Productivity enhancements of compound parabolic concentrator tubular solar stills

Productivity enhancements of compound parabolic concentrator tubular solar stills

Renewable Energy 88 (2016) 391e400 Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene Prod...

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Renewable Energy 88 (2016) 391e400

Contents lists available at ScienceDirect

Renewable Energy journal homepage: www.elsevier.com/locate/renene

Productivity enhancements of compound parabolic concentrator tubular solar stills T. Arunkumar a, b, *, R. Velraj a, D.C. Denkenberger c, Ravishankar Sathyamurthy d, K. Vinoth Kumar e, Amimul Ahsan f a

Institute for Energy Studies, Anna University, Chennai, 600025, Tamilnadu, India Department of Physics, Dr. N.G.P Institute of Technology, Coimbatore, 641048, Tamilnadu, India Department of Civil and Architectural Engineering, Tennessee State University, Nashville, TN, USA d Department of Mechanical Engineering, Hindustan Institute of Technology and Science, Kelambakkam, Chennai, 603103, India e CHOGEN Powers Pvt. Ltd., Chennai, Tamil Nadu, India f Department of Civil Engineering, Institute of Advanced Technology, University Putra Malaysia, 43400, UPM, Serdang, Selangor, Malaysia b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 4 June 2015 Received in revised form 3 October 2015 Accepted 19 November 2015 Available online xxx

The performance of compound parabolic concentrator assisted tubular solar still (CPC-TSS) and compound parabolic concentrator-concentric tubular solar still (CPC-CTSS) (to allow cooling water) with different augmentation systems were studied. A rectangular saline water trough of dimension 2 m  0.03 m  0.025 m was designed and fabricated. The effective collector area of the still is 2 m  1 m with five sets of tubular still e CPC collectors placed horizontally with north-south orientation. Hot water taken from the CPC-CTSS was integrated to a pyramid type and single slope solar still. Diurnal variations of water temperature, air temperature, cover temperature and distillate yield were recorded. The results showed that, the productivity of the un-augmented CPC-TSS and CPC-CTSS were 3710 ml/day and 4960 ml/day, respectively. With the heat extraction technique, the productivity of CPC-CTSS with a single slope solar still and CPC-CTSS with a pyramid solar still were found as 6460 ml/day and 7770 ml/ day, respectively. The process integration with different systems cost was found slightly higher but the overall efficiency and the produced distilled water yield was found augmented. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Compound parabolic concentrator Single slope solar still Pyramid solar still Cooling water

1. Introduction The world of living creatures depends on water sources. Rapid population growth and industrialization are two main reasons for increasing water demand, and consequent reductions in ground water level. Two methods of ameliorating these issues are desalination and waste water treatment technologies. One particularly promising route is solar desalination, which can be implemented with simple solar stills. Many researchers have studied different solar still configurations. Fath et al. [1] conducted an experimental study and compared the performance of single slope and pyramid solar still designs. On the basis of yearly performance results, the single slope still was found to be slightly more efficient and economical than the pyramidal one. Sathyamurthy et al. [2] carried out experiments with a pyramid solar still. They concluded that the wind speed

* Corresponding author. Department of Physics, Dr. N.G.P Institute of Technology, Coimbatore, 641048, Tamilnadu, India. E-mail address: [email protected] (T. Arunkumar). http://dx.doi.org/10.1016/j.renene.2015.11.051 0960-1481/© 2015 Elsevier Ltd. All rights reserved.

increasing from 1.5 to 3 m/s and to 4.5 m/s has the effect of increasing the still productivity by 8 and 15.5%, respectively. Taamneh and Taamneh [3] experimentally studied the pyramidshaped solar still with fan. The productivity of the pyramid solar still is enhanced by 25% compared to conventional solar still. A comparative performance of a pyramid solar still and a hemispherical solar still has been investigated by Arunkumar et al. [4]. The results elucidate that the pyramid solar still demonstrates the better performance than the hemispherical one. M. Federalize et al. [5] proposed a new radiation model for single slope solar still. Sandeep et al. [6] studied the modified single slope single basin active solar still with improved condensation technique. They found that the modified design shows a productivity increment of 14.5% compared with the normal design. Srivastava and Agrawal [7] developed a twin reflector booster single slope solar still with floating absorbers. The result showed that the modified designs of solar still improved the performance by 68%. Pearce and Denkenberger [8] computationally studied reflectors outside a solar still that approximated a compound parabolic concentrator (CPC). They showed that for reflector heights 2.5 times the width of the still, the

