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RoR plant layouts; storage over RoR

Short answer

RoR layout: weir, intake, desander, headrace (free-flow canal or pressure tunnel), forebay/surge tank, penstock, powerhouse, tailrace. Free-flow canal suits gentle slopes; pressure tunnel for steep terrain. Storage plants provide firm winter power, regulate flow, support peak demand, allow multipurpose use, and reduce spill and imports, unlike RoR's seasonality.

Sketch and explain layouts of the run-of-river plant. Also explain the importance of storage hydropower plants over run-of-river plants.

Layouts of a run-of-river plant

A RoR plant has: a diversion weir/barrage, intake, gravel trap, settling basin (desander), headrace (canal or tunnel), forebay or surge tank, penstock, powerhouse and tailrace. Two common layouts:

(a) With a free-flow headrace canal

 Plan
                          Forebay
 Weir/Intake--Desander--=========+
 ~~~~ River ~~~~~~~~~~~~~~~~~     | Penstock
                                  v
                            Powerhouse-->Tailrace-->River

(b) With a pressure tunnel

 Section
 Weir   Intake   Headrace tunnel (pressure)
 ___|~~~|======================+ Surge tank
                               | Penstock
                               PH  --> Tailrace
  • In (a), water flows with a free surface in the canal at a gentle slope, then drops in a penstock from the forebay. It is cheap in gentle terrain.
  • In (b), water flows under pressure through a tunnel, suitable in steep, rocky or landslide-prone terrain. It needs a surge tank.

Importance of storage over RoR plants

  • Gives firm power in the dry season, while RoR depends on river flow.
  • Regulates flow, so it increases installed capacity and energy and the plant factor.
  • Can supply peak load and respond to demand and the grid.
  • Multipurpose: flood control, irrigation, water supply, fishing, tourism.
  • Reduces the need for imports of power in the dry season.
  • Less spill of the monsoon surplus.
  • But it needs high capital, a long time, and resettlement/environment issues.

✓ Answer checked by Claude Opus 5.5 (high effort)

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