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Learning to think about micro-pumped storage

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  • keithwins
    Hi again, I m still trying to wrap my head around the possibilities for pumped storage. These are the questions I want to sort through: How does stored water
    Message 1 of 15 , Aug 1, 2007
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      Hi again,

      I'm still trying to wrap my head around the possibilities for pumped
      storage. These are the questions I want to sort through:

      How does stored water (upper reservoir) translate into available
      energy (I would think a fairly simple system efficiency * potential
      energy analysis might suffice here, but I'm uncertain)?

      What considerations go into thinking about the delivery of power from
      such a system (i.e., flow resistance and flow rates, turbine capacity,
      spin-up time, etc)?

      Are there small turbines that can also be used (efficiently) as pumps,
      or do these two functions require separate equipment?

      What kinds of turbines would be most efficient for such a system?

      Any pointers to info, ideas, formulas, etc would be appreciated.

      Thanks for any leads.

      Warmly, Keith
    • davis ron
      -Water Storage for Microhydro A small amount of storage in a micro hydro system can act as a battery does in an auto. A battery accumulates power slowly while
      Message 2 of 15 , Aug 1, 2007
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        -Water Storage for Microhydro


        A small amount of storage in a micro hydro system can
        act as a battery does in an auto. A battery
        accumulates power slowly while the auto is running and
        can release it rapidly later, as when starting the
        engine.
        The amount of energy stored in the battery is small,
        but the fact that it can be stored and used on demand
        makes it very useful. The same principle can be
        applied to small scale waterpower, and in some
        situations with dramatic results.
        A little storage can make it possible to use a very
        small or even intermittent waterpower source to do
        valuable work . Storage can also make it practical to
        use a shared water resource, such as an irrigation
        ditch, as a waterpower source.
        These thoughts came to me while working at our
        microhydro demonstration site in the Andes near the
        Bolivian capital, La Paz. There we use a very small
        stream to run a number of machines and power tools
        such as a grain mill, table saw, compressor,
        alternator, and more.
        These are all driven directly by the Watermotor, so we
        get about 80% of the power from the water as usable
        energy and therefore need relatively little water to
        run our machines.
        Even so, the combination of dry season plus a newly
        installed potable water system upstream can reduce the
        flow to less than what we need to run some of our
        tools, without drying up the stream bed.
        As an example, for full power operation the table saw
        needs about 500 liters per minute, and sometimes this
        is simply not available.

        But actually we seldom use this saw for more than a
        few minutes at a time, and rarely for more than an
        hour or two per day.
        If we can get this much power we can keep our shop in
        operation throughout the dry season.

        How much storage would we need for this amount of use?
        Surprisingly little, when we check the figures.
        An example : let us say the water available to us is
        100 liters per minute—only 20% of what we need to run
        the table saw, and we have a 6000 liter storage tank
        (2 x 2 x 1.5 m). This amount plus the water arriving
        during operation adds up to nearly 15 minutes of
        continuous power, and over two hours of operating time
        over an 10 hour workday.

        . In practical terms we would never run out of
        waterpower.
        Of course, this only applies to machines that are used
        intermittently, as are most shop tools, especially in
        small shops.

        Ferro-cement Tanks
        A tank is often a useful thing for other
        reasons—bathing and irrigation among them. We have
        been building subterranean tanks for years using
        ferro-cement which makes construction easy and low in
        cost. This technique uses woven wire (chicken wire)
        for reinforcing rather than steel bars. The tank walls
        are usually no more than 1" thick.
        Ferro-cement is especially advantageous in locations
        where the materials must be carried to the worksite.


        For more information contact Ron Davis or Diane
        Bellomy at:
        Campo Nuevo
        Email: watermotor@...
        Casilla 4365, La Paz, Bolivia.
        Telephone: (591-2) 2485022 or (591-2)2485159
        Mobile: (591-2) 71527700


        --- keithwins <keith@...> wrote:

        > Hi again,
        >
        > I'm still trying to wrap my head around the
        > possibilities for pumped
        > storage. These are the questions I want to sort
        > through:
        >
        > How does stored water (upper reservoir) translate
        > into available
        > energy (I would think a fairly simple system
        > efficiency * potential
        > energy analysis might suffice here, but I'm
        > uncertain)?
        >
        > What considerations go into thinking about the
        > delivery of power from
        > such a system (i.e., flow resistance and flow rates,
        > turbine capacity,
        > spin-up time, etc)?
        >
        > Are there small turbines that can also be used
        > (efficiently) as pumps,
        > or do these two functions require separate
        > equipment?
        >
        > What kinds of turbines would be most efficient for
        > such a system?
        >
        > Any pointers to info, ideas, formulas, etc would be
        > appreciated.
        >
        > Thanks for any leads.
        >
        > Warmly, Keith
        >
        >
        >




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      • phil
        hi I m just awaiting parts for mine 1x 1,000 litre ibc as main tank. submersible pump in main tank 3/4 height tube comes out into cut top of 1 x 500litre ibc
        Message 3 of 15 , Aug 1, 2007
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          hi

