Effective design of solar still by using phase change material.
In many countries water scarcity is the major problem because of its increasing population and industries which leads to severe disease and death. Desalination is a process which produces fresh water from saline or brackish water. The desalination can be done in various methods such as reverse osmosis, multi flash method and solar still. Amond these solar still desalination is the best method which is working based on renewable energy a source which is not harming the environment and freely available energy source. The Solar still is a simple device to produce fresh water from the saline or dirty water. Several researchers are involved in developing the efficiency of the solar still by changing various parameters. A.A.El Sebaii et al  analyzed that the productivity of active single basin solar still is improved with the presence of phase change material. The increased of mass of phase change material is the main parameter influencing the performance of solar still during summer climatic conditions. The daily productivity of solar still with 3.3cm of stearic acid is increased to 9.005 kg/m2. A.A.El Sebaii et al  investigated the performance of active single basin solar still with sensible heat storage medium is influenced the fresh water productivity. The sand is taken as sensible heat storage medium and the productivity has increased to 4.005 kg/m2 which is 37.8% higher than conventional solar still. S.A.El Agouz et al  has investigated the effect of mass of water, water film thickness, water film velocity and air velocity. The result showed that the inclined solar still with make-up water has increased productivity up to 57.2% compared to conventional solar still. As like the water film thickness, velocity and wind velocity plays an important role in enhancing the performance of solar still. Velmurugan et al  analyzed the performance of stepped solar still with fins and sponges. The theoretical and experimental investigations were carried out with fins, sponges and combinations of both. The result revealed that the average daily water production with combinations of fins and sponges has 80% higher two other solar stills. Aneesh somwanshi et al  has investigated the efficiency enhancement of single basin solar still with makeup water flowing over the glass cover. The yield has increased between 41.3% and 56.5%. The investigation was carried out in four different climatic conditions in India. Therefore the distillate output is higher in hot and dry places and least in warm and humid climatic conditions. The result showed that mass flow rater of water over the glass cover with 0.075 kg/s provides higher yield than other and it is cost effective in hot and dry climatic plains. T.Arunkumar et al  experimentally investigated the distillate yield of concentrator coupled solar still with phase change material. The experiment was studied with and without the effect of phase change material. The result showed that the distillate output is higher with presence of phase change material and increased up to 26% higher than conventional solar still. Omar Ansari et al  investigated about the desalination of brackish water using passive solar still with three different phase change materials. The paraffin with three different melting temperatures has selected as energy storage materials in Morocco climatic conditions. The result showed that the paraffin with high melting temperature stores energy for long time period and provides better result. It was concluded that the section of phase change material is mainly depends on the maximum of brackish water temperature that can be reached by the brackish water in the basin. M.Zerroual et al  has investigated about the scarcity of water in Algeria is expected to double in next thirty years. The demand has to overcome especially in Saharan region during low rainfall periods. For this two experiments are conducted they are cooled by flowing water on north glass cover throughout the run and by an intermittent shading of the north glass cover. The daily average output has increased to 11.82% with flow of cooling water over north glass cover and increased only 2.94% with intermittent shading of north glass cover. Atul Sharma et al  has studied about the development of phase change materials for low temperature energy storage applications using binary mixtures of commercial grade acids such as Lauric acid (LA), Myristic acid (MA), Stearic acid (SA) and Palmitic acid (PA). The combination of PA-SA gives better result for lower temperature applications in melting temperature range of 34-42[degrees]C. MA-PA binary mixing shows better result for higher temperature applications with melting range of 56-58[degrees]C. K.Swetha et al  has investigated the performance of single slope solar still using phase change material. The performance of single slope solar still has compared with Lauric acid and sand as heat energy storage medium under the basin liner and is analyzed with numerical calculations and energy balance equations. The result shows that the still with lauric acid as energy storage medium has increased the productivity up to 36% and using sand the productivity increased up to 13%. In this paper suggested that the effect of mass obtains higher distillate output. Saravanan.M et al  was deal with the thermal performance of single basin solar still with and without latent heat storage medium. Here the paraffin wax was selected as heat energy storage system. The total productivity of solar still with and without latent heat energy storage medium is obtained as 4.85 kg/m2 and 5.14 kg/m2 respectively. Kantesh.D.C  has defined the effect of phase change material mainly influences the productivity of double slope solar still. With presence of PCM (Bitumen) and without PCM the efficiency was increased about 27.00% and 25.19% respectively. Naga sarada somanchi et al  have investigated the solar still with different depth of water and also the performance of solar still with three different phase change materials. The result shows that magnesium sulfate heptahydrate provides higher productivity than sodium sulphate and titanium oxide. Miqdam.T.Chaichan et al  have discussed the extracted storage capacity of phase change materials with the help of solar tracking system. The working time of the system is increased to 3 hours with the presence of paraffin wax as PCM and solar tracking system. The heating efficiency concentrating efficiency and aslo the productivity is increased by about 64.07%, 112.87% and 307.54% respectively. Hitesh.N.Panchal  has investigated the augmentation of distillate output of double basin solar still with vaccum tubes in Gujarat climatic conditions. The experimental result showed that the daily output of double basin solar still with vacuum tubes and vacuum tubes with black gravel increases the daily output about 56% and 65% respectively. P.Prakash et al  conducted the study about the parameters affecting the performance of solar still. The study has considered about various operational parameters such as minimum water depth, area of absorption, glass cover temperature, inlet water temperature and also study carried out about some special design of solar still. Among these parameters the temperature difference between glass cover and basin water plays a virtual role in affecting the productivity of solar still.
