Parametric Study on a Solar Still Located in Aswan, Egypt of Hot and Dry Climate

International Journal of Engineering & Technology IJET-IJENS Vol:3 No: 46 Parametric Study on a Solar Still Located in Aswan, Egypt of Hot and Dry Climate Soubhi A. Hassanein, M. Attalla 2 Mechanical Engineering Department Aswan Faculty of Energy Engineering Aswan University, Aswan, Egypt 2 Mechanical Engineering, Power and Energy Department Faculty of Engineering, Qena - South Valley University, Qena, Egypt Corresponding author. Tel: +2 4482, Fax: +2 97 34823, E-mail address: soubhi_a@yahoo.com, P. O.: 828 Aswan, Egypt. Abstract-- All over the world access to potable water to the people are narrowing down day by day. Most of the human diseases are due to polluted or non purified water resources. Solar distillation proves to be both economical and eco-friendly technique particularly in rural areas. So a parametric study on a solar still located in Aswan, Egypt, is presented in this research. Solar Stills operate on the same principles that produce rainfall. The Sun is allowed into and trapped in the Still. The high temperatures produced destroy all pathogens. The water evaporates, and condense on the glass. The glass is sloped to the south, and the condensed water runs down the glass and is collected in a trough. The water is allowed out of the collector through tubing, and is collected in glasses. Static solar technologies as well as one axis sun tracking were compared. In addition to the effect of some parameters such as unit orientation, cooling water rate, radiation and convection loss was studied in detail. The results show that The highest water productivities per unit area are obtained by using combining of both FPC and PTC, cooling condensing surface,and directed in south orientation. Index Term-- Parametric Study; Solar Distillation; Solar Thermal Collector; Water Productivity. Nomenclature T a Ambient temperature o C T g glass temperature o C FPC Flat plate collector PTC parabolic trough collector Greek Letters Subscripts a ambient g glass. INTRODUCTION Solar energy is the main source through which life is sustained on earth. The lack of drinking water has been a great challenge for humanity which continues to the present and will continue in the future. The lack of drinking water is directly related to 8% of the world's illnesses and to % of total infantile death. Worldwide, the distribution of drinking water is not proportional to the needs for each area. This is translated into a surplus of water in some areas whereas others have significant shortages. To seek solutions for this problem, several processes were proposed among which is solar desalination with its two conversion modes. The first conversion uses flat plat collector generally used for a temperature lower than c. In order to reach a higher temperature (> c), solar concentrators are required and this is the second conversion. Solar collectors are composed of a concentrator and a focal absorber. The quality of the concentrator is closely related to the quality of the reflecting surface and the precision machining surface. A shortage of water at places with a hot climate may make the application of solar energy for water desalination practical. Solar desalination exhibits considerable economic advantages over other salt-water desalination processes because of cost-free energy, reduced operating costs and its simple structure. Solar desalination systems are suitable and more economical. The intensity and availability of the solar energy in Egypt (Aswan) is among the highest in the world. The use of solar energy in thermal desalination processes is one of the most promising Applications of renewable energies to seawater desalination. Solar Stills are effective in removing Salts/Minerals (e.g.,na, Ca, As, Fl, Fe, Mn). Bacteria (e.g., E. Coli, Cholera, Botulinus). Parasites (e.g., Giardia, Cryptosporidium). Heavy Metals (e.g., Pb, Cd, Hg). A solar distillation system may consist of two separated devices - the solar collector and the distiller - or of one integrated system.the first case is an indirect solar desalination process, and the second one is a direct solar desalination process. Many small-size systems for direct solar desalination and several pilot plants of indirect solar desalination have been designed and implemented. A solar collector field is connected to a distillation system. Therefore, on the one hand, a variety of solar collectors may be used in order to convert solar energy to thermal energy. In most of them, a fluid is heated by the solar radiation as it circulates along the solar collector through an absorber pipe. This heat transfer fluid is usually water or synthetic oil the fluid heated at the solar collector field may be either stored at an insulated tank or used to heat another thermal storage medium. The solar collectors may be static or sun- tracking devices. The second ones may have one or two axes of sun tracking. Otherwise, with respect to solar concentration Solar collectors may be flat plate, line-axis concentrating, or point focusing. Different solar collectors are already commercially available; nevertheless, many collector improvements and advanced solar technologies are being developed. 37-8282-IJET-IJENS February 23 IJENS