          I'm just awaiting parts for mine 1x 1,000 litre ibc as main tank.
          submersible pump in main tank 3/4 height tube comes out into cut top
          of 1 x 500litre ibc which contains waterwheel or could go for pelton
          as pump will give pressure.
          to get water back needs pump which could be driven off pelton or
          small waterwheel under it getting as much power out as possible.

          archimedes wheel?.

          get power off pelton and waterwheel.

          just to get your brain going

          borg




          --- In microhydro@yahoogroups.com, "keithwins" <keith@...> wrote:
          >
          > Hi again,
          >
          > I'm still trying to wrap my head around the possibilities for pumped
          > storage. These are the questions I want to sort through:
          >
          > How does stored water (upper reservoir) translate into available
          > energy (I would think a fairly simple system efficiency * potential
          > energy analysis might suffice here, but I'm uncertain)?
          >
          > What considerations go into thinking about the delivery of power
          from
          > such a system (i.e., flow resistance and flow rates, turbine
          capacity,
          > spin-up time, etc)?
          >
          > Are there small turbines that can also be used (efficiently) as
          pumps,
          > or do these two functions require separate equipment?
          >
          > What kinds of turbines would be most efficient for such a system?
          >
          > Any pointers to info, ideas, formulas, etc would be appreciated.
          >
          > Thanks for any leads.
          >
          > Warmly, Keith
          >
        • Tom Spicher
          Keith The concept of pumped storage is quite simple, water is pumped up during off peak hours or days and is allowed to flow down during peak hours. The only
          Message 4 of 15 , Aug 1, 2007
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            Keith

            The concept of pumped storage is quite simple, water is pumped up during off peak hours or days and is allowed to flow down during peak hours. The only real advantage is on a widespread system. Pump efficiency typically is in the order of 90%. Turbine efficiency (Francis) is in the order of 94%, so there is a net loss of power but it becomes available during peak times when it is 2-3 times more valuable. Usually based upon one (or more) units doing both pump and turbine work. Occasionally, usually at very high heads, separate units are used to pump and generate. Some irrigation systems use power from one level of water to pump up to a higher level, often with a single shaft. For background reports the US Bureau of Reclamation has lots of diverse information, see www.usbr.gov .

            Tom
            ----- Original Message -----
            From: keithwins
            To: microhydro@yahoogroups.com
            Sent: Wednesday, August 01, 2007 8:43 AM
            Subject: [!! SPAM] [microhydro] Learning to think about micro-pumped storage


            Hi again,

            I'm still trying to wrap my head around the possibilities for pumped
            storage. These are the questions I want to sort through:

            How does stored water (upper reservoir) translate into available
            energy (I would think a fairly simple system efficiency * potential
            energy analysis might suffice here, but I'm uncertain)?

            What considerations go into thinking about the delivery of power from
            such a system (i.e., flow resistance and flow rates, turbine capacity,
            spin-up time, etc)?

            Are there small turbines that can also be used (efficiently) as pumps,
            or do these two functions require separate equipment?

            What kinds of turbines would be most efficient for such a system?

            Any pointers to info, ideas, formulas, etc would be appreciated.

            Thanks for any leads.

            Warmly, Keith





            [Non-text portions of this message have been removed]
          • Keith Winston
            Hi there, I m confused: how much head are you accounting for (that is, height between upper and lower reservoir? And, are you expecting falling water to give
            Message 5 of 15 , Aug 4, 2007
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              Hi there,

              I'm confused: how much head are you accounting for (that is, height
              between upper and lower reservoir? And, are you expecting falling water
              to give you all the energy you need to pump the water back up, and more?
              No, that won't work...

              I have been crunching numbers, and it appears you need several thousand
              gallons, and 100' head, to equal one biggish storage battery (200 Ah),
              more or less. Doesn't look good...

              Keith


              phil wrote:
              >
              > hi
              >
              > I'm just awaiting parts for mine 1x 1,000 litre ibc as main tank.
              > submersible pump in main tank 3/4 height tube comes out into cut top
              > of 1 x 500litre ibc which contains waterwheel or could go for pelton
              > as pump will give pressure.
              > to get water back needs pump which could be driven off pelton or
              > small waterwheel under it getting as much power out as possible.
              >
              > archimedes wheel?.
              >
              > get power off pelton and waterwheel.
              >
              > just to get your brain going
              >
              > borg
              >
              > --- In microhydro@yahoogroups.com
              > <mailto:microhydro%40yahoogroups.com>, "keithwins" <keith@...> wrote:
              > >
              > > Hi again,
              > >
              > > I'm still trying to wrap my head around the possibilities for pumped
              > > storage. These are the questions I want to sort through:
              > >
              > > How does stored water (upper reservoir) translate into available
              > > energy (I would think a fairly simple system efficiency * potential
              > > energy analysis might suffice here, but I'm uncertain)?
              > >
              > > What considerations go into thinking about the delivery of power
              > from
              > > such a system (i.e., flow resistance and flow rates, turbine
              > capacity,
              > > spin-up time, etc)?
              > >
              > > Are there small turbines that can also be used (efficiently) as
              > pumps,
              > > or do these two functions require separate equipment?
              > >
              > > What kinds of turbines would be most efficient for such a system?
              > >
              > > Any pointers to info, ideas, formulas, etc would be appreciated.
              > >
              > > Thanks for any leads.
              > >
              > > Warmly, Keith
              > >
              >
              >

