The developed device is fully self-reliance and suitable for rural and isolated communities having limited infrastructure.