International Journal of Engineering & Technology IJET-IJENS Vol:3 No: 47 The main solar collectors suitable for seawater distillation are as follow: flat-plate collectors (FPC), evacuated tube collectors (ETC), compound parabolic collectors (CPC) and parabolic trough collectors (PTC). On the other hand, there is a solar converter system that acts simultaneous ly as solar energy conversion and as thermal storage: salinity gradient solar ponds (SP). The selection of the most suitable collector for a given application should take into account: the operation temperature required; the ratio between beam and global solar radiation; the environmental temperature the solar irradiance transient and other technical and economic factors. A theoretical model to calculate the absorbed average temperature as well as the distillate flow rate as function of solar flux was developed by Bechir Chaouchi, Adel Zrelli, Slimane Gabsi []. The experimental results were compared with those calculated theoretical. A small difference in the absorber average temperature was found between both results. The use of solar energy in seawater distillation under Spanish climatic condition has been done by Lourdes Garcia Rodriguez et al [2] his results shows that direct steam gereration parabolic troughs are a promising technology for solar assisted seawater desalination. The experimental and theoretical study of a solar desalination system located in Cairo Egypt is presented by Zeinab S. Abdel Rehim, Ashraf Lasheen [3] using a modified unit to enhance the performance of the solar desalination, the modification unit includes a solar parabolic trough. His results shows that fresh water productivity is increased by an average of 8% due to the modification. Parametric analysis was conducted by Y.J. Dai, R.Z. Wang, H.F. Zhang [4] to optimize the desalination unit with humidification and dehumidification. The effect of some operating conditions such as flow rates, temperature of feed water, air and cooling water was studied in detail. A parametric investigation was theoretically performed by Hiroshi Tanaka et al [ ] for the vertical multiple effect diffusion type solar still which consists of vertical partitions in contact with saline soaked wicks with narrow gaps between the partitions coupled with a heat pipe solar collector. A detailed review of different studies on active solar distillation system was done by K. Sampathkumar [6] that review threw light on scope for further research and recommendation in active solar distillation system. This paper presents performance evaluation of solar still tested under Aswan climatic conditions of Egypt, in summer seasons 2. Hourly and daily measurements of still productivity, temperature of water film, glass cover, ambient and solar radiation were recorded. 2. EXPERIMENTAL APPARATUS AND MEASURING INSTRUMENTS The experimental set up of solar still under investigation is shown schematically in Fig.. Fig. 2 shows a photo graph of the solar still rig which composed of the following component:- 2- Flat plate collector (FPC): FPCs are static and no concentrating solar energy conversion systems. Water usually use as heat transfer fluid, which circulates through absorber pipes made of metal. The absorber pipes are assembled on a flat plate and they usually have a transparent protective surface in order to minimize heat losses. They may have different selective coatings to reduce heat losses and to increase radiation absorption. Thus the thermal efficiency increases although the collector cost also increases, (FPC) dimensions 2 cm length wide*. 2-2 Tank: Rectangular tank of m length *. m wide at base its height 7 cm at one end and 4 cm at other end which make covering glass inclined where, an evaporation water can condensed on the glass. The tank was made from stainless steel which is insulated at all outer side as shown in fig. 2. A forced cooling to the glass surface to increase the amount of fresh water productivity was used. 2-3 Trough concentrator: The parabolic trough is solar concentrator, reflector and collector. It is manufactured from wood internally covered by glass. Its length is m and diameter of 3 cm. The cupper pipe is fixed on the axis line with the focal of the parabolic. 2-4 Pump: Used to circulate the fluid ( water ) in the pipe. Pump characteristic: H,max, =3 m Q,max =2 L/min Motor characteristics Volt current Power Capacity Frequency 22 2.A.37 kw 6 µf HZ 2- Scalar vessel: Used to collect and measure the amount of fresh water productivity 2-6 Digital Thermometers: Used to measure the water temperature inside the tank and the temperature of the glass. Also the temperature of the ambient was measured using the k type thermocouple. 3. EXPERIMENTAL WORK The experimental procedures carried out to study effect of some parameter as orientation of flat plate collector, combined both flat plat collector and trough collector, and quantity of cooling water over glass cover on performance of solar still. So after running the apparatus the following measurement was taken according to the experimental runs as in table () ambient air temperature. (2) water temperature. (3) glass temperature. (4) quantity of collected condensate water () Radiation flux. 37-8282-IJET-IJENS February 23 IJENS