              --
              Keith Winston
              Earth Sun Energy Systems
              Hyattsville, MD 20781
              301-980-6325
              send me mail at
              keith at the company below
              www.EarthSunEnergy.com
            • nando
              Keith: First do not state amp-hours you need to state watts ( because amp hours defines the capacity to the bank but the voltage is missing -- and voltage *
              Message 6 of 15 , Aug 5, 2007
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                Keith:

                First do not state amp-hours you need to state watts ( because amp hours defines the capacity to the bank but the voltage is missing -- and voltage * amp-hours = watt-hours which is the real capacity of the bank -- in reality there is another factor that needs to be included and it is the watt-hours that should remain in the bank to protect the bank for long life use).

                the energy needed is Water volume * head * gravity = gross watts, also it is the same for the energy produced, the difference is the efficiencies involved in the process to produce the energy and to raise the water to the upper tank or reservoir -- for small systems this over all efficiency runs around 75 to 80 % for each way and in many cases lower.

                We made one, that had an over all efficiency of around 45 % in summer, not needed during most of the winter times, but allowed the small town to have the necessary energy for the for or five hours in the evening with some lights during the rest to the night ( 12 houses -- later 22 homes) .

                This set up is not longer needed since they were able to re-route another water source to supply all the water needs, including the water house use.
                The upper reservoir is used to supply pressure to the homes water needs.

                Nando

                ----- Original Message -----
                From: Keith Winston
                To: microhydro@yahoogroups.com
                Sent: Saturday, August 04, 2007 5:14 PM
                Subject: Re: [microhydro] Re: Learning to think about micro-pumped storage


                Hi there,

                I'm confused: how much head are you accounting for (that is, height
                between upper and lower reservoir? And, are you expecting falling water
                to give you all the energy you need to pump the water back up, and more?
                No, that won't work...

                I have been crunching numbers, and it appears you need several thousand
                gallons, and 100' head, to equal one biggish storage battery (200 Ah),
                more or less. Doesn't look good...

                Keith

                phil wrote:
                >
                > hi
                >
                > I'm just awaiting parts for mine 1x 1,000 litre ibc as main tank.
                > submersible pump in main tank 3/4 height tube comes out into cut top
                > of 1 x 500litre ibc which contains waterwheel or could go for pelton
                > as pump will give pressure.
                > to get water back needs pump which could be driven off pelton or
                > small waterwheel under it getting as much power out as possible.
                >
                > archimedes wheel?.
                >
                > get power off pelton and waterwheel.
                >
                > just to get your brain going
                >
                > borg
                >
                > --- In microhydro@yahoogroups.com
                > <mailto:microhydro%40yahoogroups.com>, "keithwins" <keith@...> wrote:
                > >
                > > Hi again,
                > >
                > > I'm still trying to wrap my head around the possibilities for pumped
                > > storage. These are the questions I want to sort through:
                > >
                > > How does stored water (upper reservoir) translate into available
                > > energy (I would think a fairly simple system efficiency * potential
                > > energy analysis might suffice here, but I'm uncertain)?
                > >
                > > What considerations go into thinking about the delivery of power
                > from
                > > such a system (i.e., flow resistance and flow rates, turbine
                > capacity,
                > > spin-up time, etc)?
                > >
                > > Are there small turbines that can also be used (efficiently) as
                > pumps,
                > > or do these two functions require separate equipment?
                > >
                > > What kinds of turbines would be most efficient for such a system?
                > >
                > > Any pointers to info, ideas, formulas, etc would be appreciated.
                > >
                > > Thanks for any leads.
                > >
                > > Warmly, Keith
                > >
                >
                >

                --
                Keith Winston
                Earth Sun Energy Systems
                Hyattsville, MD 20781
                301-980-6325
                send me mail at
                keith at the company below
                www.EarthSunEnergy.com





                [Non-text portions of this message have been removed]
              • Keith Winston
                Hi Tom, thanks for your reply. I understand the basic principles of pumped storage just fine. What I m trying to see is if pumped storage can be constructed,
                Message 7 of 15 , Aug 5, 2007
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                  Hi Tom, thanks for your reply. I understand the basic principles of
                  pumped storage just fine. What I'm trying to see is if pumped storage
                  can be constructed, in a relatively low-head environment (maybe 30m) to
                  provide electrical storage for a small community (5-6 houses) in a
                  cost-competitive way compared to a battery bank (which is expensive and
                  has lots of disadvantages). This would require construction of both the
                  upper AND lower reservoirs, so it would also be expensive, and MUCH
                  smaller than the commercial systems out there (a few thousand kWh or
                  storage, perhaps). So I'm trying to get very specific about my
                  questions, and the answers. For example,

                  Are there small turbines that can also be used (efficiently) as pumps,
                  or do these two functions require separate equipment (WHEN DONE ON A
                  SMALL SCALE, FOR LACK OF AVAILABLE EQUIPMENT)?

