Tidal Energy — Sizing Calculator

WaveForge internal design tool · dial in a site & weight, see honest output

Inputs — dial it in

Sliders update everything live. Type exact values if you prefer.

Tidal range / surge R

Open-ocean swing low→high tide. 6 m ≈ 20 ft. Bay of Fundy ≈ 16 m.

Impounded basin — surface area A

m²

≈ 447 m × 447 m square. Wider = more free energy (∝ area).

Total channel width W (gates)

Sets the power profile, not total energy. Wider → higher peak / shorter burst; narrower → steadier, toward continuous. (Channel depth assumed ≈ tidal range.)

Gravity mass (weight) M

= 5,000 tonnes. Reclaimed barges + ballast. Must stay buoyant to be tide-lifted.

Real-world efficiency η (turbines × conversion)

~0.35 is realistic for a tidal plant (La Rance-class).

Tides per day

/day

2 = semidiurnal (most coasts). 1 = diurnal.

① Tidal-flow path — the bulk

Impoundment + bidirectional turbines · E = ½·ρ·g·A·R²

Theoretical energy / tide—

Usable energy / tide (×η)—

Average continuous power—

② Gravity-store path — dispatch

Buoyant weight, lifted by tide, dropped on demand · E = M·g·R

Free energy / cycle—

Average continuous power—

Note—

③ Flow & power profile — channel width → drainage → peak

Total energy/tide is FIXED by area × range². These set how fast you deliver it — peak vs continuous.

Water exchanged / tide (tidal prism = A×R)—

Channel cross-section (≈ W×R)—

Average flow rate—

Drainage time (let-it-rip)—

Peak power (during drain)—

vs. average continuous (energy ÷ 24h)—

Wide channels → high peak, short burst. Narrow channels (or throttling) → lower peak, longer window, toward continuous dispatch. Total energy is the same either way — only the shape changes. (Basin volume below low tide ≠ free energy; it's pumped-storage capacity.)

What the tidal-flow path supports

Homes (≈1.2 kW continuous each)—

…or green hydrogen (if all power → electrolysis, ~52 kWh/kg)—

Energy per day (tidal-flow path)—

✓ Free levers (more energy from the tide): wider area, bigger tidal range, more buoyant mass. You're capturing more of what the tide already does.

✗ Not free (storage, not generation): digging deeper than the range, pumping the basin down, inflating floats. Useful for longer dispatch — but you get out ≤ what you put in.

Formulas. Tidal-flow: E_tide = ½·ρ·g·A·R² (ρ = 1025 kg/m³ seawater, g = 9.81). Gravity-store: E = M·g·R (free lift only through the tidal range R). Average power = total daily energy ÷ 86,400 s.
The one rule. Free energy per cycle is capped at (what the tide lifts/moves) × g × (tidal range). Everything beyond that is a (lossy) battery. This tool only ever reports the free harvest.
Range & scale. Tidal range can be amplified by site geometry & resonance (why the Bay of Fundy reaches ~16 m) — site selection is the biggest free lever. But at utility scale, large-scale extraction damps the range (the Garrett–Cummins limit), so real max output sits below A×R². Negligible at single-site / community scale, where this tool's estimate holds.
Internal design tool — physics estimates, not a guaranteed yield. Not for public posting.