---
title: "Micro hydro scheme components and classification"
subject: "Energy Resources"
chapter: 5
key: "semester_6/energy_resources:micro-hydro-scheme-components-classification"
source: https://www.bctengineer.com/q/semester_6/energy_resources/micro-hydro-scheme-components-classification
site: BCT Engineering
---

# Micro hydro scheme components and classification

Energy Resources · Chapter 5: Micro and small hydro power systems

- Asked in: year not given, 6 marks
- Video: [Hydro power plant, Parts of Hydro plant, Components of Hydro plant #HydroPlant #PowerPlant](https://www.youtube.com/watch?v=3ixtdPORwsw) — Mechanical Engineering Management
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/energy_resources/micro-hydro-scheme-components-classification
- Whole chapter: https://www.bctengineer.com/md/semester_6/energy_resources/chapter-5

## Question

Explain the main components of a run-of-river micro hydropower scheme with a layout sketch. How are hydropower plants classified by capacity and by head?

## Short answer

Main components: diversion weir/intake, headrace canal, settling basin, forebay, penstock, powerhouse (turbine and generator), tailrace. Capacity classification: Pico <5 kW, Micro 5–100 kW, Mini 100 kW–1 MW, Small 1–10 MW. Head classification: low <15 m, medium 15–50 m, high >50 m.

## Answer

A run-of-river scheme diverts part of the stream flow through a channel and penstock to a turbine and returns it to the river, with little or no storage.

#### Layout
```text
  river  weir/intake
   ~~~~>[==]--> canal --> [forebay/
                           settling tank]
                              \  penstock
                               \  (gross
                                \  head)
                         [powerhouse]
                         turbine+gen --> load
                           tailrace--> river
```

#### Components
- **Diversion weir and intake:** raises the water level, directs flow into the canal; trash rack and gate keep out debris and control flow.
- **Headrace canal (or pipe):** carries water with a small slope to the forebay.
- **Settling basin (desilting tank):** removes sand and silt to protect the turbine.
- **Forebay:** small tank at the head of the penstock; gives storage for load changes and has a trash rack, spillway and air vent.
- **Penstock:** steel, HDPE or PVC pipe taking water down to the turbine; designed for pressure and water hammer.
- **Powerhouse:** turbine (Pelton, cross-flow, Turgo, propeller, or pump as turbine), governor or electronic load controller, generator, and control panel.
- **Tailrace:** returns the water to the river.
- **Transmission and distribution** lines to users.

#### Classification

| Basis | Class | Range (commonly used) |
|---|---|---|
| Capacity | Pico | below 5 kW |
| | Micro | 5–100 kW |
| | Mini | 100 kW–1 MW |
| | Small | 1–10 MW |
| Head | Low | below 15 m |
| | Medium | 15–50 m |
| | High | above 50 m |

Class limits vary by country and textbook. Low-head sites use Kaplan or cross-flow turbines; high-head sites use Pelton or Turgo turbines.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the settling basin for?
   A. Storing water for the dry season
   B. Reducing penstock pressure
   C. Removing sand and silt to protect the turbine
   D. Generating power
   Answer: C. Silt wears turbine runners. (Key point: Settling basin)

2. What does the forebay do?
   A. Returns water to the river
   B. Small tank at the head of the penstock giving storage for load changes
   C. Raises the water level in the river
   D. Houses the generator
   Answer: B. It has a trash rack, spillway and air vent. (Key point: Forebay)

3. Micro hydro is commonly defined as...
   A. 5-100 kW
   B. Below 5 kW
   C. 100 kW-1 MW
   D. 1-10 MW
   Answer: A. Below 5 kW is pico, 100 kW-1 MW is mini. (Key point: Capacity classes)

4. Which head class and turbine pair is correct?
   A. High head uses Kaplan
   B. Low head (below 15 m) uses Pelton
   C. Medium head is above 50 m
   D. High head (above 50 m) uses Pelton or Turgo
   Answer: D. Low-head sites use Kaplan or cross-flow. (Key point: Head classes)

## Related in Energy Resources

- [Micro hydro net head, power and energy](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Amicro-hydro-power-output-numerical) — Energy Resources, chapter 5
- [Site investigation for micro hydro plant](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Amicro-hydro-site-investigation-head-measurement) — Energy Resources, chapter 5

## Related in other subjects

- [Layout of hydropower scheme components](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydropower-scheme-layout) — Hydro Power, chapter 5
- [Daily pondage run-of-river components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Adaily-pondage-ror-components) — Power Plant Design, chapter 3
- [Types of hydropower plants by head, turbine, load](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Ahydropower-plant-types-classification) — Hydropower Engineering, chapter 2
- [Components of a run-of-river plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aror-components-functions) — Power Plant Design, chapter 3, asked 2×