3rd International Conference on Engineering & Gaza Reconstruction DESIGN AND MANUFACTURING OF A SOLAR WATER DISTILLATION UNIT

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1 Abstract DESIGN AND MANUFACTURING OF A SOLAR WATER DISTILLATION UNIT Juma Yousuf Alaydi Assistant Professor, Industrial Engineering Department, IUG, Gaza During the ware on Gaza there was real shortage of drinking water in the houses due to shortage of electrical supply, which has great affect on the human life especially on children. This paper presents one real application of solar energy. The project aims to produce distilled water for houses without contaminants. A parabolic dish unit is built to collect the solar energy, and concentrate it in the focus point of the parabolic dish. In the focus point, there is an evaporation chamber where the raw water evaporates. The evaporated water flows through pipes to condenser; where it turns into water. Then the fresh water is collected in a small tank. The unit tracks the sun using mechanical system controlled electrically. Results of the tested water is found to be with average level of Chloride of ppm, TDS of ppm and EC of MS/cm. Keywords: Distilled water, solar energy, sun collector. 1. Introduction Water treatment using solar energy has many forms. This project studies the solar water distillation as one form of water treatment to get more acceptable fresh water for drinking, irrigation, scientific uses, industrial uses and other uses. Distillation process can reduce contamination level to an acceptable level to fit the desired use. It depends on the heat generated from the solar energy to enable the water to reach the boiling degree then to transfer its vapor to a condenser to get the distilled water. Gaza strip suffers two major problems of water, the scarcity and low quality of water. In Gaza strip, the main source of water is the coastal aquifer which lies along the Mediterranean Sea and recharged from Wadi Gaza that runs from Hebron Mountains. The sustainable yield of the aquifer is about 55 million m 3 /year, the sustainable amount is the amount of water that can be extracted from the aquifer without causing either the water level or the water quality to be deteriorated. Actually, the people of Gaza consumes about 120 million m 3 /year. So, the over pumping of the coastal aquifer for some times has resulted in stripping out its sustainable amount by 65 million m 3. In Gaza strip there are about 4000 wells for domestic and agriculture purposes, it can save about 120 million and another 5 million received from Israeli Water Company (Mekerot) [1], [2]. The other problem is the low quality of water in Gaza strip. The two major quality problem causes in Gaza strip are the high level of chloride and the high level of nitrate. The chloride contaminants come from different sources; one of them is a direct result of the coastal aquifer over-pumping. As a result of over-pumping, the water table falls causing the salty water of Mediterranean sea to infiltrate to the ground water. Consequently, the water in many parts of the strip is saline that it may damage the yield crop and will not be suitable for domestic uses.

2 The other quality problem reason is the high level of nitrate. The main source of nitrate is the organic and artificial fertilizers used for agriculture and the domestic sewage. The world health organization (WHO) standard for NO3 is 45 mg/liter and the Palestinian one is 70 mg/liter. But the actual level of NO3 is many times larger than this value. The area geology and climate causes the impurities to interfere to the groundwater aquifer system from the surface easily. The main contaminants are organic fertilizers and wastewater followed by sewage sludge and artificial fertilizers. To build solar water treatment units, sufficient amount of solar energy must be available. Gaza strip has a relatively high radiation through the year. The amount of radiation varies from time to time in one day and from season to season. The hours of sunshine through the year are approximately 2861 hour. The daily average solar radiation on a horizontal surface is about 600W/m 2. Solar insulation has an annual average of 5.4 kwh/m 2.day, the daily insolation is watt/m 2 [3]. The relative high level of solar radiation and the existence of such water problems guides to thinking in using this free and available energy to try to solve problems of water; especially the problem of water low quality. So, this project comes as a trial to share in solving the problem of water. Using the solar energy, we will get fresh water. The concept is to collect the solar radiation as possible as in a focus point, then to transit the raw water to a chamber fixed in the focus point where the process of evaporation occurs. The vapor then transfers through pipes to a condenser to be turned into drops of water. It is a solar distillation. Distillation is defined as: a process in which a liquid or vapor mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat. Distillation is based on the fact that the vapor of a boiling mixture will be richer in the components that have lower boiling points. Therefore, when this vapor is cooled and condensed, the condensate will contain more volatile components. At the same time, the original mixture will contain more of the less volatile material. 2. Building The Unit 2.1. Components of the Unit: Parabolic Dish Collector The parabolic collector is the main part of the unit. It is used to collect the solar energy and concentrate it in a focus point. Parabolic dish collector is similar in appearance to a large satellite dish, the dish covered by mirrors to reflect the solar radiation to the focus point. The most important feature of the parabolic dish is the ability to reflect the solar radiation in a defined point called focus point. The diameter of the dish is 145 cm with measured depth of 22 cm and calculated focal length of 59 cm. To measure the depth, a ruler and a wooden bar are used. The bar is fixed across the dish and ruler measure the depth vertically from the bar to the vertex of the dish. The focal length (f) is calculated by substitution in equation (1) f = (D * D) / (16 * c) (1) Where c= depth, D = diameter, By substitution in the equations for D=145 cm, and c=22 cm the value of f=59 cm.

