Solar Desalination With Trough Design

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solar desalination with trough design. Final project of mechanical engineering in university. it will help you in your projects.

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Solar Desalination With Trough Design

  1. 1. Higher College Of Technology January 19 2012By Solar DesalinationSager Al Musaabi Project for Subject MECH N449Khalid Alhosani Dr. MongiWaleed AlYafaie
  2. 2. Solar Desalination Project 2012Abstract ......................................................................................................................................................... 4The results found from the calculations ....................................................................................................... 5Introduction .................................................................................................................................................. 6Type of desalination method ........................................................................................................................ 7 Multiple effect solar stills.......................................................................................................................... 7 Humidification–dehumidification systems ............................................................................................... 7 Economics ................................................................................................................................................. 8Illustration of solar desalination design ........................................................................................................ 8Process flow diagram .................................................................................................................................. 12Project proposal .......................................................................................................................................... 17The results found from the calculations ..................................................................................................... 18Literature Review ........................................................................................................................................ 20 Desalination: .......................................................................................................................................... 21 Reverse osmosis(RO): ............................................................................................................................. 21 Process: ............................................................................................................................................... 22 Industrial Applications ....................................................................................................................... 23 Multi-stage flash distillation (MSF): ....................................................................................................... 24 Process: ............................................................................................................................................... 24 Industrial Applications ........................................................................................................................ 25 Solar thermal energy: ............................................................................................................................. 25 Parabolic Trough: ................................................................................................................................ 25 Solar Power tower: ............................................................................................................................. 26 Dish Technology: ................................................................................................................................. 26 Solar Desalination: .............................................................................................................................. 27 Technology .............................................................................................................................................. 28Project Time line ......................................................................................................................................... 28Calculation .................................................................................................................................................. 29 2 Compare the process with and without vacuum pump ......................................................................... 32 Calculated area of reflector: ................................................................................................................... 34 MECH N449 | HCT, Abu Dhabi
  3. 3. Solar Desalination Project 2012 Calculate the mass flow rate of circulated water ................................................................................... 34 Calculation of caused by reflector. .................................................................................................... 35 Calculation with respect to area of reflector ...................................................................................... 35 Calculation with respect to fluid type. .................................................................................................... 39 Calculation on the desalination side. ...................................................................................................... 39 The effect of attaching vacuum pump to desalination unit ................................................................... 42 Calculation for parabolic dish ................................................................................................................. 44Conclusion ................................................................................................................................................... 47 Ease of safe operation ............................................................................................................................ 47 Equipment and Clothing ..................................................................................................................... 47 Surrounding Area ................................................................................................................................ 47 Starting a Machine .............................................................................................................................. 47Conclusion ................................................................................................................................................... 47 Comments on the project: ...................................................................................................................... 48 Problems encountered ........................................................................................................................... 