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Fig. 1. Direct and Beam radiation measuring instruments. (a) Pyranometer, (b) Pyrheliometer.

output per unit area per day roughly triples with only ~10% increase in cost and moderate maintenance (weekly tilts), indicating that CPCs have a significant economic advantage in producing solar distilled water. Hasan Mousa and Mousa Abu Arabi [9] developed a

desalination and hot water production system using a solar still enhanced by an external solar collector. Shanmugan et al. Performed an energy and exergy analysis of a single slope, single basin solar still [10]. Ragh vendra singh studied a solar still integrated with an evacuated tube collector in natural convection mode [11] and Shiv kumar et al. [12] investigated the solar still with evacuated tube collector in forced convection mode. Many researchers have analyzed the impact of cooling of the condensation surface of solar stills. Aneesh and Anil Kumar [13] found that the distillate output increases slightly with an increase in water flow rate over the top cover. Suneesh et al. [14] investigated a ‘V’ type solar still with cotton gauze cooling. They concluded that water flowing over the condensation surface increases the productivity. Tiwari and Rao [15] evaluated the performance of a solar still with water flow over the glass cover. Tiwari and Maduri [16] incorporated the flow of waste hot water in the basin along with water flow over the glass cover and obtained an increase in distillate output commensurate with the increase in inlet water temperature in the basin. Lawrence et al. [17] studied

Fig. 2. Unmodified compound parabolic concentrator with tubular covers.

Fig. 3. Schematic view of TSS with rectangular basin.

Fig. 4. Schematic view of CTSS with rectangular basin.

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the effects of water flow over the cover and heat capacity of water in the basin. They found an increase of 7%e10% in efficiency of the solar still due to water flow over the glass cover. Abu-Hijleh [18] theoretically investigated the effectiveness of film cooling under different operating characteristics; his results indicated that the proper use of the film cooling parameters can increase the still efficiency by 6% but poor parameters can reduce still efficiency. Abu-Hijleh and Mousa [19] extended the earlier work and included the evaporation effect of a water film flowing over the glass cover. Water flowing over the condensing cover has been studied by many other authors working in the field of desalination [20e33]. Nader Rahbar [34] studied the tubular solar still with a CFD simulation. They concluded from the analysis the productivity is directly proportional to the water temperature and inversely proportional to the glass temperature. The heat and mass transfer in a tubular solar still was experimentally investigated by Zhili Chen et al. [35]. They concluded that distillation increases as heating power (<300 W) increases. Ahsan and Fukuhara [36] analyzed the heat transfer model of tubular solar still. They formulated the heat balance of humid air and water in the tubular solar still. An experimental comparative study was made between conventional and tubular solar still by Ahsan et al. [37]. They showed that the

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new tubular solar still design has the better economic performance than the conventional one. Ahsan and Fukuhara [38] theoretically studied the condensation mass transfer in tubular solar still. Arunkumar et al. [39] experimentally studied a concentric tubular solar still with water and air as a coolant. They concluded that cold water flow through the tubular solar still shows a better performance than air. Arunkumar et al. [40] experimentally studied a tubular solar still with and without heat extraction by passing air through the annulus space. They reported that heat extraction plays a significant role in the production of a tubular solar still. Many attempts have been made to analyze the performance of single slope solar still. Ibrahim and Elshamarka [41] experimented with the modified basin type solar still and concluded that the maximum fresh water productivity achieved was 2.93 L/m2/day. Rahmani et al. [42] experimentally studied the natural circulation in a solar still and reported the distillate yield of 3.72 L/m2/day with 45.15% efficiency. Integration with another system may enhance the system productivity of single slope solar still. Several modifications with the use of phase change material, integrating solar water heater and nano fluids are also identified [43e53]. Arunkumar et al. [54, 55] experimentally investigated the effect of cover cooling in Concentrating parabolic collector integrated solar still. Similarly

Fig. 5. Pictorial view of TSS with basin.

Fig. 6. (a) A close-up view of CPC-CTSS and (b) Water storage basin.

