• Energy Research

Abstract The performance of parabolic trough solar collector (PTC) coupled with single slope solar still at various water mediums is assessed based on productivity, energy, exergy, exergoeconomic, and enviroeconomic methodologies and also Energy payback time. Six solar still systems are considered; conventional solar still (CSS), CSS coupled with PTC (CSS + PTC), CSS contains steel wire mesh in the basin (CSS + WM), CSS contains wire mesh and coupled with PTC (CSS + WM + PTC), CSS contains sand in the basin (CSS + SD), and CSS contains sand and integrated with PTC (CSS + SD + PTC). Experiments are conducted under hot and cold climate conditions of Sohag city, Egypt. Findings show that the maximum freshwater yield in summer is achieved in case of CSS + SD + PTC with an increase of 1.21% compared to CSS and 102.1% compared to CSS + SD + PTC in winter. The maximum increase of the energy and exergy output per year compared to CSS is achieved in case of CSS + SD + PTC of 216.6% and 325%, respectively. Incorporation PTC with the still for all studied water mediums is found promising in terms of energy payback time, cost and freshwater yield compared to CSS without PTC. The exergoeconomic and environmental parameters of the active systems are found more effective related to those of passive systems.

Abstract This study experimentally investigates the performance of solar still coupled with a parabolic trough solar collector (PTSC) at different cooling rates based on energy, exergy, exergoeconomic, and enviroeconomic standpoints. Different solar still systems are considered; conventional solar still (CSS), solar still with heat sink condenser (MSS) and coupled with PTSC (MSS + PTSC), MSS having an umbrella and coupled with PTSC (MSS + PTSC + U), MSS with PTSC and condenser forced air cooling (MSS + PTSC + FA), and MSS + PTSC with condenser forced water cooling (MSS + PTSC + FW). Experiments are conducted under hot climate conditions of Sohag city, Egypt. Results indicated that the freshwater yield of all studied systems in ascending order is as follow; CSS + PTSC, MSS + PTSC + U, MSS + PTSC, MSS + PTSC + FA, and MSS + PTSC + FW in summer with value of 7.74, 8.02, 8.68, 9.11, and 9.45 kg/m2, respectively. The maximum exergy efficiency of 1.34% in summer is achieved in case of MSS + PTSC + FW system. The economic analysis shows that distilled water cost is minimum for MSS + PTSC + FW (~0.02 $/L), while it is maximum for MSS + PTSC + U (~0.022 $/L). It can be concluded that high freshwater production and less distilled water cost are making the enhanced solar desalination system feasible and competitive. Minimum exergy efficiency occurs in case of CSS + PTC with a value of 1.197% and MSS has higher average daily exergy efficiency. MSS + PTSC achieves the best performance-based exergoeconomic approach. MSS + PTSC + FW is by far the best system in cutting down CO2 emissions.

Abstract The objective of this study is to improve the heat transfer characteristics of PCM storage unit, applicable to solar still system, using hollow cylindrical pin fins embedded in PCM. Hollow cylindrical pin fins act as thermal conductivity enhancer (TCE). In view of this, three cases are considered namely, Case 1: without PCM (conventional solar still), Case 2: solar still with PCM, Case 3: solar still with pin fins heat sink embedded in the PCM. The performance of the three cases is experimentally evaluated and compared to each other under the same climate conditions. The results revealed that the presence of PCM negatively affects the daytime freshwater productivity with a significant increment in the overall freshwater yield of the still. Also, solar still with PCM-based pin finned (Case 3) achieves the best thermal performance compared to conventional still (Case 1) and solar still with only PCM (Case 2). It is perceived that the total daily cumulative yield of distillate water of Case 3 is higher than those of case 1 and case 2 by 17 % and 7 %, respectively. Finally, the findings indicated that inclusion of PCM in the solar still systems for cases 2, 3 extends the production of fresh water after sunset by approximately 5h and 7h, respectively.

