A note on the power potential of tidal currents in channels

• A set of one-equation formulas are derived to assess tidal stream energy.
• One-equation formulas agree well with complex numerical models.
• One-equation formulas agree well with, and expand upon, existing theoretical formulas.

This paper presents a set of three simple one-equation formulas that can be used for rapid initial assessment of the tidal power potential of fast moving currents in both large straits and small tidal channels (as may exist close to isolated communities). The three formulas enhance previous published theoretical estimates and are consistent with each other in that any one of them can be used depending on which two of the following three input parameters are known: (i) the variation in water level at either end of the channel (or just at the ocean end for a channel connected to an enclosed bay); (ii) the peak undisturbed natural flow rate through the channel; or (iii) the approximate channel geometry and seabed drag coefficient. The formulas are derived using an electrical analogy of the dynamics of flow through a channel. Example calculations are given and the results compare favourably with previous estimates of power potential by alternative theoretical formulas and detailed numerical models.