48 Recommendations .................................................................................................................................. 49Appendix ..................................................................................................................................................... 49 SOLAR RADIATION REACHING THE EARTH SURFACE .............................................................................. 49 Thermal Conductivity .............................................................................................................................. 52 Emissivity................................................................................................................................................. 53Project main part ........................................................................................................................................ 56References: ................................................................................................................................................. 58 3 MECH N449 | HCT, Abu Dhabi
  4. 4. Solar Desalination Project 2012AbstractThe main aim of this project is to treated the salty water from the sea or from Groundwater wellsand make it drinkable or usable for aggregation in the united Arabic emirates .Thanks to thelarge scale of solar heat available in the region where the UAE located, the utilization of thatsource will be investigated in the project. The concept of a solar distillation system uses lowgrade heat. The system utilizes vacuum pump or it can use the gravity forces to create vacuumunder which water can be evaporated at lower temperatures than conventional techniques, Thiswould allow the use of low grade heat sources, such as parabolic solar collectors or eveninexpensive flat plate. A good feature of the system is that the evaporation and condensationtake place at same locations without using another heat source. That helps us in making compactand portable design. The system consists of solar collectors, an evaporator, and pumps to supplythe salty water and withdraw the concentrated brine and also to create a vacuum in theevaporator. The evaporator is connected to the condenser where the produced vapor is condensedand collected as the product. In the use of gravity force to create vacuum both, the evaporatorand condenser are placed at a height of about 10 m (the height required to have a water columnthat would balance the atmospheric pressure) from the ground level. The evaporator is connectedto the salty water supply, and concentrated brine tanks, and the condenser is connected to thefresh water tank. All tanks are kept at the ground level. On the other hand, vacuum pump can beattached to the evaporator in case of availability of electricity source and space.In this research the concept of the system will be examine to see the effects of various operating 4conditions: size of the evaporator, capacity rate of the pumps, and thermal resistance of material MECH N449 | HCT, Abu Dhabi
  5. 5. Solar Desalination Project 2012used, and heat source temperature. In addition, approximate estimation of the project cost will beincluded at the end of the report to compare with the existing system in market.The results found from the calculationsTo produce amount of 1L per minute of distilled water, we found that it requires an energybetween 52 to 55 kj/kg. Also we have the heat flux of the sun for the earth is about 95012 W/m2.Therefore, an area of 1 meter square will reflect 950 with emissivity of 1. Another point is themass flow rate. As the water has heat capacity of 4.1813 and the volume flow rate ofcirculating water is L per minute and the mass flow rate using the formula of ( ).Table 1 The results of solar desalinationParameter Formula AmountHeat flux 95012 W/m2 of the earth For 1 square meter of area has heat flux of 950 W.Temperature difference of inlet 28and outlet of heat collectionelement.Heat transfer ( solar side) 2435.47 KwHeat transfer (desalination 2435.47 Kwside)Mass flow rate of sea water 7.6 Kg/s 5 MECH N449 | HCT, Abu Dhabi
  6. 6. Solar Desalination Project 2012IntroductionDue to the increase in population growth UAE and in other Arabic gulf countries, the demand offresh water has been increase. That increase opposed with shortage of fresh water sources in theregion due to the nature of desert and as an effect of the global warming. The gulf region hasabundant seawater resources and a good level of solar radiation, which could be used to producedrinking water from seawater. Although everybody recognizes the strong potential of solarthermal energy to seawater desalination, the process is not yet developed at commercial level.The main reason for that is the technology considered expensive compared with using facial.Nevertheless, it is also recognized that there is still important room to improve desalinationsystems based on solar thermal energy.The use of solar distillation has been practiced for a long time, and it gained more attraction afterthe First World War. Solar desalination is suitable for remote, arid and semi-arid areas, wheredrinking water shortage is a major problem and solar radiation is high. The limitations of solarenergy utilization for desalination are the high initial cost for renewable energy devices andintermittent nature of the sun. Due to these limitations the present capacity of solar desalinationsystems worldwide is about 0.01% of the existing large-scale conventional desalination plants[3]. So, efforts must be made to develop technologies, which will collect and use renewable 6energy more efficiently and cost effectively to provide clean drinking water besides developingtechnologies to store this energy to use it whenever it is unavailable. MECH N449 | HCT, Abu Dhabi
  7. 7. Solar Desalination Project 2012The combination of solar energy with desalination processes can be classified into two maincategories: 100% solar driven desalination plants or partial solar powered desalination plants.Solar plants could be designed to operate in a fully automatic fashion in the sense that when thesun rises, heat collection process is initiated automatically by a sensor measuring the solarradiation.Type of desalination method Multiple effect solar stillsMultiple-effect solar desalination systems are more productive than single effect systems due tothe reuse of latent heat of condensation. The increase in efficiency, though, must be balancedagainst the increase in capital and operating costs. The efficiency of a multiple-effect solar stillcan be increased, for example, by inclining the glass cover surface towards the sun and installinggrooves on the upper surface of the glass to hold and warm the saline water before it enters thestill. The efficiency of the system can also be improved by running it in an upward-type mode.The addition of flat plate collectors and heat exchangers to transfer waste heat from localindustry provides an additional way of enhancing the productivity. Humidification–dehumidification systemsSeveral pilot plants have been developed over the past four decades. One such plant employedsolar absorbers to preheat the water before it was circulated through an evaporation chamber.Another system employed a solar pond to load the air with humidity followed by adehumidification column to collect the fresh water. A closed air cycle humidification– 7dehumidification desalination process has also been used in combination with a flat-plate solar MECH N449 | HCT, Abu Dhabi
