There should be little doubt that the world needs to diminish its dependence upon fossil fuels for electricity generation. Marine renewable energy (MRE), in the forms of offshore wind, tidal, wave, or ocean thermal energy, remains the largest under-exploited energy source, with the potential to supply more than the total electricity demand in the world. It is estimated that the global wave energy resource alone is about 32,000 terawatt hours (TWh) per year, compared with the global electricity supply of ~24,000 TWh per year in 2014.1 Global potential for tidal power could be up to 1,000 TWh per year.2 The various MRE technologies differ significantly in their readiness for large-scale exploitation. The most mature technology is that of offshore wind generation, which has evolved from extensive experience on land. The least mature is wave energy generation, numerous devices for which are still in early developmental stages. Mechanical energy from tides is a centuries-old technology based upon impoundment of tidal waters, and barrage-based installations (the tidal range approach) for electricity generation has been considered in Canada (the Bay of Fundy) and Europe for more than 100 years. One turbine installed in a dam at Annapolis Royal, Nova Scotia, has been in operation since 1985. New technologies designed to convert the energy of flowing water (i.e., tidal stream), rather than impounded water, are rapidly developing and offer significantly fewer environmental effects than those based on barrages or tidal lagoons.
In Canada, significant opportunities exist for MRE on all three coasts. Of the options, tidal stream energy is particularly attractive because its timing and scale are eminently predictable, and its development can be incremental, which is an important consideration when the environmental effects are uncertain. Large-scale tidal stream devices generating one to two megawatts of electricity offer considerable potential, especially for isolated communities on all three coasts where tidal flows exceed one to two meters per second. In addition, arrays of such large-scale devices could make valuable contributions to established electricity grids, especially where, as in the Bay of Fundy, a large tidal resource exists in a region of strong energy demand.