Solar powered multi-stage natural vacuum low temperature desalination process
Presenters: Jeff Steinwinder & Edith Martinez-GuerraTeam Members: Hugo Guerra & Ben Spiller
Advisor: Dr. Veera Gnaneswar Gude
Mississippi Water Resources Conference April 5, 2016
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Outline1. Overview 2. Proposed System3. Material and Methods4. Experimental Data5. Results and Discussions6. Conclusions and Future Work
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Natural Desalination Desalination is an engineering
technique that essentially mimics the natural water cycle
Process is related to heating, evaporating and condensing the freshwater from the saline waters
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http://www.eduplace.com/kids/sla/graphics/sla_3d1.jpg
Desalination: an overview
Desalination◦ Producing freshwater through heat exchange or membrane
processes
Thermal and membrane technologies◦ Thermal include phase-change (evaporation –
condensation)◦ Membrane include physical separation
Energy supplied through heat and electricity depending on process◦ Fossil fuel sources or renewable energy such as solar
energy
Various saline water sources◦ Seawater and brackish ground water (2500-200,000 mg/L)
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http://water.usgs.gov/edu/graphics/desalinationprocess.gif
Desalination: an overview
Thermal Membrane
Reverse Osmosis and Electrodialysis
Processes are costly, energy intensive (prime electricity), maintenance and require professional workers to oversee daily functions.
Typically chosen for small, large-scale production
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Multi-stage flash distillation
Process yields low production rates and requires multiple stages.
Energy intensive but can be supplied from waste heat and process integration
Large-scale public integration
Desalination needs in USA
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http://droughtmonitor.unl.edu/data/pngs/20160329/20160329_usdm_home.png
http://www.kleinfelder.com/index.cfm/services/design-engineering/structural-engineering/carlsbad-desalination-plant/
Carlsbad Desalination Plant - Carlsbad, CA
The Proposed System Solar Energy: low grade energy source ◦ High conversion efficiency; less heat losses
Low pressure/vacuum ◦ Creation of natural vacuum (evaporates water at low temperatures)
Multiple Stage System◦ 3 open boundary control volumes ◦ System works in parallel in terms of mass flow◦ Linear system in terms of heat exchange
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Heat Exchanger Stage 1 Stage 2 Stage 3
Flow of Usable Heat
Surroundings
Brine Water Tank
Fresh Water Tank
Saline Water Tank
HE
SC Panels
PV Panels
EC
EC
EC
Battery Bank/Data Logger
~ 10 m
Waterline
Waterline
Waterline
Thermocouple - -
Transducer - -
Pump - -
The Proposed System: Schematic
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The Proposed System: Construction Stage Construction◦ Plexiglas
◦ Predrilled and screwed
◦ Aluminum sheet separation
◦ Circulating pumps
Data Collector◦ Thermocouple
◦ Pressure Transducers
◦ Rain Collectors
• Solar Collectors• Installation and connection
• Wooden base frames
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Components: Evaporator/Condenser
Each stage contains an evaporator/condenser system Mass Conservation Heat Transfer Heat Losses and control
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Data Acquisition
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CR1000 dataloggers
PC200W software Thermocouples J
Pressure transducers (0-50psia) Rain gauge (tipping bucket)
12 V battery
Monitored Data Temperature◦ Water at each stage◦ Vapor at each stage
◦ Condenser at each stage◦ Incoming water- to coil
◦ Out of coil water
Fresh water quantity
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Temperature Results Condensation temperatures: 55, 65, and 75 °C◦ 10 hours of heat and 8 hours to cool down
Similar trend for other two stages
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Results
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Temperature and freshwater production profiles for the three-stage desalination unit at a hot water sourcetemperature of 65°C: (a) temperature profiles in stage 1 and (b) hourly freshwater production rates andcumulative volume in 10 hour heat supply window. (c) and (d) show for second stage.
Efficiency Results Energy Balance◦ Water into the coil- 150 kg/hr◦ 20 L of water in first stage
◦ 10 L of water in 2nd and 3rd stage◦ Latent heat for each stage
Water production in 1st stage:◦ 5, 10, 10.5 L/d approx. for 55, 65, and 75 °C
respectively
Results for 0. 3 m2 (lab-scale)
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Temperature (°C)
Efficiency (%)
Effluent (ml/hr)
55 45 120
65 55 230
75 58 250
Future Work Insulation for reactor and piping system Studies using solar collectors Natural vacuum
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Acknowledgements
U.S. Environmental Protection Agency Mr. Joe Ivy Civil and Environmental Engineering Department Ms. Crystal Byrd, Ms. Maria Solis, Ms. Monica Pistorius
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