Notices
Results 1 to 12 of 12

Thread: Digging pumped storage reservoirs near the ocean?

  1. #1 Digging pumped storage reservoirs near the ocean? 
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    I've been looking all over online for this, but it's hard to find data for. Even wiki's excavation page is mostly dedicated to archaeology.

    I've been wondering how practical it would be to create large amounts of pumped storage capacity for the power grid by digging big reservoirs near the ocean. I followed this link of Harold's over in the physics section, and it seemed very interesting:

    Quote Originally Posted by Harold14370
    Not exactly new, though.
    http://en.wikipedia.org/wiki/Pumped-...droelectricity
    In 1999 the EU had 32 GW capacity of pumped storage out of a total of 188 GW of hydropower and representing 5.5% of total electrical capacity in the EU.
    So, I'm thinking, we could dig a reservoir near the ocean, and let it fill up during peak hours, and the pump the water back out during low power consumption times. It would have to be covered, of course, in order to keep rain water from getting in.

    But I'm guessing there's probably a reason we don't do this. Is it really logistically hard to dig that close to the ocean? I know that water will naturally want to seep in during the dig, and that makes things difficult. Is that the kind of obstacle that would make the project simply too expensive to be worth doing?

    In general, what kinds of costs are we talking about? How deep/large a reservoir would even be possible? Or even better, what would be realistic?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Isotope Bunbury's Avatar
    Join Date
    Sep 2007
    Location
    Colorado
    Posts
    2,590
    Might be more feasible to use exisiting natural coastal features, but of course there are many challenges. The Severn Barrage is one such proposal, but it affects millions of people and ducks.


    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Jun 2009
    Posts
    7
    I'm not sure how the engineers are going to go about on the design and construction, but basically the seawater needs to be contained in another section of the reservoir during the high tide and then released during low tide in order to take advantage of the flow to generate electricity. Obviously cost is a big consideration over here.
    Reply With Quote  
     

  5. #4 Re: Digging pumped storage reservoirs near the ocean? 
    Time Lord
    Join Date
    Apr 2008
    Posts
    5,328
    Quote Originally Posted by kojax
    we could dig a reservoir near the ocean, and let it fill up during peak hours, and then pump the water back out during low power consumption times.
    As for digging a reservoir, I think more likely we'd lay rubble into shallow coastal waters, on the low-tide mark, to form a hole when empty. That way we needn't buy up or seize waterfront property... plus rubble may come from highway blastings or other excavation.

    As for pumping, if you're by the ocean pumping seems redundant since the tide is naturally pumping all the water in the world ~4m twice a day. Why not just hold some back (either way) and run turbines off the difference? With multiple reservoirs: continous generation. The moon is pretty reliable.

    Why not? Environmental impact seems enormous. It's big on the map. Though in truth marine life tends to flourish where there is strong tidal/current action - which such scheme would provide.

    Seepage and precipitation are negligable.

    Cost, as hinted earlier, depends largely on lease/compensation for use of the area, and availability of suitable fill material.
    A pong by any other name is still a pong. -williampinn
    Reply With Quote  
     

  6. #5 Re: Digging pumped storage reservoirs near the ocean? 
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by Pong
    Quote Originally Posted by kojax
    we could dig a reservoir near the ocean, and let it fill up during peak hours, and then pump the water back out during low power consumption times.
    As for digging a reservoir, I think more likely we'd lay rubble into shallow coastal waters, on the low-tide mark, to form a hole when empty. That way we needn't buy up or seize waterfront property... plus rubble may come from highway blastings or other excavation.

    I hadn't thought about that. So, instead of digging a deep hole in the ground along the coast, it might be more efficient to build a wall around an area of ocean? And strangely.... that makes a lot of sense.

    The only advantage of digging is that the earth around a dug reservoir naturally reinforces it, so it can hold more water with weaker materials. If you try it in the ocean, you'll need very strong materials.

    As for pumping, if you're by the ocean pumping seems redundant since the tide is naturally pumping all the water in the world ~4m twice a day. Why not just hold some back (either way) and run turbines off the difference? With multiple reservoirs: continous generation. The moon is pretty reliable.
    I'd want to dig the reservoirs much deeper than the height difference of the tides. Energy storage capacity increases by the square of the depth, but only has a linear relationship with horizontal area. It's purpose is to function as a very efficient battery, rather than a primary means of generating power.