Abstract In this study, a comprehensive exergetic performance investigation of a single slope a passive solar still system is theoretically presented. Energy and exergy methodologies have been applied for all components of the solar still comprising glass cover, brackish water, and basin-liner. Also, exergy irreversibility analysis was conducted to identify and localize the sources responsible for the exergy destruction and losses in the system for further analysis and improvement. The theoretical model was solved numerically by using fourth-order Runge–Kutta method and the program was written by MATLAB. To examine the validity of the model, the numerical results were verified with the available experimental data in the literature. The numerical results were in good correspondence with the experimental data for the components’ temperatures and output productivity. The results showed that the maximum energy and exergy efficiencies of the proposed system are 32.5 % and 2.23 %, respectively. It is observed that the exergy efficiency has much lower value than the energy efficiency. The maximum irreversibility or exergy destruction in each component, i.e. glass cover, saline water, and basin-liner, has been estimated as 61.1, 50.2 and 717 W/m2, respectively, related to the maximum solar exergy input of 1005 W/m2. Furthermore, the results showed that exergy destructions rates in the solar still is proportional to the received solar insolation. From irreversibility analysis, it is found that the basin liner accounts for the highest exergy destruction (86% of the total exergy destruction).

Abstract The limit production of freshwater is considered the main problem of solar still. So, the objective of this work is studying the performance of single slope solar still coupled with phase change materials as a thermal storage unit and its effect on the still productivity. In view of this, different cases are considered namely, Case 1: solar still without phase change material (conventional solar still), Case 2: solar still coupled only with phase change material attached to the still base, Case 3: solar still with hollow cylindrical pin fins imbedded in the phase change material, case 4: solar still with phase change material and steel wool fibers in the still basin and case 5: solar still with only steel wool fibers in the still basin. The performance of the solar still for the five cases is experimentally evaluated and compared to each other's under the same climate conditions of New Borg El-Arab City, Egypt (Longitude/Latitude: E 029°42′/N 30°55′). The results revealed that the presence of phase change material negatively affects the daytime freshwater productivity with a significant increment in the overall freshwater yield of the still. Also, solar still with phase change material-based pin finned (Case 3) achieves the best thermal performance compared to conventional still (Case 1) and solar still with phase change material (Case 2). It is perceived that the total daily cumulative yield of distillated water of Case 3 is higher than those of case 1 and case 2 by 17 and 7%, respectively. Additionally, placing steel wool fibers in the basin accompanied with phase change material significantly enhances the daytime freshwater productivity with a considerable reduction in overnight productivity and an increase of the overall day productivity. Moreover, using steel wool fibers in the basin with a phase change material based solar still (case 4) enhances the total daytime freshwater productivity by 14% with a drop in the overnight productivity by 80%, compared to case 2. Among all tested configurations, case 5 achieves the highest accumulated daily freshwater productivity (approximately 25% an enhancement in the daily productivity compared to case 1) and thermal efficiency with minimum cost.

Abstract In this study, comparative performance assessment of different passive solar stills systems based on energy matrices, exergy, economic, exergoeconomic, environmental, exergoenvironmental, enviroeconomic, and exergoenviroeconomic viewpoints is performed. Six systems of passive solar stills are considered namely, traditional solar still (TRD still), solar still with phase change materials (PCM), solar still with PCM embedded in a pin fin heat sink (PCM-PF), solar still with PCM incorporated with steel wool fibers in the basin (PCM-SWF), solar still with SWF only in the basin (with SWF) and finally solar still with pin fined heat sink in the basin (with PF). The performance of the six systems is experimentally evaluated and compared to each other under the same meteorological conditions of New Borg El-Arab City, Egypt (Longitude/Latitude: E 029°42′/N 30°55′). The results indicated that PCM-based solar stills systems performed poor performance based on energy matrices, freshwater production cost, exergoeconomic, exergoenvironmental and exergoenviroeconomic parameters. Whereas, solar still with SWF gives the highest performance among all studied systems by employing these enhanced (exergy/economic/environmental) approaches. The daily energy and exergy outputs for conventional still are the minimum at 2.5 and 0.1528 kWh/day, respectively and still with SWF are the maximum at 2.856 and 0.1869 kWh/day, respectively. The annual amount of CO2 emission mitigated for conventional still, still with PCM, still with PCM-PF, still with PCM-SWF, still with SWF and still with PF are 33.02, 35.88, 38.26, 37.05, 41.6 and 38.35 tons, respectively based on energy approach. Whereas, the corresponding values based on exergy are 0.961, 0.6652, 0.6217, 0.756, 1.56 and 1.189 tons, respectively.

