Micro-hydro: from falling water to electricity
Run a village micro-hydro plant. Change how far the water falls, how much flows, and the turbine, and see how many homes you can light, and how much energy is lost on the way.
Core concept
The potential energy of water high on a hill becomes kinetic energy in the pipe, then electrical energy in the turbine and generator; the power is about 9.8 × flow (m³/s) × fall (m) kW, times the efficiency, and the rest is lost as heat and sound, never destroyed
Topic: Energy
Thousands of Nepali villages get their electricity from micro-hydro plants. A canal takes water from a stream to an intake high on the hillside. From there a pipe, the penstock, carries it down to a powerhouse, where it spins a turbine joined to a generator. The water's gravitational potential energy: What is needed to make things move, heat up, light up or grow. All key words becomes kinetic energy as it falls, then rotational energy in the turbine, then electrical energy. Each second, a flow of 1 m³ (1000 L) of water falling 1 m gives about 9.8 kW. No machine changes all of it: friction: A force that slows things down when two surfaces rub together. All key words in the pipe and the turbine, and heating in the generator, turn part of it into heat and sound. Energy is never destroyed; it only changes form. This is the law of conservation of energy.
What you will learn
- Describe the energy changes in a hydropower plant.
- State the law of conservation of energy.
- Calculate the power of falling water and the electrical power from the efficiency.
- Explain why the head (height of fall) and the flow both matter.
Before you start
- Know that power is energy per second, measured in watts.
Materials
- A plastic bottle, a cork, plastic spoons and a pin (for a model water wheel)
Equipment
- A tap or a jug of water, a small dynamo and an LED
Procedure
- Record the power with a 50 m fall, 100 L/s and the new turbine.
- Record with falls of 10 m, 25 m and 100 m.
- Record in the dry season, when only 50 L/s flows.
- Record with the old turbine.
How this simulation is simplified
- The power of the falling water is 9.8 × flow (in m³/s) × fall (in m) kW.
- The old turbine and generator are 50% efficient, the new ones 70%.
- Each home uses 200 W (lights, a TV and a phone charger) in the evening.