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Daily pondage ROR with 150 m head

Short answer

For 150 m head and 10 m³/s per unit, shaft power is about 13.2 MW (Ns≈132), suited for Francis turbine. Components: diversion weir, intake, gravel trap, desander, daily pondage (~90,000 m³ storage), headrace tunnel, surge tank, penstock, butterfly valve, Francis turbine-generator, tailrace, switchyard.

Discuss major components of a Daily Pondage Run off the River type hydropower project with tentative head 150 m and discharge 10 m³/s per unit. Illustrate with suitable schematic diagram.

For a head of about 150 m and 10 m³/s per unit, the unit output is roughly

P≈9.81×10×150×0.9≈13.2 MW (shaft)P \approx 9.81 \times 10 \times 150 \times 0.9 \approx 13.2\ \text{MW (shaft)}

and the specific speed at 600 rpm is Ns=60013244/1505/4≈132N_s = 600\sqrt{13244}/150^{5/4} \approx 132, which lies well inside the Francis range (60–300). So the project is a medium-head daily pondage run-of-river (PROR) scheme with vertical Francis units of roughly 12–13 MW each.

Schematic

 River ==|== Diversion weir + gated spillway
         |
      Intake (trash rack, gates)
         |
      Gravel trap -> Desander (2 or more bays)
         |
     [ DAILY PONDAGE ] -- spillway/flushing
         |
      Headrace tunnel (pressurised)
         |
      Surge tank
         |
      Penstock (steel, ~150 m head)
         |
      Butterfly valve
         |
      Francis turbine + Generator (~13 MW)
         |                 |
      Draft tube        Unit transformer
         |                 |
      Tailrace -> River  Switchyard -> Grid

Major components

  1. Diversion weir and spillway: raise water level and pass monsoon floods; undersluice keeps the intake free of sediment.
  2. Intake: sized for total design discharge (10 m³/s × number of units) plus flushing water; trash rack and gates.
  3. Gravel trap and desander: remove particles larger than about 0.2 mm, as sediment at 150 m head quickly erodes Francis runners and guide vanes.
  4. Daily pondage: stores off-peak inflow; for example, to run a 10 m³/s unit for 5 peak hours when the dry-season inflow is only 5 m³/s, storage =(10−5)×5×3600=90,000= (10-5)\times 5 \times 3600 = 90{,}000 m³ is needed.
  5. Headrace tunnel: carries water under low pressure to the surge tank.
  6. Surge tank: absorbs water hammer when governor closes the wicket gates and supplies water on load increase.
  7. Penstock: about 150 m static head plus water hammer allowance (typically 20–30%), with anchor blocks and expansion joints.
  8. Main inlet valve: butterfly valve, suitable for medium head.
  9. Francis turbine: spiral casing, stay vanes, wicket gates, runner and draft tube; vertical shaft; runner set below tailwater as required by cavitation.
  10. Generator: vertical synchronous generator at 11 kV, e.g. about 15 MVA at 0.85 pf, with excitation system and governor.
  11. Tailrace: returns water to the river below the powerhouse.
  12. Electrical system: unit step-up transformer (11/132 kV), switchyard, station supply and diesel generator for black start.

✓ Answer checked by Claude Opus 5.5 (high effort)

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