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Harvesting Power When Freshwater Meets Salty

Posted by samzenpus on from the power-up dept.

ckwu writes "As a way to generate renewable electricity, researchers have designed methods that harvest the energy released when fresh and saline water mix, such as when a river meets the sea. One such method is called pressure-retarded osmosis, where two streams of water, one saline and one fresh, meet in a cell divided by a semipermeable membrane. Osmosis drives the freshwater across the membrane to the saltier side, increasing the pressure in the saline solution. The system keeps this salty water pressurized and then releases the pressure to spin a turbine to generate electricity. Now a team at Yale University has created a prototype device that increases the power output of pressure-retarded osmosis by an order of magnitude. At a full-scale facility, the estimated cost of the electricity generated by such a system could be 20 to 30 cents per kWh, approaching the cost of other conventional renewable energy technologies."

7 of 151 comments (clear)

  1. Big problem here... by Andy+Dodd · · Score: 4, Informative

    It requires saline that is MUCH more concentrated than seawater... So you need to somehow concentrate the saltwater before using it.

    Although this might allow for some rather unconventional solar power projects - feeding brine from salt concentration ponds might be workable here.

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    retrorocket.o not found, launch anyway?
    1. Re:Big problem here... by Acapulco · · Score: 4, Insightful

      I know this will probably cause a host of issues that I'm not thinking here, but the (to me) most obvious solution would be to pair this with a de-salinization plant. What if instead of de-salinizing all the water they stop at X% of water remaining in the solution, and then use that super-concentraded saline water with the power generation plant.

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    2. Re:Big problem here... by ShanghaiBill · · Score: 4, Informative

      If it's concentrated enough, why can't you use sea water as "fresh", since it is powered by the difference in salinity, not the absolute value.

      Research has been done on this, and I believe that a pilot plant may be built in the UAE or Oman in the next few years. It will use brine, concentrated in solar ponds, as the source of NaCl, and plain seawater as the sink.

    3. Re:Big problem here... by Dahamma · · Score: 4, Insightful

      No, more like using electricity generated from your brakes to charge your battery and improve fuel economy. What a concept!

  2. Re:I pay 11 cents per kWh by mcrbids · · Score: 4, Insightful

    Unless maybe we stop subsidizing fossil fuels?

    --
    I have no problem with your religion until you decide it's reason to deprive others of the truth.
  3. Re:I pay 11 cents per kWh by Tumbleweed · · Score: 5, Insightful

    Renewable is going nowhere until they're at parity.

    No amount of greenwashing and tree hugging circlejerking will change the fundamental economics of this.

    The problem here is you're not comparing apples to apples. The 'cost' of fossil fuels doesn't include environmental cleanup that isn't necessary with renewables. It also doesn't take into account the real cost - when you take out all the tax incentives for fossil fuels, the math becomes quite different.

    Also, the cost of fossil fuels will continue to go up due to environmental laws and more difficult to process sources (like tar sands), fighting unnecessary wars to secure foreign oil sources; meanwhile, while the cost of renewable technology keeps going down.

  4. Re:I pay 11 cents per kWh by crioca · · Score: 4, Informative

    You should note that, despite what many believe, we don't really "subsidize" fossil fuels to any major degree. The majority of the "subsidies" people whine about are just plain old tax deductions - the same ones that other businesses get. The oil companies didn't even get those deductions for a long time, and people complained when they finally got to deduct for exploration and drilling expenses in the same way normal businesses deduct for operations.

    Bullshit:

    http://www.nei.org/corporatesite/media/filefolder/60_Years_of_Energy_Incentives_-_Analysis_of_Federal_Expenditures_for_Energy_Development_-_1950-2010.pdf

    http://www.elistore.org/Data/products/d19_07.pdf