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Creating Clean Water and Energy – at the Same Time!

Creating Clean Water and Energy – at the Same Time!

Predictions of worldwide record droughts in the years ahead, along with news of hitting peak oil prices, have led scientists to seek ways to solve both issues. A Cambridge, Massachusetts-based desalination start-up called Oasys has come up with a way to supply both clean water and inexhaustible energy.

Yale researchers Rob McGinnis and Dr. Menachem Elichalem have created a desalination system called Engineered Osmosis. This process relies on the design on of a membrane-based water separation and power generating system. Current membrane systems rely on normal hydraulic pressure to push the water through the membranes, thus using a lot of energy and still being limited by the osmotic pressure. 

Using natural process

Engineered Osmosis uses the natural water flux as the driver for transport between membranes; hydraulic pressure is used only to create intentional resistive force. One such use of Engineered Osmosis is to create potable water from a process known as “forward osmosis” (FO). This process draws “pure” water from its contaminants to a solution of concentrated salts via this semi-permeable membrane in what is known as an osmotic pressure gradient.

Magic membrane

Forward osmosis does not require mutiple stages, large heat transfer areas and large pumping volumes, to create clean water like current desalination processes. Instead, FO uses a draw solution, dissolved solutions in water that are easily rejected by semipermeable membranes, in the form of concentrated solution of ammonium (created by the dissolution of ammonia and carbon dioxide in water). Both the draw solution and salt are rejected by the membrane and the solution is directed towards a distillation column where low temperature heat strips the ammonia and carbon-dioxide gases for reuse. This then produces freshwater containing less than 1ppm of ammonia.

Good for water AND energy

Osmosis can not only create fresh water, it also can create sustainable energy. Oasys and another company called Statkraft have harnessed the basic elements of osmosis to create energy. Statkraft is a renewable energy company in Norway created the first osmotic power plant in Tofte on November 24, 2009. The plant generates power by exploiting what happens when fresh and salt water are mixed. River water is pushed on one side of the membrane and salt water on the other, which draws the fresh water towards the salt and raises the pressure to the salty side of the membrane. With help of pressurized exchangers, the water will help spin a turbine. 

The membrane can produce around 3 watts of power per square meter – 5 watts at most. This means a 5 million square meter factory could only produce 25 KW of energy, not very practical for normal applications. Oasys, on the other hand, believes that it can produce 200 watts of power due to the high pressure ammonia-carbon dioxide salt used during the forward osmosis process. Instead of using fresh water supply, the power plants will contain two tanks, one for the salt water and the other for the newly desalinated water. The waste heat from the power plant would desalinate the water and if the plant needs more power during peak hours, the salt and fresh water could be combined to create more power. While the efficiency is still only at 50-80 percent, much of the energy input is waste heat. Oasys recently opened up a small plant in South Boston and secured a $10 million Series A round of financing [PDF].

Water shortages and power issues are not something in the distant future. Companies like Oasys are turning to natural processes, something as simple as osmosis, in ways that it can not only hydrate the world but also power it.

 

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5:37AM PDT on Jun 9, 2011

Great concept. We need to encourage by some subsidies to start. Also we need to reach the scale quickly

10:56AM PDT on May 2, 2011

There's no reason to be paying outrageous prices for water.
How to Avoid Paying The Price of Gold For Water

4:54AM PDT on Mar 22, 2011

If they have any use for pumping cold nutrient rich water to use as cooling water, when they let the used cooling water loose at the surface, those nutrients pumped up from the bottom with make surface phytoplankton be more fruitful and multiply which will both take some CO2 out of the air and make everything above the phytoplankton in the food chain also be more fruitful and multiply--which is good news for fish that people like to eat and for the people who like to eat them.

6:34AM PST on Feb 6, 2011

There is no limit in what we can imagine and invent and devise, IF we put our resources to explore them. GREED is the reason we haven't moved faster to explore other avenues than polluting coal, oil, gas, nuclear. It always has, and it always will, take people to push their governments to do the right thing.

Citizenship is a verb. -- Martha Eberle

9:33AM PST on Jan 17, 2011

Waste heat? Waste heat in energy captured as we need effecient refineries that capture gas as well as crude and mining the gas deposits that are in the ocean floor The same frozen gas that caused the gulf oil spill can be mined as used as energy, In fact removing these hazards would make drilling easier. We also need oil and gas pipelines to lower the cost of energy. Lower fuel bills strengthens the economy. Being careful and cautious saves money and time.
We are failing to mind water from the glaciers and poles water by pipeline could bring deserts to bloom with food production.

12:48PM PST on Jan 5, 2011

When folks use their God-Given imagination and compassion, they will change this world into a beautiful, healthy,functioning organism. Bless them and you, Jasmine.

11:51PM PST on Dec 29, 2010

Sounds relatively easy and many less developed and dry countries could benefit - in terms of aid & the technology

9:46AM PST on Dec 28, 2010

This is hopeful.

6:56AM PST on Dec 28, 2010

Clean potable water is always a great idea. If enough can be made, food can be had for the world.

9:53PM PST on Dec 27, 2010

Very interesting. Thank you so much.

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