A widely-quoted estimate of the practical UK tidal resource is 12 TWh/y (Black and Veatch, 2005). I believe this is an underestimate, because it is based on an incorrect physical model of the flow of energy in a tidal wave. In a shallow-water-wave model of tide, the true flow of energy is greater than the Black-and-Veatch flow by a factor of d/h, where d is the water depth and h is the tide's vertical amplitude. The tidal resource may therefore have been underestimated by a factor of about 10.
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