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distilled output is collected directly from this assembly. In this case, beam radiation received by CPC trough is reflected to the blackened metal tube placed at its focal line. In this work, the detailed analysis of tubular solar stills is presented. The various configurations like compound parabolic concentrator assisted tubular solar still (CPC-TSS), compound parabolic concentrator-concentric tubular solar still (CPC-CTSS) (to allow cooling water), CPC-CTSS with single slope still and CPC-CTSS with pyramid solar still were studied based on the experimented data. 2. Materials

Fig. 7. Pyramid solar still: (a) 3D view of solar still with dimensions (b) dimensions of each individual glass.

some research opportunities are identified by Nagarajan et al. [56] by using ethylene glycol nano fluids from automobile radiators. D.G. Harris Samuel et al. [57] made a review on increasing the surface area of water. Therefore, in the present study, a compound parabolic concentrator was coupled to a single slope or pyramid solar still. Compound parabolic concentrators (CPCs) consist of curved segments of reflectors with two parabolas. They have been called ‘ideal light collectors’ as they concentrate light at the thermodynamic limit. In general, CPCs are used for steam generation and water heating processes, since they are able to produce higher temperatures than flat plate collectors. But in this study an attempt is made to use this concentrator for solar desalination. The tubular absorber assembly of the CPC is converted as solar still basin and

The pyranometer and pyrheliometer were used to measure global and direct radiation, respectively and they are shown in Fig. 1(a, b). The experiments were performed from January to November 2013 at the Solar Energy Laboratory, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore, India. The unmodified CPC is shown in Fig. 2. A tubular solar still with CPCs as solar collectors and concentric tubes with rectangular trays inside as receivers was fabricated. The tubular still was fabricated with borosilicate glass concentric tubes with 2.5 mm thick, 0.05 m outer diameter and 5 mm annulus space. The design and fabrication of any solar concentrator basically depends upon its reflector and the absorber used. The reflector used in the present work was fabricated with fibre material with ultraviolet stabilized aluminum polyester foil adhered to it. Five CPCs of 2 m length each with half acceptance angle of 23.5 were used to collect solar radiation. The tubular stills were placed at the focus of the CPC collector. Black painted rectangular basins with water were placed inside the concentric tubes. The annulus of concentric tube receivers were provided with inlets and exits for raw water supply to basin, cooling water circulation through the annulus space and draining the distillate. A sponge unit can be used to remove the salt content in the basin of the solar still. The lack of cleaning will definitely affect the overall efficiency of the system. Because salt and other dust particles may reduce the absorptivity of the absorber, the productivity decreases due to heat loss factors. The collected salts and other dust particles are packed tightly and disposed into municipality waste wagon. The effective surface area of the still was 2 m  1 m with five sets of tubular still e CPC collectors placed horizontally with a north-south orientation. The cycle interval of the cleaning process will be required once in every ten days of its operation. The following segments in the distillation systems are properly cleaned in every cycle. 1. Tubular top cover, absorber, inlet tube and outlet tube. 2. Single slope solar still's top cover, inner cover, absorber and water collecting segment. 3. Pyramid solar still's top cover, inner cover, absorber, and water collecting segment.

Fig. 8. Pictorial view of CPC-TSS experimental setup.

The schematic view of TSS and CTSS are shown in Figs. 3 and 4. The pictorial view of the tubular cover is illustrated in Fig. 5. The pictorial view of CPC-CTSS and rectangular water storage basin is shown in Fig. 6(a, b). A storage tank mounted on a steel structure supplied raw water and cooling water. The cooling water exit was connected to a square pyramid solar still. The pyramid glass cover inclination was 48.9 (Fig. 7(a, b)). The bottom and side walls of the pyramid still were insulated with sawdust. The top cover is placed on the grooves which are provided at all sides for leveling. The total height of solar still from bottom to apex point is 400 mm which makes with an angle of inclination at all sides of glass at 29 with horizon. The area of basin and glass are found as 1 m2 and 1.16 m2 respectively. The

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Fig. 9. Schematic view of CPC-CTSS with single slope solar still.

the lower surface of the inner tube by releasing its latent heat. The condensed water, under gravity, trickled down and was finally collected in a measuring jar through a drainage provided at the lower periphery (see Fig. 13(a, b)). Similarly, the condensate from the pyramid and single slope solar stills also collected using measuring jars from the drains provided on the sides. Fig. 14 facilitates the understanding of the entire process of CPC-CTSS. Technical details of the complete system are provided in Tables 1 and 2. Multi channel K-type thermocouples with digital recording were used to measure basin water temperatures, inner and outer cover temperatures of the tubular still, humid air temperatures inside the stills, pyramid still cover temperature, single slope solar still cover temperature, cooling water temperature and ambient temperature. Graduated measuring jars were used to collect and measure the condensate from the tubular solar still, single slope solar still and pyramid stills. The reliability and error analysis of the various instruments are presented in Table 3. Fig. 10. Pictorial view of CPC-CTSS with single slope solar still.