                  Since I do a lot of hydronic heating work, I know that no one uses
                  turbine pumps in residential applications. Except if a centrifugal pump
                  counts (i.e. an ordinary circulator pump).

                  Anyway, any specifics are helpful. I'm looking at the USBR site, found
                  one interesting manual. Thanks.

                  Keith



                  Tom Spicher wrote:
                  >
                  > Keith
                  >
                  > The concept of pumped storage is quite simple, water is pumped up
                  > during off peak hours or days and is allowed to flow down during peak
                  > hours. The only real advantage is on a widespread system. Pump
                  > efficiency typically is in the order of 90%. Turbine efficiency
                  > (Francis) is in the order of 94%, so there is a net loss of power but
                  > it becomes available during peak times when it is 2-3 times more
                  > valuable. Usually based upon one (or more) units doing both pump and
                  > turbine work. Occasionally, usually at very high heads, separate units
                  > are used to pump and generate. Some irrigation systems use power from
                  > one level of water to pump up to a higher level, often with a single
                  > shaft. For background reports the US Bureau of Reclamation has lots of
                  > diverse information, see www.usbr.gov .
                  >
                  > Tom
                  > ----- Original Message -----
                  > From: keithwins
                  > To: microhydro@yahoogroups.com <mailto:microhydro%40yahoogroups.com>
                  > Sent: Wednesday, August 01, 2007 8:43 AM
                  > Subject: [!! SPAM] [microhydro] Learning to think about micro-pumped
                  > storage
                  >
                  > Hi again,
                  >
                  > I'm still trying to wrap my head around the possibilities for pumped
                  > storage. These are the questions I want to sort through:
                  >
                  > How does stored water (upper reservoir) translate into available
                  > energy (I would think a fairly simple system efficiency * potential
                  > energy analysis might suffice here, but I'm uncertain)?
                  >
                  > What considerations go into thinking about the delivery of power from
                  > such a system (i.e., flow resistance and flow rates, turbine capacity,
                  > spin-up time, etc)?
                  >
                  > Are there small turbines that can also be used (efficiently) as pumps,
                  > or do these two functions require separate equipment?
                  >
                  > What kinds of turbines would be most efficient for such a system?
                  >
                  > Any pointers to info, ideas, formulas, etc would be appreciated.
                  >
                  > Thanks for any leads.
                  >
                  > Warmly, Keith
                  >
                  > [Non-text portions of this message have been removed]
                  >
                  >

                  --
                  Keith Winston
                  Earth Sun Energy Systems
                  Hyattsville, MD 20781
                  301-980-6325
                  send me mail at
                  keith at the company below
                  www.EarthSunEnergy.com
                • phil fox
                  when its done i ll send you the pics borg Keith Winston wrote: Hi there, I m confused: how much head are you accounting for (that
                  Message 8 of 15 , Aug 5, 2007
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                    when its done i'll send you the pics

                    borg

                    Keith Winston <keith@...> wrote:
                    Hi there,

                    I'm confused: how much head are you accounting for (that is, height
                    between upper and lower reservoir? And, are you expecting falling water
                    to give you all the energy you need to pump the water back up, and more?
                    No, that won't work...

                    I have been crunching numbers, and it appears you need several thousand
                    gallons, and 100' head, to equal one biggish storage battery (200 Ah),
                    more or less. Doesn't look good...

                    Keith

                    phil wrote:
                    >
                    > hi
                    >
                    > I'm just awaiting parts for mine 1x 1,000 litre ibc as main tank.
                    > submersible pump in main tank 3/4 height tube comes out into cut top
                    > of 1 x 500litre ibc which contains waterwheel or could go for pelton
                    > as pump will give pressure.
                    > to get water back needs pump which could be driven off pelton or
                    > small waterwheel under it getting as much power out as possible.
                    >
                    > archimedes wheel?.
                    >
                    > get power off pelton and waterwheel.
                    >
                    > just to get your brain going
                    >
                    > borg
                    >
                    > --- In microhydro@yahoogroups.com
                    > <mailto:microhydro%40yahoogroups.com>, "keithwins" <keith@...> wrote:
                    > >
                    > > Hi again,
                    > >
                    > > I'm still trying to wrap my head around the possibilities for pumped
                    > > storage. These are the questions I want to sort through:
                    > >
                    > > How does stored water (upper reservoir) translate into available
                    > > energy (I would think a fairly simple system efficiency * potential
                    > > energy analysis might suffice here, but I'm uncertain)?
                    > >
                    > > What considerations go into thinking about the delivery of power
                    > from
                    > > such a system (i.e., flow resistance and flow rates, turbine
                    > capacity,
                    > > spin-up time, etc)?
                    > >
                    > > Are there small turbines that can also be used (efficiently) as
                    > pumps,
                    > > or do these two functions require separate equipment?
                    > >
                    > > What kinds of turbines would be most efficient for such a system?
                    > >
                    > > Any pointers to info, ideas, formulas, etc would be appreciated.
                    > >
                    > > Thanks for any leads.
                    > >
                    > > Warmly, Keith
                    > >
                    >
                    >

