Introduction to Wave and Tidal Energy

What is the most significant challenge facing wave energy development?

Extreme weather at sea can create enormous waves containing many thousands of times more energy than the average, and wave energy devices have to be able to survive these conditions. To date, no one has been able to design a device that combines being effective at extracting energy from average conditions and also able to avoid responding to the extreme conditions. This means that wave energy devices have to be built to withstand loads that are many, many times greater than they experience most of the time, resulting in high structural costs compared to the energy output.

What are the two fundamental concepts for power generation from the tides?

Like the tidal mills of old, tidal barrages use the difference in water height between high water and low water, converting the potential energy in the water. In contrast, tidal stream devices extract energy from the moving water in a tidal stream, the kinetic energy.

What are the costs of wave and tidal energy compared to offshore wind energy?

Wave energy development is still at a stage where there are no significant commercial deployments and consequently no operational history from which it is possible to determine the cost of energy. The lack of deployments, despite a number of subsidy support schemes, suggests that the costs are still many time that of wind energy.

Tidal stream energy is a little further down the cost curve, with a number of pre-commercial devices in, or shortly to enter, operation. But here again, their costs have not been market tested and substantial subsidy levels are said to be required, whereas offshore wind is more or less competitive with long term wholesale power prices.