3 The aperture area of the collector is the area of a circle with a diameter of 145 cm; it is the projected area of the parabolic dish. Then, the area is 1.65 m 2 Fig. 1 The parabolic Dish The reflector surface that was used to reflect the solar radiation was mirror layer, the layer's thickness is 4 millimeter, and the sheets are divided into rectangular bars of 2cm width and 100 cm length then the rectangular bars are divided into 2*2cm square pieces, these small pieces give a chance to cover all surface of the dish and this result in a higher degree of radiations reflection as well as higher efficiency Sun Tracker As the unit depends on the sun as a main source of operating, it is necessary to track the sun to collect the most possible amount of energy which is needed for the unit to operate. Tracking the sun will increase the efficiency and the productivity of the unit. The sun tracker used in this unit is an axial tracker. The unit is fixed in a position between the south and the north, and the sun tracker enables it to move from the east to the west Evaporation Chamber Fig.2. The Evaporation Chamber

4 The evaporation chamber is fixed in the focus point of the dish; where the reflected radiations are concentrated. In the evaporation chamber the process of converting the raw water into vapor occurs. The raw water enters the chamber through an inlet at the bottom of the chamber. The chamber is cylindrical made of stainless steel with a diameter of 20 cm and a height of 30 cm. The thickness of the chamber surface is 1 mm to achieve a quick and more efficient transfer of energy from solar radiation to the chamber. The type of chamber material selected to withstand the high temperature in the focus point, avoid poison corrosion occurrence due to the reaction between raw water full of salts and the chamber material and to maintain it easily. The chamber is covered by a rock wool to prevent the vapor to be condensed into water in the chamber itself and to keep the temperature inside the chamber high. For cleaning purposes, the surface of the chamber at the bottom is inclined with a small inclination angel and an outlet is opened to remove the cumulative salts. The bottom surface of the evaporation chamber on which the reflected radiation falls is painted with a dull black paint. This will improve the efficiency of the unit; by increasing the ability of absorbance of the chamber surface and decreasing the amount of re-reflected radiation from the surface of the evaporation chamber. The chamber opened from the above to allow the water vapor to escape from it. The outlet is of diameter 5 cm. It is connected with U- shape tube to facilitate the process of water vapor escape from the chamber. The U-shape tube is connected to a one inch tube through which the vapor will enter the pipes which are connected to the condenser Water Level Sensor The amount of water in the evaporation chamber is determined by the water level sensor. The high degree of temperature was one obstacle in selecting the type of the sensor. The sensor must not be deteriorated by the high temperature. The magnetic sensors are not effective in such purposes, because the effectiveness of the magnet will be decreased by the high degree of temperature along the time. An electrical sensor is used in this chamber. The sensor consists of two coils positive and negative one. The sensor will not work until the circuit of the coils is closed. This will occur when the two coils are in the water simultaneously. Thus, the amount of water required to feed the chamber is determined, then the height on which the sensor will fixed is determined. When the water level reaches that height the pump will stop to pump more water. The height of the electric sensor is fixed at 13 cm to allow for a maximum of 4 liters to be pumped to the evaporation chamber Other components: Two tanks are used for fresh and raw water. Pipes: pipes are divided into two stages, the first is the upper stage that passes above the dish and this stage is made of stainless steel, and second is the stage passes under the dish and is made of plastic. This division became as a result of high temperature above the dish which causes the plastic pipes to melt also the cost is another reason. Condenser: After the water vapor get out the evaporation chamber and flow through the pipes, it will enter the condenser. In the long path of the condenser the vapor transform into water. The condenser is submerged in the tank of the raw water. The resultant heat will be used in heating the raw water before entering the system.

5 2.2. Description of The Process The tank of the raw water is filled, and then the raw water is pumped by the pump through the pipes to the evaporation chamber, the amount of water in the evaporation chamber is determined by the water level sensor. At that time, the radiation of the sun is collected and reflected to the focus point where the chamber is fixed. In the evaporation chamber the process of evaporation occurs. The water is transformed into vapor under the high degrees of temperature and pressure. The vapor escaped from the chamber from one outlet to the pipes through which it will begin to condense. Through the pipes, the vapor will transit to the condenser. In the condenser vapor will be transformed into water. Then, water will collect in the fresh water tank. 3. Results and Analysis Results were recorded for two weeks started in the middle of June, Table A1 and Fig. 1 show the amount of water per day. Then sample of every day was tested to determine the level of Chloride (CL), Electrical Connection (EC) and Total Dissolved Solids (TDS). Table A2 shows the level of the components, Fig. 2, 4.3 and 4 shows the level of TDS, CL and EC respectively in the tested water and illustrates the corresponding standard value [4] Amount of Water Tha amount of water per day Amount of water(l) Day Fig.3: Results of amount of water per day 3.2.Quality of Water Level of TDS Level(mg/L) Day TDS in tested water TDS in Standard Fig.4: Level of TDS in distilled water