                    --
                    Keith Winston
                    Earth Sun Energy Systems
                    Hyattsville, MD 20781
                    301-980-6325
                    send me mail at
                    keith at the company below
                    www.EarthSunEnergy.com






                    When i do right no-one remembers When i do wrong no-one forgets. Your technology will be assimilated for other uses.

                    [Non-text portions of this message have been removed]
                  • nando
                    KEITH: You may be better off if you use a turbine/generator and turbine/pump for the whole process, though you may be able to have a single turbine attached to
                    Message 9 of 15 , Aug 5, 2007
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                      KEITH:

                      You may be better off if you use a turbine/generator and turbine/pump for the whole process, though you may be able to have a single turbine attached to a generator and to a pump for the whole process, in one case, the generator producing electrical; power and in the other case, the pump bringing the water up to the upper reservoir.

                      the arrangement needs to be examined to determine the best procedure, also the definition of the upper reservoir for the time that power is needed.

                      One of the problems is the water volume available in the stream and how it is directed to the turbine in reference to the upper reservoir.

                      My suggestion is for you to present what is available with accurate water volume and heads measurements to determine the best path for your project.

                      Consideration of electrical power generation during the upper reservoir re-filling time may be necessary ( limited night for the houses).

                      Regards

                      Nando


                      ----- Original Message -----
                      From: Keith Winston
                      To: microhydro@yahoogroups.com
                      Sent: Sunday, August 05, 2007 12:35 PM
                      Subject: Re: [!! SPAM] [microhydro] Learning to think about micro-pumped storage


                      Hi Tom, thanks for your reply. I understand the basic principles of
                      pumped storage just fine. What I'm trying to see is if pumped storage
                      can be constructed, in a relatively low-head environment (maybe 30m) to
                      provide electrical storage for a small community (5-6 houses) in a
                      cost-competitive way compared to a battery bank (which is expensive and
                      has lots of disadvantages). This would require construction of both the
                      upper AND lower reservoirs, so it would also be expensive, and MUCH
                      smaller than the commercial systems out there (a few thousand kWh or
                      storage, perhaps). So I'm trying to get very specific about my
                      questions, and the answers. For example,

                      Are there small turbines that can also be used (efficiently) as pumps,
                      or do these two functions require separate equipment (WHEN DONE ON A
                      SMALL SCALE, FOR LACK OF AVAILABLE EQUIPMENT)?

                      Since I do a lot of hydronic heating work, I know that no one uses
                      turbine pumps in residential applications. Except if a centrifugal pump
                      counts (i.e. an ordinary circulator pump).

                      Anyway, any specifics are helpful. I'm looking at the USBR site, found
                      one interesting manual. Thanks.

                      Keith

                      Tom Spicher wrote:
                      >
                      > Keith
                      >
                      > The concept of pumped storage is quite simple, water is pumped up
                      > during off peak hours or days and is allowed to flow down during peak
                      > hours. The only real advantage is on a widespread system. Pump
                      > efficiency typically is in the order of 90%. Turbine efficiency
                      > (Francis) is in the order of 94%, so there is a net loss of power but
                      > it becomes available during peak times when it is 2-3 times more
                      > valuable. Usually based upon one (or more) units doing both pump and
                      > turbine work. Occasionally, usually at very high heads, separate units
                      > are used to pump and generate. Some irrigation systems use power from
                      > one level of water to pump up to a higher level, often with a single
                      > shaft. For background reports the US Bureau of Reclamation has lots of
                      > diverse information, see www.usbr.gov .
                      >
                      > Tom
                      > ----- Original Message -----
                      > From: keithwins
                      > To: microhydro@yahoogroups.com <mailto:microhydro%40yahoogroups.com>
                      > Sent: Wednesday, August 01, 2007 8:43 AM
                      > Subject: [!! SPAM] [microhydro] Learning to think about micro-pumped
                      > storage
                      >
                      > Hi again,
                      >
                      > I'm still trying to wrap my head around the possibilities for pumped
                      > storage. These are the questions I want to sort through:
                      >
                      > How does stored water (upper reservoir) translate into available
                      > energy (I would think a fairly simple system efficiency * potential
                      > energy analysis might suffice here, but I'm uncertain)?
                      >
                      > What considerations go into thinking about the delivery of power from
                      > such a system (i.e., flow resistance and flow rates, turbine capacity,
                      > spin-up time, etc)?
                      >
                      > Are there small turbines that can also be used (efficiently) as pumps,
                      > or do these two functions require separate equipment?
                      >
                      > What kinds of turbines would be most efficient for such a system?
                      >
                      > Any pointers to info, ideas, formulas, etc would be appreciated.
                      >
                      > Thanks for any leads.
                      >
                      > Warmly, Keith
                      >
                      > [Non-text portions of this message have been removed]
                      >
                      >

