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RE: [microhydro] microhydro installation

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  • John Bertl
    VirgilioYour site is very much like my site except I have ten more feet of head, one hundred feet more of the same size penstock and a generator of 100 kva
    Message 1 of 4 , Mar 26, 2013
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      Virgilio
      Your site is very much like my site except I have ten more feet of head, one hundred feet more of the same size penstock  and a generator of 100 kva 3phase with a line voltage of 598.  My water turbine is a Francis and it is huge with a double runner.  My penstock is corrugated metal culvert with collars and O-rings.  My turbine is located nine feet above the tailrace but the tailrace can rise as much as thirteen feet.  (When it does, I must shutdown.)

      You asked for comments in general without any specific direction.  Here is what I see.

      1. Your flow and head conditions can produce 84 kw gross power.  With 80% efficiency of the turbine and 90% efficiency of the generator, you could produce 60 kw.

      2. You provide two 20 kw turbines which will only provide 36 kw given a generator efficiency of 90%.  Also, two 20 kw turbines given 80% efficiency will only consume 1.19 cubic meters of water per second not 2 cubic meters per second.

      3. You say the turbines must be crossflow.  Assuming the diameter of the turbine is three feet, (just under one meter), the total length of your two nozzle must be five feet six inches (1.65 meters) long plus the thickness of all stiffener disk in the runner to prevent the blades from bending.  The width of your nozzle must be 0.08 meters (3.14 inches).  Your rotation speed will be 90 rpm.  This slow of a driver will require gearing up to get your generator to it’s necessary speed.  This will add significant additional power losses.

      4. A small diameter runner will provide a faster driver speed but will significantly increase the length of your crossflow.  For example, if your runner was only one foot in diameter, you would be five meters long and rotate at 270 rpm.

      I would recommend you purchasing a vertical axial pump for these conditions.  One is all you need.  It would be in the high 80s in efficiency for your conditions, about 30 inches in inlet size and cost about $25,000  with induction motor included.  I know you cannot purchase a crossflow for that price.  If you need help or want more info, contact me directly.


      To: microhydro@yahoogroups.com
      From: virlabor54@...
      Date: Tue, 26 Mar 2013 14:00:11 +0800
      Subject: [microhydro] microhydro installation



      Hi everyone,

      I have one microhydro site which i would like everyone to comment.

      Parameters are:

       1)    Flow (Q) = 2 m3/second
       2)    Net head = 4.3 meters 
       3)    Required turbine:  2 units crossflow at 20kw capacity each
       4)    Penstock lenght:  20 meters with a diameter of 1.2 meters
       5)    Generator: 1 unit - 60kva, 3phase,  380 volts line to line

      As approved by the funding agency, crossflow turbine has to be used. I need your comments or suggestions regarding this design ( using crossflow turbine) at 4.43 meters head

      Regards,
      virgilio 


    • John Bertl
      In thinking about your E-mail, I am coming to the conclusion I made a mistake in understanding your question. I understood that your funding agency is
      Message 2 of 4 , Mar 26, 2013
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        In thinking about your E-mail, I am coming to the conclusion I made a mistake in understanding your question.  I understood that your funding agency is requiring you to install a "used" crossflow turbine and not a new turbine.  What I think you might have meant was that the funding agency (which is most likely tied to the crossflow manufacturers), is requiring you to install a crossflow turbine as a condition for the funding.  This makes my recommendation for a non crossflow turbine invalid.  However, from an economic standpoint, I estimate a new crossflow to cost $45,000 to $60,000 each, and maybe more.  A used vertical turbine with one stage costs $25,000 or less.  This saves $100,000 in turbine cost and provides 1/3 more power to the grid than your two 20kw crossflows.  In addition, the vertical turbine would require only one set of controls, have a much small footprint requiring a much small powerhouse and possibly could be located closer to the source which would reduce the length of the penstock.  All these possibilities reduce the cost further.  A crossflow seems to make sense only if the funding is 100%.

        I'm sorry for my original misunderstanding.


        To: microhydro@yahoogroups.com
        From: virlabor54@...
        Date: Tue, 26 Mar 2013 14:00:11 +0800
        Subject: [microhydro] microhydro installation



        Hi everyone,

        I have one microhydro site which i would like everyone to comment.

        Parameters are:

         1)    Flow (Q) = 2 m3/second
         2)    Net head = 4.3 meters 
         3)    Required turbine:  2 units crossflow at 20kw capacity each
         4)    Penstock lenght:  20 meters with a diameter of 1.2 meters
         5)    Generator: 1 unit - 60kva, 3phase,  380 volts line to line

        As approved by the funding agency, crossflow turbine has to be used. I need your comments or suggestions regarding this design ( using crossflow turbine) at 4.43 meters head

        Regards,
        virgilio 


      • Nando
        Virgilio: Where is the site located ? An alternate solution would be a propeller turbine , either two propellers or a single one, two if the site needs to
        Message 3 of 4 , Mar 26, 2013
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          Virgilio:
           
          Where is the site located ?>
           
          An alternate solution would be a propeller turbine , either two propellers or a single one, two if the site needs to continue producing some power if one of the turbine needs to shut down.
           
          The tailrace has to be defined to determine if the turbine can be operational if the tailrace goes up too much during high seasonal flows and the site can not release the water fast enough down the stream.
           
          A Francis is an alternate solution but it would be quite large and heavy .
           
          There are other alternatives that could be considered to attain the harvested desired power like Axial pumps and in this case a vertical one  which in a sense it is a propeller turbine but most of the time the blades are not adjustable to compensate the power under  variable flow conditions.
           
          Reason why I suggest a propeller turbine with adjustable blades .
           
          Using two bankis , here you have a problem and it is the diameter and the length of each turbine and the calculations needed to have quite well evaluated to maximize the efficiency of each turbine to obtain the optimum RPM and at the same time to have the optimum efficiency ( to be able to use the water rear flow to harvest at least an additional 17 to 19 % power )  so you will need to get a good company that can supply a guaranteed efficiency % and there are a very few one available capable of doing such high analysis job.
           
          You have not informed about the tailrace behavior around the site to see how to implement a draft tube to see if the overall system can be made operational 100 % of the time or the need to shut down when the tailrace goes up too high ( the water going down stream is not released fast enough to keep the tailrace low).
           
          Propeller or any other turbine for such a site may have the tailrace problem and therefore the site needs a good analysis to see how to solve the problem is such problem can be present periodically during the water high flows..
           
          Nando
          ----- Original Message -----
          Sent: Tuesday, March 26, 2013 01:00
          Subject: [microhydro] microhydro installation

           

          Hi everyone,

          I have one microhydro site which i would like everyone to comment.

          Parameters are:

           1)    Flow (Q) = 2 m3/second
           2)    Net head = 4.3 meters 
           3)    Required turbine:  2 units crossflow at 20kw capacity each
           4)    Penstock lenght:  20 meters with a diameter of 1.2 meters
           5)    Generator: 1 unit - 60kva, 3phase,  380 volts line to line

          As approved by the funding agency, crossflow turbine has to be used. I need your comments or suggestions regarding this design ( using crossflow turbine) at 4.43 meters head

          Regards,
          virgilio 

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