6 Level of Cl Level(mg/L) Day Cl in tested water Cl in Standard Fig.5: Level of Cl in distilled water Level of EC Level (micro s/cm) Day EC in tested water EC in Standard 3.3. Hypotheses Testing Fig.6: Level of EC in distilled water Hypotheses testing were used to prove that the amount of the water produced by the unit is larger than or equal the amount of the water produced by the flat collector. Also, it was used to prove that the percent of the components of the distilled water is within the standard or not. The samples of the water that mentioned in Table A1 and Table A2 were entered in Minitab and the samples were tested using One-Sample T-test. Hypothesis Related to the Amount of the Water Hypothesis #1: To prove that the amount of the water produced by the unit is larger than or equal that amount produced by the flat collector. The flat collector usually produces about 3 to 4 liter per day for the same area of the designed dish (1.6m 2 ). The mathematical representation of this hypothesis is as follows: H O : µ = 4 (P.O.I) (2) H 1 : µ 4 (Claim) (3)

7 Table 3: Results of the amount of water. One-Sample T: Amount of Water Test of mu = 4 vs. > 4 Variable N Mean St Dev Amount of water SE Mean % lower bound T 2.42 P Table 3 represents the results of the test and from the table, it was concluded that at significance level (α) equals 0.05 and according to the p-value, there is no enough evidence to accept null hypothesis. So the alternative hypothesis is accepted. Which means that the amount of water produced from the device is greater than 4 liter Hypotheses related to the components of the water Hypothesis # 1: To prove whether the chloride in the water that produced by the unit is within the standard or not. The mathematical representation of this hypothesis is as follows: H O : µ = 250 (P.O.I) (4) H 1 : µ 250 (Claim) (5) Table 4 represents the results of the test and from the table, it was concluded that at significance level (α) equals 0.05 and according to the p-value, there is no enough evidence to accept null hypothesis. So the alternative hypothesis is accepted. This means that the CL is less than 250 [4]. Table 4: Results of the percent of chloride hypothesis test One-Sample T: Cl Test of mu = 250 vs. < 250 Variable N Mean St Dev Cl SE Mean % upper bound T P Hypothesis # 2: To prove that the TDS in the water that produced by the unit is within the standard or not.the mathematical representation of the hypothesis is as follows: H O : µ = 1000 (P.O.I) (6) H 1 : µ 1000 (Claim) (7) Table 5 represents the results of the test and from the table, it was concluded that at significance level (α) equals 0.05 and according to the p-value, there is no enough evidence to accept null hypothesis. So, the alternative hypothesis is accepted. This means that the TDS is less than 1000 [4]. Table 5: Results of the level of TDS hypothesis test

8 One-Sample T: TDS Test of mu = 1000 vs. < 1000 Variable N Mean St Dev TDS SE Mean % upper bound T P Hypothesis # 3: To prove that the EC in the water that produced by the unit is within the standard or not. The mathematical representation of the hypothesis is as follows: H O : µ = 1500 (P.O.I) (8) H 1 : µ 1500 (Claim) (9) Table 6 represents the results of the test and from the table, it was concluded that at significance level (α) equals 0.05 and according to the p-value, there is no enough evidence to accept null hypothesis. So the alternative hypothesis is accepted. This means that the EC is less than 1500 [4]. Table 6: Results of the level of EC hypothesis testing. One-Sample T: EC Test of mu = 1500 vs. < 1500 Variable N Mean St Dev EC SE Mean % upper bound T P Conclusions The project of this paper is one of the applications of solar technology. The project succeeded to collect the solar radiation, evaporate the water, condense the steam and produce distilled water. The concept of the unit working is that the parabolic dish covered with mirrors to reflect the solar radiation to the focal point where chamber is fixed. With area of the parabolic collector is 1.65 m 2, high evaporation process helps to produce 5 liters per day approximately. The water quality produced is very suitable because the evaporation method is used. It can be used for drinking after mixing, pharmaceuticals, laboratories, industry and micro irrigation. And that is shown in the result chapter by using the hypotheses test which assures that the levels of CL, TDS and EC are within the standards. In addition to produce water with high quality, the operation of the unit is very easy, it does not need a complex maintenance and depends on solar energy as input for the unit that makes the operation cost very low.

9 Appendix Table A1: Amount of water per day Date 15/6 16/6 17/6 18/6 20/6 21/6 22/6 23/6 24/6 25/6 27/6 28/6 29/6 30/6 1/7 The amount of water (Liter) Table A2: Level of components in water that produced by the unit Day Chloride (mg/l) TDS (mg/l) EC (Ms/cm)

10 Reference [1] Renewable Energy Policy Network for the 21 st Century, REN21, (2007), Renewable 2007 Global Status Report. [2] United Nations Environment Programme, (2007), Global Trends in Sustainable Energy Investment [3] Imad A. Khatib. (2008). Harnessing Solar Energy to Meet Energy Needs for Water Desalination in Gaza Strip, Journal of Applied Sciences in Environmental Sanitation, Vol.3, No.3, PP [4] Palestinian Health Ministry. Public Health Ministry. Retrieved March 18 th, 2009