                      --
                      Keith Winston
                      Earth Sun Energy Systems
                      Hyattsville, MD 20781
                      301-980-6325
                      send me mail at
                      keith at the company below
                      www.EarthSunEnergy.com





                      [Non-text portions of this message have been removed]
                    • Tom Spicher
                      Well Kieth, this is getting more complicated. Pumps are successfully used as turbines and in combination on a pump/generation package. One of the drawbacks
                      Message 10 of 15 , Aug 5, 2007
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                        Well Kieth, this is getting more complicated. Pumps are successfully used as turbines and in combination on a pump/generation package. One of the drawbacks is that the motor/generator requires excitation. When connected to a grid this is not a problem. As an isolated system it becomes quite a problem. Many locations require extensive permitting for dams even on off stream locations. There is always the possibility that a local rain storm will over top the dam and destroy the dam, the resulting flow may do some damage to adjacent properties. Even if a reservoir is just dug out, the berm may be considered a dam.

                        The centrifugal pumps used are fairly effective in both directions. Valving at the pump allows start-up against a head so it doesn't overload the motor with excess flow.

                        The other aspect when grid connected is that some utilities get nervous about "unusual" systems connected to their system. It may be necessary to just use the excitation to develop synchronous action for the pump motor and when generating use separate feeds to the households.

                        Tom
                        ----- Original Message -----
                        From: Keith Winston
                        To: microhydro@yahoogroups.com
                        Sent: Sunday, August 05, 2007 10:35 AM
                        Subject: [!! SPAM] Re: [microhydro] Learning to think about micro-pumped storage


                        Hi Tom, thanks for your reply. I understand the basic principles of
                        pumped storage just fine. What I'm trying to see is if pumped storage
                        can be constructed, in a relatively low-head environment (maybe 30m) to
                        provide electrical storage for a small community (5-6 houses) in a
                        cost-competitive way compared to a battery bank (which is expensive and
                        has lots of disadvantages). This would require construction of both the
                        upper AND lower reservoirs, so it would also be expensive, and MUCH
                        smaller than the commercial systems out there (a few thousand kWh or
                        storage, perhaps). So I'm trying to get very specific about my
                        questions, and the answers. For example,

                        Are there small turbines that can also be used (efficiently) as pumps,
                        or do these two functions require separate equipment (WHEN DONE ON A
                        SMALL SCALE, FOR LACK OF AVAILABLE EQUIPMENT)?

                        Since I do a lot of hydronic heating work, I know that no one uses
                        turbine pumps in residential applications. Except if a centrifugal pump
                        counts (i.e. an ordinary circulator pump).

                        Anyway, any specifics are helpful. I'm looking at the USBR site, found
                        one interesting manual. Thanks.

                        Keith

                        Tom Spicher wrote:
                        >
                        > Keith
                        >
                        > The concept of pumped storage is quite simple, water is pumped up
                        > during off peak hours or days and is allowed to flow down during peak
                        > hours. The only real advantage is on a widespread system. Pump
                        > efficiency typically is in the order of 90%. Turbine efficiency
                        > (Francis) is in the order of 94%, so there is a net loss of power but
                        > it becomes available during peak times when it is 2-3 times more
                        > valuable. Usually based upon one (or more) units doing both pump and
                        > turbine work. Occasionally, usually at very high heads, separate units
                        > are used to pump and generate. Some irrigation systems use power from
                        > one level of water to pump up to a higher level, often with a single
                        > shaft. For background reports the US Bureau of Reclamation has lots of
                        > diverse information, see www.usbr.gov .
                        >
                        > Tom
                        > ----- Original Message -----
                        > From: keithwins
                        > To: microhydro@yahoogroups.com <mailto:microhydro%40yahoogroups.com>
                        > Sent: Wednesday, August 01, 2007 8:43 AM
                        > Subject: [!! SPAM] [microhydro] Learning to think about micro-pumped
                        > storage
                        >
                        > Hi again,
                        >
                        > I'm still trying to wrap my head around the possibilities for pumped
                        > storage. These are the questions I want to sort through:
                        >
                        > How does stored water (upper reservoir) translate into available
                        > energy (I would think a fairly simple system efficiency * potential
                        > energy analysis might suffice here, but I'm uncertain)?
                        >
                        > What considerations go into thinking about the delivery of power from
                        > such a system (i.e., flow resistance and flow rates, turbine capacity,
                        > spin-up time, etc)?
                        >
                        > Are there small turbines that can also be used (efficiently) as pumps,
                        > or do these two functions require separate equipment?
                        >
                        > What kinds of turbines would be most efficient for such a system?
                        >
                        > Any pointers to info, ideas, formulas, etc would be appreciated.
                        >
                        > Thanks for any leads.
                        >
                        > Warmly, Keith
                        >
                        > [Non-text portions of this message have been removed]
                        >
                        >