water collection segment was placed at the desired position for collecting the evaporated water and it is of dimensions 0.66 m  0.038 m  0.015 m. The water storage single slope solar still was designed with width and length of 0.50 m. The bottom and sides of the still were coated with black paint for good absorption of solar radiation. An inlet pipe of 13 mm diameter was used for pouring water into the still. The outer box for the still was made up of wood of thickness 4 mm with the length and breadth of 0.70 m. The top cover of the still was made up of glass of thickness 4 mm. The pictorial view of CPC-TSS is shown in Fig. 8. The schematic and photographic view of single slope solar still with CPC-CTSS is shown in Figs. 9 and 10. Figs. 11 and 12 show the schematic view and pictorial view of pyramid solar still with CPC-CTSS. 3. Methods The cooling water was supplied from the storage tank through a control valve at the fixed mass flow rate of 10 ml/min. The evaporated water from the inner tray of the tubular still was condensed at

4. Results A novel investigation approach on technology integration (Compound parabolic concentrators, pyramid, and single slope solar stills) was focused for process efficiency augmentation. The basins of the tubular stills receive radiation due to their direct exposure to the sun, focusing of direct radiation from the CPC and some part of reflected diffuse radiation from the CPC. Because the basins are black, the vast majority of this radiation is converted into thermal energy, and this heat flows to the water, air and glass tubes. Hence there is a temperature gradient between different parts of the tubular still as shown in Fig. 15(a, b). When the tubes are not cooled by water, the temperature levels are higher in all the parts (Fig. 15(a)). The maximum water temperature was observed as 95  C, the maximum air temperature was 80  C with maximum outer cover temperature of 54  C. Due to continuous extraction of heat by the cooling water circulated through the annulus space of the receiver tube, the water and inner tube temperatures are comparatively low throughout the day. The cooling water exit temperature is almost equal to inner glass tube temperature. The

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Fig. 11. Schematic view CPC-CTSS with pyramid solar still.

Fig. 12. Photographic view of CPC-CTSS with pyramid solar still.

Fig. 13. (aeb) Mechanism of CPC-TSS.

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Fig. 14. Block diagram of desalination process in the tubular solar still.

Table 2 Technical details of the CPC-CTSS.

Table 1 Design parameters of the concentric tube. Parameters Length Outer diameter Inner diameter Thickness of the tube Gap between the two glass layers Weight Material

Values 2m 0.05 m 0.045 m 2.5 mm 5 mm 7 kg Borosilicate

maximum water temperature, air temperature and outer cover temperature are measured as 77  C, 67  C and 50  C respectively (See Fig. 15(b)). The ambient water was passed through the concentric arrangement maintaining a flow rate at 10 ml/min. Fig. 16 shows the variation of water, air and cover temperature of single slope solar still coupled with CPC-CTSS. The maximum water temperature was observed as 70  C, the maximum air temperature was 61  C with maximum outer cover temperature of 41  C. It was expected that these temperatures would be lower because there is no concentrating system directly coupled. In another configuration, cooling water that has been warmed in the tubular still is fed into pyramid still. This still is also receives radiation and this further

Parameters Tubular cover Length Absorptivity of the glass tube (ac) Reflectivity of the glass tube (rc) Emissivity of the glass tube (εc) Transmittivity of the glass tube (tc) Outer diameter of outer tube Inner diameter of inner tube Thickness of the tubes Weight of glass Material CPC details Aperature area of the CPCs overall Reflectivity of the cover (re) Emissivity of the envelope (εe) Transmissivity of the envelope (te) Base material Reflector foil Half acceptance angle Concentration ratio Absorber Thermal conductivity (Kabsorber) Absorptivity (ar) Length, breadth and height Thickness of the absorber

Values 2m 0.05 0.05 0.85 0.9 0.05 m 0.045 m 2.5 mm 7 kg Borosilicate 2.04 m2 0.03 0.85 0.92 Teak wood Aluminum 23.5 2.5 385 W/m K 0.90 2 m  0.03 m  0.025 m 2 mm

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5.1. Economic analysis

Table 3 Accuracies and error for various measuring instruments. SL. no.

