Tidal Power is a form of hydropower that converts the energy of tides into electricity or other useful forms of power. Tidal energy is generated by the relative distances and motion from the Earth, Sun and the Moon and their respective gravitational forces. A tidal energy generator uses this phenomenon to generate energy. The stronger the tide, either in water level height or tidal current velocities, the greater the potential for tidal energy generation.

The magnitude of the tide at a location is the result of the changing positions of the Moon and Sun relative to the Earth, the effects of Earth rotation, and the local shape of the sea floor and coastlines. Periodic changes of water levels, and associated tidal currents, are due to the gravitational attraction by the Sun and Moon.

Tidal power is not widely adopted, though it has strong potential as a renewable energy resource for electricity generation. Tidal motion is more predictable power generation than wind or solar. Because the Earth's tides are caused by the tidal forces due to gravitational interaction with the Moon and Sun, and the Earth's rotation, tidal power is practically inexhaustible and classified as a renewable energy source.

Tidal power can be classified into two main types:

• Tidal stream systems use the kinetic energy of moving water to power turbines in a similar way to windmills that use moving air. This method is popular due to its low cost and lower ecological impact compared to barrages.

• Barrages make use of the potential energy in the difference in height (or head) between high and low tides. Barrages are essentially dams across the full width of a tidal estuary.  They are very high civil infrastructure cost projects.  There is a worldwide shortage of viable sites, and many environmental issues.

• Tidal lagoons are similar to barrages, but they can be constructed as self-contained structures, not fully across an estuary, and are claimed to incur much lower cost and impact overall.

Modern advances in turbine technology may eventually see large amounts of power generated from the ocean, especially tidal currents using the tidal stream designs, but also from the major thermal current systems such as the Gulf Stream.  Tidal stream turbines may be arrayed in high-velocity areas where natural tidal current flows are concentrated.  This occurs often in such places as the west and east coasts of Canada, the Strait of Gibraltar, the Bosporus, and numerous sites in south east Asia and Australia. Such flows occur almost anywhere where there are entrances to bays and rivers, or between land masses where water currents are concentrated.  (Information provided by Wikipedia)

Investments in Tidal Power can come in the form of direct investments in tidal power generation plants or by investing in companies with new technologies for tidal power generation. Due to the fact that tidal power is not widely invested in, tidal power and investing in tidal power technologies can be considered very speculative.