Water as an Energy Source

Water can provide renewable energy in three main ways: hydroelectric dams (falling water), tides (rising and falling sea levels), and waves (movement of the sea surface). All three use moving water to turn a turbine connected to a generator, which produces electrical energy. No boiler is needed.

How electricity is made from water

• Turbine: moving water spins blades.
• Generator: the spinning turbine turns a coil/magnet to make electricity.
• Energy transfers: gravitational or kinetic energy of water → kinetic energy of turbine → electrical energy in the generator.

Hydroelectric power (HEP)

Water is stored high behind a dam. It has gravitational potential energy. When released, it flows down through a turbine and turns a generator. This can produce large amounts of power and can start quickly when demand rises.

Tidal energy

Tides are caused mainly by the Moon’s gravity. A tidal barrage traps water at high tide and lets it flow through turbines at low tide (and vice versa). Tidal stream turbines sit in fast tidal currents like “underwater wind turbines.” Tides are very regular and predictable.

Wave energy

Waves move devices that bob up and down or push air through a turbine. Wave power is strongest on windy, open coasts and is more variable than tides.

Where the energy comes from

• Hydroelectric and waves: driven by the Sun (Sun heats water → water cycle; Sun drives winds → waves).
• Tides: driven by the Moon (and partly the Sun), not by the wind.

Advantages and disadvantages

• Renewability: All are renewable.
• Reliability: Tidal is highly predictable; hydro with reservoirs is reliable and quick to start; waves are less predictable.
• Scale and availability: Hydro can be very large but needs suitable valleys/rivers; tidal needs large tidal ranges or fast currents; waves need energetic coasts.
• Environmental impact: No fuel burning during operation (low air pollution). Dams can flood habitats and block fish migration; tidal barrages can affect estuaries and sediment; wave farms may affect marine life and views. High upfront costs for all.

Common misconceptions

• Tides are not caused by wind; they are mainly due to the Moon’s gravity.
• Dams do not create energy; they store water high up, which stores gravitational potential energy.
• “Clean” does not mean “impact-free”; water projects can change habitats.