Instrument

Accuracy

Range

% Error

1 2 3 4 5

Pyranometer Digital thermometer Thermocouple Anemometer Measuring jar

±30 W/m2 ±1  C ±1  C ±0.2 m/s ±10 ml

0e1750 W/m2 0e100  C 0e100  C 0.4e30.0 m/s 0e1000 ml

3 2 2 1 2

The cost estimation for various components of the different incarnations of the tubular solar still CPC is given in Table 4. The total cost of the fabricated CPC-CTSS without the water cooling apparatus was approximately $263. With an output of 3.7 L/day, a life of 15 years, an equivalent of 80% of sunny days, and an interest rate of 6%, this is approximately $0.024/L water. With the water

Fig. 15. Variation of basin water, internal air and tubular glass temperatures.

heats the water in the basin. Fig. 17 shows the basin water, pyramid still humid air and cover temperatures at various hours of the day. The maximum water temperature was observed as 80  C, the maximum air temperature was 71  C with maximum outer cover temperature of 51  C. The various parts if both of the stills reach maximum temperature at around 1 pm. The total day production of the various types of stills is given in Fig. 18. The productivity of CPC-TSS and CPC-CTSS is 3710 ml/day and 4960 ml/day, respectively. With the heat extraction technique, CPC-CTSS with single slope solar still and CPC-CTSS with pyramid solar still is 6460 ml/day and 7770 ml/day. 5. Discussion Initially, the experiment started with the CPC-TSS. The cold water flow was found highly beneficial because the water in the basin approaches the boiling point. The evaporated water mixes with heated air in the tubular space. The flow of cold water extracts the heat from the inner tube. Arunkumar et al. [39,40] studied the CPC-assisted tubular solar still with air and cold water flow through the annulus space, to enhance the condensation while the heat extracted was not utilized. The heat extracted from the inner surface of tube was capable of enhancing the production of an additional solar still. In the present work, a single slope or pyramid solar still were connected with the CPC-CTSS. The direct link system can reduce the warm up time of solar stills. These two solar still receive energy from the sun and the CPC-CTSS. The temperature of the system increased quickly and the productivity was found augmented. In the present novel system, the CPC acts as a heat source and delivers waste heat extracted from cover surface to a pyramid or single slope solar still. The output of the pyramid coupled still was found higher than the single slope because the area of pyramid was more than the single slope.

cooling arrangement, cost would be increased by the water tank ($15.18). Since this tank could be filled at the same time the water supply for the CPC absorbers is filled, the added time would be negligible. Therefore, the total cost of the fabricated CPC-TSS with the water cooling apparatus would be approximately $279. With the same assumptions, but an output of 5.0 L/day, this is approximately $0.019/L water. This shows that despite the increased cost of the cooling system, the total cost of water found decreased. The next step was to add the single slope still. This increased the cost to $319 and increased the output to 6.5 L/day. With the same assumptions, this would decrease the cost to $0.017/L water, showing that the investment in the single slope still was worthwhile. The final step was to remove the single slope and add the pyramid still. This increased the cost to $359 and increased the output to 7.8 L/

Fig. 16. Variation of different temperatures for single slope solar still.

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 The pyramid and single slope solar stills are operated with solar energy and waste heat from the CPC-CTSS.  The cold water flow cooled the cover significantly more than the basin water.  The productivity of CPC-TSS and CPC-CTSS were 3710 ml/day and 4960 ml/day, respectively. With the heat extraction technique, the CPC-CTSS with single slope solar still and CPC-CTSS with pyramid solar still is 6460 ml/day and 7770 ml/day, respectively. Since the collector area of the CPC-TSS and CPC-CTSS were 2 m2, the outputs were 1.9 L/m2/day and 2.5 L/m2/day, respectively. The collector areas of the single slope solar still and pyramid solar still were 0.25 m2 and 1 m2, respectively. Therefore, the outputs of the combined systems were noted to be 2.9 L/m2/day and 2.6 L/m2/day, respectively. The total solar irradiation received by a horizontal surface during a clear day was observed to be 7.5 kWh/m2. The CPCTSS and CPC-CTSS had costs of $130/m2 and $140/m2, respectively. The combined single slope solar still and pyramid solar still systems had costs of $140/m2 and $120/m2, respectively. With this information, results can be extrapolated and scaled-up to different size collectors in different locations.

Fig. 17. Variation of different temperatures for pyramid still.

Acknowledgment This project has received funding from Indian Ministry of New and Renewable Energy (MNRE) is acknowledged. Project sanctioned number NREF/TU/2010/001. References

Fig. 18. The experimental productivity for the different configurations.

