Water Desalination via Energy-Efficient Capacitive Deionization (CDI) Technology

Water Desalination via Energy-Efficient Capacitive Deionization (CDI) Technology

SUBMITTED BY:CHAITANYA G3PG10IT0062/8/20141

ContentsIntroductionGlobal Perspective: water scarcityDesalination : Emerging necessityWhat are possible solutions ?What makes salt water salty ?Ion spongeSystem ConceptConclusionReferences

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Introduction

The IWMI's (International Water Management Institute).Population growth, climate change, widespread mismanagement and increasing demand for energy could lead to a major global water crisis.Water use has been growing at more than twice.By 2025, 1 800 million people will be living in countries with absolute water scarcity, and two-thirds of the world population could be under stress conditions.

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Global Perspective: Water Scarcity

Water is a precious resourceIn addition to the physical water scarcity, there is also economic water scarcity.Examples: Egypt imports more than half of its food because it does not have enough water to grow it domestically. Australia is faced with major water scarcity in the Murray-Darling Basin as a result of diverting large quantities of water for use in agriculture. 2/8/20144

Australia, inland from Brisbane landscape after a severe drought.

Photo: Jonathan Wood/Getty Images (From IEEE Spectrum, April 2008)2/8/20145

Desalination: Emerging necessityCurrently, there are 18 countries classified as water scarce .

The majority of these countries are in the Middle East and northern Africa, however, a few countries are found in Europe, Asia and the Caribbean.

By 2025, approximately 29 countries in the world are expected to experience water scarcity.

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Jubail water desalination plant (Saudi Arabia) the largest in the world

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Desalination: Quest for energy efficiency and low-cost solutions

To reduce costs, many coastal desalination plants are designed to treat large volumes of water

Similar facilities in inland areas may cost twice as much to operate because of smaller plant sizes, higher concentrate disposal costs, higher water pumping costs, and higher energy costs 2/8/20148

What are possible solutions?

More than one out of six people lack access to safe drinking water around the world. Thats roughly 1.1 billion people.

Small decentralized water treatment plants with an autonomous power supply can help solve the problem

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Example of one possible solution

Mini-plant installed on the rooftop in Jordan (Image courtesy of Fraunhofer-Gesellschaft,2008) 2/8/201410

So, we are going to

Learn about new technologies, engineering design process and how engineers help to make our world better

Small-scale, decentralized system for water desalinationLow power consumption and low costEase of coupling the system with solar/wind power elements

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The First Question: What makes salty water salty?

Fresh water

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-Na+ (sodium cations)Cl- (chloride anions)

Salt ions2/8/201412

So, we need to get rid of the salt ions

and Charles-Augustin de Coulomb came up with a clue for the solution about 220 years ago:

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+Charges of same polarity repelCharges of opposite polarities attractwhich is due to the electric fields associated with the charges 2/8/201413

So, we need to apply an external electric field to salty water!No external electric field applied the water is electrically neutral and salt ions are flowing freely within it

Fresh waterExternal electric field causes the salt ions to flow towards the opposite polarity of the field and away from the same polarityExternal positive chargeExternal negative charge

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THE IDEA

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Two specific questions

Now that we have a concept for our design, we should then start the design process

Two questions then will emerge:

Whats the ion sponge?How do we create the electric field between the electrodes?2/8/201416

Ion Sponge

Q: What are we trying to trap? A: Na+ and Cl- ions

Q: What size pores do we need to hold the ions?A:0.2 0.3 nanometers

Thus, the sponge material should be such that the pores are at least several times the size of the ions2/8/201417

Discovered in 1997 by Andrei V. Rode and co-workers at the Australian National University in Canberra, Australia

Produced by firing a high-pulse, high- energy laser at graphite or disordered solid carbon

THE BEST AND THE COOLEST:IS THE CARBON NANOFOAM(CN)2/8/201418

SYSTEM CONCEPT2/8/201419

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Attach the ion sponge material to the electrode (or use it as an electrode) Attach power wires Provide for a constant separation between the electrodes it defines the strength of the electric field inside Choose your low-power source Make the electrodes choose size, shape, materialand then comes the water!CDI CELL CONCEPT2/8/201420

Brackish Water: Where?Brackish water is found in river estuaries, tidal pools and under ground, among other places

Desalination of brackish water is of much importance: Theres even the Brackish Groundwater National Desalination Research Facility

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Salinity TestingWe need a device that can measure the levels of salinity from about zero to a maximum of 30 pptThe finer the resolution the better Example:KoiMedic Digital Salt Meter:Range: 0 to 10 pptResolution: 0.1 pptPrice: ~$85

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Complete Solution: Summary

Prepare the water vessel with a flow valveAssemble the CDI cell and put into the vesselPrepare the brackish water solution with the known salinity level (use the salinity meter to verify)Run the test, while timing your measurements; plot the graph of salinity vs time

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CONCLUSIONWater is becoming a precious and scarce resource in many parts of the worldDesalination of brackish and salty water may be the solution for a variety of regionsSmall-scale, decentralized, low-power desalination systems with minimal environmental impact are desperately needed in places that cannot affordTechnology is at the frontlines of innovation and socio-economic impact and CDI is one such example.

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REFERENCESwww.ieee.comwww.wikipidia.comwww.ucl.ac.uk/news/news-articleswww.hannainst.com/manuals/manHIwrri.nmsu.edu/tbndrc/inland.html www.water-technology.netwww.google.com

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ANY QUERIES???? 2/8/201426

THANK YOU 2/8/201427

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