                        --
                        Keith Winston
                        Earth Sun Energy Systems
                        Hyattsville, MD 20781
                        301-980-6325
                        send me mail at
                        keith at the company below
                        www.EarthSunEnergy.com





                        [Non-text portions of this message have been removed]
                      • Doug Fortune
                        ... Keep in mind there might be an alternative reservoir for a slow-accumulate fast-dump-on-demand system: compressed air. The theory is that you have an
                        Message 11 of 15 , Aug 5, 2007
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                          Nando wrote:
                          > energy needed is Water volume * head * gravity = gross watts

                          Keep in mind there might be an alternative reservoir for
                          a slow-accumulate fast-dump-on-demand system: compressed air.

                          The theory is that you have an underground storage "tank",
                          such as a deep water well, that you fill with compressed
                          air when you have excess power, and some means (turbine?
                          or reverse air compressor? turning an electrical generator)
                          taps that resource when needed. Inefficient I suppose, but
                          large capacity!

                          I don't have any experience with this, its just a
                          "thinking outside the box" brainstorming idea...

                          Doug






























                          .
                        • Keith Winston
                          Thanks Nando, I subsequently noted kWh (a few thousand hours) in a later email. I used Amp hours since that s how storage batteries are rated, but of course I
                          Message 12 of 15 , Aug 5, 2007
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                            Thanks Nando, I subsequently noted kWh (a few thousand hours) in a later
                            email. I used Amp hours since that's how storage batteries are rated,
                            but of course I understand it's not a measure of energy storage...

                            Anyway, when I crunch the numbers using a simple potential energy
                            approach like you suggest (U (joules) = m (kg) x g (9.8 m^2/s) x h (m))
                            I get sorta depressing numbers. For example 1000 m^3 reservoir with 30 m
                            of head seems to only translate into only 80 kWh. Doesn't seem like so
                            much power for rather large reservoirs. About equivalent to 70 large
                            storage batteries (1.2 kWh). Of course, you can in principle run the
                            reservoir dry, but only discharge the batteries 50%, so call it 140
                            batteries. As against 1 million kg of water, with 30 meters head. I wish
                            the numbers worked out better.

                            Keith


                            nando wrote:
                            >
                            > Keith:
                            >
                            > First do not state amp-hours you need to state watts ( because amp
                            > hours defines the capacity to the bank but the voltage is missing --
                            > and voltage * amp-hours = watt-hours which is the real capacity of the
                            > bank -- in reality there is another factor that needs to be included
                            > and it is the watt-hours that should remain in the bank to protect the
                            > bank for long life use).
                            >
                            > the energy needed is Water volume * head * gravity = gross watts, also
                            > it is the same for the energy produced, the difference is the
                            > efficiencies involved in the process to produce the energy and to
                            > raise the water to the upper tank or reservoir -- for small systems
                            > this over all efficiency runs around 75 to 80 % for each way and in
                            > many cases lower.
                            >
                            > We made one, that had an over all efficiency of around 45 % in summer,
                            > not needed during most of the winter times, but allowed the small town
                            > to have the necessary energy for the for or five hours in the evening
                            > with some lights during the rest to the night ( 12 houses -- later 22
                            > homes) .
                            >
                            > This set up is not longer needed since they were able to re-route
                            > another water source to supply all the water needs, including the
                            > water house use.
                            > The upper reservoir is used to supply pressure to the homes water needs.
                            >
                            > Nando
                            >
                            > ---
                            >
                            > .
                            >
                            >
                          • nando
                            The idea could be attainable but one needs to determine if such arrangement is possible for a small entrepreneur. Large compressed air reservoirs require a lot
                            Message 13 of 15 , Aug 6, 2007
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                              The idea could be attainable but one needs to determine if such arrangement is possible for a small entrepreneur.
                              Large compressed air reservoirs require a lot of capital to just determine where to locate the underground storage "caves = tanks" .

                              One needs to examine, closely, what the process is and how to implement it in a practical way.

                              I believe that for most people, the solution is toward the water reservoir versus the air "tank" reservoir, cheaper in principle .

                              Nando


                              ----- Original Message -----
                              From: Doug Fortune
                              To: microhydro@yahoogroups.com
                              Sent: Sunday, August 05, 2007 10:07 PM
                              Subject: [microhydro] Re: Learning to think about micro-pumped storage



                              Nando wrote:
                              > energy needed is Water volume * head * gravity = gross watts

                              Keep in mind there might be an alternative reservoir for
                              a slow-accumulate fast-dump-on-demand system: compressed air.

