Tidal power harnesses the energy from water moving from tidal forces in order to generate electricity. Unlike other primary energy flows, it is a predictable source of energy because tides occur at expected times. This predictability has an advantage over wind and solar power since the sun may or may not shine on a particular day and the wind doesn't always blow the expected amount. Tidal power is still not a dispatchable source of electricity as it is available when nature provides it, not necessarily when it is needed.
Tidal power is not a widely used energy resource at the moment because its costs outweigh the advantages. Previously only very specialized locations were able to support these technologies. However, recent improvements are making tidal power much more cost effective and adaptable to a wider range of locations. If support for tidal power continues to increase the industry will likely grow.
There are three basic methods used for generating power from tides, these methods are constantly being researched, adapted and improved. However, all three use the basic principle of converting the mechanical energy of tidal movements into electricity. Locations where tidal power generation is available have geographic features that restrict what types of tidal generators can be used, which makes it necessary to have a range of systems available.
Main article: Dynamic tidal power
Dynamic tidal power is a technology that uses the difference between the potential energy and kinetic energy of tides. Long dams are built from coasts straight out into the sea or ocean - meaning that the tides in the areas where these systems can be implemented usually flow parallel to their respective coasts.
This technology is still in the experimental phase and requires a full scale demonstration plant to fully prove feasibility.
Main article: Tidal stream generator
Tidal stream generators make use of moving water to power turbines - similar to the way wind turbines use wind to create power. There are several variations of tidal stream generators all of which use very similar processes but have different designs and can be found on the tidal stream generator page.
Main article: Tidal barrage
Tidal barrage systems work similarly to hydroelectric dams, they capture the energy from water moving in and out of a bay or river due to tidal forces. Again, there are several variations of this method that all use a similar process and are further discussed in the main article.
Tidal power offers a renewable resource to areas that currently rely heavily on imports for their energy. Building tidal power generation plants would boost local economies and create many jobs. Furthermore, tidal power generation - if built properly - would significantly reduce the CO2 footprint of local areas.
The environmental impact of tidal power systems could be significant. Unfortunately, in areas where any tidal power stations might be built happen to be some of the most densely populated ecosystems in the ocean. Changes in water levels and flow rates might harm plant and animal life and alter the sea water composition. Also, turbines needed to generate power move quickly, and if protection is not built in, marine animals can be caught in the blades. If aquatic life drops in the area, birds typically found there might migrate to different places. An entire ecosystem could be significantly altered. Further research is needed in order to determine just how large of an impact such stations might have.
The methods used to harness the energy from tides tend to be quite expensive, not only to build but also to maintain. Depending on the specific type of tidal power, the cost per MW can be over double the cost of similar sustainable energy resources such as wind and solar. Therefore, a significant improvement in technology is required in order to make tidal power more feasible. However, judging from the amount that such technologies have improved in such a short period of time (tidal power has only been around for the past few decades), costs will continue to fall, though by how much still remains a question.
The Bay of Fundy, located on the east coast of Canada between Nova Scotia and New Brunswick, is home to the highest tidal fluctuations in the world. An incredible amount of water flows into the bay during high tide, in fact more than four times the flow of all the world’s freshwater rivers - up to 160 billion tonnes - flows in an out of the bay in one tidal cycle. Having such quantities of water flowing in and out on a predictable schedule give the Bay of Fundy enormous potential for the development of tidal energy projects. Currently the Fundy Ocean Research Center for Energy (FORCE) is the leading research center for tidal energy in the Bay of Fundy also acting as host and watchdog to researchers developing tidal technology. Below is a video of the intense tidal fluctuations found in the Bay of Fundy.