Dynamic Tidal Power (DTP)
Dynamic Tidal Power or DTP is the most complicated, least well understood tidal power scheme yet conceived. Basically, dynamic tidal power make use of the fact that ocean tides don’t operate strictly perpendicular to the shore, but also flow in parallel to the shore as well. This feature of tides would allow a type of barrage to be built perpendicular to the shore to harvest energy from the tides as they flow parallel to the shore as the diagrams below illustrate.
In the diagrams above, red represents relative high water and blue represents relative low water. The heights are relative to the barrage that is shown in black and which looks like a large “T.” The concept is based on the fact that tides flowing in one direction will tend to build up behind a barrier, like the barrage, and so create a height difference that can be used to generate power. When the tide shifts direction, something that happens every 12 hours, the height difference shifts sides.
The system only works if the barrage is at least 30 kilometers long and only if the turbines work in BOTH directions. So far, the system is 100% theory and has never been put to the test. The science and math are sound, but without experiment there is no way to be certain the scheme will really work.
Advantages of Dynamic Tidal Power
The main advantage of dynamic tidal power is that a single installation could produce anywhere from 8 to 15 gigawatts of power, orders of magnitude more than any other tidal energy system. An 8 GW installation could generate over 20 terawatt-hours of electricity in a year, which is enough for more than three million Europeans.
The second advantage to DTP is that it is stable. Because it generates power no matter which direction the tide is moving, the system is more continuous than other forms of tidal energy. It is more reliable than any other renewable like solar or wind because the tides are constant, predictable, and not influence by cloud, lack of wind, drought, etc.
Dynamic tidal power doesn't require a high head. In other words, water levels need not be dramatically higher on one side of the barrage compared to the other to generate the large amounts of power anticipated. This means that many more locations are suitable for DTP than for tidal barrage or tidal stream generators.
Finally, DTP offers the potential for combined function such as port protection, integration with wind turbines, aquaculture and research facilities, and more.
Disadvantages of Dynamic Tidal Power
Of course, dynamic tidal power is not a silver bullet. It has three major disadvantages. First, DTP is untested, so there is no way to be certain it will work without building a facility. This brings up the second problem, which is cost. A 30 km barrage is a very expensive undertaking and will cost tens of billions of dollars to build before we can even be certain it will work. This is to say nothing of the engineering difficulties associated with building a 30 km dam out into the ocean.
Finally, there is no way to be certain of the environmental impacts of DTP. Overall they are likely to be less than the use of barrage systems, but blocking off large lengths of coastal flow may disrupt mating patterns, migration patterns, and more. The ecologic impact could be tremendous.
All the various technologies needed to build dynamic tidal power schemes are available, but they have not been used together in a setting similar to DTP. China’s National Energy Administration has formed a consortium to investigation whether they will build a DTP plant and has signed a cooperation agreement with the Netherlands who has also been exploring the feasibility of DTP. The Netherlands, given its low lying land, is an ideal place for DTP because of the combined functions such a dam would have.