Interest in the power potential of tidal streams is growing worldwide. While the latest assessment for Canadian coastlines estimates a resource of approximately 42 GW, these results are based on the average kinetic energy flux through the channel. It has been shown, however, that this method cannot be used to obtain the maximum extractable power for electricity generation. This work presents an updated theory for the extractable power from a tidal stream in a channel linking a bay to the open ocean. The maximum average extractable power from a channel linking a bay to the open ocean may be estimated, within approximately 15 per cent, as 0.22ρ gaQ0, where a is the amplitude of the dominant tidal constituent in the open ocean and Q0 is the maximum volumetric flowrate in the undisturbed state.

This work presents a case study for the power potential of a tidal stream connecting a bay to the open ocean. The extractable power, averaged over the tidal cycle, from Masset Sound, located in Haida Gwaii, Canada, is estimated as 79 MW when only the dominant M2 tidal constituent is included in the analysis. The value increases to 87 MW when the three dominant constituents are included. It is shown that extracting the maximum power from Masset Sound will decrease both the maximum water surface elevation within the bay and the maximum volume flowrate through the channel to approximately 58 per cent of their undisturbed values.