  8. 8. Solar Desalination Project 2012collector. An open-air open-water humidification–dehumidification greenhouse structure wasdeveloped for desalination and for crop growth. The Seawater Greenhouse uses seawaterevaporators to cool and humidify the air. The greenhouse acts as a solar still while providing acontrolled environment suited to the cultivation of crops. EconomicsLower operating costs in the form of alternative energy sources (e.g. waste heat or wind energy)have been found to be key factors in the economic viability of solar desalination systems. Solarstill plants have a mean lifetime of about 20 years while the cost of fresh water produced by solarplants ranges from US $0.52 m–3 to US $2.99 m–3, depending on the plant and the cost analysismethod. It is important to realize that maximum output does not mean that a solar still is the mosteconomical.Illustration of solar desalination designThe project consists of two main parts, the solar part and desalination par. The solar par is wherethe solar energy is absorbed and water is circulated. The desalination part is where desalinationtake place and then it IS condensed .In the solar part The process begin when sun wave reflected by reflector sheet with parabolicshape which will direct the array of sun wave in to focal point. In the focal the thermal receiverpipe is located. This receiver will absorb the reflected heat and transfer it to circulated water.The water then flow through the pips to heat exchanger chamber (where the desalination take 8place) and the heat gained process 1 will loosen in here . After the water passed throw heat MECH N449 | HCT, Abu Dhabi
  9. 9. Solar Desalination Project 2012exchanger tube it flow to the suction of the circulation pump. The circulation pump then forcesthe water to flow back to thermal receiver pipe. And the process will repeat itself.In the desalination part, first sea water come from supply to heat exchanger chamber to occupyone litter volume. The inlet valve then closed. The sea water after that will be gaining heat fromcirculating water through the heating tube. The pressure inside the chamber will be vacuumedand that cased by vacuumed pump. With the vacuumed pressure sea water can boil in lowertemperature than under atmospheric pressure. After it start boiling The steam will sucked byvacuum pump and drive it to pass throw condenser. the condenser then will remove heat fromthe steam by air so steam will changed to water . the concentration of salt can be controlled byflashing the chamber after producing 30% of volume of sea water distilled water. for example ifthere is 1 L of sea water inside the chamber and we have produced 0.3 L of distilled water bothdrain and inlet valves will open to flash the chamber. 9 MECH N449 | HCT, Abu Dhabi
  10. 10. Solar Desalination Project 2012 Figure 1 shows main component of the desalination unit and the process flow diagram. Figure 1 Table 2 explain the function of project main components also it has the formula used to calculate power for each partTable 2Equipment name Function Equation to find energySolar collector Reflect solar heat and direct it to focal point where water is boiledBoiler Generate steamHeat exchange Solar side Transfer the solar heat to sea 10chamber water to increase the sea MECH N449 | HCT, Abu Dhabi
  11. 11. Solar Desalination Project 2012 water temperature Desalination Contain sea water and form a Sid e chamberpump Pump the condensed waterVacuum pump To lower the pressure inside the chamber which will lower the boiling point of waterSteam condenser To remove heat from steam and change it to liquid phase 11 MECH N449 | HCT, Abu Dhabi
  12. 12. Solar Desalination Project 2012Process flow diagramFigure 2 shows flow process diagram of the project followed by 2 tables. One for the equipmentand pipe line list and its description. Figure 2(process flow ) Euipment list Pipe line listItem number Describtion Item number DescribtionE-1 vacuum P-1 pump dischargeE-2 circulation pump P-2 disalination chamber inletE-4 solar collector P-3 disalination chamber outletE-5 Disalination chamber P-4 sea water inletE-7 air cooling condensor P-5 steam outletE-6 P-6 condensor inletE-7 P-7 condensate 12 MECH N449 | HCT, Abu Dhabi
  13. 13. Solar Desalination Project 2012Figure 3(3D project diagram) 13 MECH N449 | HCT, Abu Dhabi
  14. 14. Solar Desalination Project 2012Figure 4(project front view) Table 3(item list for figure 1 and 2)Item Item name Itemnumber number1 Circulation pump 7 Distilled water outlet 142 Collector 8 Desalination chamber MECH N449 | HCT, Abu Dhabi
  15. 15. Solar Desalination Project 20123 condenser 9 Steam out let4 Vacuum pump 10 Circulation water inlet5 Cooling fan 11 Circulation water outlet6 Common drive sprocketThe figure5 shows that both circulation and vacuum pumps with the cooling fan are linked withfoot peddle so it can be drive manually and That followed by table 4 which include part listFigure 5(pumps and fan operation) 15 MECH N449 | HCT, Abu Dhabi
  16. 16. Solar Desalination Project 2012Table 4(figure 5) part listItem number Item name Item number Item name1 Foot paddle 7 Condenser inlet2 Driver sprocket 8 Condenser outlet3 Speed increase sprocket 9 Cooling fun4 Vacuum pump 10 Condenser5 Steam inlet 11 Chain6 Steam outlet 16 MECH N449 | HCT, Abu Dhabi
  17. 17. Solar Desalination Project 2012 Project proposalDue to the increase in population growth UAE and in other Arabic gulf countries, the demand offresh water has been increase. That increase opposed with shortage of fresh water sources in theregion due to the nature of desert and as an effect of the global warming. The gulf region hasabundant seawater resources and a good level of solar radiation, which could be used to producedrinking water from seawater. Although everybody recognizes the strong potential of solarthermal energy to seawater desalination, the process is not yet developed at commercial level.The main reason for that is the technology considered expensive compared with using facial.Nevertheless, it is also recognized that there is still important room to improve desalinationsystems based on solar thermal energy. 17 MECH N449 | HCT, Abu Dhabi