    That way people can go crazy with solar and wind power, and the power grid won't be constantly fluctuating every time there's a cloudy day.



    Cost, as hinted earlier, depends largely on lease/compensation for use of the area, and availability of suitable fill material.
    One possibility I've been wondering is if the entire dug reservoir could be located underground, with a roof built over the top, and then soil over the top of that roof, so a terrain above is still useful as real estate?

    Would it bother you to live in a house that had been built over the top of a reservoir?
    Reply With Quote  
     

  7. #6  
    Time Lord
    Join Date
    Apr 2008
    Posts
    5,328
    Ah, I get it now. This would be a well with electric pumps discharging to sea, plus hydro turbines in deep chutes dropping water from the sea. Or it could be lakeside, if scaled so not to significantly change lake level. It does seem a pretty good battery!

    I'm sure building this like jetty/breakwater will be much cheaper than digging down. If the coastal water isn't deep enough, build it farther out even apart from the mainland. We build this kind of thing all over my area, having ...well, rocky mountains practically sliding into the ocean already. The rubble is best moved by barge. An ideal site would be a fjord (deep inlet) - just pile a sill at the mouth, then pump it dry.

    If you had cause to dig down anyway, like mining, then your scheme would more than offset additional costs of digging by the ocean.
    A pong by any other name is still a pong. -williampinn
    Reply With Quote  
     

  8. #7  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by Pong
    I'm sure building this like jetty/breakwater will be much cheaper than digging down. If the coastal water isn't deep enough, build it farther out even apart from the mainland. We build this kind of thing all over my area, having ...well, rocky mountains practically sliding into the ocean already. The rubble is best moved by barge. An ideal site would be a fjord (deep inlet) - just pile a sill at the mouth, then pump it dry.

    If you had cause to dig down anyway, like mining, then your scheme would more than offset additional costs of digging by the ocean.
    Yeah, I have to agree that probably using natural terrain is the best, or existing artificial terrain.

    On the flip side, if it became popular enough after all the natural options are used up, I think it could turn into very stable construction work for a lot of Americans to just go digging them. As an industrial pursuit, the advantage is that you can never have too many of them built, so after a certain amount of corporate machinery forms, we can keep them working for a long time.

    Do you think the digging costs would begin to get cheaper after a while, or is this not one of those kinds of things that benefits from economy of scale or refinement of procedure? I think some things do, and some things don't, and I'm never clear on which.
    Reply With Quote  
     

  9. #8  
    Time Lord
    Join Date
    Apr 2008
    Posts
    5,328
    Quote Originally Posted by kojax
    Do you think the digging costs would begin to get cheaper after a while..?
    I think you mean small pit vs. deep chasm. Totally depends on local geology.
    A pong by any other name is still a pong. -williampinn
    Reply With Quote  
     

  10. #9  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by Pong
    Quote Originally Posted by kojax
    Do you think the digging costs would begin to get cheaper after a while..?
    I think you mean small pit vs. deep chasm. Totally depends on local geology.
    I'm thinking along the lines of capital investment. Once a business has been doing something for a while, they start to purchase machines that are specialized to that specific task. Their engineers start finding ways to optimize the process.

    I'm wondering if the excavation process itself might start to get cheaper after a number of storage plants have been created?
    Reply With Quote  
     

  11. #10  
    Time Lord
    Join Date
    Apr 2008
    Posts
    5,328
    No 'cause we already have plenty of companies that just excavate. They'd bid on the project.
    A pong by any other name is still a pong. -williampinn
    Reply With Quote  
     

  12. #11  
    Forum Ph.D.
    Join Date
    Jan 2009
    Posts
    951
    isn't screwing around with coastal wet lands generally an environmental NO,NO?
    Reply With Quote  
     

  13. #12  
    Time Lord
    Join Date
    Apr 2008
    Posts
    5,328
    It is, especially in the Pacific Northwest where refuges like marshlands are rare, naturally. I had in mind rocky coasts where mountain slopes continue down under sea. But your topography may vary.

    Sometimes "screwing around" happens to benefit nature and man both. For example my local wildfowl marsh resulted from diking to protect airport, farmland, housing developments, and secure waterways. This bit of river delta won't ever be washed out thanks to human intervention.
    A pong by any other name is still a pong. -williampinn
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •