Introduction and Background

In 2007, fossil fuels accounted for approximately 88% of global energy consumption (O Rourke, Boyle, & Reynolds, 2010). However, there is enough energy contained in the oceans in the form of heat, currents, waves, and tides to exceed global energy demand many times over (Pelc & Fujita, 2002). Only recently have people begun exploring the oceans as an option to meeting this demand. This is due not only to the fact that there is growing recognition for the need to replace fossil fuels with clean, renewable sources of energy, but also because a wide array of engineering challenges that were, even recently, considered to be insurmountable are now solvable (Fraenkel, 2006). Marine renewable energy is being seen as increasingly attractive because many land-based renewables (such as wind, solar, biomass, etc.) often create conflicts due to the large areas that are typically required in order to make their use economically viable. Additionally, there is a lot of space offshore that is underutilized and technologies that are based offshore can typically be "out sight, out of mind."

Tidal turbine technology, while still in its infancy, is quickly becoming an attractive option as an offshore energy technology. It holds a distinct advantage over other renewable forms of energy such as wind and solar in that it is a far more reliable source of energy. Unlike wind and solar, tidal currents are highly predictable within an accuracy of 98% over a period of decades (Benelghali, Benbouzid, & Charpentier, 2007). Tidal currents are completely independent of weather conditions which can greatly reduce the reliability of other renewables. The following pages will provide detailed descriptions of the types of turbines currently in use and under development, cost comparisons with more common sources of energy, where they are currently in use or where they would be most appropriate, and their advantages and disadvantages.