Renewable Energy - Hydro, Tidal, and Wave Power

Vocabulary flashcards for key terms and concepts related to hydroelectric, tidal, and wave power generation.

Hydroelectrical Power History and Role

Well-established technology, provides a significant fraction of energy supplies, principal electricity source in about 30 countries, provides about 20% of world electricity supply.

Power Output Formula

Pressure head multiplied by volumetric flow rate (W).

Hydroelectrical Power History and Role

Well-established technology, provides a significant fraction of energy supplies, principal electricity source in about 30 countries, provides about 20% of world electricity supply.

Power Output Formula

Pressure head multiplied by volumetric flow rate (W).

Types of Hydroelectric Plants Classified by Head

Medium head, Low head (h

Francis Turbine

Most common type for HEP applications, radial flow turbine, efficiency up to 95%, limited at low heads, poor choice for high heads/speeds.

Propellers

Axial flow turbine, normally used in low head applications, uses Kaplan Turbines.

Impulse Turbine

Simplest example is the Pelton Wheel, jets of water are 'fired' at cups, very high efficiency, used for high head situations (>250m).

Three Gorges Dam

China, commissioned in 2012, Installed Capacity: 22.5 GW, Annual generation: ~100 TWh (2014).

Tidal Power: Barrage

Use of twice-daily upstream flow (from the sea) and downstream ebb (to the sea) of the tides. Minimum tidal range considered useful for exploitation ≈5 m.

Tidal Power: Technical Considerations

Cycle may occur on ebb or flow tides, or both. Turbine speed is low. Large numbers of turbines required to generate sufficient power.

Tidal Power: Flood Pumping

Enables the energy recovered per cycle to be increased. Additional seawater is pumped into the basin near high tide.

Tidal Power: Tidal Stream

Make use of water flow caused by tides. Resemble a horizontal axis wind turbine. Reduced environmental impact compared to barrage or fence tidal systems.

Wave Power

Caused by wind over the surface of water, form of solar energy, depends on wavelength, wave height and wave period. No large scale commercially viable solution as yet.

Main wave generator types - Fixed devices

Attached to the seabed. Attached to the shore, or Constructed near the shore for the waves to enter.

Main wave generator types - Floating devices

Waves go through, changing the volume pushing air through a turbine. A float that moves with the waves which is attached to an electrical generator.

Wave power: Tapered Channel (TAPCHAN)

Tapered channel amplifies wave height, which spills over into reservoir. Very simple with limited moving parts, but requires particular geography to be economical.

Wave power: Islay LIMPET

World’s first commercial wave power station. Example of an Oscillating Water Column (OWC).

Wells Turbine

Always spins the same direction as the air flow approaches from either side. Suited to the oscillatory flow produced by waves passing through a chamber with air above.

Wave power: Salter Duck

Power generated through a gyroscopic electrical motor.

Wave power: Pelamis wave generator

Self orientates into the waves, sections moves up and down and side to side, relative motion forces hydraulic fluid through generators to produce power.