International Journal of Engineering & Technology IJET-IJENS Vol:3 No: 48 T ABLE I EXPERIMENTAL RUNS FPC PTC Direction Cooling Notes Run No yes No East No FPC 2 yes No West No 3 yes No South No 4 yes yes South No No yes South No FPC 6 Yes No South Yes 6.9 ml/s 7 Yes No South Yes 8. ml/s 8 Yes Yes South Yes 6,9mL/s 9 yes Yes south No without glass cover with glass cover 4. RESULTS DISSCUSSIONS In this part, the obtained experimental results will be comprehensively discussed. The results include the effect of orientation, combining both flat plat collector and trough collector, and quantity of cooling water over glass cover on solar still performance. 4- Temperature and radiation flux Distributions Fig. 3- shows variation of (ambient, glass cover, and water) temperature versus time for different solar technology( PTC, FPC, and combination of PTC and FPC). I could be seen from the fig. that (ambient, glass cover, and water) temperatures increase as time go on to a maximum value and all decrease after that. Also it could be seen from the fig. that the water temperature has the higher values followed by glass cover temperature, followed by ambient temperature at most times. Fig. 6 shows solar radiation flux versus time at Aswan. It could be seen from the fig. that the solar flux increase as time goes on to a maximum value and it decrease after that as time increase. 4-2 Effect of orientation on solar still performance Fig. 7 shows condensate water productivity versus time for different flat plate orientation. It could be seen from the fig. that as the time increase the water produce increase to a maximum value and decrease after that, and this could be explained as time increase the ambient temperature and solar radiation increase which make more water evaporate and condensed. Also It could be seen from the fig. that the effect of orientation for flat plate collector has a little bit effect on water productivity, and this could be explained as the flat plate collector is plain i. e its not concave only concentration has a focus which change with direction of sun, but it could be seen that the south direction has a little bit more values for water productivity than others direction. 4-3 Solar technology comparison Fig. 8 shows Comparison between amounts of water productivity by (flat plate collector and concentrator, concentrator only, flat plate collector only) in south direction (flat plate collector without glass). It could be seen from the fig. that the PTC has the highest values followed by combination of both FPC and PTC followed by FPC as this could be attributed to high concentration of small area of PTC compared to both FPC and combination of both FPC and PTC. Fig. 9 shows accumulated water produced versus time using different technology as (PTC, FPC, and combination of PTC and FPC. It could be seen from the fig. that the PTC has the highest values followed by combination of both FPC and PTC followed by FPC as this could be attributed to high concentration of small area of PTC compared to both FPC and combination of both FPC and PTC. 4-4 Influence of cooling cover glass on the distillation yield Fig. shows Water productivity versus time for FPC under different rates of cooling water over condensate glass cover. It could be seen that as the cooling water increase the condensate water increase. Fig. Water productivity versus time for combination of FPC and PTC with and without cooling. It could be seen from the fig. that water productivity for FPC and PTC with cooling has higher values more than water productivity using FPC and PTC without cooling. Fig. 2 shows accumulated water versus time produced using different cooling water rate on glass cover. It could be seen form the fig. that as cooling water rate increase the produced accumulated water increase. 