Hydroelectricity

Energy of falling water

Vertical fall

• The power of water:
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• most common type
• medium or large scale plants
• completely submerged
• radial and axial flow (mixed flow) turbine
• medium head

Water enters radially and emerges out axially so the discharge is parallel to the axis of shaft

Adjustment of the pitch -> we can change the angle of the blades to match the new conditions, can reduce the output power by turning the guide vanes when demand falls

• Axial flow turbine
• Rapid rate of revolution
• Require large quantity of water (low head)

Change the angle of blades when the power demand changes

• Require lower quantity of water
• High heat turbine
• Tangential flow turbine
• Has double cups

Variant of the Pelton Wheel - vary cup depth

• Tangential
• Radial
• Axial
• Mixed (radial and axial)

• Reaction
• Impulse

The water hits the turbine as a jet in an open environment with the power deriving from kinetic energy of the flow

The turbine is totally embedded in the fluid and is powered from the pressure drop across the device

• Greater than 250m
• Pelton Wheel
• Impulse turbines

• 50m to 250m
• Francis Turbine

• Less than 60m
• Kaplan Turbine
• Reaction Turbine

• Axial-flow turbine
• Area that water enters is the entire swept area
• Good for large volume (low head) flows

• Impulse type
• Water enters in a flat sheet rather than a round jet

• Infinitely renewable
• No fuel required
• Non-polluting
• 80% efficiency
• Flood water can be used for agriculture
• Long life equipment
• Limited required maintenance
• long lasting
• last for 50+ years

• People need to be evacuated to make room
• Landscape clearing results in soil erosion
• Limited natural flow in summer period
• Bad for fish (Increase in T causes O2 levels to drop)
• Killing of fish in turbines