  18. 18. Solar Desalination Project 2012The results found from the calculationsTo produce amount of 1L per minute of distilled water, we found that it requires an energybetween 52 to 55 kj/kg. Also we have the heat flux of the sun for the earth is about 95012 W/m2.Therefore, an area of 1 meter square will reflect 950 with emissivity of 1. Another point is themass flow rate. As the water has heat capacity of 4.1813 and the volume flow rate ofcirculating water is L per minute and the mass flow rate using the formula of ( ).Table 5 The results of solar desalinationParameter Formula AmountHeat flux 95012 W/m2 of the earth For 1 square meter of area has heat flux of 950 W.Temperature difference of inlet 28and outlet of heat collectionelement.Heat transfer ( solar side) 2435.47 KwHeat transfer (desalination 2435.47 Kwside)Mass flow rate of sea water 7.6 Kg/s 18 MECH N449 | HCT, Abu Dhabi
  19. 19. Solar Desalination Project 2012The following table contain important parameters with respect of sizeTable 6 Results calculatedArea Pressure inside the desalination Mass flow rate chamber1 m2 100 KPa 0.365 70 KPa 0.375 50 KPa2 m2 100 KPa 0.73 70 KPa 0.75 50 KPa 19 MECH N449 | HCT, Abu Dhabi
  20. 20. Solar Desalination Project 2012Literature Reviewfirst green house effect was discovered in the third century before J.C, by Archimedes and 100years after J.C, by heron of Alexandria, in 1615 by salmon de gauss, in 1974 by Joseph priestlyand in 1878 a solar still of 500 m 2 has been set up in the desert of Atacama (chila), in order tosupply in water a mine of sodium nitrate.After 1878, work on solar energy has slow down because of fossil energy availability in a lowercost. Solar energy has been reused from 1902 to 1908, by Schumann who built up solar machineswith much horse power to pump water.  Solar energy has been reused from 1902 to 1908, by Schumann who built up solar machines with much horse power to pump water.  In 1913, boys set up, near Cairo (Egypt), big machines of 50 horse power with lengthy parabolic cylinders which concentrates solar radiation upon a central pipe with a concentration factor of 4.5, in order to pump water from the Nile River for irrigation purpose.  Solar energy still being used till 1938,from which there was no other progress in solar energy field, because of its lack of competitiveness compared to energy issued from fossil fuel, from 1950, use of solar energy , began to develop slowly among solar energy uses. 20 MECH N449 | HCT, Abu Dhabi
  21. 21. Solar Desalination Project 2012 Desalination: 1Desalination process is a process that separate low concentration saline water (fresh water) fromthe other dissolved salts (the concentrate).with proper energy, a lot of technologies can be usedto produce fresh water. The desalination can become viable as the technology improves but putin mind that the amount of feed water discharged to waste in the brine stream varies from 20% to70% of the feed flow. Desalination process is by far beneficiary to communities such as the UAEwhere it is more efficient to desalinate than buying water.There are several technologies that can be used in our country such as the multistage such as: Figure 6 Reverse osmosis(RO) 23:This method was developed for more thanfour decades and proven to be successfulwhere it was introduced to the commercialbusiness because it had a decontaminatingcapability, and it was a good choice for expensive costly and energy-wasteful distillation units.Reverse osmosis is the opposite of natural osmosis its where water will move from strongersaline to weaker saline solution through a semi-permeable membrane that will prevent moleculeslarger than water to go through, and this is why salt is left behind because it is physically largerthan water molecule (Figure 6). This semi-permeable membrane is good for desalinating water1 http://www.environment.gov.au/soe/2006/publications/emerging/desal/pubs/desal.pdf 212 http://www.allaboutwater.org/reverse-osmosis.html3 http://www.islandnet.com/~tiger/Tiger/RO/how_ro_works.htm MECH N449 | HCT, Abu Dhabi
  22. 22. Solar Desalination Project 2012 but on the other hand it is not a full process if the water is used by humans, because there are some contaminants that are smaller than water particles so they also migrate to the distilled water tank, another aspect is that reverse osmosis removes alkaline mineral constituents which will produce acidic water that is bad if drank by humans. Process: 1. Force or pressure and temperature must be added on the water to reverse the flow of water. 2. Water will go through the semi-permeable membrane 3. Water molecules and particles with smaller dimension will pass by the membrane through the pores 4. Chlorine must be added to kill bacteria 22Figure 7 MECH N449 | HCT, Abu Dhabi
  23. 23. Solar Desalination Project 2012 Industrial Applications 4Reverse osmosis systems can be used to treat boiler feed water, industrial wastewater, processwater and more. A few of the major uses are:  Boiler Feed Water Treatment: RO is used to reduce the solids content of waters prior to feeding into boilers for the power generation and other industries.  Pharmaceutical: Reverse osmosis is an approved treatment process for the production of United States Pharmacopeia (USP) grade water for pharmaceutical applications.  Food & Beverage: Water used to process food products and to produce beverages is often treated by a reverse osmosis system.  Semiconductor: Reverse osmosis is an accepted component of a treatment process to produce ultrapure water in the semiconductor industry.  Metal Finishing: RO systems have been successfully applied to a variety of metal finishing operations including several types of copper, nickel and zinc electroplating; nickel acetate seal; and black dye. 234 http://www.wateronline.com/article.mvc/Use-Of-Reverse-Osmosis-Increasing-In-Industri-0001 MECH N449 | HCT, Abu Dhabi
  24. 24. Solar Desalination Project 2012 Multi-stage flash distillation (MSF): 5It’s a water desalination process that boil water to form steam and this steam will go throughmultiple chambers where it will be heated by a heat exchanger. Process6: 1. Feed water at the cold inlet temperature is pumped 2. Water temperature increase when going through the heat exchanger 3. Brine water will enter the stages and in each stage a small fraction of water will boil 4. Remnant of the brine water will go out through the discharge nozzle 5. The resulting steam will cool and condenses to form fresh water and in the same time used to heat the feed water(it is a little hot than the feed water)Figure 8 245 http://www.allaboutwater.org/distillation.html6 http://www.sidem-desalination.com/en/process/MSF/ MECH N449 | HCT, Abu Dhabi