4- Effect of radiation and convection losses on water productivity in solar still Fig. 3 shows water productivity versus time using trough concentrator and flat plate collector (with glass) and for trough concentrator and flat plate collector (without glass). It could be seen from the fig. that using trough concentrator with flat plate collector (with glass) give more values of water productivity than using trough concentrator with flat plate collector (without glass) and this could be explained as using FPC with glass cover make radiation from FPC less which mean higher solar energy will gain to water which mean more water will be evaporate and condensate. And this trend continued to a certain time after that It could be seen that using trough concentrator with FPC (without glass) give higher water productivity than (TC with FPC with glass cover) and this could be explained as this stage water has been absorbed heat and using FPC without glass will cool water as it will loss heat through radiation thus water will be more condensate as it cooled than using FPC with glass cover.. CONCLUSION Based on the results the following conclusions are drawn as follows: -As time goes on, all temperatures (ambient, water, glass) increases and begin to decrease between (2: - 4: ) PM which go on line to the variation of the solar radiation. 2- The best direction for flat plate collector is in the south direction. 37-8282-IJET-IJENS February 23 IJENS

Temperature o C Temperature o C International Journal of Engineering & Technology IJET-IJENS Vol:3 No: 49 3- when the amount of cooling water increased for condensing surface, the productivity of fresh water increased. 4- The radiation and convection losses affected water productivity as it give lower values. - The highest water productivities are obtained by using combining of both FPC and PTC, cooling condensing surface,and directed in south orientation. 6- The solar still unit used proven to be an efficient device to utilize solar energy for obtaining fresh water from saline water. REFERENCES [] Bechir Chaouchi, Adel Zrelli, Slimane Gabsi Desalination of brackish water by means of a parabolic solar concentrator Desalination 27 27 8-26 [2] Lourdes Garcia Rodriguez, Ana I. Pamero Marrero, Carlos Gomez Camacho Comparison of solar thermal technologies for applications in seawater desalination Desalination 42 22 3-42 [3] Zeinab S. Abdel Rehim, Ashraf Lasheen Experimental and theoretical study of a solar desalination system located in Cairo Egypt Desalination 27 27 2-64 [4] Y.J. Dai, R.Z. Wang, H.F. Zhang Parametric analysis to improve the performance of a solar desalination unit with humidification and dehumidification Desalination 42 22 7-8 [] Hiroshi Tanaka, Yasuhito Nakatake, Katsuhiro Watanabe Parametric study on a vertical multiple effect diffusion type solar still coupled with a heat pipe solar collector Desalination 7 24 243-2 [6] K. Sampathkumar, T.V. Arjunan, P. Pitchandi, P. Senthilkumar Active solar distillation- A detailed review Renewable and Sustainable energy reviews Volume 4, Issue 6, August 2, Pages 3-26 Sun Solar Radiation Distillation channel Flat plat collector Solar radiation Basin 6 4 3 2 Fig. 2. Photograph of solar still set up Water temperature glass temperature Ambient temperature insulated pipe pump trough collector Fig.. Schematic of an active solar still integrated with both flat plate collector and trough collector Fig. 3. Daily variations of ambient, glass cover and basin water temperatures versus time for parabolic trough concentrator 6 4 3 2 Water temperature glass temperature Ampient temperature Fig. 4. Daily variations of ambient, glass cover and basin water temperatures versus time for flat plate collector. 37-8282-IJET-IJENS February 23 IJENS

Temperature o C Productivity kg/m 2.day Productivity kg/m 2.day Water acomulated kg/m 2.day Productivity kg/m2.day International Journal of Engineering & Technology IJET-IJENS Vol:3 No: 6 4 3 2 Water temperature glass temperature Ambient temperature Fig.. Daily variation of ambient, glass cover and basin water temperatures versus time for both parabolic trough concentrator and flat plate collector. 2 9 8 7 6 4 3 2 Irradiance Wm 2 6 7 8 9 23467892 Fig. 6. Measured irradiance (perpendicular to device surface)..2.8.6.4.2 East West South 7 2 7 7 6 4 3 2 FPC +PTC PTC FPC Fig. 8. Comparison between amounts of water productivity by (flat plate collector and concentrator, concentrator only, flat plate collector only) in south direction (flat plate collector without glass). 4 3 3 2 2 FPC+PTC PTC FPC 7 2 7 Fig. 9. Accumulative fresh water productivity for different solar technology. 6 4 3 2 Cooling rate 6.9 ml/s Cooling rate 8. ml/s Fig.. Water productivity versus time for FPC under different rates of cooling water over condensate glass cover. Fig. 7. Water productivity versus time under different flat plate orientation 37-8282-IJET-IJENS February 23 IJENS

Productivity kg/m 2.day Water Acomulated kg/m 2.day Productivity kg/m 2.day International Journal of Engineering & Technology IJET-IJENS Vol:3 No: 6 4 FPC+PTC with cooling 6.9 FPC+PTC without cooling 3 2 8 9 2 3 4 6 7 8 9 2 Fig.. Water productivity versus time for combination of FPC and PTC with and without cooling. 4 3 3 2 Cooling rate 6.9 ml/s Cooling rate 8. ml/s 2 Fig. 2. Accumulative fresh water productivity for flat plate collector under different cooling rate of glass cover..2.8 With glass Without glass.6.4.2 Fig. 3. Comparison between amount of water productivity by using concentrator and flat plate collector (with and without glass). 37-8282-IJET-IJENS February 23 IJENS