Project Details

Power Calculations:

                                                     P= hv’gµ

  • P= Power, watts, W
  • h = Head, metres, m
  • v’= volume flow rate, metre cubed per sec, m3/s
  • g = gravity, metres per second per second m/s2
  • µ = efficiency factor

The head was initially thought to be 25m from map contours, but a more simple approach revealed it to be 8.3m by simply using a measured length and repeating uphill.

v’, or the volume flow rate is indeed critical to the success of the project. The flow rate has been measured at 10-20L/s in summer, but more than 50L/s+ after rainfall and more commonly available in winter (via a timed bucket fill method). This is a crude measure but is fairly accurate under low flow conditions, under high flow conditions it is more difficult as it is nearly impossible to concentrate the whole of burn flow into a bucket. So the high flow measure there is by simply estimating the doubling or trebling in flow. Which was easier to read at the pond for cold water supply at the proposed 25m head inlet.

km2 m2
Catchment area 1.6 1600000
Rainfall 1.5 m
Volume of rainfall in catchment 2400000 m3
Losses 10% 240000
Annual Flow 2160000 m3
Daily Flow 5918 m3/day
Flow / Hour 247 m3/hour
Flow/sec 0.07 m3/sec

The other method to calculate flowrate is to work back from the catchment area, as summarised in the above table which gives a flowrate of 70L/s. This is based on an annual rainfall of 1500mm which is likely in this area[i]. However the nature of rainfall in Scotland is that it will rain heavily for short periods and so the flow rate is likely to range from as low as 10L/s on after a dry summer spell to possible up to 100L/s after days of heavy rain. This was also backed up by looking at sepa flow data for local rivers.

  • To conclude in winter the flowrate is likely to be in the order of 40L/s average, whereas in summer the average will be nearer 20L/s.

Power Generation:


  • Units: Metric
  • Flow: 15.0 lps
  • Used Flow: 10.4 lps
  • Pipe Head: 8.5 m
  • Pipe Length: 120 m
  • Pipe Efficiency: 90 %
  • Pipe Diameter: 110 mm (This value was locked and may not have been the diameter recommended by the calculator)
  • Number of Powerspouts: 1 (This value was locked and may not have been the number recommended by the calculator)
  • Nozzles: 2
  • JetDiameter: 23.7 mm
  • ActualPipeEfficiency: 84 %
  • Speed: 442 rpm
  • Output: 365 W
  • TotalOutput: 365 W


  • OuputVoltage: 351 V
  • CableEfficiency: 90 %
  • CableLength: 40 m
  • LoadVoltage: 350 V
  • ActualLoadVoltage: 350 V
  • CableMaterial: Copper
  • CableSize: 1.5 mm^2 (This value was locked and may not have been the size recommended by the calculator)
  • CableAWG: 15 AWG
  • CableCurrent: 1.0 A
  • ActualCableEfficiency: 100 %
  • ActualTotalOutput: 364 W


[i] From metoffice data, available online here:, viewed 01/11/2011

[2] Data from the powerspout calculator available online here:


15 thoughts on “Project Details

    • hi Nick,
      Pipe was hdpe black plastic piping, as seen on It is 125mm, 110mm Internal and came in two 100m coils and 1x 50m coil. Total cost was about £1400 ex VAT. Cheers


  1. Hi Ewan,

    Paul suggested you might be able to advise me. I am just starting on a microhydro project in West Wales and would like to use 2 off powerspouts and will be going the legal route so i can get grid connection and FIT payment and was wondering if you had managed to get the 2 off powerspouts approved under the ROOFIT for FIT payment.

    • Hi Dave,
      Took about a year to get and at the time the initial application was made it went under roofit scheme which i believed was soon to be outdated as of oct/nov 2012, replaced by FIT. However, we did get in the end (came through only oct 2013) and its really helping with the costs/justification for system. Worth pursuing but i wouldn’t bet on it to justify your system, instead see it as a bonus if you get it. The main grey area was that you are meant to get an accredited produce installed by an accredited installer. There are very few (including powerspout) turbines that are accredited like PV panels etc.

      • Hi Ewan,

        What a great project – I am quite jealous. I guess it is only this govt which can make things so complicated. As it has now gone back to ROOFIT I believe that there is no requirement for the equipment to be MCS approved. I will require professional help with the wiring and commissioning.
        Many thanks


      • Thats good from your viewpoint then, the wiring is actually fairly easy but to get FIT, best to get it completed by approved electrician and get certificate. I would be interested to track your project so feel free to drop a me a link of pics/progress, cheers Ewan

  2. Hi Ewan,

    I will post on the Navitron forum -under hydro -Micro hydro installation by Regen. Would it be all right if I copied your electrical schematic to append to the G59 that Western Power want me to fill in. As I allready have 4kw PV I cannot go the G83 route apparantly.
    Best Wishes


    • HI Dave, yeh thats fine. So long as its the same set up as mine. Just overlay my meter serial number with a text box, All the best, Ewan

  3. Thanks Ewan,
    Hi Ewan
    The set up will be basically the same – just the numbers change ie powerspouts running at 750-800 watts each so inverter will be sb2200 or maybe windyboy 1800

    Best wishes


  4. Hi Ewan,

    Thanks for the great blog. I am looking at doing the exact same scheme in South West Scotland. I was just wondering if you could provide a ballpark of what it cost you in total for the entire thing?

    Kind Regards,


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