Table 4 Cost estimation for the components of the solar still. Component

Cost ($)

CPCs (2 m  1 m) Borosilicate glass tubes (10 pieces  2 m) Rectangular basin (5  2 m) Black paint and primers CPC-TSS total cost Water tank CPC-CTSS total cost Singe slope solar still CPC-CTSS plus singe slope total cost Pyramid solar still CPC-CTSS plus pyramid total cost ($)

125.05 116.11 13.40 8.93 263.49 15.18 278.67 40.37 319.04 80.37 359.04

day. With the same assumptions, this would decrease the cost to $0.016/L water. This shows that the pyramid still is was observed even better than the single slope still.

6. Conclusion In this work, an experimental investigation of tubular solar still designs with CPCs was performed. The following conclusions are drawn from the analysis:

[1] H.E.S. Fath, M. El-Samanoudy, K. Fahmy, A. Hassabou, Thermal-economic and comparison between pyramid shaped and single-slope solar still configurations, Desalination 159 (2003) 69e79. [2] Ravishankar Sathyamurthy, Hyacinth J. Kennady, P.K. Nagarajan, Amimul Ahsan, Factors affecting the performance of triangular pyramid solar still, Desalination 344 (2014) 383e390. [3] Yazan Taamneh, Madhar M. Taamneh, Performance of pyramid-shaped solar still: experimental study, Desalination 291 (2012) 65e68. [4] T. Arunkumar, R. Jayaprakash, Amimul Ahsan, A Comparative Experimental Testing in Enhancement of the Efficiency of Pyramid Solar Still and Hemispherical Solar Still, 2, 2012, pp. 1e7. [5] M. Feilizadeh, K. Soltanieh, M.R. Jafarpur, Karimi Estahbanati, A new radiation model for a single-slope solar still, Desalination 262 (2010) 166e173. [6] Sandeep, Sudhir Kumar, V.K. Dwivedi, Experimental study on modified single slope single basin active solar still, Desalination 367 (2015) 69e75. [7] Pankaj K. Srivastava, S.K. Agrawal, Experimental and theoretical analysis of single sloped basin type solar still consisting of multiple low thermal inertia floating porous absorbers, Desalination 113 (2013) 198e205. [8] D.C. Denkenberger, J.M. Pearce, Compound parabolic concentrators for solar water heat pasteurization: numerical simulation, in: Proceedings of the Solar Cookers International Conference in Granada, Spain, July 12e16, 2006. [9] Hasan Mousa, Mousa Abu Arabi, Desalination and hot water production using solar still enhanced by external solar collector, Desalination Water Treat. 51 (2013) 1296e1301. [10] S. Shanmugan, V. Manikandan, K. Shanmugasundaram, B. Janarathanan, J. Chandrasekaran, Energy and exergy analysis of single slope single basin solar still, Int. J. Ambient Energy 33 (2012) 142e151. [11] Ragh Vendra Singh, Shiv Kumar, M.M. Hasan, M. Emran Khan, G.N. Tiwari, Performance of a solar still integrated with evacuated tube collector in natural mode, Desalination 318 (2013) 25e33. [12] Shiv Kumar, Aseem Dubey, G.N. Tiwari, A solar still augmented with an evacuated tube collector in forced mode, Desalination 347 (2014) 15e24. [13] Aneesh Somwanshi, Anil Kumar Tiwari, Performance enhancement of a single basin solar still with flow of water from an air cooler on the cover, Desalination 352 (2014), 92e02. [14] P.U. Suneesh, R. Jayaprakash, T. Arunkumar, David Denkenberger, Effect of air flow on “V” type solar still with cotton gauze cooling, Desalination 337 (2014) 1e5. [15] G.N. Tiwari, V.S.V. Bapeshwara Rao, Transient performance of a single basin solar still with water flowing over the glass cover, Desalination 49 (1984) 231e241. [16] G.N. Tiwari, Garg HP. Maduri, Effect of water flow over the glass cover of a single basin solar still with an intermittent flow of waste hot water in the basin, Energy Convers. Manag. 25 (1985) 315e322.

