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posted by Fnord666 on Wednesday March 08 2017, @11:43AM   Printer-friendly
from the won't-it-float? dept.

Pumped storage is a decades-old technology with a relatively simple concept: When electricity is cheap and plentiful, use it to pump water up into a reservoir above a turbine, and when electricity is scarce and expensive, send that pumped water down through a turbine to generate more power. Often, these pumped storage facilities are auxiliary to other electricity-generating systems, and they serve to smooth out fluctuations in the amount of power on the grid.

A German research institute has spent years trying to tailor pumped storage to ocean environments. Recently, the institute completed a successful four-week pilot test using a hollow concrete sphere that it placed on the bottom of Lake Constance, a body of water at the foot of the Alps. The sphere has a diameter of three meters and contains a pump and a turbine. Much like traditional pumped storage, when electricity is cheap, water can be pumped out of the sphere, and when it's scarce, water can be let into the sphere to move the turbine and generate electricity.

The Fraunhofer Institute for Wind Energy and Energy Systems Engineering envisions spheres with inner diameters of 30m, placed 700m (or about 2,300 ft) underwater. Assuming the spheres would be fitted with existing 5 MW turbines that could function at that depth, the researchers estimate that each sphere would offer 20 MWh of storage with four hours discharge time.

https://arstechnica.com/science/2017/03/german-institute-successfully-tests-underwater-energy-storage-sphere/


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  • (Score: 0) by Anonymous Coward on Wednesday March 08 2017, @12:34PM (4 children)

    by Anonymous Coward on Wednesday March 08 2017, @12:34PM (#476408)

    can we boil water at 700 meters below sea-level?
    teh diagram doesn't show a pipe going to surface to suck down "air" from surface?

  • (Score: 1) by shrewdsheep on Wednesday March 08 2017, @01:53PM (2 children)

    by shrewdsheep (5215) on Wednesday March 08 2017, @01:53PM (#476428)

    Indeed this is one of the finer points not mentioned. My guess is that the reservoir is kept at atmospheric pressure when lowered into the water. When filled with water, the air is compressed into a small volume. When water is pumped out the air returns to atmospheric pressure. As to how relevant the base pressure is in practice, I have no idea. I would believe that it would not be a great technical difficulty to pump out some air before going under water. OTOH the boiling problem you mention might make this undesirable.

    • (Score: 2) by JoeMerchant on Wednesday March 08 2017, @02:53PM

      by JoeMerchant (3937) on Wednesday March 08 2017, @02:53PM (#476451)

      At 700m, pressure is ~70atm, so if the air in the sphere is at surface pressure, it will compress to less than 2% of its original volume.

      --
      🌻🌻 [google.com]
    • (Score: 1, Insightful) by Anonymous Coward on Wednesday March 08 2017, @08:00PM

      by Anonymous Coward on Wednesday March 08 2017, @08:00PM (#476680)

      i assumed the sphere made from concret is lowered from surface filled with water.
      concret like compression but doesnt like stretching.
      since water is not compressible if the sphere is lowered full of water it will experience any
      outward pressure.
      water is not compressible .. how ever it can cavitate .. thus pumping
      a full sphere out will lower the pressure leading to the boiling of the enclosed water
      same as water boils at lower temperatures in the mountain ...
      thus it is wrong to call it "air" when the "empty sphere is rather full of low pressure steam?

  • (Score: 2) by fishybell on Wednesday March 08 2017, @06:45PM

    by fishybell (3156) on Wednesday March 08 2017, @06:45PM (#476628)

    Why do you assume they're boiling the water?