The worldwide potential of electric power from tidal currents is potentially between 100 and 120 GW. The technology uses the ebb and flow currents off coasts to drive submerged turbines. The high load factor and the predictable resource characteristics make tidal energy an attractive, reliable power source. The technology is advancing rapidly towards maturity; several projects have now reached a relatively mature stage and are close to completion, but challenges remain. Topics for ongoing research include hydrodynamics and turbine design, as well as the power conversion interface (including...