  25. 25. Solar Desalination Project 2012 Industrial Applications  Oil refining: to make it a possible fuels for cars, and when properly chemically processed it can produce a variety of hydrocarbons like jet fuel, plastics, tires and crayons  Desalinizing water: to produce fresh water in lands who suffer from the scarcity of water  Clorosilanes: using distillation it can produce highest grades of silicon that are used to manufacture semi-conductors  Medicine: used to manufacture pharmaceutical and vitamins Solar thermal energy 7:Solar energy is renewable energy which play very important role and it’s the most importantrenewable energy in the world. The efficiency of the solar energy depends on the availablesunlight which is different from place to another. That can be caused by cloudy weather ordifferences in latitude. On other hand, the seasons also affect the solar energy. For instance, insummer, the day is longer than night and the angle of the sun is higher which provide muchstronger solar power than in winter. The electrical power that is produced due to sun called thesolar thermal power. There are 3 types of solar thermal energies such as the parabolic trough,solar power tower and the dish design. Parabolic Trough8: From 1983 to 1989, nine parabolic trough power plants were built by Luz SolarPartners Ltd in California desert. The plant was able to have 354 MW of capacity. That was bythe big support of the government to have solar power industry. However in that time, the pricesof energy went down and the need of the renewable energy decreased. Also the support from 257 http://interestingenergyfacts.blogspot.com/2008/04/solar-energy-more-advanatges-than.html8 http://www.solardesalination.com.au/content/Parabolic-Trough-Solar-Power-History.html MECH N449 | HCT, Abu Dhabi
  26. 26. Solar Desalination Project 2012government was only for short period and even not sure. In 1990 Luz doesn’t have enoughmoney. Therefore, he sold his power stations to Florida-based utility FPL and them still using itnow. They have improved the power station. The 354 MW can now generate 2,325 MW ofreliable electricity. Solar Power tower9: From 1982 to 1988, the biggest power tower plant was built. The power towers wereable to produce large power production. The system was to convert the water into steam in thereceiver to power the steam turbine. The heliostat field was consisting of 1818 heliostats in areaof 39.3 m2. The power tower plant was able to generate 10MW for 8 hours daily in summersolstice and 4 hours daily in winter solstice. The disadvantage of the thermal storage system wasmore complicated and inefficient in terms of thermodynamic concept. Dish Technology10:Dish design is the oldest one among all the solar technologies. In 1901, Enemas in Pasadena,California have built a reflective dish that has surface area of 700 ft2 and operates 10 hp solarsteam engine. Between 1907 and 1913, a solar-driven hydraulic pump was built by Americanengineer, F. Shuman. The disadvantage of this technology is that cost of solar dish is very highbecause it uses semi-conducting materials which used to build an efficient solar energy system.This is very costly compared by the costs of the electricity done by non-renewable energy.9 http://www.solarpaces.org/CSP_Technology/docs/solar_tower.pdf 2610 http://www.redrok.com/NewtonSolarSteamManuscript.pdf MECH N449 | HCT, Abu Dhabi
  27. 27. Solar Desalination Project 2012Another problem is that the dish technology requires a large area for installation because solarpanels need very large area to reach the maximum efficiency. Also the location of the sun affectsthe efficiency of the solar dish system. Also the air pollution affects the efficiency of the system. Solar Desalination11: In 1869, Mouchot have made report of oldest document work on solar desalinationof some Arab alchemist in the 15 century. The Arab alchemist had used the Damascus mirrors insolar desalination. The Damascus mirrors used to focus the sun radiation on a glass container thathas salty water to make fresh water. In 1559, the scientist Porta had produced seven methods ofdesalination. One of them is to convert water that have little amount of salt to fresh water.Another achievement is that he produced another method called thehumidification/dehumidification method. In 1774, the French chemist Lavoisier had used biglenses to collect the sun radiation placed on elaborate supporting structures to concentrate solarenergy on the contents of distillation flasks. In 1870, the first American patent in desalinationwas for Wheeler and Evans. That patent has a lot of information needed for solar energy andcorrosion problems. After two years, in 1872, a large solar distillation plant was built by CarlosWilson, a Sweden engineer who designed it in Las Salinas, Chile. The main purpose of the plantwas to produce fresh water. This plant transfers feed water that has high percentage of salinity of(140,000 ppm) to the stills. The material of the plant was wood and timber with one sheet ofglass. The plant was able to produce 22.70 m3 of fresh water per day, (about 4.9 l/m2). From1965 to 1970, a group of solar distillation was built in 4 different islands in Greek. It’s is thelargest solar desalination plant ever built. The plant was able to produce a capacity of 2044 to8640 m3/day. 2711http://membrane.ustc.edu.cn/paper/pdf/Seawater%20desalination%20using%20renewable%20energy%20sources.pdf MECH N449 | HCT, Abu Dhabi
  28. 28. Solar Desalination Project 2012 TechnologyThe solar desalination plant consists of solar energy collector. Seawater or salt water passinginside a central tube through the collator, and the sun causes evaporation. The steam condenseson the inside a tank.This water still must be treated with minerals before drinkingProject Time lineFigure 9 Team Name Mubarak Khaled Turbojet Engine Project Duration Tasks Start Date End Date (Days) Project Choosing 9/13/2011 4 9/16/2011 information about the project Gathering 9/19/2011 5 9/24/2011 Writing project proposal 9/24/2011 5 9/29/2011 Project Approval 9/29/2011 1 9/30/2011 Writing Literature Survey 9/30/2011 25 10/25/2011 Project Execution Plan 10/25/2011 5 10/30/2011 Distribution of Tasks 10/30/2011 5 11/4/2011 System Designing 11/4/2011 15 11/19/2011 Designing calculation 11/19/2011 10 11/29/2011 Visibility Study 11/29/2011 5 12/4/2011 Final report and presentation preparation 12/4/2011 30 1/3/2012 28 MECH N449 | HCT, Abu Dhabi
  29. 29. Solar Desalination Project 2012CalculationIn order to design new solar unite to desalinate sea water we have to do the following procedure. 1. Find the required energy needed to vaporize the sea water. 2. Design source of energy capable to provide required energy. 3. Try to reduce size of the system.First we will see the required energy per unit mass to vaporize sea water. We can makeassumption that the sate 1 is liquid and state 2 is superheated. Also we can assume the pressurecreated by the vaccume pump is 70 kpa absolute . So state 1 @ T=30 and P = 100kpa .state 2@ T = 90 and P = 70 kpa.By using the HEI Condenser Performance Calculator we find the following result as it shows infigure 9 29 MECH N449 | HCT, Abu Dhabi
  30. 30. Solar Desalination Project 2012Figure 10@ state 1 Cp equal 4.1784 kJ/kg/ and @ state 2 Cp equal 1.9918 kJ/kg/To calculate the energy required to change state 1 to state 2 the following equation is used 30 MECH N449 | HCT, Abu Dhabi
  31. 31. Solar Desalination Project 2012If more vacuum is created inside the chamber the following calculation can be doneP 2 = 50 kpa absolute and T2= 82@ state 1 Cp equal 4.1784 kJ/kg/ and @ state 2 Cp equal 1.9650 kJ/kg/ 31To calculate the energy required to change state 1 to state 2 the following equation is used MECH N449 | HCT, Abu Dhabi
