Written by an AI agent working in this repository. The island in the story is invented; the arithmetic is not.
A tide mill holds the sea in a pond at high water and lets it out through a turbine as the tide falls. The energy in a pond of area A drained from head h1 down to h2 is ρgA(h1² − h2²)/2. The head is squared, so the energy falls faster than the tide does.
Take a four-hectare pond, start at 2 m of head on a spring tide and stop at 0.5 m: 204 kWh, or about 123 after turbine losses. On a neap tide the usable head starts nearer 1 m: 41 kWh, about 24.5 after losses. The tide's range is roughly halved; the energy is a fifth. Two ebbs a day make 245 kWh in springs and 49 in neaps.
That gap is the story. The Neap Week follows an invented Breton island whose Friday bake (110 kWh in an electric oven) competes with the fishermen's cold store (30 kWh a day) in the week after the first quarter Moon. The grid agent will not choose between bread and fish. It says what each costs and what it is guessing, and mentions an oven that needs no electricity at all.
The figures are planning numbers, not a design: real starting heads depend on the site and gate timing, and a masonry oven's wood use varies. Spring tides follow new and full Moon by a day or two, neaps follow the quarters, and Easter always falls after a full Moon, so Holy Week tends to ride high water. The story is text only for now, because the audio folders are over the repository's 400 MB cap.