Loading ...
Sorry, an error occurred while loading the content.

RE: [microhydro] Need clearification

Expand Messages
  • Hillis, Peter
    Rupert, The units given were correct:, power (watts) = rho (kg/m3) x g (m/s2) x Q (m3/s) x H (m) x Eff (per unit) Your formula ignores rho (approx 1000 kg/m3)
    Message 1 of 7 , Sep 23, 2001
    View Source
    • 0 Attachment
      Rupert,

      The units given were correct:,

      power (watts) = rho (kg/m3) x g (m/s2) x Q (m3/s) x H (m) x Eff (per unit)

      Your formula ignores rho (approx 1000 kg/m3) so that is why you think there
      is a decimal point in the wrong place. Using flow in m3/sec and including
      rho the result will be in watts.

      Admittedly gravity and rho only vary by about half a percent each (unless
      you are using sea water as some Japanese pump storage schemes do) so are
      really only of importance when performing efficiency tests to ensure
      manufacturers have meet guarantees.

      Peter.




      -----Original Message-----
      From: evansengineering@... [mailto:evansengineering@...]
      Sent: Friday, 21 September 2001 07:22
      To: microhydro@yahoogroups.com
      Subject: Re: [microhydro] Need clearification


      I am not quite sure why you are worrying about the variation in g due to
      altitude and latitude, when you appear to have the decimal point in the
      wrong
      place! ( If flow is in mt3/sec the power will be in kW not watts )

      Head (metres) X flow (lt/sec) X (9.8 or 10 if you like !!!) = theoretical
      power at 100% (Watts) Take 65% overall efficiency for a small plant and
      you won't be far out.
      Regards
      Rupert (in a pedantic mood !)


      [Non-text portions of this message have been removed]



      NOTE: The advertisements in this email are added by Yahoogroups who provides
      us with free email group services. The microhydro-group does not endorse
      products or support the advertisements in any way.

      More information on micro hydropower at http://microhydropower.net

      To unsubscribe: send empty message to microhydro-unsubscribe@...

      Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    • evansengineering@cs.com
      Dear Peter, You my be concerned by what is correct in terms of scientific notation but my objective (and I appreciate that it may not be your way ) is to
      Message 2 of 7 , Oct 15, 2001
      View Source
      • 0 Attachment
        Dear Peter,
        You my be concerned by what is 'correct' in terms of scientific notation but
        my objective (and I appreciate that it may not be your way ) is to make
        hydraulics easily understood and applicable by non-technical farmers and the
        like. If you take the flow in litres per second, times the head in metres and
        multiply it by 10 and an efficiency figure of about 65%, you will have the
        power in watts at the output of the generator. Anyone capable of more
        accurate calculation can do it for themselves. I thought this group was more
        interested in practical engineering and application than arguing about
        detailed maths and perpetual motion machines.

        With this in mind I am restarting training courses (I first ran them 20 years
        ago) at what will be 'The International Centre for Water Engineering.' They
        last from 1 week to about 4 months and are aimed at training field workers in
        hydro equipment, irrigation structures and flood control. It is very hands-on
        and will involve the design and installation of at lease one real project
        during each course.

        If anyone is interested in taking part or being a recipient of suitably
        trained field workers, please let me know.

        Regards
        Rupert Evans
        www.microhydro.com


        [Non-text portions of this message have been removed]
      Your message has been successfully submitted and would be delivered to recipients shortly.