                              The theory is that you have an underground storage "tank",
                              such as a deep water well, that you fill with compressed
                              air when you have excess power, and some means (turbine?
                              or reverse air compressor? turning an electrical generator)
                              taps that resource when needed. Inefficient I suppose, but
                              large capacity!

                              I don't have any experience with this, its just a
                              "thinking outside the box" brainstorming idea...

                              Doug

                              .




                              [Non-text portions of this message have been removed]
                            • nando
                              Keith: Depressing numbers because you may be looking for something with higher energy needs, maybe you need to see and think a bit different, like where I
                              Message 14 of 15 , Aug 6, 2007
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                                Keith:

                                Depressing numbers because you may be looking for something with higher energy needs, maybe you need to see and think a bit different, like where I could place a reservoir and how big to attain certain power production for this much time.

                                One needs to remember the great number of hydro electric plants already installed throughout the earth which have a "storage tank" -- which is large to cover energy needs.

                                In some places, a the reservoir was placed some distance from the turbine site, even the gate opening had to be done long time before the power generation to allow the water to reach the turbine

                                Nando

                                ----- Original Message -----
                                From: Keith Winston
                                To: microhydro@yahoogroups.com
                                Sent: Sunday, August 05, 2007 11:19 PM
                                Subject: Re: [microhydro] Re: Learning to think about micro-pumped storage


                                Thanks Nando, I subsequently noted kWh (a few thousand hours) in a later
                                email. I used Amp hours since that's how storage batteries are rated,
                                but of course I understand it's not a measure of energy storage...

                                Anyway, when I crunch the numbers using a simple potential energy
                                approach like you suggest (U (joules) = m (kg) x g (9.8 m^2/s) x h (m))
                                I get sorta depressing numbers. For example 1000 m^3 reservoir with 30 m
                                of head seems to only translate into only 80 kWh. Doesn't seem like so
                                much power for rather large reservoirs. About equivalent to 70 large
                                storage batteries (1.2 kWh). Of course, you can in principle run the
                                reservoir dry, but only discharge the batteries 50%, so call it 140
                                batteries. As against 1 million kg of water, with 30 meters head. I wish
                                the numbers worked out better.

                                Keith

                                nando wrote:
                                >
                                > Keith:
                                >
                                > First do not state amp-hours you need to state watts ( because amp
                                > hours defines the capacity to the bank but the voltage is missing --
                                > and voltage * amp-hours = watt-hours which is the real capacity of the
                                > bank -- in reality there is another factor that needs to be included
                                > and it is the watt-hours that should remain in the bank to protect the
                                > bank for long life use).
                                >
                                > the energy needed is Water volume * head * gravity = gross watts, also
                                > it is the same for the energy produced, the difference is the
                                > efficiencies involved in the process to produce the energy and to
                                > raise the water to the upper tank or reservoir -- for small systems
                                > this over all efficiency runs around 75 to 80 % for each way and in
                                > many cases lower.
                                >
                                > We made one, that had an over all efficiency of around 45 % in summer,
                                > not needed during most of the winter times, but allowed the small town
                                > to have the necessary energy for the for or five hours in the evening
                                > with some lights during the rest to the night ( 12 houses -- later 22
                                > homes) .
                                >
                                > This set up is not longer needed since they were able to re-route
                                > another water source to supply all the water needs, including the
                                > water house use.
                                > The upper reservoir is used to supply pressure to the homes water needs.
                                >
                                > Nando
                                >
                                > ---
                                >
                                > .
                                >
                                >





                                [Non-text portions of this message have been removed]
                              • Keith Winston
                                Thanks for all the responses! Just to be clear: I assume this would have to be coupled with a smallish battery bank, which could be used to excite the
                                Message 15 of 15 , Aug 6, 2007
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                                  Thanks for all the responses!

                                  Just to be clear: I assume this would have to be coupled with a smallish
                                  battery bank, which could be used to excite the generators, also in
                                  order to provide power during what I call "spin-up": the delay between
                                  loads coming on-line (someone starts their washing machine) and the
                                  gates open wider to increase generation. The batteries would be a
                                  crucial buffer.

                                  I am imagining, right now, using closed storage tanks vs. open
                                  reservoirs, but since I haven't been to the site yet, I'm not sure what
                                  might work there. I have only seen a low-res topo map. It seems like I'd
                                  be thinking about something at least 2000 m^3. That's about 500,000
                                  gallons. Whew. Seems like a lot... 25m square and 3m high, if we poured
                                  it out of concrete like a basement. Thing is, with the water going back
                                  and forth through these pumps, it seems like having them closed will
                                  save one a lot of filter cleaning, and also an open pond/reservoir will
                                  become an ecological niche which won't like being drained/emptied and
                                  refilled regularly...

                                  Keith
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