Turbine Selection by Head — 450 m Head of Water For an available head of approximately 450 m at a hydropower site, which turbine type is generally preferred?

Introduction:
Choosing the turbine type depends primarily on site head and discharge, summarized by specific speed. High heads with relatively small discharges suit impulse machines, while low heads with large discharges suit axial-flow reaction machines.

Given Data / Assumptions:

• Gross head ≈ 450 m (very high head).
• Standard water properties; feasible penstock designs.
• Goal: select an appropriate turbine family.

Concept / Approach:
Pelton turbines (impulse type) are the go-to choice for high heads (typically above ~250–300 m), converting the entire head into jet kinetic energy before striking buckets. Francis turbines suit medium heads, whereas Kaplan (propeller) turbines serve low heads. At 450 m, Pelton provides excellent efficiency and manageable runner speeds via multiple jets if needed.

Step-by-Step Solution:
Classify head: 450 m → high-head regime.Match to turbine: Pelton wheel designed for high head, low to moderate discharge.Reject others: Francis (medium head), Kaplan (low head).

Verification / Alternative check:
Specific-speed charts place 450 m sites in the Pelton domain; many alpine stations use Pelton runners at similar heads.

Why Other Options Are Wrong:
Kaplan: optimized for very low head and high flow.Francis: best for medium heads and mixed-flow conditions.none of these: incorrect since Pelton fits.

Common Pitfalls:
Overlooking cavitation limits and runner speed; Pelton mitigates these at high heads.

Final Answer:
Pelton wheel