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  •  modular pumped hydro: say more (0+ / 0-)

    I was thinking about this myself as a possible solution to sites with highly variable wind: large water tanks of the type used for municipal water supplies, with additional tanks buried underground by about the same depth as the wind turbine foundations.  The vertical drop would provide the most efficient use of land area to get a given amount of kinetic energy back from the system.  

    In my design the tanks would be sited between and behind the wind turbines, right on the same site, so the power switching could be localized there as well.  Each turbine would be backed up by a water tank system.  Excess electricity would pump water from bottom tank to top, and during calm periods, water would be released from top to bottom through an axial turbine generator mounted above the bottom tank.  It wouldn't be hard to make that water supply available for firefighting if needed.  

    So what's being done now?  Got any links?  

    •  The problem with the tower ... (1+ / 0-)
      Recommended by:
      G2geek

      ... is the capital cost ~ the farther the vertical distance, the power is stored per cubic foot of water, so modular pumped hydro has been mostly focused on terrain with substantial vertical drops to exploit.

      That is, 1,000 ft is 10 times the power storage in the top tank as 100 feet.

      Gravity Power is a new tech start-up that is trying to get around the restriction to mountainous terrain by going down, and trying to increase the power storage capacity of a column of water by having a hydraulically lifted weight.

      Support Lesbian Creative Works with Yuri anime and manga from ALC Publishing

      by BruceMcF on Wed Jun 22, 2011 at 05:50:37 AM PDT

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      •  Gravity Power: nice one, but complex. (0+ / 0-)

        I was considering the areas of the US that are basically flat, and areas that may have adequate terrain but are ecologically sensitive.  I was also considering the velocity and inertial mass of a straight vertical water column compared to any configuration where the water supply pipes have to make turns on their way through the terrain.  

        Gravity Power has a very clever idea there, using weights in something that amounts to huge hydraulic cylinders.  

        However they're talking about going down 3,000 - 6,000 feet: a difficult task that requires new drilling technology.  So they are also seeking capital to develop the drilling machine as well as the rest of their plan.  Though, their drill design is basically a tunnel boring machine mounted vertically, so much of the basic stuff about cutters and jacks and so on is existing tech.  

        One of the difficult parts will be to remove the spoils from the hole without reliance on conversion to mud that will be a serious disposal problem.  Though, that mud could be used in wind turbine foundations for bulk mass, thereby reducing the required concrete from e.g. 300 cubic yards for a large turbine (I did the calculations & designs for that on the project I was working on) to a cylinder using less than 100 cubic yards.  

        The current alternative to mass concrete is to use crushed rock for mass within a concrete cylinder but that still requires trucking it in, whereas drilled mud from the gravity storage system is produced on site and can be pumped directly into the turbine foundation cylinders.  It can also be mixed with a small amount of cement along the way to stabilize it somewhat.

        Another limit on their tech will be subsurface water and aquifers, the latter probably raising ecological issues similar to those for fracking though hardly as severe.  

        Another will be seismic conditions: an earthquake could fracture their casings or otherwise put the equipment out of service, though a quake severe enough to do that would probably knock down the wind turbines and any above-ground water tanks as well.

        That said, the idea of using a large weight (presumably cast iron core with a steel jacket) in that manner is very clever and I can see how it increases the stored energy density of the system.  It also does so entirely safely: any disruption or destruction of the system would at most produce a geyser of plain water above it, which is basically harmless aside from minor local flooding.  

        If this succeeds, and other methods such as molten salt storage for utility-scale solar (solar thermal --> steam --> steam turbines) also succeed, it may be possible to get a 100% renewables-based grid.  So even though I'm a pro-nuker, I'm not "attached" to nukes: what matters is to get the fossil fuels, particularly coal, out of the energy mix ASAP using whatever works.  

        You should get in touch with Jerome a Paris here and see if he's interested in finding capital to help Gravity Power get their drilling machine built and then a prototype installation built.  

        •  There's no need to be limited to flat terrain ... (1+ / 0-)
          Recommended by:
          gmoke

          ... given a long distance UHVDC electricity superhighway system with sufficient geographical spread to take advantage of stabilizing volatile outputs through the "wind is normally blowing somewhere" effect, it naturally runs in the near vicinity to terrain with substantial lift.

          Storage is not a "per windturbine" resource, anymore than existing dispatch of hydro power is tied to whether a specific coal powered plant is down for maintenance ~ its a grid resource. And with the inter-grid system that we need in any event, its a resource with a radius on the order of a thousand miles.

          Velocity is not an issue, since its a water column ~ in a modular pumped hydro system laid out in the open, the works can all be at the bottom by the bottom tank, and the access to the top tank is just passive piping and the tank at the top. Effectively, the water in the pipe is sufficient head to generate power, and the role of the top tank is to replenish that until the volume has all been transferred to the bottom tank.

          But, yes, Gravity Power could possibly flip the modular pumped hydro cost equation on its head, by focusing on increasing the storage capacity per linear foot, rather than focusing on reducing the cost per linear foot.

          Support Lesbian Creative Works with Yuri anime and manga from ALC Publishing

          by BruceMcF on Wed Jun 22, 2011 at 02:47:16 PM PDT

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          •  Gravity Power - Pendulum Power (0+ / 0-)

            I'm going to post this as a diary today:

            http://gravityassistedpower.com/
            Feltenberger pendulum - gravity assisted power for water pumping and electrical generation

            There are two advantages to the Feltenberger Pendulum:  reducing friction at the pivot point of the pendulum to near zero, so the Pendulum swings easily and needs only an occasional force to maintain motion.

            and using a double-reciprocating pendulum which swings back and forth as well as sliding in and out of a piston.  how it captures the momentum from the swinging pendulum.

            Their first production model,

            ...the GP210 is a General Purpose piston pump that is used to pump water for irrigation or through a filtration system to produce safe drinking water.

            GEC donated a GP210 to help the earthquake victims in Haiti where it easily produced daily drinking water for around 4,000 people with only three hours of operation a day.  

            The pendulum on the GP210 weighs just 40 lbs. and is 48 inches long.  It is a hand-powered machine that allows its operators to pump up to 1,000 gallons of water per hour.  

            A selector pin on the axle alters the length of the linear stroke to change the flow rate/pressure of the water being pumped.  This allows the operator to pump pressurized water, up to 60psi, through a reverse osmosis system with nearly the same effort required to maintain the swinging pendulum with no water pressure.  There is NO other HAND-OPERATED pump in existence today that can pump water at these volumes or pressure.

             

            Solar is civil defense. Video of my small scale solar experiments at solarray.

            by gmoke on Thu Jun 23, 2011 at 03:45:36 PM PDT

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