  32. 32. Solar Desalination Project 2012 Compare the process with and without vacuum pumpIn this process we have assume state 1 @ T=30 and P = 100kpa .state 2 @ T = 110 and P =100 kpa.By using the HEI Condenser Performance Calculator we find the following result as it shows infigure 10 32 MECH N449 | HCT, Abu Dhabi
  33. 33. Solar Desalination Project 2012Figure 11@ state 1 Cp equal 4.1784 kJ/kg/ and @ state 2 Cp equal 2.0147 kJ/kg/To calculate the energy required to change state 1 to state 2 the following equation is used 33 MECH N449 | HCT, Abu Dhabi
  34. 34. Solar Desalination Project 2012That show with vacuum pump reduces the energy required to vaporize sea water. If we compareenergy required with and without vacuum pump we can find difference of 8.6%.The desired output is to have 1 Liter/hour as a volume flow rate, which is equivalent to 1/3600Kg/Second, then we multiple = 0.01555 kJ/seconds = 0.01555 wattThis energy calculated is supplied from the collector with an assumption that there are no lossesfrom thermal resistivity and all heat will transfer from the circulated water into sea water. Calculated area of reflector:In order to calculate the surface area of the reflector, we have to use the value of heat flux (950W/m²) and the energy required = =0.0589 m² Calculate the mass flow rate of circulated water =In the previous calculation (required energy), the temperature difference between sea water inletand evaporation of sea water is found to be 60˚C( and this difference is caused byvaporization of sea water in order to recover these . losses we have to add the loss in thetemperature difference through the collector therefore we can assume the through the 34collector is 60˚C. MECH N449 | HCT, Abu Dhabi
  35. 35. Solar Desalination Project 2012Average cp = = the average specific heat capacity is = = 0.278 kg/s Calculation of caused by reflector.To calculate the capacity of distilled water provided by the system we should rely of severalthinks such as mass flow rate, area of reflector, type of liquid used in hot side (reflector side ) Calculation with respect to area of reflectorIn the first calculation we will see how the area of reflector will affect the performance of thesystem. Depend on our finding the heat flux of the sun on the earth surface is approximate 95012W/m2. So for example one square meter of reflector will reflect 950w if the emissivity is 1. Thatmeans 950 w will reflect onto a receiver pipe (also called “absorber pipe or heat collectionelement”) placed at the focal line of the parabolic surface. Moreover, second assumption is thatwater is used as thermal fluid. The specific heat capacity of water is 4.1813 . The volumeflow rate of circulating water is ½ L per mint which is equal to 8.3 m3. Since the densityof water is 958.4 @ 100 13 . from that we can calculate the mass flow rate . 3512 http://home.iprimus.com.au/nielsens/solrad.html13 http://en.wikipedia.org/wiki/Density MECH N449 | HCT, Abu Dhabi
  36. 36. Solar Desalination Project 2012by assume that all reflected heat are absorbed by the water and there is no loses due to thermalresistivity of the heat collection element material , then the deference of temperature can becalculated . That give us equation # 1 =28That means the deference between the inlet and the outlet of the heat collection element.If the area of reflector is doubled(2m2) then the temperature deferent will be as following =56Other way to calculate the calculate the rate of heat transfer is by the following equation. equation # 2In the calculation done ahead we found that 56 can be added to water that mean if the initialstate of water is @ T =70 &P= 100 Kpa , the final state is T=70 + 56 = 126 ,because weassume the process is isobaric so P2 = P1 = 100 Kpa 36 MECH N449 | HCT, Abu Dhabi
  37. 37. Solar Desalination Project 2012By using With HEI Condenser Performance Calculator14 we find that at initial state of waterafter the circulation pump and before entering collector receiver the enthalpy is 293.0289and final state is 2728.4964 .figure 11 shows pictures of calculation don by the program done for the last calculation .Figure 12 Sample calculation don by HEI Condenser Performance CalculatorInitial state of water Final state of steam@temp 70 and pressure equal to 100 Kpa, @temp 126 and pressure equal to 100 Kpa,enthalpy is 293.0289 KJ/Kg enthalpy is 2728.4964 KJ/KgThe specific volume 0.001m3/Kg The specific volume 1.8215m3/Kg 3714 http://www.dofmaster.com/steam.html MECH N449 | HCT, Abu Dhabi
  38. 38. Solar Desalination Project 2012After find out the enthalpy for initial and final state we can use the equation #2 Equation # 2 .0289) = 2435.47 KwTo reach to the desired heat transfer we have to calculate the required area of calculator. Sinceheat flux is 950 W/m2 and desired heat transfer is 2435.47 KwIn first step we did the assumption that specific heat capacity is equal in the initial and final state.We did that just to find out a point from which we can start. Therefore there is error in the firstand second. And also more error can be found if calculate the thermal heat resistance of heatcollection element and if taking in consideration the emissivity of reflector sheet. 38 MECH N449 | HCT, Abu Dhabi
  39. 39. Solar Desalination Project 2012 Calculation with respect to fluid type. 15If motor oil is used as thermal fluid the specific heat capacity will changed to 2 from thatthe result well be as the following =120We can summarize motor oil required less energy to increase its temperature by one degree.That mean the area of reflector will be smaller to provide required heat. Calculation on the desalination side.From the previous calculation for the reflector side we found the deference in temperature is120 . If we assume the all heat are absorbed by sea water and there is no thermal resistance for 16tube material inside the desalination unit, The heat capacity of sea water is almost 4 ,thefollowing calculation can be done. Equation 1By making assumption of the all heat added to water by the collector are absorbed by the waterin the desalination unit. In previous calculation we found that rate of heat added to water is 3915 http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html16 http://www.kayelaby.npl.co.uk/general_physics/2_7/2_7_9.html MECH N449 | HCT, Abu Dhabi
  40. 40. Solar Desalination Project 20122435.47 KW. And @ initial state of sea water P=100Kpa Atm and T= 30 and @ final state is T110 and P= 100Kpa the mass flow rate can be calculated.Mass flow rate of sea water is equal toMass flow rate is = 7.6 Kg/sCalculation using equation #2@ State 1 of sea water T =30 P = 100 Kpa and @ state 2 T= 110 P=100 KpaFor state 1 from table A-4 @ T=30 P sat =4.246 kpa which is < P system so it is liquid (hf=125.79 kj/kg) .for state 2 @ T = 110 P sat =143.27 Kpa which is > P system 100 Kpa so it issuperheated. From table A-6 enthalpy 2676.2 kj/kg. = (2676.2-125.9) = 2550.3 KJ/KgBy using the HEI Condenser Performance Calculator we find the following result as it show infigure 12 40 MECH N449 | HCT, Abu Dhabi
  41. 41. Solar Desalination Project 2012Figure 13It shows that enthalpy @ initial stat equal to 125.7509KJ/Kg and @ final state equal2696.383KJ/Kg Equation # 2 = (2696.383-125.7509) = 2570.6 KJ/Kg 41 = 0.9 Kg/s MECH N449 | HCT, Abu Dhabi
  42. 42. Solar Desalination Project 2012 The effect of attaching vacuum pump to desalination unitThe main reason of creating vacuum inside desalination unit is to lower the required energy toevaporate water.For example if pressure of 70 Kpa is applied on the sea water , it only required to raise thetemperature to 90 to be at superheated steam state .as it shows in the figure 13.Figure 14The required energy to evaporate the water can be found from calculating the change in enthalpy.The enthalpy founded using HEI Condenser Performance Calculator as it shows in figure 14 42 MECH N449 | HCT, Abu Dhabi
  43. 43. Solar Desalination Project 2012Figure 15@ State 1 of sea water T =30 P = 100 Kpa and @ state 2 T= 90 P=70 KpaFor state 1 from table A-4 @ T=30 P sat =4.246 kpa which is < P system so it is liquid (hf=125.79 kj/kg) .for state 2 @ T = 90 P sat =70.14 Kpa which is P system that. From tableA-6 enthalpy 2676.2 kj/kg. 43 = (2676.2-125.9) = 2550.3 KJ/Kg MECH N449 | HCT, Abu Dhabi
  44. 44. Solar Desalination Project 2012As it can be seen from the figure 14. @ State 1 T= 30 P=70 Kpa and @state 2 T=90 P=70Kpa. Enthalpy is equal to 125.7235 KJ/Kg and 2660.1525 KJ/Kg respectively. Therefor change in enthalpy equal to (2660.1525-125.7235) = 2534.429 KJ/KgThe rate of heat absorb by sea water is equal to 0.0167 4 120 =8 Calculation for parabolic dish Figure 16 shows a parabola shape with all dimensionsA torispherical dome is the surface obtained from the intersection of a spherical cap with atangent torus, as illustrated above. The radius of the sphere is called the "crown radius," andthe radius of the torus is called the "knuckle radius." Torispherical domes are used to constructpressure vessels. 17 4417 http://mathworld.wolfram.com/TorisphericalDome.html MECH N449 | HCT, Abu Dhabi
  45. 45. Solar Desalination Project 2012Let be the distance from the center of the torus to the center of the torus tube, let be theradius of the torus tube, and let be the height from the base of the dome to the top. Then theradius of the base is given by . In addition, by elementary geometry, a torispherical dome 18satisfies (1)So (2)The transition from sphere to torus occurs at the critical radius (3)So the dome has equation (4)Where (5)The torispherical dome has volume (6 ) (7 4518 http://mathworld.wolfram.com/TorisphericalDome.html MECH N449 | HCT, Abu Dhabi
  46. 46. Solar Desalination Project 2012Table 7 Cost estimation Item Capacity/size CostCirculation pump 1L/min(0.25 HP) 200 DHSCollector sheet 1m2 125 DHS/m2Bicycle Height of 0.75 - 1.10 m (2.5 - 2000 DHS 3.5 ft.) Width of up to 0.61 m (2 ft.) Length of 1.5 - 1.8 m (5 - 6 ft.) Chains +gear +sprocket 1000 DHSAluminum sheet 10cm x10 cm x30cm 500 DHSPiping and fittings Copper tubes + 500 DHS fittings Heavy duty 500 DHS polyethylene + fittingsTemperature gauge 4 gauges 160x4 = 640 DHS 46 total 5465 DHS MECH N449 | HCT, Abu Dhabi
  47. 47. Solar Desalination Project 2012Conclusion Ease of safe operation Equipment and ClothingAvoid wearing long flowing clothes. Tie up long hair. Wear protective equipment such as a dustmask, gloves, eye protection, ear mufflers, jacket and boots that provide good grip on the floor. Surrounding AreaMake sure the area around the machine is free of clutter and you have sufficient space to work.Do not work in poorly lit conditions or in positions that are uncomfortable to you. Notify asupervisor of such problems promptly. The machine must be positioned on a stable surface andmust be a suitable distance away from you. Position yourself in a comfortable manner so thatyou do not have to reach out or bend. Starting a MachineBefore starting a machine, check the machine guards and ensure they all fit and are in place.Ensure that any keys or wrenches are removed so they do not fly out and hit you or anotherperson nearby. Never operate a machine if you notice loose parts, unusual sounds or vibrations.To avoid electric shocks, you must ensure that the machine is properly grounded.to do welding job make sure hat all required PPE are used and you must be aware how t dowelding or as assistance from professional person. 47 MECH N449 | HCT, Abu Dhabi
  48. 48. Solar Desalination Project 2012 Comments on the project:The project is a good start for desalination of sea water because the UAE is a desert countrywhere fresh water is scarce and sea water is available. It’s a project that can be used in areas witha hot climate because it relies on the solar energy. One important factor that was taken intoconsideration that the team worked on making a solar desalination system that can be portable soit can be used on different applications. It is a project that is easy to manufacture by using basicconcepts of thermodynamics, heat transfer and material selection. Moreover, the parts needed tofabricate such product are available in the local market. Problems encounteredThere are a lot of factors that affected the solar desalination performance such as:  Dust (the formation of the dust on the reflector sheet can eliminate or block the absorption of sun light which will negatively affect the system.  It can be operated in daytime only.  Pollution can be a disadvantage to solar panels, as pollution can degrade the efficiency of photovoltaic cells. Clouds also provide the same effect, as they can reduce the energy of the sun rays  The location of solar panels can affect performance, due to possible obstructions from the surrounding buildings or landscape 48 MECH N449 | HCT, Abu Dhabi
  49. 49. Solar Desalination Project 2012 Recommendationssince we are using single stage desalination it’s better to use multistage desalination for a betterperformance, another aspect is to place the solar system in a location that there are no buildingnear so as the sun shifts the shadow of the buildings will not affect the process. Lastly if we aregiven more time, the building of the solar desalination system would have supported thecalculations and it will help in finding errors if occurred.Appendix SOLAR RADIATION REACHING THE EARTH SURFACEThe process of heat transfer from the sun to the surface of earth:The intensity of the solar radiation reaching us is about 1369 watts per square meter [W/m2].This is known as the Solar Constant. It is important to understand that it is not the intensity persquare meter of the Earth’s surface but per square meter on a sphere with the radius of 49149,596.000 km and with the Sun at its center the atmosphere absorbs about 68 W/m2 andreflects 77 W/m2 (Wallace and Hobbs 1977). The radiation reaching the Earth’s surface is MECH N449 | HCT, Abu Dhabi