Abstract In this study, a comparative performance analysis was performed between a conventional photovoltaic system and a low-concentration photovoltaic system. Two typical photovoltaic modules and two compound parabolic concentrating photovoltaic systems were examined. A Cooling system was employed to lower the temperature of the solar cells in each of the two configurations. Experimental and numerical investigations of the performance of the two arrangements with and without cooling were presented. Experiments were conducted outdoors at the Egypt-Japan University of Science and Technology, subjected to the hot climate conditions of New Borg El-Arab City, Alexandria, Egypt (Longitude/Latitude: E 029°42′/N 30°55′). A comprehensive system model was established, which comprises an optical model, coupled with thermal and electrical models. The coupled model was developed analytically and solved numerically, using MATLAB software, to assess the overall performance of the two configurations, considering the concentration ratio of the concentrated photovoltaic system to be 2.4X. The results indicated that cooling the solar panels considerably improved the electrical power yield of the photovoltaic systems. By employing cooling, the temperatures of the conventional photovoltaic system and the concentrated photovoltaic system were effectively lowered by approximately 25% and 30%, respectively, resulting in a significant enhancement in the electrical power output of the photovoltaic system by 11% and that of the concentrated photovoltaic system by 15%. Furthermore, the results revealed that the concentrated photovoltaic system outperformed the non-concentrated photovoltaic system, for both non-cooling and cooling cases, by 33% and 52%, respectively. Finally, experimental verification of the numerical results revealed a good agreement for both configurations, with an average error of 4% and 5% for the photovoltaic systems and the concentrated photovoltaic systems, respectively.

Abstract In this experimental work, the energetic and exergetic performance enhancement of solar distillation system (solar still incorporated with PCM storage unit) is performed by using two techniques. First, pin fins heat sink (PF) is embedded inside the PCM to act as a thermal conductivity enhancer. Second, black steel mesh fibers (SWF) are employed in the solar still basin with PCM. In this regard, four cases of the solar stills are studied and compared conventional still: conventional solar still (without PCM), still with PCM (With PCM), still with PCM and pin fins heat sink embedded in the PCM (With PCM-PF) and still with PCM and SWF in the basin (With PCM-SWF). The energetic and exergetic performance of the four cases is evaluated and compared under the meteorological conditions of New Borg El-Arab City, Egypt. The results show that the total daily cumulative yield of distilled water of still with PCM, still with PCM-PF, and still with PCM-SWF are greater than of conventional still by 9.5%, 16.8%, and 13%, respectively. Additionally, the inclusion of the fins heat sink in the PCM increases the average daily energy and exergy efficiencies by 17.9, and 13.2%, respectively compared to conventional one. Likewise, the energy and exergy efficiencies of still with PCM-PF are higher than those of solar still with PCM by 7.7 and, 6.8%, respectively. Furthermore, placing SWF in the basin of still with PCM significantly enhances the daytime energy and exergy efficiencies with a considerable reduction of these values in the nighttime. The total daily evaporative exergy for still with PCM-SWF is greater than those of conventional still, still with PCM, and still with PCM-PF by 13, 8, and 2%, respectively. Also, still with PCM, still with PCM-PF, and still with PCM-SWF exhibit an increment of the daily exergy efficiency 5.9, 13.2, and 17.3%, respectively compared to still without PCM. Still with PCM-PF achieved the highest accumulated daily water productivity and energy efficiency but still with PCM-SWF attained the highest daily exergy efficiency with nearly no additional cost.

Abstract The impact of salty water medium and condenser type on the performance of single slope solar still is experimentally performed. Two solar still types are examined; conventional solar still with glass condenser (CSS) and solar still with plated finned heat sink condenser (MSS). The study is investigated for three saline water mediums in the still basin; pure saline water, sand saturated with saline water and steel wire meshes submerged inside the saline water. These stills are investigated in case of still only or still incorporated with parabolic trough collector (PTC) in hot and cold climate conditions of upper Egypt. Findings show that utilizing wire mesh, sand and heat sink condenser (HSC) raises the still freshwater yield and efficiency. The maximum freshwater yield rising in summer is 67%, 7.3% and 6% due to using PTC, HSC, and sand, respectively compared to CSS. The efficiency of all still systems in summer is found greater than winter. Moreover, utilizing HSC raises the still efficiency by 11.6% in summer and 8% in winter compared to CSS. MSS achieves the greatest efficiency of 41.95% in summer and 31.96% in winter while MSS+sand+PTC accomplishes the minimum freshwater cost with a decrease of 25.2% compared to CSS.