In this work two solar stills were fabricated one is kept as reference and another one is integrated with phase change materials. Here the phase change materials are used to store the heat energy during high intensity period and release the energy when the material changes from liquid to solid state. Hence it produces the fresh water production even after sunset.
A. Conventional solar still:
A solar still is a low-tech way of distilling water, powered by the heat from the sun. In the conventional solar still, saline water is stored in the basin of still, where it is evaporated by means of the sunlight through clear glass. The pure water vapor condenses inside the glass surface and the pure water is collected in the beaker. The various factors affecting the productivity of solar still are solar intensity, wind velocity, ambient temperature, water glass temperature difference, and free surface area of water, absorber plate area, temperature of inlet water, glass angle and depth of water. The solar intensity, wind velocity, ambient temperature cannot be controlled as they are metrological parameters. Whereas the remaining parameters, free surface area of water, absorber plate area, temperature of inlet water, glass angle and depth of water can be varied to enhance the productivity of the solar stills. By considering the various factors affecting the productivity of the solar still, various modifications are being made to enhance the productivity of the solar still.
B. Solar still with phase change material:
In the experimental setup of the solar still with phase change material is shown below in the figure-1. And hence here the solar still with the phase change material is same as the conventional solar still, the difference is here another tray is used below the basin water tray of the solar still and hence the phase change material (PCM) is kept inside the second tray. Here palmitic acid is taken as phase change material and its thermo physical properties are shown below.
[FIGURE 1 OMITTED]
RESULT AND DISCUSSION
[FIGURE 2 OMITTED]
Fig 2 illuminates the variation of solar radiation with respect to the time period. The solar radiation is the main parameter affecting the productivity of solar still. The solar radiation attains the maximum point at 10:00 am to 02:00 pm.
[FIGURE 3 OMITTED]
In figure 3 illustrates the relationship between time and fresh water productivity. From the figure the productivity of fresh water is high at 01:30:00 pm and production time of fresh water is increased for three hours even after sunset. And suggested that the increase in mass of phase change material will further more increase the fresh water production for more time period.
[FIGURE 4 OMITTED]
Fig 4 shows the relationship between the fresh water production and solar intensity. From the graph that the productivity of fresh water is maximum during high solar intensity period and the production of fresh water is continued even after sunset about three hours. And it reveals that the importance of phase change material in desalination process.
[FIGURE 5 OMITTED]
Fig 5 shows the relationship between the productivity with and without phase change material. The productivity with phase change material is higher than the productivity without phase change material. And it shows that the production of fresh water continues even after sunset.
The performance of single slope solar still is influenced by various factors such as minimum depth of water, area of absorption, wind velocity and temperature difference between glass cover and basin water. Among these the selection of phase change material plays a vital role in performance of solar still. Here the production of solar still is compared with and without phase change material. The result shows that the average daily production of fresh water with and with phase change material is obtained as 1670 ml/day and 925 ml/day.
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[7.] Omar Ansari, Mohamed Asbik, 2013. "Dealination of the brackish water using a passive solar still with a heat energy storage system," Desalination, 324: 10-20.
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(1) B. Arockia Jenis, (2) I. Daniel Lawrence, (3) S. Jayabal
(1) P.G Scholar, Dept of Mechanical Engineering, Anna University Regional Campus, Madurai, India.
(2) Faculty, Dept of Mechanical Engineering, Anna University Regional Campus, Madurai, India.
(3) Faculty, Dept of Mechanical Engineering, A.C College of Emgg & Tech, Karaikudi, India.
Received 25 January 2016; Accepted 28 April 2016; Available 5 May 2016
Address For Correspondence:
B. Arockia Jenis, P.G Scholar, Dept of Mechanical Engineering, Anna University Regional Campus, Madurai, India.
Table 1: Thermophsical Properties Of Palmitic Acid SI.NO Thermo Phsical Properties Of Palmitic Acid Properties Values 1 Melting temperature 55[degrees]C 2 Thermal conductivity 0.16 W/mk 3 Specifi heat 2.0 KJ/KG-K 4 Latent heat of fusion 163 KJ/KG 5 Density 942 Kg/[m.sup.3]
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|Author:||Jenis, B. Arockia; Lawrence, I. Daniel; Jayabal, S.|
|Publication:||Advances in Natural and Applied Sciences|
|Date:||May 15, 2016|
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