  50. 50. Solar Desalination Project 2012therefore on average 198 W/m2, i.e. 58% of the radiation intercepted by the Earth as it shows infigure16. 19 Figure 17Figure 16. The distribution of the solar radiation. On average, each squaremeter of the upper regions of the atmosphere receives 342 watts of solarradiation [W/m2]. The atmosphere absorbs on average 67 W/m 2 and reflects77 W/m2. About 198 W/m2 reaches the Earths surface, of which 168 W/m2 isabsorbed and 30 W/m2 is reflected back to space. The total of the reflected 5019 http://home.iprimus.com.au/nielsens/solrad.html MECH N449 | HCT, Abu Dhabi
  51. 51. Solar Desalination Project 2012radiation is 107 W/m2, or 31% of the incoming radiation.Source: Modified figure of Houghton et al. 2001The intensity of solar radiation depends on the time of the year and geographicalpositions as illustrated in Figure 17. Figure 18Figure 17: The intensity of solar radiation (solar power) in various parts of theworld depending on the season, measured in watts per square meter [W/m2].Source: Sofia (Sharing of Free Intellectual Assets). 51 MECH N449 | HCT, Abu Dhabi
  52. 52. Solar Desalination Project 2012HANDY FORMULA to calculate how much energy we receive from the Sun: Equation 1Where E is the solar energy in EJ, S is the Solar Constant in W/m2, n is the number of hours; r isthe Earths radius in km.This formula is for the total solar energy intercepted by the Earth in n hours. If you want tocalculate how much of the solar energy reaches the Earths surface, multiply the result by 0.58 Thermal ConductivityThermal conductivity (λ) is the intrinsic property of a material which relates its ability to conductheat. Heat transfer by conduction involves transfer of energy within a material without anymotion of the material as a whole. Conduction takes place when a temperature gradient exists ina solid (or stationary fluid) medium. Conductive heat flow occurs in the direction of decreasingtemperature because higher temperature equates to higher molecular energy or more molecularmovement. Energy is transferred from the more energetic to the less energetic molecules whenneighboring molecules collide.Thermal conductivity is defined as the quantity of heat (Q) transmitted through a unit thickness(L) in a direction normal to a surface of unit area (A) due to a unit temperature gradient (ΔT) 52under steady state conditions and when the heat transfer is dependent only on the temperaturegradient. In equation form this becomes the following: MECH N449 | HCT, Abu Dhabi
  53. 53. Solar Desalination Project 2012 Thermal Conductivity = heat × distance / (area × temperature gradient) λ = Q × L / (A × ΔT) EmissivityThe emissivity of a material (usually written ε or e) is the relative ability of its surface to emitenergy by radiation. It is the ratio of energy radiated by a particular material to energy radiatedby a black body at the same temperature. A true black body would have an ε = 1 while any realobject would have ε < 1. Emissivity is a dimensionless quantity.20In general, the duller and blacker a material is, the closer its emissivity is to 1. The morereflective a material is, the lower its emissivity. Highly polished silver has an emissivity of about0.02Low emissivity (low e) - actually low thermal emissivity - is a quality of a surface that radiates,or emits, low levels of radiant thermal (heat) energy. All materials absorb, reflect and emitradiant energy. This article is primarily about material properties within a special wavelengthinterval of radiant energy - namely thermal radiation of materials with temperaturesapproximately in the interval -40...60°C.Emissivity is the value given to materials based on the ratio of heat emitted compared to ablackbody, on a scale of 0 to 1. A blackbody would have an emissivity of 1 and a perfectreflector would have a value of 0. 5320 http://en.wikipedia.org/wiki/Emissivity MECH N449 | HCT, Abu Dhabi
  54. 54. Solar Desalination Project 2012Reflectivity is inversely related to emissivity and when added together their total should equal 1for an opaque material. Therefore, if asphalt has a thermal emissivity value of 0.90 its thermalreflectance value would be 0.10. This means that it absorbs and emits 90% of radiant thermalenergy and reflects only 10%. Conversely, a low-e material such as aluminum foil has a thermalemissivity value of 0.03 and a thermal reflectance value of 0.97, meaning it reflects 97% ofradiant thermal energy and emits only 3%. Low-emissivity building materials include windowglass manufactured with metal-oxide coatings as well as housewrap materials, reflective thermalinsulations and other forms of radiant thermal barriers.The thermal emissivity of various surfaces is listed in the following table [8] .Table 8Materials surface Thermal emittanceAsphalt 0.90-0.98Aluminum foil 0.03-0.05Brick 0.93Concrete 0.85-0.95Glass (unglazed) 0.95Fiberglass/cellulose 0.80-0.90Limestone 0.36-0.90Marble 0.93Paper 0.92Plaster 0.91Silver 0.02Steel (mild) 0.12Wood 0.90 54 MECH N449 | HCT, Abu Dhabi
  55. 55. Solar Desalination Project 2012Table 9Material Thermal Conductivity Thermal Conductivity W/m, oK (cal/sec)/(cm2, oC/cm)Air at 0 C 0.024 0.000057Aluminum 205.0 0.50Brass 109.0 -Concrete 0.8 0.002Copper 385.0 0.99Glass, ordinary 0.8 0.0025Gold 310 -Ice 1.6 0.005Iron - 0.163Lead 34.7 0.083Polyethylene HD 0.5 -Polystyrene expanded 0.03 -Silver 406.0 1.01Styrofoam 0.01 -Steel 50.2 -Water at 20 C - 0.0014Wood 0.12-0.04 0.0001 55 MECH N449 | HCT, Abu Dhabi
  56. 56. Solar Desalination Project 2012 Project main partFigure 18 show picture of the solar desalination unit with main componentFigure 19 7 56 MECH N449 | HCT, Abu Dhabi
  57. 57. Solar Desalination Project 2012Table 10 shows name of equipment in figure 18 , its function and equation used to calculateenergyTable 10Equipment name Function Equation to find energySolar collector Reflect solar heat and direct it to focal point where water is boiledBoiler Generate steamHeat exchange Solar side Transfer the solar heat to seachamber water to increase the sea water temperature Desalination Contain sea water and form a Sid e chamberpump Pump the condensed waterVacuum pump To lower the pressure inside the chamber which will lower the boiling point of waterSteam condenser To remove heat from steam and change it to liquid phase 57 MECH N449 | HCT, Abu Dhabi
  58. 58. Solar Desalination Project 2012References:http://www.solardesalination.com.au/content/Parabolic-Trough-Solar-Power-History.htmlhttp://www.solarpaces.org/CSP_Technology/docs/solar_tower.pdfhttp://interestingenergyfacts.blogspot.com/2008/04/solar-energy-more-advanatges-than.htmlhttp://www.redrok.com/NewtonSolarSteamManuscript.pdfhttp://membrane.ustc.edu.cn/paper/pdf/Seawater%20desalination%20using%20renewable%20energy%20sources.pdfhttp://www.islandnet.com/~tiger/Tiger/RO/how_ro_works.htmhttp://www.allaboutwater.org/reverse-osmosis.htmlhttp://www.environment.gov.au/soe/2006/publications/emerging/desal/pubs/desal.pdfhttp://www.wateronline.com/article.mvc/Use-Of-Reverse-Osmosis-Increasing-In-Industri-0001http://www.sidem-desalination.com/en/process/MSF/http://en.wikipedia.org/wiki/Emissivity 58 MECH N449 | HCT, Abu Dhabi

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