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[17] S.A. Lawrence, S.P. Gupta, G.N. Tiwari, Effect of heat capacity on the performance of solar still with water flow over the glass cover, Energy Convers. Manag. 30 (1990) 277e285. [18] Bassam AK. Abu-Hijleh, Enhanced solar still performance using water film cooling of the glass cover, Desalination 107 (1996) 235e244. [19] Bassam AK. Abu-Hijleh, Hasan A. Mousa, Water film cooling over the glass cover of solar still including evaporation effects, Energy 22 (1997) 43e47. [20] S. Suneja, G.N. Tiwari, Effect of water flow on internal heat transfer solar still distillation, Energy Convers. Manag. 40 (1999) 509e518. [21] M. Abu-Arabi, Y. Zurigat, H. Al-Hinai, S. Al-Hiddabi, Modeling and performance analysis of a solar still desalination unit with double-glass cover cooling, Desalination 143 (2002) 173e182. [22] G.N. Tiwari, Garg HP. Madhuri, Effect of water flow over the glass cover of a single basin solar still with an intermittent flow of waste hot water in the basin, Energy Convers. Manag. 25 (1985) 315e322. [23] F.F. Tabrizi, M. Dashtbon, H. Moghaddam, K. Razzaghi, Effect of flow rate on internal heat and mass transfer and daily productivity of a weir-type cascade solar still, Desalination 260 (2010) 239e247. [24] A.A. Badran, Inverted trickle solar still: effect of heat recovery, Desalination 133 (2001) 167e173. [25] O.M. Haddad, M.A. Al Nimr, A. Maqableh, Enhanced solar still performance using a radiative cooling system, Renew. Energy 21 (2000) 459e469. ndez, Cavity geometry influence on mass flow [26] E. Rubio, M.A. Porta, J.L. Ferna rate for single and double slope solar stills, Appl. Therm. Eng. 20 (2000) 1105e1111. [27] H.E.S. Fath, Solar distillation; a promising alternative for water provision with free energy, simple technology and a clean environment, Desalination 116 (1998) 45e46. [28] Aybar HS¸, Mathematical modeling of an inclined solar water distillation system, Desalination 190 (2006) 63e70. [29] V. Bapeshwar, G.N. Tiwari, Effect of water flow over the glass on the performance of a solar still coupled with a flat plate collector, Int. J. Sol. Energy 2 (1984) 277e288. [30] B. Janarthanan, J. Chandrasekaran, S. Kumar, Performance of floating cum titled-wick type solar still with the effect of flowing over the glass cover, Desalination 190 (2006) 51e52. [31] G.N. Tiwari, V.S.V. Bapeshwara Roa, Transient performance of a single basin solar still with water flowing over the glass cover, Desalination 49 (1984) 231e241. lu, U. Atikol, An experimental study on an inclined solar [32] H.S¸. Aybar, F. Egeliog water distillation system, Desalination 180 (2005) 285e289. [33] M. Abu-Arabi, Y. Zurigat, Year-around comparative study of three types of solar distillation system, Desalination 175 (2005) 131e143. [34] Nader Rahbar, Javad Abolfazli Esfahani, Ehsan Fotouhi-Bafghi, Estimation of convective heat transfer coefficient and water-productivity in a tubular solar still e CFD simulation and theoretical analysis, Sol. Energy 113 (2015) 313e323. [35] Zhili Chen, Yang Yao, Zihang Zheng, Hongfei Zheng, Yi Yang, Li'an Hou, Guanyi Chen, Analysis of the characteristics of heat and mass transfer of a three-effect tubular solar still and experimental research, Desalination 330 (2013) 42e48. [36] Amimul Ahsan, Teruyuki Fukuhara, Mass and heat transfer model of tubular solar still, Sol. Energy 84 (2010) 1147e1156. [37] Amimul Ahsan, Monzur Imteaz, Ataur Rahman, Badronnisa Yusuf, T. Fukuhara, Design, fabrication and performance analysis of an improved solar still, Desalination 292 (2012) 105e112. [38] Amimul Ahsan, Kh M. Shafiul Islam, Teruyuki Fukuhara, Abdul Halim Ghazali, Experimental study on evaporation, condensation and production of a new tubular solar still, Desalination 260 (2010) 172e179. [39] T. Arunkumar, R. Jayaprakash, Amimul Ahsan, D. Denkenberger, M.S. Okundamiya, Effect of water and air flow on concentric tubular solar water desalting system, Appl. Energy 103 (2013) 109e115.

