In addition to its abundant solar, wind and geothermal resources, the Pacific Northwest is also uniquely situated to capture the renewable energy of the ocean. Special buoys, turbines, and other technologies can capture the power of waves and tides and convert it into clean, pollution-free electricity. Like other renewable resources, both wave and tidal energy are variable in nature. Waves are produced by winds blowing across the surface of the ocean. However, because waves travel across the ocean, their arrival time at the wave power facility may be more predictable than wind. In contrast, tidal energy, which is driven by the gravitational pull of the moon and sun, is predictable centuries in advance.

Europe has a long history of employing tidal forces to generate power, and tide mills dating back to the Middle Ages can be found across the continent. A dam with a sluice was constructed spanning a tidal inlet, or a section of a tidal estuary was turned into a reservoir.

Tidal energy has been used since about the 11th Century, when small dams were built along ocean estuaries and small streams. the tidal water behind these dams was used to turn water wheels to mill grains.

When water flows toward the shore with the incoming tide, it flows through a tidal energy system, turning a turbine that generates electricity. When the tide shifts and flows in the opposite direction, away from shore, the tidal energy system again captures the energy with a turbine and converts it into electricity.

The ocean tides on earth are caused by both the moon’s gravity and the sun’s gravity.

the ocean tides we experience on earth are caused by the sum of the moon’s gravitational gradient and the sun’s gravitational gradient.