[40] Arunkumar Thirugnanasambantham, Jayaprakash Rajan, Amimul Ahsan, Vinothkumar Kandasamy, Effect of air flow on tubular solar still efficiency, J. Environ. Health Sci. Eng. 10 (31) (2013), http://dx.doi.org/10.1186/17352746-10-31. [41] Ayman GM. Ibrahim, Salman E. Elshamarka, Performance study of a modified basin type solar still, Sol. Energy 118 (2015) 397e409. [42] Ahmed Rahmani, Abdelouahab Boutriaa, Amar Hadef, An experimental approach to improve the basin type solar still using an integrated natural circulation loop, Energy Convers. Manag. 93 (2015) 298e308. [43] Ravishankar Sathyamurthy, D.G. Harris Samuel, P.K. Nagarajan, S.A. El-Agouz, Review of different solar still for augmenting fresh water yield, J. Environ. Sci. Technol. 8 (6) (2015) 244e265. [44] P.K. Nagarajan, D. Vijayakumar, V. Paulson, R.K. Chitharthan, Yoga Narashimulu, Ravishankar Sathyamurthy, Performance evaluation of triangular pyramid solar still for enhancing productivity of fresh water, Res. J. Pharm. Biol. Chem. Sci. 5 (2) (2014) 764e771. [45] S. Ravishankara, P.K. Nagarajan, D. Vijayakumar, M.K. Jawahar, Phase change material on augmentation of fresh water production using pyramid solar still, Int. J. Renew. Energy Dev. 2 (3) (2013) 115. [46] Sathyamurthy Ravishankar, S.A. El-Agouz, Vijayakumar Dharmaraj, Experimental analysis of a portable solar still with evaporation and condensation chambers, Desalination 367 (2015) 180e185. [47] Sathyamurthy Ravishankar, P.K. Nagarajan, J. Subramani, D. Vijayakumar, K. Mohammed Ashraf Ali, Effect of water mass on triangular pyramid solar still using phase change material as storage medium, Energy Proced. 61 (2014) 2224e2228. [48] Sathyamurthy Ravishankar, P.K. Nagarajan, Hyacinth Kennady, T.S. Ravikumar, V. Paulson, Amimul Ahsan, Enhancing the heat transfer of triangular pyramid solar still using phase change material as storage material, Front. Heat Mass Transf. (FHMT) 5 (1) (2014). [49] Sathyamurthy Ravishankar, P.K. Nagarajan, S.A. El-Agouz, V. Jaiganesh, P. Sathish Khanna, Experimental investigation on a semi-circular troughabsorber solar still with baffles for fresh water production, Energy Convers. Manag. 97 (2015) 235e242. [50] Sathyamurthy Ravishankar, D.G. Harris Samuel, P.K. Nagarajan, V. Jaiganesh, Experimental investigation of a semi circular trough solar water heater, Appl. Sol. Energy 51 (2) (2015) 94e98. [51] T. Arunkumar, David Denkenberger, R. Velraj, Ravishankar Sathyamurthy, Hiroshi Tanaka, K. Vinothkumar, Experimental study on a parabolic concentrator assisted solar desalting system, Energy Convers. Manag. 105 (2015) 665e674. [52] Sathyamurthy Ravishankar, D.G. Harris Samuel, P.K. Nagarajan, Theoretical analysis of inclined solar still with baffle plates for improving the fresh water yield, Process Saf. Environ. Prot. (2015), http://dx.doi.org/10.1016/ j.psep.2015.08.010. [53] P.K. Nagarajan, J. Subramani, S. Suyambazhahan, Ravishankar Sathyamurthy, Nanofluids for solar collector applications: a review, Energy Proced. 61 (2014) 2416e2434. [54] T Arunkumar, R. Velraj, A. Ahsan, Abdul Jabbar N. Khalifa, Shams Shahriar, D. Denkenberger, Sathyamurthy Ravishankar, Effect of parabolic solar energy collectors for water distillation, Desalin. Water Treat (2015), http://dx.doi.org/ 10.1080/19443994.2015.1119746. [55] T. Arunkumar, R. Velraj, D. Denkenberger, Sathyamurthy Ravishankar, K. Vinothkumar, K. Porkumaran, Ahsan Amimul, Effect of heat removal on tubular solar desalting system, Desalination 379 (2016) 24e33. [56] P.K. Nagarajan, D. Vijayakumar, V Paulson, R.K. Chitharthan, Yoga Narashimulu, Ravishankar Sathyamurthy, Theoretical characterization of ethylene glycol nano fluid for automobiles, RJPBCS 5 (2) (2014) 772e777. [57] D.G. Harris Samuel., P.K. Nagarajan., Arunkumar. T., E. Kannan., Ravishankar Sathyamurthy, Enhancing the solar still yield by increasing the surface area of water-a review, Environmental progress and Sustainable Energy, Article in press, 2015, 10.1002/ep.12280